Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 229 PM EST Mon Dec 22 2025 Day 3 Valid 12Z Wed Dec 24 2025 - 12Z Thu Dec 25 2025 ...THERE IS A HIGH RISK FOR EXCESSIVE RAINFALL ACROSS SOUTHERN CALIFORNIA... 2100 UTC UPDATE: The primary change to the previous day 3 Excessive Rainfall Outlook was to add a high risk area along the west to east Transverse Range region of Southern California after collaboration with WFO LOX. Anomalous 850-700 mb moisture flux...5+ standard deviations above the mean...will impact Southern CA late day 2 into day 3 ahead of the amplifying mid to upper level trof off the CA coast. The heavy rainfall totals for Southern CA will likely occur over an 18 hour period, with widespread 4-7 inch totals, with isolated max amounts of 9"+. Expect a well defined south to north precip band in this anomalous moisture flux axis with hourly rainfall rates of .50-1.5"+ likely. The potential for high hourly rainfall totals will accentuate runoff over soil that is relatively dry and or over recent burn scar areas. This will pose a significant threat of flash flooding, landslides, rock falls and mud slides. The greater than normal travel during the Christmas Holiday will likely expose a potentially larger number of people to these lift threatening hazards and was taken into consideration with the upgrade to high risk.