Latest Guidance on This Weekend’s Storm (Apr 15-17, 2016)

The forecasts are relatively on track this morning from yesterday. Model agreement that a powerful storm system will move into the Rocky Mountain region is still quite good. There is still quite a bit of disagreement between models as to whether snow or rain falls, temperatures and even the position of where the storm sets up. In Colorado, these are all critical to determining what type of storm we get or even if we get a storm at all.

It’ Still Too Early To Tell

You hear me say this a lot but this far out from a storm, you have to take every model run with a grain of salt. This storm system is over the ocean and hasn’t even really formed yet. This causes two issues for modeling:

  • We don’t have good weather stations to give us data, so models are really shooting in the dark at this point in time. Without adequate data coming in from observers and station, models really are just giving us a best guess.
  • The storm system itself has not even really organized too much. Without seeing how the trough (low pressure) system forms and begins to move, we again don’t have enough data to make good guesses.
Satellite view of the Pacific. Still waiting for storm initiation

Satellite view of the Pacific. Still waiting for storm initiation

Don’t get me wrong, the accuracy of weather modeling has improved tremendously over the past few years. These programs are great at predicting patterns from even 1-2 weeks out, but the finer details are not usually spotted until much closer to the time the storm arrives.

Generally these models get more accurate within the 3-5 day time frame and are best withing 3 days of the storm arriving. We also see a huge jump in accuracy when the storm finally makes it onto land where we can get constant data from weather stations.

NWS post about uncertainty in forecasting

NWS post about uncertainty in forecasting this storm

This Storm Has a Lot of Water

This fact has not changed with any of the longer term models. Across the board, all models predict a strong storm with lots of moisture to work with. The GFS shows a ton of moisture accumulating along the front range of Colorado:

GFS quantitative precipitation forecast by 6AM Monday

GFS quantitative precipitation forecast by 6AM Monday

This model however, shows much warmer temperatures and has a large majority of it falling as rain. When you look at the total accumulated snowfall you see not much on the ground:

GFS predicted snowfall accumulation through Monday

GFS predicted snowfall accumulation through Monday

The Euro however, shows nearly all of this moisture falling as snow.

What Happens If Today’s Forecast Verified

I’ll play devils advocate again, what does this storm look like if the models are predicting exactly what will happen? This is tricky because of the two longer range models don’t agree on rain vs. snow for the storm. So we take an average between the two. Take all of these predictions with a grain of salt though, these are just based on what models show at this time and is in no way meant to be final forecast!

  • Timing
    • There is agreement that the biggest impact looks to be on Sunday from this storm, but the effects will be felt on Saturday and probably Monday as well.
  • Snowfall
    • GFS calls for about 2 inches of snow in the Castle Rock area while the Euro calls for about 20, so we can take an average of that: 11 inches roughly. If you take all the models together and pick a range, we are looking at anywhere between 0-30 inches of snow…
  • Blizzard Conditions?
    • From the data I am seeing so far, this storm does not look as windy as the last one that brought big snow and big drifting. This still has plenty of time to change but not looking like blizzard wind conditions at this time.

Summary

At this point in time, with the storm still several days away from arriving and not even on the coast of the U.S. yet you will probably hear everything from 3 feet of snow to no snow at all from the media and other weather forecasters. One way or another, neither of those predictions are right or wrong. Meteorologists all look at the same data but have different interpretations and instincts. I don’t steal other’s forecasts I make my own; often times I’m right but sometimes I’m wrong. That is the nature of being a meteorologist!

The best advice I can give at this time is stay tuned. I don’t expect the forecast to change a whole lot on Tuesday or Wednesday because the storm will still be off shore. We should begin to see model agreement by Thursday which could mean major shifts in the forecast.

Stay with us and we will update as new data comes in and we will also have updates should any major changes to the forecast look likely.

On another note: thank you to everyone who has followed me that last few days. I’ve enjoyed reading and replying to all your comments and enjoy discussing our awesome Colorado weather with you all!

