10-29-10/30/2019 Storm Recap

General Recap

Second storm has come and gone for the Colorado front range. A lot of folks have asked and the answer is yes; the amount of cold we’ve seen and the amount of snow we’ve seen this October is unusual.  A series of storm systems moved through the area and made it feel much more like late December than October. The first wave delivered snowfall mostly as expected (you can read that storm re-cap here) and while the second went mostly according to plan… there were a few things that threw us a curve-ball.

Let’s take a look!

Snow Forecast Recap

 

48 hour interpolated snowfall accumulations for Colorado

Here’s the point-by-point rundown:

Legend: [Verified Within Forecast Range] [Close to Forecast Range (+/- 1-2 inches of accumulation] [Minor Forecast Bust (+/- 2-4 inches of accumulation] [Major Forecast Bust (+/-4 inches or more/less accumulation]

City24-48 hour Forecast RangeWithin 12-24 hour Forecast RangeActual Amount
Castle Rock5-107-144.4
Parker5-107-1410.0
Highlands Ranch3-74-84.5
Elbert4-85-106.0
Elizabeth5-106-127.8
Kiowa2-53-7N/A
Centennial3-74-86.4
Denver4-85-105.0
Larkspur4-84-86.7
Monument4-84-84.8
Black Forest3-73-63.5
Littleton3-74-85.0
As of this writing no stations reported near Kiowa, data not included in counts below.
  •  Overall Forecast Range Recap:
    • 10 out of 11 verified
    • 0  out of 11 were very close to forecast range
    • 1 were minor busts
    • 0 were major busts
  • Grade of this forecast: GOOD

 

Summary

While the snow amounts and impacts played out pretty closely to the forecast, the one thing I didn’t like about this storm was the timing. It was unexpected to get the bulk of our snow in the morning, then clearing in the afternoon followed by late arrival of additional snow that evening. On top of that, the second wave which supposed to be stronger didn’t materialize for most areas.

These types of storms are tricky, storms back to back like this can do some funny things. Not only did they mess with the models but a lot of meteorologists were surprised. Not a forecast miss by any means, but something that we probably all could have done a bit better on.

Storm Arrives Early – Snow Totals Adjustments – 10/29/2019

Watches/Warnings/Advisories

***Winter Storm Warning***
In effect from Tuesday October 29, 2019 6AM – Wednesday October 30, 2019 12PM

URGENT - WINTER WEATHER MESSAGE
National Weather Service Denver CO
405 AM MDT Tue Oct 29 2019

...SNOW AND COLD TODAY THROUGH WEDNESDAY MORNING...

.A storm system will drop south out of the Northern Rockies
and will be centered near the Four Corners by tonight. The storm
system will then track east across Colorado late tonight and
Wednesday. Snow will become widespread this morning, across much
of the area, with heavier snow developing later this morning
through the afternoon.

Roads are expected to become snow covered and slippery this
morning with hazardous travel conditions by midday through tonight
into Wednesday morning. If traveling today or Wednesday morning
consider adjusting your travel plans.


COZ039>041-043>046-049-291815-
/O.CON.KBOU.WS.W.0016.191029T1200Z-191030T1800Z/
Boulder and the western suburbs of Denver-Denver-Castle Rock-
Greeley-Fort Morgan-Byers-Limon-Akron-
Including the cities of Arvada, Boulder, Golden, Lakewood,
Longmont, Aurora, Brighton, City of Denver,
Denver International Airport, Highlands Ranch, Littleton, Parker,
Castle Rock, Elbert, Fondis, Kiowa, Larkspur, Eaton, Fort Lupton,
Greeley, Roggen, Brush, Fort Morgan, Goodrich, Wiggins, Bennett,
Byers, Deer Trail, Leader, Agate, Hugo, Limon, Matheson, Akron,
Cope, Last Chance, and Otis
405 AM MDT Tue Oct 29 2019

...WINTER STORM WARNING REMAINS IN EFFECT UNTIL NOON MDT
WEDNESDAY...

* WHAT...Heavy snow expected. Total snow accumulations of 6 to
  12 inches.

* WHERE...Portions of east central and northeast Colorado.

* WHEN...From 6 AM Tuesday to noon MDT Wednesday.

* IMPACTS...Travel is expected to be very difficult. The
  hazardous conditions are expected to impact the Tuesday
  evening and Wednesday morning commute. The cold wind chills as
  low as 15 below zero could result in hypothermia if
  precautions are not taken.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If you must travel, keep an extra flashlight, food, and water in
your vehicle in case of an emergency.

The latest road conditions for the state you are calling from can
be obtained by calling 5 1 1.

Forecast/Hazards/Timelines/Impacts (The Need to Know Planning Stuff!)

Impacts

Snowfall/Travel Impacts

  • Moderate to high impacts are occurring this morning along Front Range roads.
  • Moderate to high impacts to travel look likely into Tuesday night and Wednesday morning
  • Roads are expected to become icy and snow packed in the heaviest areas of snow. Be prepared for difficult and potentially dangerous travel conditions along the front range including Denver, Palmer Divide and areas East of Denver especially later in the day Tuesday through Wednesday morning.

