SnowBrains Forecast: Southern Colorado, New Mexico on Tap for Pre-Thanksgiving Storm | 12″+ Possible

Clay Malott | | WeatherWeather
Forecasted snowfall through Wednesday night. Credit: WeatherBell

Forecast By SnowBrains Junior Meteorologist – Clay Malott

 8:50 PM MST, 11/23/2021


A moderate storm out of the southwest will bring accumulations between 4 and 12 inches for the mountains of southern Colorado and northern New Mexico between Tuesday evening and Thursday morning. 

Tuesday evening – Wednesday morning

This storm will arrive in two distinct waves, the first of which will arrive late afternoon on Tuesday. Snowflakes will begin to trickle into the San Juan mountains between about 5 and 8 pm on Tuesday. I don’t see the necessary ingredients shaping up for major upper-level vertical forcing (which leads to more widespread totals), so this storm will be strongly favorable for higher elevations because a.) there will be more precipitation and b.) temperatures will be colder (more snow per volume of water).

NBM snow forecast for the initial wave between Tuesday evening and Wednesday morning. Credit: WeatherBell

Most of the snow in the San Juans will be finished by early morning on Wednesday. As mentioned before, only the highest elevations will see significant accumulations. Upper elevations in the region should see 5-6″ by Wednesday morning. Snow levels may climb to as high as 8,500 feet towards the beginning of the storm but should drop to 6,000-7,000 feet during the heaviest precipitation. The valleys should pick up 1-2″, but there may be some rain on Tuesday evening before the snow level drops and permits snowfall in the valleys. 2-3″ may fall on the highest peaks in the central mountains near and south of Aspen, but this won’t be a particularly productive storm for these regions.

Outside of the San Juans and south-central mountains of Colorado, accumulations will be fairly minimal by Wednesday morning. Some precipitation may trickle up into the central and northern mountains, but it’s unlikely that more than 2″ will fall on even the highest peaks.

Wednesday morning – Wednesday night

Upper-level winds flip nearly 180 degrees from the southwest to the northeast on Wednesday morning. This will create a potent upslope flow for the Sangro De Cristo mountains of southern Colorado and northern New Mexico. The ECMWF (European model) perfectly shows the moisture magnitude and direction flowing into this area:

Credit: WeatherBell

When saturated air hits a mountain, it is forced up, which causes it to cool, condense, and fall as precipitation. With such a direct and strong access to moisture, the Sangres could see sustained snowfall rates of up to 0.5″ per hour. Hardly any precipitation will occur with this second wave outside of the Sangre range. When it’s all said and done by midnight or so on Wednesday, the upper peaks of the Sangre De Cristo range should see between 8 and 12″.

Forecasted snowfall through Wednesday night. Credit: WeatherBell

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