~John

Monster April Snowstorm Brewing?

This will be an important week to keep an eye on the weather, there are a lot of things going on that will impact a major storm system expected to move into the area next weekend. This post will be a bit lengthy but I feel it’s necessary to try and explain what is going on and what it means.

I’ve broken this post up into two sections: the first (usually the one most people care about) will be information on this storm. The second part, further down in the post will be for the folks who want to know more about how these storms are forecast and the mechanics behind some of the modeling.

Something is Brewing…

In the last week or so, we have seen hints a major storm system moving into Colorado by next weekend (April 15-17 time-frame.) So far the news outlets in Denver have done a pretty good job at not over-hyping this storm system but I imagine that will change as we go through the week.

We’ll start with a look at the setup of this storm:

The Euro shows a strong low pressure system moving from North to South across Colorado. This system will bring much colder air and eventually tap into moisture as it moves across the state late this week.

Euro_MLSP_04112016

  • This is a strong system, it will be able to pull colder air from the North which may make it cold enough for snow. This is a huge question mark right now as other models predict less cold air and even the Euro questions how much cold air this system will be able to tap into.
  • Every model agrees on the moisture with this storm. As it slides South, it will begin to tap into moisture flow from the Gulf of Mexico.
  • Upslope flow is another ingredient all models agree on, this will enhance precipitation along the front range of Colorado.

Still Quite A Bit of Uncertainty

At one point this week, the Euro model was making this storm look almost apocalyptic.

euro_snow04102016

Euro QPF as of Sunday April 10, 2016

This snapshot of the Euro’s QPF (precipitation) yesterday showed nearly 5 inches of precipitation falling throughout this storm. If we take an average 10:1 ratio of snowfall (as is common for Colorado) we would translate that to somewhere around 50 inches of snow. If you’re curious how we look at QPF and snowfall, read the technical sections in the later part of this post.

This is a huge number but also a number with a huge question mark. For this to realize, all of the moisture would need to fall as snow and there is not a ton of agreement on temperatures right now.

Second, this particular model backed way off on those numbers overnight, nearly cutting them in half. That being said, this would still equate to nearly two feet of snow if this materialized:

Euro QPF as of Monday morning April 11

Euro QPF as of Monday morning April 11

This is an effect I affectionately call “Model bounce” and it means one thing: uncertainty. This storm is still a long ways out and models have a tough time with these things until they get into a closer range.

So, do we get a massive blizzard? Do we have flooding rains? Does anything happen at all?

What We Know

  • Models across the board agree that a very large and powerful system will impact somewhere in the high plains of the U.S.
  • This storm system is going to have a ton of energy and a ton of moisture

What We Don’t Know

  • Where does the storm system set up? We don’t know as of yet whether Colorado will even be impacted from this storm. 100 miles North or South makes a huge difference!
  • How cold does it get? If it stays too warm, nearly all of this will fall as rain. Any colder, it will fall mainly as snow.

Takeaway

There is no reason to get too excited about this storm as of yet. If you’ve followed me for any amount of time, you know that I like to stay pretty level-headed and non-hype with my forecasting. We simply do not have enough data on this system yet and anyone that starts telling you we will get 4-5 feet of snow this early is very misinformed.

That being said, there are a couple of things that have my attention. First, the Euro model was the only model to correctly predict our last blizzard. So while there’s no reason to get too excited, we shouldn’t completely write this thing off either…

Second, there are a lot of things working against this storm for snowfall such as temperatures and positioning of the low. However, the ingredients are all there and should they set up right we could have a dozy of a spring snowstorm on our hands.

Keep an eye on your favorite weather source this week (whether it’s us or someone else.) If you follow us, we will have a ton of posts up this week as the forecast changes. If things begin to look serious later this week, we will give you plenty of notice to start preparing for it.

 


 

Quantitative Precipitation Forecasts, Snowfall Predictions and Models

Quantitative precipitation forecasts is a product that weather models output that gives us an idea about how much liquid precipitation will fall. This literally means how much water will fall from the sky. In the summer this gives us a good idea of how much rain we may see over a period of time but in the winter and spring months for Colorado it gets a bit more tricky because 5.0 inches of precipitation does not translate into 5 inches of snow.