 

Timing

  • Tuesday
    • Snow is occurring Tuesday morning, moderate intensity in some places
    • Snow will pick up in intensity after lunch time with heavier snow establishing after 3PM and into the evening hours
    • Heavy snow and wind will be likely for many areas going into Tuesday evening and overnight
  •  Wednesday
    • Heavy snow overnight and cold temperatures means the commute Wednesday morning will see moderate to high impacts
    • Snow is expected to continue through early Wednesday with the heaviest accumulations in the morning.
    • Snow begins to taper off by late morning to afternoon
    • Extremely cold temperatures will be possible overnight Wednesday into Thursday

Snowfall

A couple of factors went into adjusting snow totals from last night’s to this morning’s model runs. First, models initially backed off on snow totals last night but this morning increased them. Second, the snow intensity this morning is a bit heavier than anticipated and it began snowing a bit earlier as well. All of this points (if everything else in this storm stays the same) to higher snowfall accumluation.

Here’s the latest for the Palmer Divide and around the front range:

Palmer Divide estimated snowfall through Wednesday 3PM

Palmer Divide estimated snowfall through Wednesday 3PM

Northern Colorado estimated snowfall through Wednesday 3PM

Colorado Springs area estimated snowfall through Wednesday 3PM

Models this morning have been very consistent with totals in these amounts. Not anticipating any more changes to these totals unless something falls apart or the storm strengthens.

Summary

Pretty good sized storm on our hands. Already seeing reports of tough travel conditions not only in Denver but areas South towards the springs and Palmer Divide. Remember, a Winter Storm Warning means travel is not advised. If you can stay off the roads today that’s definitely a good idea. If you have to travel make sure you have a survival kit and any necessary supplies in your vehicle!

If we see any more updates we will be sure to pass them along, but looks like the storm is moving in!

 

Round 2 on the Way! 10/29-10/30 Storm Forecast

Watches/Warnings/Advisories

Palmer Divide weather highlights as of 4PM

***Winter Storm Warning***
In effect from Tuesday October 29, 2019 6AM – Wednesday October 30, 2019 12PM

Boulder and the western suburbs of Denver-Denver-Castle Rock-
Greeley-Fort Morgan-Byers-Limon-Akron-
Including the cities of Arvada, Boulder, Golden, Lakewood,
Longmont, Aurora, Brighton, City of Denver,
Denver International Airport, Highlands Ranch, Littleton, Parker,
Castle Rock, Elbert, Fondis, Kiowa, Larkspur, Eaton, Fort Lupton,
Greeley, Roggen, Brush, Fort Morgan, Goodrich, Wiggins, Bennett,
Byers, Deer Trail, Leader, Agate, Hugo, Limon, Matheson, Akron,
Cope, Last Chance, and Otis
311 PM MDT Mon Oct 28 2019

...WINTER STORM WARNING IN EFFECT FROM 6 AM TUESDAY TO NOON MDT
WEDNESDAY...

* WHAT...Heavy snow expected. Total snow accumulations of 6 to
  12 inches.

* WHERE...Portions of east central and northeast Colorado.

* WHEN...From 6 AM Tuesday to noon MDT Wednesday.

* IMPACTS...Travel is expected to be very difficult. The
  hazardous conditions are expected to impact the Tuesday evening
  and Wednesday morning commute. The cold wind chills as low as 15
  below zero could result in hypothermia if precautions are not
  taken.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If you must travel, keep an extra flashlight, food, and water in
your vehicle in case of an emergency.

Colorado weather highlights as of 4PM

Forecast/Hazards/Timelines/Impacts (The Need to Know Planning Stuff!)

Impacts

Snowfall/Travel Impacts

  • Minor impacts are possible to the Tuesday morning commute
  • Moderate to high impacts to travel look most likely into Tuesday night and Wednesday morning
  • Roads are expected to become icy and snow packed in the heaviest areas of snow. Be prepared for difficult and potentially dangerous travel conditions along the front range including Denver, Palmer Divide and areas North of Denver especially later in the day Tuesday through Wednesday morning.

 

Timing

  • Tuesday
    • Light snow is possible Tuesday morning but accumulations look light for any areas that do see snow.
    • Heaviest snow looks likely after 3PM as of this update
    • Heavy snow and wind will be likely for many areas going into Tuesday evening and overnight
  •  Wednesday
    • Heavy snow overnight and cold temperatures means the commute Wednesday morning will see moderate to high impacts
    • Snow is expected to continue through the day Wednesday with the heaviest accumulations in the morning.
    • Snow begins to taper off after 12PM with clearing towards evening
    • Extremely cold temperatures will be possible overnight Wednesday into Thursday

 

Snowfall

So far the models are showing a much better organized storm with a favorable track for heavy snow than the last. This is a preliminary snowfall forecast, be advised that these totals may change late tonight and possibly again by tomorrow morning as we get more data in.

Palmer Divide estimated snowfall through Wednesday 3PM

We will be watching closely and adjust snow totals as needed. There is at this time a decent chance they may be adjusted upwards so stay tuned!

Summary

A one-two punch for us this cold and snowy October. This storm looks a lot more powerful than the last so keep a close eye on the forecast. The way it’s looking you probably want to be off the roads by Tuesday evening and plan for the same Wednesday morning.

As always I’ll pass along any updates (next forecast update most likely quite late Monday night and early Tuesday) Stay tuned!

