Monthly Archives: March 2021

Brief cold snap tonight/Tuesday, then back to spring Wednesday afternoon

2PM MDT, Monday, march 29, 2021

A strong cold front is through Casper, WY and approaching Cheyenne at mid afternoon, and should move through the Colorado Front Range region this evening. Tuesday is likely to be at least 20 degrees colder than today. Only minor precipitation is expected tonight and early Tuesday. Where there is snow it will likely be just and inch or two mainly in grassy areas. The best chance is south of Denver. It is looking like we will have pleasant spring weather Wednesday through the weekend.

Minor snow possible this evening

7AM MDT, Tuesday, March 23, 2021

The latest reinforcement of cold air may bring some some clouds and snow later today and this evening. The best chances for accumulation are in the Palmer divide north to Denver where there could be an inch or two (maybe 3-5 in the foothills southwest of Denver). Farther north in Broomfield and Boulder the chances decease. Farther north than that in Longmont, Fort Collins, and Cheyenne, the chance for any measurable snow is small.

Another cold front late Friday could bring another chance for a minor snowfall, and then some springlike weather will probably move in by Sunday.

Happy Equinox: Spring today, but not tomorrow

6 AM MDT, Saturday, March 20, 2021

The equinox was at 3:37 AM, and it will feel like spring today, but winter weather will stage a comeback on Sunday. Snow is likely to begin across the Front Range region Sunday afternoon (possible some rain at first below 6000 feet). Although this storm is not as large as last weekend’s, some areas of significant snowfall are likely through Monday morning, mainly south of Fort Collins.

Most likely accumulation:

6-12 inches: above 6500 feet in Boulder, Jefferson, Gilpin, Clear Creek, and Douglas counties.

3-7 inches: west and south sides of Denver metro, Castle Rock, Broomfield, Boulder

1-3 inches: northeast side of Denver, Longmont, Fort Collins

less than 1 inch: north of Fort Collins

Cold week

The week is likely to be generally colder than average with a couple more chances of at least some light snow midweek and toward the weekend.

Minor snow possible today

7 AM MDT, Tuesday, March 16, 2021

A storm moving eastward through New Mexico today and tonight will bring significant snow to the CO/NM border areas, but its impact in the Front Range region will be minor. Some parts of the area will likely get by without any measurable snow, while others may pick up an inch or two during the late afternoon or overnight hours.

After that it should be dry Wednesday afternoon through Saturday, with mild temperatures back in place by the time of the Spring equinox at 3:27 AM MDT on Saturday. The next cold front might arrive as early as Sunday.

Tonight: lose an hour, gain a snowstorm

6:30 AM MST, Saturday, March 13, 2021

Since yesterday there is more forecast confidence that there won’t be a significant rain phase in the lower elevations, although there will probably be some rain and drizzle today. The heaviest period is expected to be snow later this afternoon through Sunday morning. At this time of year nighttime snowfall allows for better accumulation efficiency than during the day. Periods of accumulating snow are likely all the way into Sunday evening. We are now seeing the storm organize to the southwest and moisture streaming toward the Front Range from the east (lots of fog over the high plains). The short range models have moistened this storm a little since yesterday.

So I’ve bumped up some of the accumulation ranges a little. There are still some modeled solutions calling for widespread 5 feet in the mountains and 2-3 feet in the lower elevations, but I continue to believe that is unlikely.

20-36 inches: southeastern Wyoming, Colorado Front Range above 6500 feet for Larimer, Boulder, Gilpin, and Jefferson counties (lesser amounts as you move south toward the Pikes Peak region). I do expect some reports over 3 feet, most likely in Wyoming, or some small regions of either Larimer or Boulder Counties in Colorado.

18-24 inches: Fort Collins, Boulder, Broomfield, west and northwest Denver suburbs.

12-18 inches: most of Denver area, Longmont

4-9 inches: Colorado Springs (heaviest on north side)

Pulling back on the snow amounts

Noon MST, Friday, March 12, 2021

There is a lot more forecast guidance now available for the main snowy period from late Saturday afternoon to Sunday afternoon, including the short range, high resolution weather models. Although there is a still a large range of snowfall possibility, a majority of the guidance does point to less precipitation and slightly denser snow than the previous outlook. It still looks like the heaviest amounts will be in southeastern Wyoming, fairly minor amounts in Colorado Springs, and a transition to the lesser amounts somewhere south of Denver. A small portion of the guidance suggests rain in the urban corridor through Saturday evening, but I still think it is likely that most precipitation will be snow when the heavier period begins late Saturday afternoon.

Updated most likely accumulation

20-30 inches: southeastern Wyoming (some 36-inch amounts on east-facing slopes).

18-28 inches: east slopes of Colorado mountains above 6500 feet and north of I-70.

10-20 inches: east slopes above 6500 feet south of I-70 and north of Pikes Peak

12-20 inches: Fort Collins, Boulder, Broomfield, and northwest Denver suburbs

8-15 inches: most of metro Denver, Longmont

less than 6 inches: Colorado Springs

Outlier possibilities on the high end

The very big amounts that have been talked about the last few days (and die hard on social media), are still possible, but the chances appear to be around 10%.

Outlier possibility on the low end

Similarly on the low end is an unlikely but still plausible scenario where the numbers above can be cut in half. That’s about a 10% chance in Wyoming and maybe 20% in Colorado.

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.