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Get the snow shovels ready

Noon MDT, Thursday, March 11, 2021

Timing changes since yesterday

The onset of the storm is a little delayed compared to previous outlooks. Significant precipitation is unlikely before Friday evening. The heaviest period of snow is likely to be late Saturday into Sunday.

Key features of weekend storm

The absolute heaviest snow is likely in eastern Wyoming. Cheyenne may very well exceed 2 feet and rival its biggest snow of record (~26″).

Heavy accumulations are likely from metro Denver northward (Colorado Springs will likely be south of the heaviest snow, but should still expect some snow & wind).

Rain?

Relatively warm, moist air will be drawn in from the southern plains, and a significant portion of the precipitation on the eastern plains may fall as rain. The rain area has trended westward with time, but it still appears that precipitation will be mainly snow for the urban corridor. I would not be surprised to see a little rain in the Denver-Boulder area prior to Saturday evening.

Most likely amounts

2-3 feet southeastern Wyoming and the east slopes of the Colorado mountains & foothills north of the Colorado Springs area. I expect to see a sub-region in this area report over three feet.

20-29 inches Fort Collins, Boulder, Broomfield, and the west suburbs of Denver

16-24 inches Denver, DIA, Longmont

Do I think there can be more? Yes, I’d put that at 20% chance. Also, the same chance (20%) that there could be less than the ranges given above.

Weekend Storm Update

12:40 PM MST, Wednesday, March 10, 2021

What has changed

Although the areas of forecast uncertainty are mainly the same, here are some changes since my update yesterday.

There is a slight northward shift in the overall guidance. This means there is less chance for significant snow from Colorado Springs southward, and more chance for the biggest amounts in eastern Wyoming.

A slight warming of the atmosphere over eastern Colorado on Friday could mean that rain might play a role in the early stages.

The extreme guidance (3-6 feet of snow for the Front Range region) is more of an outlier solution now.

Initial precipitation

Before we get to the main event Friday night through early Sunday, it looks like there may be a period of snow (maybe a little rain) Thursday evening into early Friday. This could be significant around Cheyenne (3-6 inches), lesser amounts from Denver to Fort Collins (1-4″) and probably little or nothing south of Denver metro.

The main event, Friday night to Sunday

All of these rough estimates are for metro Denver northward.

10-20 inches (1-2 inches of liquid) urban corridor

20-36 inches in mountain towns (Evergreen, Nederland, Estes), with the highest amounts more likely as you go north

Lesser possibilities:

  1. More northward shift of the storm will reduce snow amounts in Colorado, or
  2. the less likely slower and farther south scenario comes through, resulting in more snow than the numbers above.

Daylight Savings

You may have to shovel with an hour less of sleep on Sunday morning!

Potential remains for significant storm over the weekend

12:15 PM MST, Tuesday, March 9, 2021

Before I get to the weekend storm, there is a cold front and some unsettled weather for later tonight. Snow in the mountains should make roads a bit snow-packed at the high passes by tomorrow morning. As the front moves east there may be some areas with squally rain or rain-changing-to-snow showers over the urban corridor in the late night or early morning. Accumulation should be spotty and minor. Then we are in for a cooler period through Friday with some chance of snow Thursday night or Friday morning.

The storm with potential major impact would be Saturday and Sunday. From the various long-range model guidance it looks like the Front Range region will probably get at least a two-day period with intermittent snow amounting to at least an inch of liquid equivalent and 10-20″ of snow, but the snow will fall over a long period of time and there may be some melting reducing the total on the ground.

However, as you may have gathered from selected things other people are posting, there is a subset of the guidance that has consistently shown an evolution of the storm that would result in a very major snowfall, measured in feet. Later in the week some of the high-resolution short-range models that forecast for 2-3 days lead time will be weighing in on this storm. So more updates to come.

Major storm possible by weekend

5:45 AM MST, Monday, March 8, 2021

I don’t usually write about a major storm that’s roughly five days away because of the uncertainty at that lead time. So consider this a heads-up regarding a possibility. Both of our long-term models (the GFS and the European Centre) are forecasting a major spring snowstorm for central and eastern Colorado and southeastern Wyoming during the Friday-Sunday period (widespread over a foot, some local areas ~3 feet). I will update during the week to fill you in on whether that really appears to be coming together and expected timing.

Rain & snow this afternoon/evening

5:20 AM MST, Thursday, March 4, 2021

A storm system moving eastward across southern Colorado today will bring precipitation to the Front Range region. The best chance for significant accumulating snow is south of Denver and north of Colorado Springs. The storm will have a relatively small area of influence, but it may snow hard for a few hours where it does have impact. Rain is also likely to be part of this storm, especially at the start. Mild weather is likely to return on Friday as we head into the weekend.