 

10-27-10/28/2019 Storm Recap

 

General Recap

Another snow storm in the books in what is quickly becoming a notably cold and active October along the front range. This storm behaved relatively as expected, but due to the snowfall banding areas within just a few miles of each other saw drastically different snowfall amounts. That’s mainly why we emphasize ranges over pinpoint numbers because when you get events like this most will fall in those ranges with a few falling outside here and there.

Snow Forecast Recap

24 hour interpolated snowfall accumulations for Colorado

Here’s the point-by-point rundown:

Legend: [Verified Within Forecast Range] [Close to Forecast Range (+/- 1-2 inches of accumulation] [Minor Forecast Bust] [Major Forecast Bust]

City24-48 hour Forecast RangeWithin 12-24 hour Forecast RangeActual Amount
Castle Rock3-75-103.9
Parker4-85-105.5
Highlands Ranch3-74-94.5
Elbert2-54-95.3
Elizabeth2-54-97.0**
Kiowa2-53-74.0
Centennial3-73-75.0
Denver3-74-86.6
Larkspur3-75-10N/A
Monument3-75-104.8
Black Forest3-74-85.5
Littleton3-74-97.0
Elizabeth amount is from nearest reporting station. It may be changed when better data comes in, not included in counts below.
As of 10AM no stations reported near Larkspur.
  •  Overall Forecast Range Recap:
    • 8 out of 10 verified
    • 2  out of 10 were very close to forecast range
    • 0 were minor busts
    • 0 were major busts
  • Grade of this forecast: GOOD

 

Summary

Another system is through and the forecast turned out pretty well for the most part. There were some specific areas near the reporting stations that may have seen significant differences from the numbers above. Unfortunately, with snow band storms like this we don’t have the ability to forecast down to the detail needed to account for things like that. If I could do that I’d probably be in line for a nobel prize!

For the most part though, folks ended up within or close to our forecast range. The cool thing to notice is a lot of places fell within our range for 12-24 hour and 24-48 hour ranges which makes me happy because it means the forecast stayed consistent and ultimately turned out pretty well!

Turning focus to the next storm moving in on Tuesday and looks like it could be a doozy. Should have an update on that posted on my website shortly so stay tuned!

10/27-10/28/2019 Storm Update – Cold and Snow on the Way!

A very active storm system is moving into the area starting with a series of cold fronts tonight (Saturday) that will begin to drop temperature significantly overnight and into Sunday. Highs for many areas along the Palmer Divide will be in the 20’s for Sunday. Quite the change from today’s 60’s and 70’s!

There have been a few forecast changes relating to timing, strongest intensity/impacts to the storm and snowfall amounts.

Here’s where we stand as of this evening…

Watches/Warnings/Advisories

 

Winter Weather Highlights for the Palmer Divide/ S. Denver area as of 7PM this evening (10/26/2019)

***Winter Weather Advisory***
In effect from 12PM Sunday Oct 27 – 6PM Monday Oct 28

Boulder and the western suburbs of Denver-Denver-Castle Rock-
Including the cities of Arvada, Boulder, Golden, Lakewood,
Longmont, Aurora, Brighton, City of Denver,
Denver International Airport, Highlands Ranch, Littleton, Parker,
Castle Rock, Elbert, Fondis, Kiowa, and Larkspur
154 PM MDT Sat Oct 26 2019

...WINTER WEATHER ADVISORY IN EFFECT FROM NOON SUNDAY TO 6 PM MDT
MONDAY...

* WHAT...Snow expected. Total snow accumulations of 5 to 10
  inches.

* WHERE...Boulder and the western suburbs of Denver, Denver and
  Castle Rock.

* WHEN...Light freezing drizzle is expected for a few hours Sunday
  morning. After that, it will snow the rest of Sunday through
  Monday. The main accumulation will be Sunday night.

* IMPACTS...Travel could be difficult at times. The worst
  conditions are expected Sunday night into Monday morning.

***Winter Storm Warning***
In effect from 3AM Sunday Oct 27 – 6PM Monday Oct 28
The Winter Storm outline area for the Palmer Divide is mainly in the foothills of Western Douglas County. There are additional Winter Storm Warnings for mountain locations

The Southern Front Range Foothills-
Including the cities of Bailey, Central City, Evergreen,
Georgetown, Idaho Springs, and Westcreek
154 PM MDT Sat Oct 26 2019

...WINTER STORM WARNING IN EFFECT FROM 3 AM SUNDAY TO 6 PM MDT
MONDAY...

* WHAT...Freezing drizzle followed by heavy snow. After a light
  glaze of ice, total snow accumulations will be 8 to 14 inches.

* WHERE...The Southern Front Range Foothills.

* WHEN...Freezing drizzle is expected early Sunday morning, then
  snow Sunday through Monday. The heaviest snow will be Sunday
  night.

* IMPACTS...Travel will be very difficult at time, with the worst
  conditions Sunday night into Monday morning.

Forecast/Hazards/Timelines/Impacts (The Need to Know Planning Stuff!)

