Banded Snowfall will Make or Break this System

Winter Weather Watches/Warnings/Advisories (as of 12PM)

Front range and Palmer Divide now included in latest Winter Weather Advisory

Winter Weather Advisory (4PM Friday  – 8AM Saturday)

Cities/Areas Included

The Northern Front Range Foothills-
The Southern Front Range Foothills-Fort Collins-
Boulder and the western suburbs of Denver-Denver-Castle Rock-
Briggsdale-Greeley-Fort Morgan-Byers-
Including the cities of Estes Park, Glendevey, Nederland,
Red Feather Lakes, Bailey, Central City, Evergreen, Georgetown,
Idaho Springs, Westcreek, Fort Collins, Hereford, Loveland, Nunn,
Arvada, Boulder, Golden, Lakewood, Longmont, Aurora, Brighton,
City of Denver, Denver International Airport, Highlands Ranch,
Littleton, Parker, Castle Rock, Elbert, Fondis, Kiowa, Larkspur,
Briggsdale, Grover, Pawnee Buttes, Raymer, Stoneham, Eaton,
Fort Lupton, Greeley, Roggen, Brush, Fort Morgan, Goodrich,
Wiggins, Bennett, Byers, Deer Trail, and Leader

Hazards

Plan on slippery road conditions. The hazardous conditions could impact the evening commute.
A Winter Weather Advisory for snow means periods of snow will
cause primarily travel difficulties. Expect snow covered roads
and limited visibilities, and use caution while driving.

Winter Storm Watch (11PM Friday– 11PM Saturday)

Cities/Areas Included

Including the cities of Yuma, Wray, Burlington, Arapahoe,
Cheyenne Wells, St. Francis, Bird City, Atwood, Oberlin, Norton,
Goodland, Colby, Hoxie, Hill City, Sharon Springs, Oakley,
Quinter, Grinnell, Grainfield, Tribune, Leoti, Benkelman,
Culbertson, Trenton, Stratton Ne, Palisade, and McCook

Hazards

Heavy mixed precipitation possible. Total snow accumulations of 4 to 6 inches and ice accumulations
up to around a tenth of an inch will be possible. Winds could gust as
high as 55 mph.

You can visit the National Weather Service for more watch and warning information outside of the Palmer Divide region.

We also have a warnings page set up for Castle Rock here.


A Tough Forecast – Model Mayhem!

If you’ve been following this storm on TV or social media you’ve seen a ton of different forecasts for this storm. There’s a reason behind that: uncertainty. Depending on which streams of data and models you’re looking at you’ll see vastly different results of what is expected out of this storm.

Here’s a look at some of the major models:

The European model is not too impressed with this storm. This bears some weight as it is one of the more accurate models, but not as high of resolution and isn’t run as often.

The GFS has impressive snowfall amounts, but places a lot of that well East of Denver and the Palmer Divide

Nam3K has heavier snowfall over the Palmer Divide

HRRR shows similar results to the Nam3K. It shows banded snowfall with higher amounts across the Palmer Divide.

A few things to note here when reading these models:

  • The GFS and Euro are lower resolution and only run a few times per day, so they can lag behind other models in picking up trends
  • The Euro is one of the most accurate, for us to get a big storm and for that model to miss it within 24 hours would be rare… but it can happen
  • The Nam3K and HRRR are higher resolution models that are run several times a day so they can pick up on weather changes quicker

Discrepancy = Uncertainty

When models don’t agree, that means there is a lot of uncertainty. It means that you have to monitor things as the storm moves into the area and you can expect several changes (maybe even significant changes) to a forecast in the few hours before the storm. That will be the case here, this forecast most likely won’t be the final product we release about this storm. It may have several iterations, so stay tuned.

