Hydrometeorological Discussion National Weather Service / California Nevada RFC / Sacramento CA 645 AM PDT Mon Apr 20 2026 ...COOLER AND UNSETTLED THROUGH WEDNESDAY... ...BEST PRECIP ANTICIPATED OVER NORTHERN/CENTRAL CA... .METEOROLOGICAL CONDITIONS (MON AM - SUN AM)... A disturbance that moved off the Aleutian Islands last weeks has shifted to the southeast and settled just west of the northern CA coast generally just outside of 130W this morning. Slower model solutions were definitely the way to go with the progression of this system toward the west coast and eventually as it spreads inland for the middle of the week. Radar imagery shows the leading edge of the precip making its way onshore with a band of precip along coastal sections between the Golden Gate and CA/OR border. So far...precip gauges overnight have recorded anywhere from 0.01- and 0.33-inch with the greatest amounts over the King Range located on Cape Mendocino. Through today...look for the upr low to slowly make its way eastward and move within 130W overnight...continuing to spread precip inland across much of northern CA and reaching back across the Monterey Bay area. Overall totals will generally range from 0.50- to 1.00-inch. Then into tomorrow...the system will increase its forward speed and shift inland across northern CA. This will bring an area of widespread precip across northern/central CA reaching past the crest over northern/central NV. Best totals will fall over the length of the Sierra with 1.00- to 2.00-inches possible. Also...SPC is painting an broad area of general thunderstorms across much of northern and central CA on Day 2...which covers the period from Tuesday 12 UTC through Wednesday 12 UTC. Convective cells could result in localized heavier precip amounts. Wednesday will see lingering precip across the northern half of the area as cyclonic flow continues over the region. Best totals will continue to be over upslope portions of the northern/central Sierra with another 0.10- to 0.33-inch anticipated. Then Thursday will be a general dry day before a disturbance moving across the Pacific toward the central/southern CA coast possibly moves close enough to bring scattered light precip later Friday through Saturday. Overall totals at this point do not look overly impressive. Freezing levels will bottom out as the core of the cooler airmass moves across northern/central CA toward northern NV late Tuesday into early Wednesday...dropping down to 5000- to 6500-feet. These will rebound as the upr low shifts east. 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. |