Impacts

Snowfall/Travel Impacts

  • It appears there will be minor impacts Sunday morning and through the day Sunday. Biggest concern is icy roads from freezing rain, slick spots will be possible. We are not expecting anything beyond minor impacts due to snow earlier in the day Sunday
  • Moderate to high impacts to travel look most likely into Sunday night, early Monday morning and through the morning commute Monday morning.
  • Roads are expected to become icy and snow packed in the heaviest areas of snow. Be prepared for difficult travel conditions along the front range including Denver, Palmer Divide and areas North of Denver
  • Mountain areas will see potentially dangerous travel conditions late in the day Sunday and overnight into Monday. Please take this into account if you have mountain travel planned.

Timing

  • Sunday
    • Freezing rain will be possible into Sunday Morning, especially North of Denver
    • Snow will be likely throughout the day but accumulations look light Sunday morning and early Sunday afternoon along the front range
    • Snow will become heavy later in the day Sunday into the evening and overnight hours
    • Very cold temperatures in the 20’s and teens are likely later on Sunday
  •  Monday
    • Heavy snow overnight and cold temperatures means the commute Monday will see moderate to high impacts
    • Snow is expected to continue through the day Monday with the heaviest accumulations in the morning.
    • There is potential for snow later in the day but accumulations look likght
    • Temperatures will struggle to reach the 30’s for most areas on Monday. Extreme cold is likely later Monday and into Monday night.
  • Tuesday
    • Uncertainty is high at this time but there is potential for the second storm to impact the area on Tuesday and Wednesday

Snowfall

WPC product is uploaded below, this tends to over-do snow just a bit but given the cold nature of this storm and the higher snow accumulation potential and liquid/snow ratios being in the 15:1 range or even better, this seems accurate.

MMWAVWX forecast snowfall accumulation ranges for the Palmer Divide and South Denver as of 7PM 10/26/2019

Please note: there are some spotty areas (especially along and West of I-25) that could bust high on this range. Some areas may see up to or slightly more than a foot. Those areas will be spotty, for the most part locations should end up in these ranges.

Livestream Tonight

I will be doing another livestream tonight so make sure to tune in. I’ll zoom in on more areas for snowfall forecasts and take a look at what the models are saying along with answering any questions.

Tune in at 10PM tonight! You can catch it on my Facebook Page, it will pop up as soon as I go on!

 

Summary

This storm has been keeping a lot of meteorologists on their toes, with the shifting models, storm track, timing and impacts it’s been a fun one to watch!

I would not be surprised to see another curve ball or two as we get in the late forecast hours of this event. As always I’ll be sure to post any updates as needed!

Regarding the next storm; that moves in sometime during the Tuesday – Wednesday timeframe and so far it’s looking interesting. Let’s get through a good chunk of this one then I’ll switch gears to that one!

 

Active October Continues – Next Storm(s) on Tap -10/25/2019

Looks like we have an active period of weather coming up over the weekend and into next week. Still a lot of details to hash out on this one, but models are picking up on not just one, but a series of storm systems that will move through the state. There looks to be a few differences between this storm and the last one we experienced including the speed, the amount of cold air to work with, but a lot are coming into agreement at least to some degree that this could be decently spread across the front range, including the foothills, Denver Metro area and Palmer Divide.

Here’s what we know so far…

Timing

  • Strong cold front
    • Moves through late Saturday into early Sunday
    • Currently looks like 9PM – 12AM as the first bursts of cold air, with cooler air filtering in through the overnight hours and into early Sunday morning
  • Snow
    • A  prolonged period of snow is possible throughout the day Sunday. Be aware, heavy snow is possible later in the day Sunday, we’ll try to nail down more details on the exact when and where over the next day or two
    • Additional chances for snow on Monday and late Tuesday into early Wednesday
    • A couple of different waves of energy will produce the snow
  • Temperature
    • Most areas will struggle to reach the 30’s late on Sunday, Monday and Tuesday.
    • Low temperatures could be in the single digits to near zero for higher elevation areas and in the low teens to single digits for the Denver area
    • Wednesday also looks cold.
    • Halloween looks cool overall but models disagree on how cold. Some models show extremely cold temperatures so this will be something we have to watch for.

 

Storm Energy

Euro 500mb on Monday afternoon. Notice the trough across the Rockies. This feature builds in through the day on Sunday and continues into Monday, this will provide our cool and unsettled weather.

Euro 500mb Wendesday around midnight. Again a strong low pressure system is over Colorado and the overall track it takes will dictate what we see. In this model run it is a bit too far North for us than an optimal “big snow” scenario… but worth a close watch for any shift in the track.

A lot of the energy from this period will come from an active storm track that will swing a series of troughs from the Pacific Northwest, across the Western U.S. and eventually into Colorado. While snowfall amounts and these storms don’t look terrible impressive right now, we always have to keep an eye on storms like this. They will be powerful and depending on exactly what track they take could mean big differences in what we see.

I’m not comfortable saying any of these storms being a “major event” as of right now, but would like to point out the potential is there. So we will have to keep an eye on them very closely.

Morning update from the NWS:

The combination of upslope flow at low
levels with the upper troughiness over the state and the upper
level jet on top of it will generate moderate to heavy
precipitation rates Sunday afternoon and Sunday night. It is
possible that areas along the Front Range foothills and I-25
Urban Corridor could see snowfall accumulations in excess of 6
inches by Sunday night.

Snowfall

We’ve got enough information this morning to post a very preliminary guess at what snow looks like for this first series of storms. Keep in mind, this could change drastically over the next 24-36 hours. We will have a whole host of models coming into better range today so we should get a better idea and be able to refine snowfall totals with that information.

