Monthly Archives: January 2017

Snowy and Cold into Thursday

11:45 AM, Wednesday, January 4, 2017

The winter storm is upon us. Steady accumulating snow has been falling this morning in northern Larimer County and southeastern Wyoming and that area should spread south this afternoon and replace the intermittent light snow currently in the Denver-Boulder area. A large area of light snow tonight and Thursday will likely be punctuated with periods of heavier snow this evening into early Thursday. Expect a snowy commute this evening (mainly from Denver northward) and Thursday morning will likely bring very cold temperatures, snow-packed roads, and airport delays. Snow should taper off from north to south Thursday morning and early afternoon.

 

Temperatures along the Front Range today and Thursday will struggle to make it to the teens, and nighttime lows should be -5 to +5.

 

Mountain Snow

Lots of snow with 1-2 feet through Thursday (lingering into Friday in southern Colorado).

Front Range Snow

The heaviest periods of snow will likely organize in west-to-east bands this evening into early Thursday morning, and mainly form Denver northward.

1-4″ Colorado Springs

3-6″ south Denver suburbs, Castle Rock, Aurora, DIA, Longmont, Greeley

5-10″ north Denver suburbs, Golden, Broomfield, Boulder, Fort Collins, Cheyenne

8-12″ Idaho Springs, Nederland, Estes Park

 

Why so much snow when it’s so cold and dry?

It’s true that the temperatures and dewpoints are quite low along the Front Range. But unusually moist and less cold Pacific air is in western Colorado and is riding over the top of our very cold low-level air along the Front Range. So weak upslope flow (easterly) combined with copious Pacific moisture from the west is helping to make it snow east of the continental divide.

 

Next week’s big storm

A very wet Pacific storm and accompanying atmospheric river (long fetch of unusually moist air from the ocean) will likely make headlines this weekend due to extreme rain and snow in California. Some of that moisture should make it to Colorado late Sunday and Monday and may result in more heavy mountain snows (and maybe valley rain) in western Colorado. It does not appear the Front Range will get much precipitation from that, but temperatures are likely to be quite balmy Sunday and Monday.

Significant snow late Wednesday and Thursday

12:35 PM, Tuesday, January 3, 2017

The first round of snow in this cold spell was minor as expected (especially from the Denver-Boulder area southward), but the next snowy period beginning late Wednesday is likely to be more widespread and significant, with impacts on local travel Wednesday evening and Thursday.

 

Mountains

The mountains and West Slope areas will continue a snowy week, with the main activity Wednesday and Thursday. Initially the heaviest snow will likely be north of I-70 on Wednesday, but spread throughout all mountain areas by Wednesday night. Snowy conditions may linger into Friday, especially to the south in the San Juans and Sangre de Cristo ranges. An additional 1-2 feet is likely in some areas creating avalanche hazards and winter driving conditions.

 

Front Range region

A lull in the snow (other than some flurries) is likely for the lower foothills and plains into Wednesday. But as the coldest part of the latest cold spell enters the region late Wednesday, a period of widespread snow (possibly a few heavy periods) is likely. The snow may hold off until after the Wednesday evening commute, but I think you should play it safe and plan on a snowy evening commute, especially north of Denver. Wednesday evening through Thursday morning will likely bring most of the snow, but light snow may linger into early Friday. Plan on wintry travel throughout the Front Range region on Thursday.

 

Temperatures will be at there coldest Wednesday night through Friday morning with nighttime lows -5 to +9 and Thursday daytime not getting out of the teens.

 

Most probable accumulations:

3-6″ high plains, DIA, Longmont, Greeley, Colorado Springs

5-10″ in and near foothills, Castle Rock, western suburbs of Denver, Broomfield, Boulder, Nederland, Cheyenne

localized reports over 10″ in lower foothills and Palmer Divide region

There is still some uncertainty about amounts (with small chances of lower or higher amounts). I would not be surprised to see the National Weather Service issue a winter storm warning for Wednesday evening in and along the foothills as new data become available later today. I’ll update tomorrow.

 

The next storm

We should enjoy a much milder weekend (especially Sunday). But a series of storms is hitting California with a particularly intense one beginning late in the weekend. Some of that moisture should make it to Colorado next week. Since the winds will be mainly westerly, it probably won’t produce much for the Front Range foothills and plains, but mountain areas may get another good round of snow.

 

Wintry week to start the new year

10:40 AM, Monday, January 2, 2017

At 10:30 AM (Monday) the leading edge of a much colder airmass had crossed the Colorado-Wyoming border into Colorado. Temperatures in Front Range region should fall this afternoon and will likely stay in the 20s and colder through the week (maybe teens in Cheyenne). It may take a little longer for the cold air to get to the Colorado Springs area. Nighttime temperatures should drop to around zero on the coldest night (midweek), but likely hover in the single digits and teens in the more persistently cloudy areas. There will be several chances for snow this week, the first tonight and tomorrow looks most focused on the mountains and up in the Cheyenne area.

 

Snow- mountains

It will be a snowy week near and west of the continental divide. By week’s end 1-2 foot totals  may be commonplace in mountain areas. Although areas of clouds and snow are possible all week, the peak times will probably be tonight (especially north of I-70), again on Wednesday in all mountain areas, and again Friday.

 

Snow- Front Range

Snow is likely to organize in long, narrow west-east bands where local amounts may be notably higher than the area-wide average. Although the Denver area received a bunch of snow in these set-ups earlier this season, it appears that the best chance for these west-east snow bands tonight and Tuesday morning will be in Larimer County and southern Wyoming. Several inches could accumulate quickly in the bands. In the Denver-Boulder area odds favor little or no accumulation (there is only a very small chance of a snow band developing). There may be some areas of ice fog or freezing drizzle developing by morning.

 

Another chance for accumulating snow of several inches late Wednesday and Wednesday night is likely to be more widespread. There may be still another chance for accumulating snow Friday.