CW3E AR Update: 22 January 2021 Outlook

January 22, 2021

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Active Weather Pattern Forecast Across the Western U.S. this Weekend through Next Week

  • A series of upper-level shortwave disturbances will bring multiple episodes of precipitation to the southwestern U.S. this weekend into early next week
  • At least 1–3 inches of precipitation are forecasted in the Southern Sierra, coastal Southern California, and Central Arizona in association with these shortwave disturbances
  • Significant snowfall accumulations are possible over the higher terrain in the southwestern U.S.
  • There is increasing forecast confidence in a landfalling AR and major precipitation event next week over California
  • However, there is still considerable uncertainty in the location, duration, and intensity of this landfalling AR
  • More than 5 inches of total precipitation are possible over the California Coast Ranges, Sierra Nevada, and Southern California Transverse Ranges during the next 7 days

Click images to see loops of ECMWF IVT & IWV forecasts

Valid 0000 UTC 22 January – 0000 UTC 30 January 2021





Probability of AR Conditions Along Coast: dProg/dt

Model Runs: 00Z 17 Jan – 00Z 22 Jan 2021 (every 12 h)





Summary provided by C. Castellano, C. Hecht, J. Kalansky, and F. M. Ralph; 22 January 2021

*Outlook products are considered experimental