Closer look at this Atmospheric River: Snow levels, magnitude, impact on UT, CO, WY

The first moderate to strong atmospheric river (AR) of the season is on track for Central and Northern California. Let’s drill down on the details.

Forecast Integrated Vapor Transport (IVT) at 38N/123W, Central CA, GEFS/GFS interpretation

The main surge hits California Sunday-Monday (10/24-25). It’s preceded by 1-2 smaller waves with high snow levels.

TAHOE ZONER/S LINE
THR/FRI>10,000′
SAT8,000′
SUN6,000′
MON6,000′
Tomer forecast snow levels for Lake Tahoe Zone, 10/21/2021.

Overall, total precipitation through Monday could run +500% of normal for parts of Central and Northern California with flash flooding possible. Localized 8-11″ liquid totals possible in the deep purple color. Snowfall at higher elevations would be significant.

Forecast total liquid precipitation for through 10/25/2021. GFS interpretation.

Impacts to UT, WY, CO

Looking down the road, moisture from this Pineapple Express should hit the mountains of UT, WY, and CO. The key timeframes to watch:

SNOW TIMEFRAME10/23-2410/25-28
TETONSMINORMAJOR
WASATCHMINORMAJOR
CO ROCKIESMINORMIX
TOMER FORECAST SNOW TIMELINE 10/21/2021

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