Remember, it’s early so these are preliminary and WILL change over the next 24-36 hours. This is a good first shot though!

Predicted snowfall ranges through Monday PM

As our friend Billy would say, there’s more!

Another wave of energy moves through late Tuesday and into Wednesday. This means additional cold air and snow will filter in the area adding on to what we already have on the ground.

Currently what the EURO model shows for around midnight on Tuesday

Some of the models show another shot of heavy snow along the front range. So overall we will be watching a lot of things next week.

Summary

What do you need to do right now?

Nothing at the moment, just realize that if you have plans on Sunday through Wednesday they may be impacted by cold and inclement weather. Snow to some degree looks likely but we don’t know exact numbers yet. Halloween looks chilly as well (for right now, it’s at the edge of the models range so accuracy is always a question) so plan on that possibility if you’re outdoors as well.

We will have to keep a close eye on all these waves towards the end of the weekend and into early next week. Some models show a decent shot at accumulating snow in what I’d call a “moderate” range, but because of the power of the storm systems and how close their tracks will be to an “optimal” track for big snow… they will need to be watched closely over the next 24-48 hours.

Expect refinements to our snowfall forecast throughout the day on Friday and Saturday based on the information coming in. Stay tuned, we will keep you updated!

10/23-10/23/2019 Front Range Storm Recap

General Recap

A pretty decent storm for this time of year. There wasn’t a ton of cold air to work with, which is probably why Denver and points North and East didn’t see a ton of accumulation. Not only that, but Northeasterly flow can create downsloping and dry out the air off of the Cheyenne Ridge. Denver tends to do better with Easterly and sometimes Southeasterly upslope storms.

As you can see, the areas we called out were generally the ones that did best. The foothills West and Southwest Denver were heavily favored to see the heaviest snowfall and they did. Additionally the Palmer Divide also saw a decent brunt of the storm and most areas finished up within the forecast range if not slightly higher.

Snow Forecast Recap

Here’s a quick recap of how our snowfall forecast evolved over the days and hours leading up to the storm event and how things finished out. Despite a ton of uncertainty in the models there were some consistencies and it helped to not overthink the short term models too much. The closer in stuff tended to bounce a lot and some of the more short term models wrote this storm off completely within 6 hours of its arrival. Model bouncing is common and its why if you don’t know how to read them, how they behave and how the meteorology behind them and around them works, you can have a tough time with accurate forecasts with just model watching.

Here’s the point-by-point rundown:

Legend: [Verified Within Forecast Range] [Close to Forecast Range (+/- 1 inch of accumulation] [Minor Forecast Bust] [Major Forecast Bust]

City24-48 hour Forecast RangeWithin 12-24 hour Forecast RangeActual Amount
Castle Rock4-84-85.5
Parker4-84-84.0
Highlands Ranch2-63-75.5
Elbert4-84-84.25
Elizabeth4-82-56.3
Kiowa2-62-5N/A
Centennial1-41-44.5
Denver0-31-44.5
Larkspur5-105-107.5
Monument5-105-108.0
Black Forest4-84-810.0
Littleton2-53-54.5
  •  Overall:
    • 7 out of 12 verified
    • 4  out of 12 were very close to forecast range
    • 0 were minor busts
    • 0 were major busts
    • No data as of this report from Kiowa
  • Grade of this forecast: GOOD

 

Modeling Review

The winner of this storm by far was the European model. It zeroed in on the foothills and Palmer Divide and never let go.

EURO model run from 6AM Monday morning

Euro from early Wednesday morning October 23

 

Compare both of those to what actually transpired again…

Keep in mind, the EURO’s skill (rough accuracy) is pretty darn good within 48 hours, but all of them become more accurate to some degree within that timeframe. I think the biggest thing to note with this storm was how the other models flip-flopped a bit and even backed off but the EURO stayed consistent through the entire period.

Important to note as well; as good as the EURO is, it too can be wrong. My biggest advice if you want to learn how to forecast using models is understand how they work, what their strengths and weaknesses are and learn to spot patterns over several series of model runs instead of getting hung up on one run or the other. Models will bounce back and forth, they always do but it’s a good idea not to get too “hung up in those details” and look for the overall patterns.

Summary

Phew, we won’t have much time to take a break as our medium range models are picking up on a potentially prolonged period (several days) of cold and snowy weather next week. The forecast went very well with this storm, but we will have to quickly change gears for the next.

The EURO’s view of the storm system next week

Models are all picking up on a series of potential storm systems next week. Not a lot of agreement on timing, strength or anything else, but definitely worth keeping an eye on. The setup with next week’s storm is a whole different animal than the one we just saw.

We will be watching closely over the next few days and will have several updates as needed so stay tuned!

 

Storm Update – Palmer Divide/ Foothills Still Highest Snow Accum.

Busy day ahead from a weather standpoint. A lot of watches have been upgraded in one form or another, Denver is now included in a Winter Weather Advisory for travel conditions tonight and a Winter Storm Watch remains for the Colorado Springs area. The good news is, we are starting to get decent agreement between most of the models but a few are still holding out a bit in terms of who sees the heaviest snow. The good news is we have enough to get a good idea of where the trouble spots will be.

