####018004226#### AGUS76 KRSA 271621 HMDRSA Hydrometeorological Discussion National Weather Service / California Nevada RFC / Sacramento CA 830 AM PST Tue Feb 27 2024 ...LARGE LOW TO BRING WIDESPREAD PRECIP AND MOUNTAIN SNOW TO THE REGION LATE THIS WEEK INTO THE WEEKEND... .METEOROLOGICAL CONDITIONS (SHORT TERM: TUE AM - FRI AM)... A surface and upper low resides offshore of the soCal coast this morning resulting in some light showers. Lightning detection has picked up some strikes near the core of the system as well. The low will move southeastward offshore the rest of the morning reaching the Baja coast by this evening. This may produce a few additional showers for parts of coastal soCal today as the low passes. The system will move through Baja tonight into Wednesday morning again potentially dropping a couple showers across srn CA. Not expecting more than a few hundredths of an inch or so. Behind the low, zonal flow will briefly set up keeping the region through Wednesday morning. Meanwhile, the next system will approach as a surface and upper low in the Gulf of Alaska. A front will head towards the PacNW and nrn CA later Wednesday bringing initial showers into the north coast Weds afternoon. The low will head south the rest of Weds pushing the front towards the region spreading precipitation across northern CA Thursday morning. The system will continue to approach the rest of Thursday sending precip into central CA as well. Heaviest precip is expected along the north coast (particularly near the Smith Basin, the srn OR Cascades, Shasta, and the northern/central Sierra. Forecast was a blend of WPC guidance and the latest NBM. QPF for Weds/Thurs: 1.50-4" north coast, 1-2.75" srn OR Cascades/Shasta, 1.25-3.25" northern/central Sierra, and 0.25-0.75" rest of northern/central CA. Freezing levels fluctuating the next couple days but generally 5-8 kft north of I-80 and 7-10 kft to the south. This will be a colder system for late this week lowering freezing levels down to 2.5-5 kft north of I-80 and 4.5-7 kft to the south to Point Conception by the end of the near term early Friday. .METEOROLOGICAL CONDITIONS (LONG TERM: FRI AM - MON AM)... Upper level low/trough and associated front will bring precip to most of the region Friday into the weekend. There are differences in the details of lows and in timing leading to lower confidence in precip amounts. The QPF clusters show various members showing different precip amounts but generally heaviest amounts along the Nrn Ca coast and along the Sierra. There is uncertainty in how quickly precip will move into Srn CA and taper off over the region. The GFS still showing several upper/sfc lows with one near the ORCA border during the day on Saturday. The GFS is faster moving trough to the east on Sunday with ridge moving onto the west coast drying out the region by Sunday night. The EC is slower with one disturbance moving through the north and another one dropping down off the Pac NW coast Sunday into Sunday night. The Canadian timing is in between the two. The forecast generally uses a blend of NBM and WPC with some of the previous forecast. Precipitation amounts for Friday and Saturday generally around 1-3 inches for the Nrn CA coast and Shasta area and 2-5 inches for the Sierra and 1-2 inches for the Central Ca coast and 0.5-1.5 inches for Santa Barbara through SW corner of San Bernardino County and around 0.1-1 inch for Orange and western Riverside and San Diego Counties. Precip tapering off on Sunday to around a quarter an inch or less. Freezing levels around 2000-4000ft over Nrn Ca and 4000-6000 ft for Central CA and 7000 ft and higher for Srn CA and 5000-7000 ft over NV on Friday drop to around 1500-4000 ft over Nrn and Central CA and 4000-7000ft over Srn CA and NV Saturday morning and around 1000- 2000ft over Nrn CA and 1500-3500 ft along the Sierra and 4000-7000ft Srn CA and 2000-5000 ft over NV Saturday night. QPF graphics are available at www.cnrfc.noaa.gov/qpf.php AS/Osborne $$