AGUS76 KRSA 181520 HMDRSA Hydrometeorological Discussion National Weather Service / California Nevada RFC / Sacramento CA 830 AM PST Wed Feb 18 2026 ...SERIES OF DISTURBANCES TO MOVE IN FROM THE NORTHWEST THROUGHOUT THE WEEK BRINGING PERIODS OF WIDESPREAD PRECIP, T-STORMS, AND MOUNTAIN SNOW... .METEOROLOGICAL CONDITIONS (SHORT TERM: WED AM - SAT AM)... Radar imagery shows shower activity across a large portion of California as a low pressure system tracks down the coast and a cold front/moisture plume with IVT ~400 units moves onshore over southern California. The Heaviest precipitation over southern CA will move out of the area over the next few hours with shower activity remaining across much of the State. An additional 1+ inches are currently forecast over the mountains of San Diego and Riverside Counties over the next 24 hours, most of which has already fallen or will fall in the next couple of hours. An additional .5 to 1 inch is forecast for coastal locations and the Sierra where showers and thunderstorms move onshore. Locally higher amounts are possible where thunderstorms form and track. An additional system is forecast to move in behind the current disturbance tonight and into Thursday morning bringing another round of precipitation to the forecast area. Similar to the current system, the low will track southeastward and push another moisture plume inland along the central and southern California Coast with shower and thunderstorm activity across the north in association with the low. The heaviest precipitation accumulations of >1 inch for 12Z Thursday to 12Z Friday currently target the central and southern Sierra, Big Sur Coast, and eastern Transverse and Peninsular Ranges where onshore moisture flux will be strongest. Precipitation will taper off on Friday into Saturday until another disturbance begins to move across the north. Models continue to struggle with the exact timing of this system with ensembles generally favoring an earlier onset while deterministic products are a bit later. Similar to the previous few days, freezing levels will be quite low in association with the next couple of systems into Friday morning. Levels across the north will generally sit below 3,000 feet throughout the 3-day window before rising early saturday under the WAA of the weekend storm. Freezing levels across the south will fluctuate between 4 and 6k feet, north-to-south. .METEOROLOGICAL CONDITIONS (LONG TERM: SAT AM - TUE AM)... A large surface/upper low will approach the western U.S. on Saturday bringing widespread precipitation to northern and central CA through early next week. There remains uncertainty on the arrival timing of precip as the det models continue to show a later onset of showers compared to the ensembles. Ensembles have slowed down a bit since yesterday, but remain about 12-24 hrs ahead of the det GFS/ECMWF. The latest NAM is on the earlier side now as well, though not as early as the NBM. Looking at the 24 hr QPF clusters ending Saturday afternoon (00z Sunday), there is disagreement among the ensemble members on the arrival and spread of precip from the low. Cluster 1, comprising of 30% CMC 50% GEFS and 48% ECMWF is the slowest with showers confined mostly to the immediate nrn CA coast north of Point Reyes. The other 2 clusters push precip further inland to varying degrees at either Shasta (cluster 2: 30% CMC, 33% GEFS, 24% ECMWF) or into the northern Sierra and past the Golden Gate (cluster 3: 40% CMC, 17% GEFS, 28% ECMWF). The official forecast is on the slower side of the ensembles but quicker than the det models with lighter showers along the coast north of Point Reyes and into Shasta Saturday morning. The low will continue to rotate offshore of the PacNW throughout the weekend sending bands of precipitation into nrn and cntrl CA. The system will draw in additional warmer moisture on Monday into central/southern CA. Some uncertainty as to when or even if that precip will arrive. For the current period, nearly all of the precip is expected north of Point Conception with a few lighter showers over Santa Barbara/Ventura counties. There is good agreement that the bulk of the impacts from this larger system will be across nrn coastal CA into Shasta and the northern Sierra, but uncertainty as to how far south of these areas higher totals may travel. The official forecast for Saturday was a blend of the 50% NBM and the det NBM to slow down some of the precip. The rest of the period made use of the latest det NBM. QPF 12z Sat-12z Tues: 3-6" nrn CA coast north of Point Reyes (up to 8.50" King Range), 5-7" Shasta, 3-7.25" northern Sierra, 1-2.50" central Sierra, 0.25-1.25" southern Sierra, 1-3" central coast mountains, 0.50-1.75" rest of Bay ARea/central coast, 1-3.50" Sac Valley, 0.10-1" SJ valley, and 0.10-0.50" around Point Conception. This low will be drawing in a warmer moist airmass raising freezing levels this weekend from sw to ne. On Saturday, the Sierra will start at around 3-6 kft rising to 5-9 kft by the evening. This increase will continue Sunday reaching 7-10.5 kft in the evening. Levels will lower a bit into Tuesday down to 5.5-10 kft as troughing from the main low descends a little into nrn CA, but the core of the main system will still be offshore of the PacNW. 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. QPF graphics are available at www.cnrfc.noaa.gov/qpf.php CH/AS $$ |