CW3E AR Update: 2 February 2024 Outlook

February 2, 2024

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Strong Atmospheric River to Drive High-Impact Precipitation Event Over California

  • A strong AR and low pressure system are forecast to make landfall over Central CA Sun 4 Feb and progress down the CA coast through Mon 5 Feb.
  • There is uncertainty between the GFS and ECMWF deterministic models on the strength of the low pressure system and AR as well as the landfall location.
  • The GFS is forecasting the low pressure and AR to be stronger than the ECMWF and make landfall further north in CA.
  • The GEFS and West-WRF ensemble are forecasting AR3 conditions (based on Ralph et al. 2019 AR scale) over the central CA coast, with AR1/2 conditions in northern and southern CA.
  • This AR is forecast to bring significant precipitation to much of CA, including heavy rainfall along the central and southern CA coasts and heavy snowfall in the Sierra Nevada.
  • The WPC is forecasting greater than 6 inches of precipitation over the Sierra Nevada and Transverse Ranges over the next 7 days.
  • The WPC Excessive Rainfall Outlook indicates a Moderate Risk (level 3 of 4, or at least 40% chance) for flash flooding in Central CA coast for the 24 hour period ending 4 AM PT Mon 5 Feb and Los Angeles Metro Area for the 24 hour period ending 4 AM PT Tue 6 Feb.
  • NWS San Francisco has issued a high wind warning from the South Bay area to San Luis Obispo County for southerly wind gusts possibly exceeding 60 mph from 4am to 10pm Sunday 4 Feb

Click images to see loops of GFS IVT and IWV forecasts

Valid 1200 UTC 2 February 2024 – 1800 UTC 6 February 2024


















Summary provided by M. Steen, S. Bartlett and S. Roj; 2 February 2024

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