Most likely accumulation of wet snow:

3-6 inches in some areas from the south Denver suburbs to the northern suburbs of Colorado Springs (Palmer Divide, Castle Rock)

For the Denver area (Denver, Douglas, Arapahoe & southern Jefferson counties) there is a small chance for a fast 3-6 inches after some rain, but the odds favor minor accumulation of less than 2 inches.

North of I-70 (Boulder, Broomfield, Longmont, Fort Collins) the chance for any accumulating snow after some rain is small.

Snow still on the way for this evening

3:10 PM MST, Wednesday, February 24, 2021

I don’t have time for a full blog except to say that for the areas I forecasted 4-7″ in yesterday’s blog (Boulder-Broomfield, west side of Denver, Castle Rock, Colo Springs), it’s looking like the 7-inch end of that range is likely for areas along the foothills from Boulder down though the Palmer Divide, and I wouldn’t be surprised to see some local reports exceeding that amount. There will probably be a period of heavy snow between nightfall and midnight. Enjoy!

Snow Wednesday evening

5:15 AM, Tuesday, February 23, 2021

A cold front will move through this evening making Wednesday a colder day, but not bitter cold. The snow will likely hold off until Wednesday evening, but it is possible that it will start as early as mid-late Wednesday afternoon, as a storm system moves just south of the Front Range region. Accumulations are likely to range from around 6 inches in and near the foothills, to less than an inch on the northeastern plains.

4-7″ Nederland, Boulder, Broomfield, Castle Rock, western suburbs of Denver, Colorado Springs.

2-4″ Cheyenne, Fort Collins, Longmont, eastern side of Denver.

less than 2″ for much of Weld County and east/northeast of DIA.

Cold front and some snow this evening

6AM MST, Saturday, February 20, 2021

A cold front this evening will halt the trend toward milder weather and bring some clouds and snow. The best chance for some minor accumulation (1-3″) appears to be the from Boulder and Adams County south to Douglas and northern El Paso counties. This includes Denver metro. There is less chance for accumulating snow in Larimer and Weld counties and the northern part of Boulder county.

After a colder day on Sunday, we should be in for some mild weather on Monday and Tuesday. The next chance for snow and cold is in the Wednesday-Thursday time period.

The cold and snow won’t completely let go just yet

5:30 AM MST, Wednesday, February 17, 2021

The good news is that the continuation of cold weather for another two days won’t be record cold like what we experienced over the last week. Daytime temperatures are likely to be near freezing, and nighttime lows mainly in the teens through Friday morning. Both Denver and Boulder were above freezing on Tuesday, so our stretch of days below 32 ended.

Snow is likely in most parts of the Front Range region later today and tonight. Accumulation, where it occurs, is most likely between mid afternoon today and the predawn hours on Thursday. Amounts should range from a dusting on the eastern plains to 2-4 inches in and near the foothills. There will probably be some 6 inch reports in the foothills.

Temperatures are expected to return to more average levels Friday and Saturday. Then it looks like another cold front Sunday, followed by a warm up on Monday and Tuesday.

Snow later today, and even colder

6:20 AM MST, Saturday, February 13, 2021

The coldest surge of this arctic air mass, along with a weak storm system, will move into the Front Range region later today bringing 3-5 inches of snow and the coldest weather of the season (that weak storm won’t be so weak at it moves from the southern Plains to the Northeast later this weekend). The snow for the Front Range region will be mainly from mid-afternoon today through early morning Sunday.

Record Lows:

Sunday is looking like the coldest Valentines Day of record. The record low maximum temperatures are 14 in Boulder (1905) and 8 in Denver (1895). The thermometer may struggle just to get into the single digits in either place.

We should be close to the record lows on Sunday morning. Those are -6 in Boulder and -10 in Denver, both from 1903.

Monday morning will probably be the coldest morning under clear skies. The record in Boulder (-12 from 1903) and is within reach, but Denver’s old record (-20 from 1881) is more of a long shot.

Length of time below 32:

In Boulder, January of 1930 saw a 12-day stretch that remained below 32, the longest such stretch. At the current climate station location (since 1990) there have been three 7-day stretches below freezing: December 1990, February 2014, and December 2015. We will reach 7 days on Monday, and although it may be close to 32 on Tuesday or Wednesday, there is a chance that we will extend this stretch below freezing to 9 days. Later in the week it should warm up.