Hydrometeorological Discussion National Weather Service / California Nevada RFC / Sacramento CA 100 PM PDT Tue Apr 7 2026 ...ANTICIPATED A SHIFT TO COOLER AND WETTER LATER WED THROUGH SUN... .METEOROLOGICAL CONDITIONS (TUE PM - MON AM)... Dry conditions continue this afternoon as an upr ridge along the west coast slides inland. An area of low pressure has moved within 140W as it slowly tracks toward the CA coast basically along 38N. Ahead of this feature...a convergent area of moisture has advected northward and become entrained into the circulation with a broad area of PW values near 1.00-inch. For Wednesday...the higher moisture content air will reach the CA coast while the upr low remains just outside 130W. With increasing diffluent flow over portions of northern CA...scattered precip will begin to develop during the afternoon hours in a line from Cape Mendocino over to Oroville and Susanville along with points north. SPC continues to paint an area of general thunderstorms over the interior of northern CA during this period. The upr low continues to slowly track to the east on Thursday...moving within 130W. With better forcing over northern CA...precip is expected to increase with the best totals along coastal sections from the Eel River basin northward...and then inland over the Shasta Lake drainage down through the northern/central Sierra. Overall totals will range from 0.25- to 0.50-inch. Finally by Friday and Saturday...a secondary disturbance dropping southeast from the Gulf of Alaska will kick the initial upr low parallel to the central and southern CA coast before swinging inland (slightly farther north in the 07/12Z GFS and EC...more south closer to the CA/MX border in the 07/12Z CMC). This will bring the best precip to central and southern CA. Also...as the secondary disturbance is moving closer to the northern CA coast...precip should continue across northern CA. It should be said...at this time there continues to be a lower confidence with the secondary system as the trajectory of the system varies quite a bit with the most recent models. As a result...the Sunday (Day 6) forecast trends closer to the latest WPC QPF and NBM. Freezing levels will start elevated on Wednesday...9000-feet northwest to 13000-feet southeast. Then as each of the systems move toward the region...freezing levels will drop to 4000-feet northwest...about 5000-feet along I-80...and 5500- to 7000-feet over central sections...and 7500- to 9000-feet south. Afternoon update changes resulted in increases for northern CA in the range of 0.10- to 0.33-inch on average...relatively unchanged in central CA (except southern Sierra increases 0.10- to 0.33-inch) and similar to slightly down for coastal southern CA. Over NV...northwest portions of the state remained similar...with an area of plus 0.10-inch for south-central NV. |