Here’s the rundown of the latest…

Watches/Warnings/Advisories

NWS Alerts as of 6 AM 10/23/2019

***Winter Storm Warning***
In effect 6PM Weds through 8 AM Thurs

The Southern Front Range Foothills-Castle Rock-
Including the cities of Bailey, Central City, Evergreen,
Georgetown, Idaho Springs, Westcreek, Castle Rock, Elbert,
Fondis, Kiowa, and Larkspur
354 AM MDT Wed Oct 23 2019

...WINTER STORM WARNING IN EFFECT FROM 6 PM THIS EVENING TO 8 AM
MDT THURSDAY...

* WHAT...Heavy snow expected. Total snow accumulations of 4 to 8
  inches with locally up to 12 inches in the southern Foothills.

* WHERE...The Southern Front Range Foothills and Castle Rock.

* WHEN...From 6 PM this evening to 8 AM MDT Thursday.

* IMPACTS...Travel could be very difficult. The hazardous
  conditions could develop during this evenings rush hour, and
  may linger into early Thursday morning.


PRECAUTIONARY/PREPAREDNESS ACTIONS...

If you must travel, keep an extra flashlight, food, and water in
your vehicle in case of an emergency.

***Winter Weather Advisory***
In effect 6PM Weds through 8 AM Thurs

Boulder and the western suburbs of Denver-Denver-
Including the cities of Arvada, Boulder, Golden, Lakewood,
Longmont, Aurora, Brighton, City of Denver,
Denver International Airport, Highlands Ranch, Littleton,
and Parker
354 AM MDT Wed Oct 23 2019

...WINTER WEATHER ADVISORY IN EFFECT FROM 6 PM THIS EVENING TO
8 AM MDT THURSDAY...

* WHAT...Snow expected. Total snow accumulations of 2 to 4
  inches.

* WHERE...Boulder and the western suburbs of Denver and Denver.

* WHEN...From 6 PM this evening to 8 AM MDT Thursday.

* IMPACTS...Plan on slippery road conditions. The hazardous
  conditions could impact the Thursday morning commute.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Slow down and use caution while traveling.

***Winter Storm Watch***
In effect 8PM Weds through 10 AM Thurs

Canon City Vicinity/Eastern Fremont County-
Colorado Springs Vicinity/Southern El Paso County/Rampart Range
Below 7400 Feet-Pueblo Vicinity/Pueblo County Below 6300 Feet-
358 AM MDT Wed Oct 23 2019

...WINTER STORM WATCH IN EFFECT FROM THIS EVENING THROUGH
THURSDAY MORNING...

* WHAT...Heavy snow possible. Total snow accumulations of 3 to 9
  inches possible, however these snowfall amounts are prone to
  change depending on where the heavier snow bands develop.

* WHERE...Southern El Paso, eastern Fremont, and Pueblo counties.

* WHEN...From this evening through Thursday morning.

* IMPACTS...Travel could be very difficult. The hazardous
  conditions could impact the morning commute.

* ADDITIONAL DETAILS...Rapidly deteriorating travel conditions
  will be possible across portions of the area tonight as heavy
  snow bands develop. There is still some uncertainty on where
  these heavier snow bands will set up.

Forecast/Hazards/Timelines/Impacts (The Need to Know Planning Stuff!)

Impacts

Snowfall/Travel Impacts

  • There will be likely impacts to Wednesday evening commute and possible impacts to Thursday morning commute. Heavy snow is expected after 6-8PM along the Palmer Divide. If you have travel plans, please ensure you’re off the roads or well on your way home no later than 8.
  • The highest chance of travel impacts will be areas South of Denver along the Palmer Divide, in the foothills in western Douglas County and the foothills West of Denver.
  • Roads are expected to become icy and snow packed in the heaviest areas of snow. Be prepared for difficult and even dangerous travel conditions in some areas.

Timing

  • Wednesday
    • Wednesday will start out calm with patchy fog in some areas
    • Rain and rain/snow mix showers will be possible between 3-6PM
    • Transition to snow between 5-8PM, this transition will occur quickly so be prepared for rapidly deteriorating conditions on the roads, especially South of Denver in the higher elevations.
  •  Thursday
    • Snow showers will begin to taper off by Thursday morning from North to South between 5-8AM.
    • Spotty snow showers may continue through mid morning for some areas along the Palmer Divide
    • Snow should be completely ended by around noon on Thursday with improving travel and clearing conditions.
  • Friday
    • No snow is expected

Snowfall

WPC product is uploaded below, this tends to over-do snow just a bit but I like these numbers +/- an inch or two as a range. You can see my forecast ranges below.

WPC snowfall model through Thursday 12PM

Our official forecast ranges are listed below:

  • Castle Rock
    • 4-8 inches
  • Parker
    • 4-8 inches
  • Highlands Ranch
    • 3-7 inches
  • Elbert
    • 4-8 inches
  • Elizabeth
    • 2-5 inches
  • Kiowa
    • 2-5 inches
  • Centennial
    • 1-4 inches
  • Denver
    • 1-4 inches
  • Larkspur
    • 5-10 inches
  • Monument
    • 5-10 inches
  • Black Forest
    • 4-8 inches
  • Littleton (putting this on for a reason)
    • 3-5 inches

 Model Output as of This Morning (for those interested)

Euro snowfall forecast

GFS snowfall forecast

Nam3K snowfall forecast

Summary

A decent sized October storm on tap for tonight, I don’t think it will be the worst storm we’ve ever seen but areas South and West of Denver could see pretty decent travel difficulties in the overnight hours tonight. We are getting decent model agreement so we are fairly comfortable with our forecast right now, but some of the higher resolution models are getting less excited about this storm.

