####018004003#### AGUS76 KRSA 211514 HMDRSA Hydrometeorological Discussion National Weather Service / California Nevada RFC / Sacramento CA 830 AM PDT Thu Mar 21 2024 ...A LOW PRESSURE SYSTEM WILL BRING PRECIP TO THE REGION FRIDAY INTO THE WEEKEND... ...ANOTHER SYSTEM WILL BRING ADDITIONAL PRECIP CHANCES TO THE NORTH EARLY NEXT WEEK... .METEOROLOGICAL CONDITIONS (SHORT TERM: THU AM - SUN AM)... A low pressure system around 45N and 140W with high pressure over the region this morning bringing generally dry conditions during the day today. The low pressure system strengthens a little as it approaches the west coast tonight with the cold front reaching the Nrn CA coast Friday morning and moving through the region into Saturday. The low is off the Pac NW coast Saturday with trough moving into the region. Moisture plume about an inch along the CA coast ahead of this system. Light precip along the NW CA coast early Friday morning then increasing and spreading south and east across the region as the front moves through. Precip spreads to around the I-80 corridor Friday afternoon and into Central CA and Srn Sierra and Nrn Nv Friday night and into Srn CA and Ern NV on Saturday as weakening front moves through the region. Precipitation amounts through Saturday night are expected to generally be around 1.5-3.5 inches with local amounts to around 4 inches along the NW CA coast and 1-3 inches for the Shasta Basin and Nrn and Central Sierra and 1- 2 inches for the Srn Sierra and 0.5-1.5 with local amounts up to 2 inches for the Central Coast and 0.25-0.75 for Sac Valley and 0.1- 0.75 for SJ Valley and generally half an inch or less for Srn CA. Freezing levels around 6500 ft over NW CA coast and around 7000-8000 ft for the Nrn Sierra and 8000ft and higher elsewhere Friday morning and dropping to around 3500-5000 ft behind the cold front over Nrn and Central CA Friday night and around 5000-8000 ft over Srn CA and NV Saturday dropping to around 3500-5500 ft over most of the region Saturday night. .METEOROLOGICAL CONDITIONS (LONG TERM: SUN AM - WED AM)... The axis of the broad upper level trof is forecast to begin shifting inland by Sunday morning, with s/wv activity on the upstream portion of the trof providing support for additional shower activity across the forecast region. Best chances for precipitation on Sunday are for coastal southern California (up to 0.5 inches) with lighter amounts (0.20 inches and lower) over central California from the Coast to the Sierra (lower in the San Joaquin Valley and northern Sierra) and a few tenths over the North Coast. Precipitation will diminish across the south on Monday as the upper level trof begins to shift further inland. Additional and weaker s/wv activity is forecast to produce light precipitation across the northern portions of the forecast region with up to 0.25 inches over the Smith basin and lighter amounts over the northern Sierra and northern Nevada. Chances for heavier precipitation ramp back up on Tuesday as a digging trof and surface low push enhanced moisture transport into northern California. Current guidance differs on timing and exact magnitude of this system, but forecasts currently suggest over an inch of precipitation in the Smith Basin, half an inch over the Shasta Basin, and a ~0.25 inches over the northern Sierra and North Bay. Only a few hundredths of an inch are currently forecast for the Sacramento Valley. Forecasts will continue to update as guidance begins to converge on a solution. Freezing levels are forecast to start the forecast window around 4,000 feet in the North and 5,000 feet in the south, rising slightly on Monday before lowering across the north again on Tuesday to below 4,000 feet. QPF graphics are available at www.cnrfc.noaa.gov/qpf.php Osborne/CH $$