The State of the Atmosphere: Sunday, November 17th, 2019

As forecast, the coldest temperatures relative to average have shifted into the Eastern United States through the first half of November. For Colorado we see the typical east/west split, with coldest anomalies across the Eastern Plains, and a warmer-than-average start to the month for the high country:

This pattern was well telegraphed. As we head into the latter half of the month and December we start to see at least periods of more active weather setting up across the West as well.

To that end, consensus is growing around an increased chance of rain and snow for much of the state by the middle of the upcoming workweek.

Ridging will be in place for Monday and Tuesday before changes arrive Wednesday and keep us cool and unsettled through the remainder of the work week. At 500mb, you can see the Euro model ridging (reds) over the area Tuesday:

With a strong trough over the Southwest on Wednesday, and our ridge pushing east:

With troughing in the west keeping us unsettled into Friday at least:

The greatest impacts this week will be focused over the Southwestern United States, with the low pictured above pumping sub-tropical moisture into the Great Basin and Four Corners. This looks to be great news for Southwest Colorado, where the early season snow seen across much of the state was lacking. The European model shows above average to well above average precipitation in these areas through Friday this week:

With a good flow of moisture and good jet dynamics at play, we expect most mountain locations to see snow this week. The setup isn't as favorable for eastern Colorado, but that said, we do expect some snow at lower elevations as well by mid week, especially along and west of I-25. A cold front Wednesday afternoon will help change rain to snow at lower elevations, with the best chance of snow looking to come Wednesday PM into Thursday for the metro areas.

An early look at probabilities shows that best chances for snowfall 3" or greater certainly favor areas west of I-25, with a strong signal for our southern mountains to see a good helping of snow this week:

Our gamblers are also support of some snow this week, though at the moment nothing too epic showing up for most locations. A light to moderate snowfall, however, is on the table –– all depending on the eventual evolution of the trough(s) across the Western United States this week.

By next weekend our active weather should work its way east, and temperatures are expected to moderate. Depending on exact track and timing of this week's troughing, we could even see temperatures back above average for next week. This is currently what the European is indicating anyway...

With perhaps another shot of colder air working down the plains Thanksgiving week:

For now, plan on a quiet start to the week before a cooler and wetter middle of latter half of the week takes over. A good chance of mountain snow looks like a good bet this week, with rain and snow potential across the urban corridor and Eastern Plains as well. Devil will be in the details with regard to eventual snow potential at lower elevations... but for now plan on Wednesday turning colder with rain and snow developing through the day. The best chance of accumulating snow for the Front Range at this time looks to be Wednesday evening into the day Thursday. A secondary low ejecting Friday into Saturday may offer another chance of snow as well, particularly for Southeast Colorado –– but this is a ways out, so we'll track it as the week progresses.

Stay tuned!

Brendan Heberton

Brendan is founder of Weather5280. He is co-founder of FreshyMap, and develops software for geospatial data analysis and visualization.

Denver, Colorado
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