QPF forecast from April 2013

QPF forecast from April 2013

For snowfall in Colorado we generally use a 10:1 ratio for snowfall; meaning for every 1 inch of QPF we see on a model we can expect 10 inches of snow from that. This is an average though and doesn’t always prove true, colder storms may see a 15:1 or 20:1 ratio, while wetter spring storms may see a 5:1 ratio.

Model Accuracy

There has been a lot of talk on model accuracy as of late. Some models just seem to handle weather better than others and the overall accuracy across models may surprise you!

model_accuracy_1YR

Here’s a look at the accuracy for models over the past year. The big 2 we often use is the ECM and the GFS. The ECM is comonly referred to by us Met types as the “Euro.” This is a model that ingests data from many different sources and creates forecasts across the world. The GFS is the American model created by NOAA and used by NASA and the NWS.

In recent years there has been a tendency to look harder at the actual accuracy numbers for these models. Many have said that the American models are falling behind other models in the world. You can see by the chart above that American models are not falling behind the Euro,they are in fact keeping up but they are just not as accurate.

Both models have undergone upgrades in recent years and both have increased in accuracy but the Euro is still by and large, the front runner.

 Models and Colorado

There is a lot of facts and science about how these models are rated for accuracy but sometimes you just can’t replace experience. I’ve been following weather for nearly 25 years now in Colorado and I’ve picked up on some patterns with modeling for our state.

When I forecast weather I tend to pay more attention to the Euro in the winter time. For whatever reason, it seems to handle our snowy storm systems better. For the summer months I tend to follow the GFS closer as it is often good at predicting severe weather setups and monsoonal weather as we approach the warmer months.

 

Period of Unsettled Weather Begins Today

A storm system approaching from our West will begin to change our weather by Sunday afternoon. This storm system has quite a bit of energy and will bring us good chances for thunderstorms, rain and even snow in some areas along the front range.

EuorMLPS

Euro projected low pressure position by Tues: this is a favorable position for moisture along the front range.

Low pressure will move across the great basin and set up over Eastern Colorado. The leading edge of this system begins to move through this afternoon and with it expect thunderstorms across the area. I don’t see much in the way of severe weather but would not be surprised to see small hail with a few of them.

HRRR_4102016_2pm

HRRR radar forecast for 2pm

A look at the HRRR model around 2pm shows snow showers beginning in a lot of the mountain areas and thunderstorms forming in advance of a cold front across the plains of Colorado. An interesting thing I saw on a few models is the hint of bigger thunderstorms across Douglas and Elbert counties into the afternoon.

Rain Very Likely… but What About Snow?

This system will set up in a favorable position for the front range of Colorado. The low should be just enough South so that we get decent upslope flow. The initial front will cause instability in the atmosphere and thunderstorms will be likely Sunday afternoon. After this initial round, cooler air and upslope flow behind the front will make for rain showers on Monday and possibly into Tuesday.

Nam4K_QPF-04102016

Nam4k QPF forecast. This tells us how much liquid moisture is expected by the time this system moves out.

A look at the Nam4k model shows us the possible moisture amounts that could fall. Notice the bias for higher moisture over the Palmer Divide region, most likely due to favorable upslope. Expect the areas in, around and North of Castle Rock to see 0.3 to 0.6 inches of rainfall. Areas to the South of Castle Rock towards Monument and Larkspur will see nearly an inch of moisture.

Nam4K snowfall forecast

Nam4K snowfall forecast

This is one of those storms that could potentially drop a ton of snow along the front range, the good news is that temperatures will remain way too warm at lower elevations to allow for snowfall. Areas South of town with higher elevations will see snowfall accumulate, possibly to the tune of 6-12 inches, so keep that in mind if travelling South on Monday or Tuesday.