Below are the snowfall range probabilities from the NWS, this should give you an idea of how likely any range is in an area close to you:

For cities in Douglas, CO county
LocationSnow Amount PotentialChance of Seeing More Snow Than
Low End
Snowfall
Expected
Snowfall
High End
Snowfall
>=0.1″>=1″>=2″>=4″>=6″>=8″>=12″>=18″
Castle Rock, CO24797%92%82%49%19%5%0%0%
Deckers, CO12497%88%63%9%0%0%0%0%
Franktown, CO13696%91%80%47%18%4%0%0%
Highlands Ranch, CO23698%93%81%43%13%2%0%0%
Larkspur, CO13696%91%79%44%15%3%0%0%
Monument Hill, CO14796%91%81%52%21%5%0%0%
Parker, CO13797%92%82%51%23%7%0%0%
Roxborough Park, CO24798%94%86%55%25%8%0%0%
For cities in Elbert, CO county
LocationSnow Amount PotentialChance of Seeing More Snow Than
Low End
Snowfall
Expected
Snowfall
High End
Snowfall
>=0.1″>=1″>=2″>=4″>=6″>=8″>=12″>=18″
Agate, CO24799%97%91%61%30%11%0%0%
Elbert, CO24797%93%85%56%25%7%0%0%
Elizabeth, CO14695%89%79%45%14%2%0%0%
Kiowa, CO24796%92%83%56%27%9%0%0%
Kutch, CO13796%89%77%47%23%8%0%0%
Matheson, CO23899%97%90%60%32%13%1%0%

Our Forecast (As of this post) and What To Expect

Expected Snowfall (through Saturday 12PM)

*These are our forecast numbers and may not always match the NWS official forecast numbers*
  • Castle Rock and surrounding areas
    • 3-7 inches
  • Parker, Lone Tree, Highlands Ranch areas
    • 3-7 inches
  • Elbert, Elizabeth, Kiowa
    • 3-7 inches
  • Larkspur, Monument
    • 4-8 inches
  • Woodland Park, Palmer Lake, W. Colorado Springs Foothills
    • 4-9 inches

Timing

  • Expect snow to begin after 2-4PM on Friday
  • Heavier snow showers are most likely between 6PM Friday and 3AM on Saturday
  • Snow showers should diminish by mid-morning on Saturday
  • **Largest chance of a travel impact will be 6PM Friday – 3AM on Saturday**
  • Friday’s evening commute may be impacted

Potential Impacts

  • Likely travel impacts will be slick roads with some accumulating snow on road surfaces
  • Friday evening and Saturday morning travel may be impacted
    • Stay tuned in case the storm position changes and thus the impact area

Remember one Thing!

Storms with snow bands are incredibly difficult to forecast. If the snow bands sets up further North or South, many of us along the Palmer Divide could come away with little to nothing. Unfortunately models can’t tell us where or how intense these bands set up, they can only show us that they will be possible. Stay tuned, because as we get later into Friday I imagine this forecast will change more!

Final Word

I’ve seen a few comments online related to forecasts like this “we have no idea what’s going to happen” and “you’re just giving a large range to cover your ass when you’re wrong.” We do the best we can with the data we have and the knowledge we’ve gained, but it doesn’t mean every forecast will be right.

I’m not trying to cover my bases or anything of that sort. My role as a meteorologist is to communicate what is most likely to happen, what could potentially happen in a worse case scenario and make sure people are prepared for all scenarios. Additionally, I feel that if we make a forecast like this one it’s a disservice to say IT WILL SNOW 3-7 INCHES. Without any gauge of uncertainty, that doesn’t tell anyone a lot of useful information. It’s much more useful to say, “3-7 is the most likely range but considerable uncertainty remains in our data, so we could see more or less depending on how the storm sets up so be prepared for a larger snowfall/impact event just in case.” That’s the reality of weather in Colorado, it’s unpredictable but that’s what makes it oh so fun!

Cheers, stay warm and stay safe tonight!

 

John R. Braddock
Storm Chaser/ Amateur Meteorologist at Mountain Wave Weather
John R. Braddock is a NOAA/NWS Certified Storm Chaser and Amateur Meteorologist living in Castle Rock, Colorado. A graduate of Colorado State University with a Bachelor's in Computer Science and a Colorado native, he specializes in short range forecasting, severe weather and mountain weather dynamics.

3 comments

    • Jason winn on February 22, 2019 at 1:04 pm
    • Reply

    I just want to say you guys are awesome. Having taken several meteorology classes in college i understand the difficult task of what you do so thank you for doing what you do.

    1. Thank you! 🙂

    • Jean Taylor on February 22, 2019 at 2:08 pm
    • Reply

    Don’t let the negative comments get to you. Your forecasts are the best and most reliable.

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