Hydrometeorological Discussion National Weather Service / California-Nevada RFC / Sacramento CA 650 AM PDT Fri Oct 16 2026 ...WARMER AND MAINLY DRY CONDITIONS THROUGH THE WEEKEND... ...COOLING NEXT WEEK AND INCREASING PRECIP CHANCES AS A LOW MOVES THROUGH... .METEOROLOGICAL CONDITIONS (FRI AM - THU AM)... An upper low remains just offshore of srn CA this morning embedded in a broad upper ridge stretched across most of the west coast. The main result is dry offshore winds across srn CA and widespread above normal temperatures region wide. The offshore low may, however, drag enough tropical moisture into se CA to cause a couple of showers this afternoon and tomorrow afternoon. Potential for isolated thunderstorms over se CA tomorrow afternoon as well. Otherwise, dry conditions are expected through the weekend along with temperature anomalies of +5 to +20 deg F. The ridge overhead will drift eastward, gradually being replaced by troughing from the northwest before a low embedded in that flow pattern approaches on Sunday. This will usher in some cooling by early next week. Widespread below normal temperatures anticipated Tuesday onward. Earlier model runs tracking this low had it going through nrn CA Monday/Tuesday, but have since evolved to predict an offshore cutoff low that will at some point make its way through srn CA next week. How closely the low sticks to the coast as it heads southward will determine how much if any precip falls over nrn/central CA Monday. Right now, things look fairly light at a 0.10" or less along the north coast into Shasta and down across the Bay Area with chances of showers increasing and becoming more widespread late Tuesday/Wednesday as the low reaches Point Conception. The GFS and the ECMWF have the low moving inland across srn CA into Thursday with most of the precip focused over coastal srn CA, the Sierra, and srn NV. Amounts are still uncertain as ensemble spread remains high. Looking at the 24 hr QPF ensembles at LAX, members have anything between 0" and 2" for Wednesday into Thursday. The official forecast was generally a blend of WPC guidance, the NBM, and the ECMWF. Expect amounts to change over the coming days, any shift in either direction of that low could significantly impact the QPF. Majority of the precip is expected Tuesday/Wednesday. QPF 12z Mon to 12z Thurs: 0.50-1" coastal srn CA (up to 1.50" Transverse Range), 0.25-1" Sierra/srn NV, 0.10-0.50" central coast, and generally 0.10" or less for the rest of nrn and central CA. Freezing levels starting at about 13-15.5 kft today gradually lowering into early next week down to 8.5-11.5 kft north of I-80 early Monday and 8.5-11 kft region wide by mid-week. Please Note: This product may NOT be routinely updated. Please refer to the following product issued by the CNRFC www.cnrfc.noaa.gov/Daily-Briefing for a graphical summary of weather and hydrologic conditions. |