Summary

The next week looks pretty topsy-turvy as far as weather goes. We will start the week unsettled, get a brief breather in the middle of the week and be back to unsettled again by the week’s end. Here’s a quick outline of timeframes:

  • Sunday-Tuesday
    • Unsettled with rain/snow and thunderstorms. Temperatures will be cooler especially on Monday
  • Wednesday-Thursday
    • Clear and warmer, some models have many areas near 80 on Thursday!
  • Friday-Sunday
    • Models are projecting another storm system moving through beginning on Friday. Thunderstorms Friday may give way to snow showers on Saturday and Sunday. Too early to tell how much snow is possible but keep an eye out for this next weekend.

Have a great Sunday!

 

Rockies Home Opener is Today!

WinterWxStory1_04082016

It will be a great day for baseball as we expect warm temperatures, mostly sunny skies and lighter winds. The big item you will want to remember today, if you are attending the game is sunscreen!

The UV index today is 7.7, this means a highs risk of sunburn from UV radiation. It’s a good idea to wear sunscreen as most people without it will begin to burn within 30 minutes.

Have an excellent Friday and go Rockies!

 

Warm Weather Continues a Bit Longer… Change on the Horizon

Colorado’s front range has experienced several days of absolutely gorgeous weather, in fact temperatures in Castle Rock have hit at least 70 in the last three days consecutively! This is not unusual for Colorado in April, the month is normally punctuated by periods of warm, dry and windy weather followed by periods of cold, rainy, cloudy and even snowy days.

Castle Rock recorded temperatures April 4-6, 2016

Castle Rock recorded temperatures April 4-6, 2016

I haven’t posted much the last few days because quite frankly, the weather has been a bit boring. I can only post, “it’ll be windy and around 70” so many times before folks lose interest. With that in mind, I’m posting now because I’m beginning to see some changes of an extended pattern change arriving as early as the latter part of this weekend.

Thursday – Sunday

I’ll have a weekend outlook on Friday with the finer details of this weekend, but in short the next few days will be more of the same. Expect temperatures to remain right around 70, winds will still be a bit breezy but lighter as we go later in the week.

It will be a great weekend to get out and about and I recommend everyone take advantage of it!

Position of 500mb weather systems and jet as of Thurs. April 7

Position of 500mb weather systems and jet as of Thurs. April 7

Ridging to our west is pumping warm, dry air in from the Southwest and the jet stream rests just to our North. This is what is responsible for our windy conditions for the past few days. In addition to the wind, this type of pattern steers storm systems away from us and to the North.

Monday April 11 — The Change Arrives

500mbair_sunApr102016

By late Sunday and into Monday we notice this pattern beginning to break down. Notice the big ridge to our West is now replaced by a trough. This generally means we can expect a cold front coupled with increased moisture in the atmosphere. At this time, the storm system looks rather weak as it moves across Colorado so I expect it to cool us slightly. Temperatures are projected to be in the low 50’s during the day and mid 30’s at night so most of this should fall as rain but I can’t rule out the possibility of a few snow showers here and there.

Wednesday April 13 — A Quick Breather

500mbair_wedsApr132016

By the middle of next week, we see a weak ridge establish over the state again. This would mean a brief period of warmer and dryer weather around the Wednesday/Thursday time period. (Some models have us flirting with 80 degree temperatures on Thursday!) This ridge will be short lived, look at the trough building to our West again! Notice that this particular storm system looks much better organized than Sunday/Monday’s system and as such we would expect to have a bigger impact from this system.

Friday April 15/ Saturday April 16 — The Fun Begins?

500mbair_satApr162016

I’ll start off by saying that models predicting this far out are subject to huge change, but there is quite a bit of agreement on a powerful storm system during this time period. The biggest question is, where will it end up? Just like winter storm systems, spring and summer storm systems in Colorado are made or broken by where the storm system actually sets up.

So we’ll play devils advocate and explore what happens if this solution verifies…

The trough maintains a lot of its strength as it crosses the Rockies which means it will have no trouble maintaining energy and pulling in moisture. At this time it doesn’t look particularly cold so I don’t expect much if any snow out of it. Should the trough tap into more colder air, snow is always a possibility but at this time its way too early to tell.

