CW3E Winter Storm and AR Update: 2 March 2023 Outlook

March 2, 2023

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Winter Storms Bury California in Heavy Snow

A series of upper-level shortwaves brought widespread precipitation to the western US during 26 Feb – 1 Mar
More than 4 feet of snow fell across the Sierra Nevada, with nearly 8 feet reported near Lake Tahoe
Significant snowfall also occurred in the Klamath Mountains and the higher terrain of the Colorado Basin

Cold Storm to Bring More Snow to California this Weekend

Another upper-level trough is forecast to impact Washington, Oregon, and California beginning on Friday
More than 3 feet of snow are forecast over the Sierra Nevada, and 1–3 feet of snow are forecast in the Klamath Mountains and southern Cascades
Low freezing levels will once again allow for significant snowfall accumulations below 3,000 feet
Major winter storm impacts are expected over the Northern California Coast Ranges and Northern/Central Sierra Nevada Saturday into Sunday

Potential for Atmospheric River Activity in California Late Next Week

Another upper-level trough is forecast to impact Washington, Oregon, and California beginning on Friday
NCEP GEFS and ECMWF EPS are both showing the possibility of landfalling AR activity over California during 9–12 March, but there is a considerable amount of forecast uncertainty given the long lead time
Overall, GEFS is showing a higher likelihood of landfalling atmospheric river (AR) activity than EPS
More than 30% of all GEFS + EPS ensemble members are forecasting maximum IVT > 500 kg m−1 s−1 over the next 10 days near Bodega Bay, CA
Forecast uncertainty in storm track and AR activity is evident in the large spread of ensemble precipitation forecasts in Northern California