The atmospheric river is flowing our way
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Friday – 10 Mar 2023 – 2:45pm
The past…
At Stevens Field so far this afternoon has been 42. The low this morning was 20. Winds so far today at the airfield have peaked at 8mph.
| Average High | Record High / Year | Average Low | Record Low / Year |
| 48 | 69 / 1989 | 14 | -2 / 1958 |
Precipitation summary… Light snow started falling this morning in the mountains. As I type at 2pm, snow is picking up quickly in the Turkey Springs area. Precip will increase through the afternoon.
Forecast discussion…
Rest of today through Sunday… We are going to catch a piece of an “atmospheric river” event. A deep subtropical moisture plume will move west to east across the region.
When a system is moving our way, one of the first questions we ask is “what’s the source region?”. In this case the source region is the central Pacific which is relatively warm and very moist.
Forecasting the amount of warm air and the snow levels is very challenging with this system.
Light snow started falling Friday morning in the mountains. Precip is ramping up across the region this afternoon. It will start as snow for much of the valley and then gradually transition to rain during the late afternoon and early evening. The best chance for precip is late Friday afternoon through Saturday afternoon. A stray thunderstorm or two is also possible Saturday and Sunday afternoons. Showers will be more hit and miss Saturday afternoon through Sunday afternoon.
Temps… High temps the rest of today will be mid-30s to low 40s. Saturday and Sunday highs will be in the low to high 40s. Friday and Saturday lows will be in the high 20s to mid-30s. Lows Sunday will be in the low 20s to low 30s.
Winds… Winds Friday and Sunday afternoons will peak in the 15-20mph range. Winds Saturday will peak in the 20-30mph range.
Snow levels…
Snow levels will rise to 8,000ft by Friday evening and will then bounce around between 8,000ft and 8,600ft Friday evening to Saturday evening. Then they’ll gradually lower to around 7,000ft by Sunday morning. As snow levels lower Saturday night, moisture will decrease, and showers will be more hit and miss.
Precip amounts…
Valley below 8,000ft: 0.40” to 0.70” rain with up to 1” of slushy snow
Valley above 8,000ft: 0.60” to 1.00” rain and 2-4” of slushy snow
Note: Folks around 8,500ft and higher are right on the cusp of this being mostly a snow event. If the warm air does not move in as I expect, you’ll get 4-8” of snow.
Mountains above 9,000ft: 18-28”
*** A half inch of rain and temps above freezing will melt snow in the valley and could lead to minor flooding in low-lying areas. It’s going to be a sloppy mess! ***
*** The Grand Junction NWS has issued a WINTER STORM WARNING for the southwest San Juan Mountains for elevations above 8,000ft. 10-20” of snow with up to 30” is possible along with winds to 60mph valid until 6am Sunday. *** I expect less snow here in the valley above 8,000ft.
*** The Colorado Avalanche Information Center has issued an AVALANCHE WARNING valid Friday at 4:30pm to 7am on Sunday. Large and dangerous avalanches will occur naturally and will also be very easy to trigger. ***
Monday through Tuesday evening… Transient ridging will dry us out a bit but spotty showers are possible, mostly over the mountains. The lucky spots in the mountains could see another 2-4” of snow and lucky spots in the valley could get up to an inch.
Temps… Highs will be in the mid-40s to low 50s. Lows Monday will be in the high teens to high 20s and on Tuesday they’ll be in the mid-20s to mid-30s.
Winds… Afternoon winds will peak around 15mph.
Wednesday through Thursday night… Another system is taking shape. The forecast models are fluctuating on timing, precip amounts, and snow levels so forecast confidence in the details is low at this time. I’ll do a “first guess” on the details in tomorrow’s post.
My next post will be tomorrow.
– Shawn