Another interesting facet of this storm; with the warmth now in the lower atmosphere combined with moisture and energy could make for a chance for severe weather. This is something I will be watching closely for into next week.

The Takeaway

Get out and enjoy the gorgeous weather that is on tap this weekend. Next week we will begin the roller-coaster that is spring weather in Colorado. We will have some nice days next week but will have some equally not nice days as well. Stay tuned here as we will update with any forecast changes and of course, we’ll be keeping an eye out for a thunderstorm threat next week as well.

 

Castle Rock’s Weekend Outlook Apr 1 – Apr 3

No snow? No joke!

WinterWxWeekendOutlook_Apr1-3-2016CR

 

This weekend will start off cooler on Friday as the last storm system departs the area. Snow on the ground combined with a bit of a breeze out of the North will make it feel a bit chillier than it actually is, however there will be ample sunshine so it should be a nice day overall.

On Saturday a ridge of high pressure will build over the area, this will keep stormy weather away from us for a few days and help to warm the area up over Colorado.

euro_04012016_MLSP

In short, this will be a wonderful weekend to get out and about, Be safe and enjoy the weekend!

 

Tracking the Next Winter Storm System

Our next storm system is set to impact Colorado starting today and lasting into Thursday. Depending on where you are, some areas will see quite a bit of snow while others will see little to no snow accumulation. All in all, the storm doesn’t look like it will impact the central and Southern front range too much.

Models

Every model across the board has this storm looking pretty unimpressive for Denver and points South. The areas that look to benefit the most will be the Northern mountains and areas along the Wyoming and Nebraska border.

Snowfall models show not too much for us South of Denver

GFS predicted snowfall by midnight Thursday

GFS predicted snowfall by midnight Thursday

NAM predicted snowfall through midnight Thursday

NAM predicted snowfall through midnight Thursday

Very unimpressive for us, but look at the Northern Mountains of Colorado and into Wyoming! These places already have blizzard watches and winter storm warnings out… this storm looks very similar to the one last week in strength but the big difference for us is location.

nam_composite_03292016_weds00Z

I used the NAM to highlight the location and how it affects which areas see the most snow and which get downslope (which dries the atmosphere out and decreases snowfall overall) The positioning of the low over North and Northeast Colorado means the areas of greatest moisture, energy and upslope occur in the Northern mountains of Colorado, the mountains of Wyoming and the Nebraska panhandle. These areas will see blizzard conditions much like we saw last Wednesday.

The Euro (which nailed last weeks’ blizzard when no other model came close) agrees with the positioning of the low.

euro_mlsp_03292016_weds00Z

What to Expect With This Storm

–Snowfall–

  • Castle Rock: 1-3 inches

  • Palmer Divide South (Larkspur, Monument…) : 0-3 inches

  • Denver: 0-2 inches

–Impacts–

  • Thunderstorms possible Tuesday evening as the front moves through

  • Expect generally wet roads South of Denver. Some roads may get light accumulation if a snow band sets up over them

  • Winds between 15-25mph are expected with gusts to 30mph

  • Best chances of precipitation are late Tuesday, late Wednesday and early Thursday

  • This storm does not look like it will adversely impact travel along the urban corridor at this time.

Summary

I’m not expecting much out of this storm as of this writing. Remember, any shift in the storm track can have huge implications for how much snow we receive, but confidence in this one missing us to the North is relatively high. The positioning of the low also means colder air will have a more difficult time working its way along the urban corridor of Denver. This leads me to believe a lot of areas that see snow will see most or all of it melt. The one exception is the higher altitudes for us South of Denver, but even then I don’t see us getting more than 2-3 inches top.

Stay tuned, if I begin to see any changes in this forecast, I’ll have updates right here!

Happy Tuesday!