Again we can’t change a forecast based on one model run, but we will keep an eye on this trend to see if it continues. The higher resolution, shorter range models can give us an early hint if a storm is going to fall apart, we’re watching for that but as of right now there’s no reason to believe things will end up outside of our forecast ranges and impacts.

As always, this is an evolving forecast so stay tuned here for any changes!

Afternoon Storm Update for Weds PM / Thurs AM Storm

Rapidly evolving forecast when it comes to this storm, here’s the latest based on this afternoon’s data and model runs.

Watches/Warnings/Advisories

Winter Storm Watch has been issued for the Palmer Divide above 6,000 feet and front range foothills.

Winter Storm Watch

In effect Wednesday evening 6PM through Thursday Noon.

The Southern Front Range Foothills-Castle Rock-
Including the cities of Bailey, Central City, Evergreen,
Georgetown, Idaho Springs, Westcreek, Castle Rock, Elbert,
Fondis, Kiowa, and Larkspur
1151 AM MDT Tue Oct 22 2019

...WINTER STORM WATCH REMAINS IN EFFECT FROM WEDNESDAY EVENING
THROUGH THURSDAY MORNING...

* WHAT...Heavy snow possible. Total snow accumulations of 4 to 8
  inches possible, with up to 12 inches in the foothills

* WHERE...The Southern Front Range Foothills and Palmer Divide.

* WHEN...From Wednesday evening through Thursday morning.

* IMPACTS...Travel could be very difficult. The hazardous
  conditions could develop during the Wednesday evening rush hour,
  and may linger into early Thursday morning.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Be prepared for winter travel conditions Wednesday evening through
early Thursday morning. Monitor later forecasts and consider
alternate plans or expect slow travel during the period of
heaviest snow.

Forecast/Hazards/Timelines/Impacts (The Need to Know Planning Stuff!)

Impacts

Snowfall/Travel Impacts

  • There will be likely impacts to Wednesday evening commute and possible impacts to Thursday morning commute. Heavy snow will be possible late Wednesday and into early Thursday.
  • The highest chance of travel impacts will be areas South of Denver. This includes mainly the areas outlined in the Winter Weather Watch above.
  • Roads are expected to become icy and snow packed in the heaviest areas of snow. Be prepared for difficult and even dangerous travel conditions in some areas.

Timing

  • Wednesday
    • Will start out mostly sunny with a transition to clouds in the afternoon. Rain showers will be possible before the colder air moves in during the afternoon hours.
    • A decent amount of models are now showing a possible impact to Wednesday evening commute, most likely at the later end of the time frame.
  •  Thursday
    • Snow showers will begin to taper off by Thursday morning. Still not exact on the timing as some models show before the morning rush and some after.
    • Either way, expect the Thursday morning commute to be impacted in some way.
    • The storm should be out of the area by Thursday afternoon with clearing conditions

As of right now, most likely time to see impacts is within the Watch timing… 5PM Wednesday through 12PM Thursday. We will get better details on timing over the next 12 hours so stay tuned for changes.

NAM3k forecast just before 8PM on Wednesday evening

Snowfall

Models still have a ton of uncertainty so we will use them along with some probabilities based on the data to put together a quick snowfall forecast. Since we have so much bouncing on the models, this is a fluid forecast and will likely change several times over the next 12-24 hours so keep an eye out here for changes.

 

As of this afternoon’s model runs we saw a slight decrease in snowfall amounts from the highest forecast models and a slight increase from the lowest forecast models. This is good because it means we are startign to get a “fuzzy” range of where we might ultimately end up with snowfall.

The graphic above is a modified capture of the WPC and seems to fit best with what I am seeing right now. We can combine this with some of the probabilisic data to see what our ranges are and if there is any uncertainty.

Douglas County area snowfall probabilities with this storm as of 12PM 10/22/2019

Elbert County area snowfall probabilities with this storm as of 12PM 10/22/2019

So here are some quick forecast ranges based on the models, WPC data and probabilistic data from above:

  • Castle Rock
    • 4-8 inches
  • Parker
    • 4-8 inches
  • Highlands Ranch
    • 2-6 inches
  • Elbert
    • 4-8 inches
  • Elizabeth
    • 4-8 inches
  • Kiowa
    • 2-6 inches
  • Centennial
    • 1-4 inches
  • Denver
    • 0-3 inches

Again, these are preliminary amounts and will change with more data. I’m slightly concerned some of the higher resolution and short range models have this storm nearly completely falling apart for most of the area. We will have to watch and see if that continues with more model runs.

Summary

So looks like we have ourselves some bit of a storm here but there are still big question marks as to who sees what. Some models are pulling the main energy of the storm further South this afternoon which could mean Denver and points North get missed completely or have very little snowfall to work with.

If things continue to pull South we’d expect highest impacts right along the Central part of the Palmer Divide (south of Castle Rock, Monument, Larkspur, Elbert, Elizabeth, Kiowa, etc…) and even higher impacts South of there into the springs.

