Hydrometeorological Discussion National Weather Service / California Nevada RFC / Sacramento CA 830 AM PST Mon Mar 4 2024 ...PRECIP MAINLY OVER SRN OR AND NRN CA AND NRN NV TODAY INTO EARLY TUESDAY AND SPREADING SOUTH INTO CENTRAL CA LATER TUESDAY AND INTO SRN CA AND SRN NV WEDNESDAY... ...DRIER CONDITIONS EXPECTED THURSDAY AND FRIDAY THEN ANOTHER SYSTEM MOVES INTO NORTH BRINGING PRECIP TO SRN OR AND NRN CA SATURDAY... .METEOROLOGICAL CONDITIONS (SHORT TERM: MON AM - THU AM)... Upper level trough shifts north and east out of the region as a low off the B.C. coast weakens and moves into the Pac NW later today into Tuesday. Another low over the Eastern Pacific approaches the west coast to around 140W 40N this afternoon and around 130W 37N Tuesday afternoon and offshore of the Central Ca coast Wednesday morning and off Srn CA coast by Wednesday evening and onshore into Srn CA/ Baja (EC farther north than GFS) overnight. Moisture plume almost an inch aims at Srn CA coast on Wednesday. Mainly light precip this morning then precip will increase and be mainly over Srn OR and Nrn CA and Nrn NV this afternoon into tonight and continue over Srn OR and Nrn CA and Nrn NV on Tuesday. Precip will decrease over the north and spread south into Central and Srn CA and Srn NV later Tuesday into Wednesday as the low gets closer to the coast (still varying solutions on track). Precip amounts for Monday through Wednesday are expected to be around 2-5 inches for the NW CA coast (around Cape Mendo and north) and 1-3 inches for Shasta and Feather Basins and generally 0.25-0.75 inches (possibly locally higher over Santa Barbara and Ventura County) along the CA coast from the Russian Basin down to San Diego and generally a quarter of an inch or less for the Central Valley and Srn Sierra and over NV (except up to an inch over Nrn Nv higher mtns). Freezing levels are expected to rise to around 3000 ft near the ORCA border and 4000 ft around I-80 and 6000 ft for the Srn Sierra this afternoon and to around 4500 ft near the ORCA border and 5500 ft near I-80 on Tuesday and around 5000-7000 ft over most of the region on Wednesday. Although some cold air from the weekend system could get trapped in some valleys for locally lower snow levels today. Max temperatures forecast to be around 5 to 20 degrees below normal today then near normal to 15 degrees below normal for Tuesday and Wednesday. Overnight temperatures generally near normal for Tuesday then near normal to 10 degrees above normal for Wednesday morning and near normal to around 10 degrees below normal (coldest in the north) for Thursday morning. .METEOROLOGICAL CONDITIONS (LONG TERM: THU AM - SUN AM)... General troffing along and just inside the west coast with a disturbance near the base of this flow making its way across southern CA. A positively tilted upr ridge over the eastern Pacific stretches from along 140W to the north-northeast reaching across Vancouver Island and western BC. Look for the disturbance near southern CA to move inland toward the Desert Southwest with scattered light precip over the southern Sierra...coastal southern CA...and portions of southern/eastern NV. Amounts should be near 0.10-inch or less. Then the offshore upr ridge will slide across the west coast on Friday before a weakening s/wv trof reaches the Pacific Northwest and northern CA coast on Saturday. 04/00Z EC a bit sharper with this system as compared to the 04/00Z GFS and CMC...which are a bit shallower and lighter with precip across northern CA. For now...followed close to the most recent NBM that brings precip down to about the I-80 corridor with the best totals over the north coast from Cape Mendocino northward. Freezing levels will generally be from 3500- to 5500-feet across northern CA.