 

Saturday March 26 Winter Storm Update

Snow continues at this hour for the Castle Rock area and for areas South into Colorado Springs. This storm is mainly affecting these areas and is not doing a whole lot for Denver or suburbs immediately South of Denver.

A 9:30AM look at the radar shows the narrow areas of light to moderate snow:

radar_3-26-2016 9-35-21 AM

Air temperatures overnight remained relatively warm which means a good portion of this snowfall has melted. 3-6 inches was my forecast yesterday and this still looks to be on track. Roads were a bit slick this morning when I was out and about but are recovering as temperatures continue to warm slightly.

This morning there is a slight bit of wind out of the North so we are getting just enough of a windchill to make it feel quite cold out. Be sure to bundle up before heading out anywhere as it will remain chilly today with high temperatures only projected to reach the lower 30’s.

windchill_wind3-26-2016 9-36-33 AM

Many areas around Castle Rock are showing light winds out of the NNE and wind chill temperatures in the teens.

The Rest of Saturday

The bulk of models have light snow continuing through the morning with most of it tapering off by about noon.

Forecast radar at 12PM (HRRR)

Forecast radar at 12PM (HRRR)

Expect the light snow to end by late morning or into early afternoon at some point. Accumulations today will be light as additional snowfall will have a difficult time overcoming melting. Expect maybe another inch or two if you are in the Castle Rock area on top of what you already have this morning.

HRRR predicts light accumulation for Palmer Divide the rest of Saturday

HRRR predicts light accumulation for Palmer Divide the rest of Saturday

Easter Sunday

The good news is the current storm will scoot out of here pretty quickly and a high pressure ridge will begin to build behind it meaning warmer and drier air will make its way into the state as early as Sunday. It will still be a bit chilly during the day, high temperature is expected to reach right around 50 degrees but a bit of wind may make it feel a bit cooler than that.

WinterWxStory_EasterForecastt

Weather looks to be quiet through late Tuesday so we won’t have a whole lot of posts up on Sunday. Monday we will begin taking a look at our next storm system and chance for snow.

Have a great weekend everyone!

 

Afternoon Update

This will be a very short post folks as I have not seen big changes to this forecast. I will start off this post by saying I don’t agree with the National Weather Service’s prediction of 5-10 inches for the Castle Rock area. I’m sticking with 3-6, but believe even that may be high, if I’m wrong and they are right I will gladly post a big picture of a crow tomorrow and eat the entire thing…

 

This is a huge reason why I’m not with the NWS on this storm; every model except the GFS takes a lot of the precipitation south of Castle Rock. I’m not saying we don’t get any snow, but anything over 6 inches is a long shot.

3-25-2016 4-03-00 PM

Snowfall accumulation probabilities for Denver and Castle Rock

Castle Rock is in the blue, you can see anything over 6 inches of accumulation is about a 20% chance of happening. The last storm was a long shot too and proved a lot of us wrong so keep in mind, it is March and anything can happen. Sometimes mother nature likes to beat the odds, in this case it looks possible but very unlikely.

Maybe I’ll be humbled again? Tune in tomorrow to see!

Final Forecast/Impacts

wwadv_03252016

A Winter Weather Advisory has been issued for the Castle Rock area and points East and South. A Winter Weather Advisory is issued when periods of heavy snow make for difficult travel conditions. I have no doubt we will see some bands of moderate to heavy snow through the night but this storm may already be winding down by morning to early afternoon. Also, as I stated above, I think the 5-10 inch range for Castle Rock  is quite overdone.

For snowfall I’m staying put on my forecast based on data I’ve seen so far. This could still change later tonight but I see no reason to change with data I’ve received today.

Castle Rock: 3-6 inches

Palmer Divide South (Larkspur, Monument…) : 5-10 inches

Denver: 0-2 inches

Expect:

  • Some bands of moderate to heavy snowfall at times

  • Winds at 15-25mph will cause minor snow drifting

  • Roads will become icy and snow packed through periods of heavier snow

  • Travel may become difficult at times earlier on Saturday

 

At the risk of repeating myself too much, I probably won’t post again ahead of this storm  unless the forecast changes drastically tonight. I will most likely have a post up Saturday morning with coverage of how the storm is going, but not much else tonight unless things change.