As such, we still need to nail down more details about the storm track and some of the specifics on who sees what. The thing that has not changed and has perhaps become more clear is the Palmer Divide area and points South are the areas to watch the most closely right now.

Should have another update tonight, stay tuned! This forecast will continue to evolve throughout the day and into tonight and tomorrow!

 

In case you are curious about the Denver metro area, here is the probabilistic snowfall data for those areas:

You can see why I’m not too excited about a lot of the areas North of the Palmer Divide. Many areas looking at at less than a 20% chance of seeing more than 6 inches of snow and some areas will struggle to reach 2 or more.

 

 

Midweek Storm Looks Interesting…

A strong and fast moving storm will make its way through Colorado this week. What’s interesting is some of the snow totals some models are spitting out vs. the fact that storms with this track and speed rarely amount to big snowfall for parts of the front range. Not only that, but models are still showing a ton of uncertainty with the storm track, who sees the most moisture and even where the upslope and downslope sets up.

As the timing of this storm is late Wednesday and into Thursday, we have no problem showing the models with this storm at this point, but keep in mind… with this much uncertainty across the spectrum, most of these are bound to change (maybe even drastically) in the next 24-48 hours. With that, here is a look and our thoughts:

GFS

 

GFS snowfall through 12PM Thursday

The GFS is a bit wonky outside of 48 hours but as we are getting close to that timeframe and it nailed the last storm pretty well we have to give it a look. The GFS has been less than excited about the snowfall potential in most of its runs and the latest show (data still coming in at time of this post) pretty much nixes snowfall North of the Palmer Divide completely. If this solution verifies we would look for 2-4 inch range realize in and around Castle Rock with 1-3 for points East of there (out into Elbert County) and some foothills areas of Douglas Count in the 4-8 inch range.

EURO

EURO 24hr snowfall through 10AM Thursday

The Euro has been pretty heavy on snowfall throughout the past couple of days, but even today it has backed off a bit. We always pay close attention to this model because it is by far the most accurate within 72 hours with decent accuracy beyond that (but like all models it falls quickly after 3-5 days.) This particular model shows a more substantial event for the foothills and Palmer Divide. If this model were to verify I’d expect 4-8 inches in and around Castle Rock and points East right along the Palmer Divide. It would be possible areas in and around the foothills in Douglas County could see 5-10 inches.

**Please note, the EURO has continuously been backing off these high totals in the past few runs so our confidence in these ranges is quite low at this point in time.

NAM

NAM 24 hr snowfall through 9AM Thursday

The NAM has just come in range and it like the GFS is not terribly impressed with this storm overall. It does however, highlight the areas right along the upper elevations of the Palmer Divide as a bullseye. This model points out Southwestern and South Central Elbert and Northern El Paso counties as areas that see the most snow. Should this model verify I’d expect to see 1-3 inches in and around Castle Rock with 3-6 inches possible East of town into Elbert and El Paso counties. Colorado Springs may also see decent accumulation with this scenario.

Canadian (For the heck of it)

Canadian (GEM) 24 hr snowfall through 12PM Thursday

I want to say up front, I hate this model more than about 24-48 hours out. It tends to grossly over-estimate snowfall and for that reason I tend to throw it out a lot… but for the heck of it I’ll post it up for this update.

I imagine a lot of folks seeing ridiculous snow totals on their weather apps today were seeing a blend of this model with the EURO perhaps. If this were to verify I’d expect 5-10 inches for Castle Rock and surrounding areas with higher elevation areas of the Palmer Divide seeing 6-12 inches and parts South towards and West of Colorado Springs getting completely hammered. Those areas could see between 8-16 inches of snow.

Want to emphasize though, this is probably the lowest confidence model in this post. The only thing of value I see is the overall pattern that some of the other models are showing that this may be more of a Southerly event. Meaning I’d expect areas South of Castle Rock, over Monument Hill and into the springs to have the highest chance of seeing decent snowfall.

SREF and EURO Ensemble

I like to post these two products because the ensemble means can shed a bit more light on whether we should be concerned about this storm or not. These products take several operational model runs with slightly different parameters and average them out, the mean is a result of all these taken together.

SREF ensemble mean

EURO ensemble mean

As you can see, the mean for both of these products is less than their operational counterparts above (except for that pesky Canadian.)

Summary – What You Need to Know

Like all storms this information WILL change within the next 24-48 hours but we will paint a quick picture of what to expect as of this evening’s data.

Timing
  • Overnight Wednesday into Thursday morning
  • Most models don’t show an impact to Wednesday evening commute, but timeframe can shift so keep a look out
Impacts
  • Be prepared for potential travel impacts late Wednesday night into Thursday morning
  • Possible impacts to Thursday morning commute. Most concerned about this manifesting in areas South of Denver into the Springs
  • Slick roads, wind and snow will be possible into early Thursday morning.

 

That’s what we know for now. Given the uncertainty we cannot get an exact bead on snowfall totals just yet, but stay tuned for those preliminary amounts on Tuesday with clarity Tuesday night into Wednesday.

Doesn’t look like a major storm as of yet but the potential is there. Uncertainty is high and forecast confidence is low, so stay tuned for changes and refinements as we get closer to the storm event.