The snowfall amounts and impacts above remain the same as of right now.

Hope everyone has a great Friday night and stay warm and be safe if out and about this evening.

 

Friday/Saturday Winter Storm Update

A quick update on where we are this morning with regards to our projected winter storm scheduled to arrive Friday afternoon and into Saturday morning.

Model Guidance

If you click through each model below, you will see a lot of uncertainty still remains about this storm. It does not look to be a major storm like we saw Wednesday and while I know we’ve said that before, the dynamics if this storm system are very different from the last. The way it is moving into Colorado, the energy is has and the track and speed are all working against it. Every model has it moving out of the state very quickly so even if it sets up in a favorable position, it may not linger long enough to dump heavy snow along the front range.

03252016_GFS_21ZSAT

GFS snowfall by Saturday PM

03252016_HRRR_04ZSAT

HRRR snowfall by Saturday PM

NAM snowfall by Saturday PM

NAM snowfall by Saturday PM

NAM4K snowfall by Saturday PM

NAM4K snowfall by Saturday PM

Since all of these models (minus the HRRR) were terrible with the last storm, we can take a look at the one that nailed it pretty early on. The MLSP part of the EURO gives us a glimpse of where it believes the storm system will set up after it moves across the Rockies.

03252016_EMCWF_00ZSAT_2

If the EURO verifies again with the positioning of the storm, it has the main energy too far South to affect areas North of the Palmer Divide much. The big question is will areas along the divide get much if any snow out of this or will the storm be too far South so that down sloping kills snowfall along the divide?

Uncertainty Remains

What do you do when half the models tell you we get snow and half don’t? We look around for a few other clues…

The SREF ensembles are a good way to look a bit closer at what many different models may be picking up on. Unfortunately, the don’t run these for the town of Castle Rock itself, but they do have one for Centennial Airport and one for Monument. I generally take a look at both of these and average the result out:

Centennial Airport snowfall ensemble: 2.72 inches

Centennial Airport snowfall ensemble: 2.72 inches

Monument Hill snowfall ensemble = 4.18 inches

Monument Hill snowfall ensemble = 4.18 inches

If you average both together and take that amount for Castle Rock you get a total of 3.45 inches. That falls in my initial forecast range of 3-6 for Castle Rock, albeit on the lower end. This may mean I shift my forecast downwards at some point on Friday if I see no change in the models.

Keep an Eye on Forecast Changes Friday Afternoon

I’m not sold at all on this storm system at this point. There are many things working against it and most models have the main energy going too far South to be any major affect on the Castle Rock area. I’m not entirely sure the Winter Storm Watch will stand in the end. Admittedly, even the NWS has mentioned this:

THE GFS IS THE ONLY MODEL
SHOWING HEAVY SNOW IN THE SRN FOOTHILLS AND PALMER DIVIDE AREA WHILE
THE OTHER MODELS KEEP THE THREAT FOR HEAVY SNOW FURTHER SOUTH OVER
SRN CO.  AT THIS POINT CONFIDENCE IS NOT HIGH AS TO WHAT TO DO WITH
THE WATCH SO WILL LET IT RIDE AND SEE IF THERE IS BETTER CONSENSUS
WITH THE LATE MORNING RUNS.


The key words in this statement: AT THIS POINT CONFIDENCE IS NOT HIGH

Forecast

At this point, I’m sticking to my forecast much like the NWS and awaiting further data through the day on Friday. For this storm, it’s best to be prepared for the impacts Saturday morning but realize that this storm may not do a whole lot. I can see dropping snow totals especially for Denver and Castle Rock this afternoon unless the models start to flip.

Castle Rock: 3-6 inches

Palmer Divide South (Larkspur, Monument…) : 5-10 inches

Denver: 0-2 inches

Stay tuned for any updates today, if we see a major shift in model guidance I will update accordingly.