Hydrometeorological Discussion National Weather Service / California Nevada RFC / Sacramento CA 710 AM PDT Tue Apr 21 2026 ...COOLER AND WETTER TODAY INTO WEDNESDAY... ...DRIER THU AND FRI BEFORE SOME SHOWERS ARRIVE FOR THE WEEKEND... .METEOROLOGICAL CONDITIONS (TUE AM - MON AM)... Radar imagery indicates a solid line of echoes streaming mainly from south-to-north while making ever so slow progress to the east...currently stretching from the northern and central Sierra down across the northern San Joaquin Valley before reaching the area around Point Conception. Some impressive precip totals over the past 24 hours with the greatest totals over Marin County...the Santa Cruz Mountains...and portions of the Big Sur coast with anywhere from 2.00- to 3.00-inches. Otherwise...the higher terrain of northern CA ranged from 0.75- to 1.50-inches with the Sacramento Valley generally between 0.50- and 1.00-inch. This line continues to produce moderate to locally heavy precip this morning. The area of low pressure has made its way within 130W overnight and is moving to the east primarily along 40N...which has allowed the cold front to push the best precip slowly inland...expected to primarily impact the length of the Sierra with the best totals today in the range of 1.00- to 3.00-inches (greatest from the American River basin south to the Merced River basin). Also...SPC continues to paint a broad area of general thunderstorms across northern and central CA inland over much of northern and western NV...as the area sits in a favorable locations of the upr low and cooling temperatures aloft. Any convection that does develop will generate localized heavier precip amounts. Into Wednesday...the upr low will open up and increase its forward speed to the east...moving across northern CA and northern NV. Scattered shower activity will be the rule in these areas with the models showing the best potential for an uptick in precip near the base of the s/wv trof from the SF Bay Area inland to the central Sierra as the disturbance moves inland during the morning and afternoon hours. Thursday is looking to be a primarily dry day across the region as the initial system moves downstream of the area while a secondary disturbance takes up shop over the eastern Pacific off the central CA out along 140W. This system is expected to make its way to the east-northeast and cross the coast on Friday with troffing lingering through Saturday. This will phase with another s/wv trof dropping southward from the Pacific Northwest...and will bring scattered light precip to the region mainly over the Sierra...coastal southern CA higher terrain...and the state of NV. Freezing levels this morning are running from 5500-feet along the northern CA coast...6000- to 9000-feet over the Sierra (highest ahead of the cold front)...and over 10000-feet for much of NV and southern CA. As the colder airmass moves overhead later today into early Wednesday...a broad area of 5000- to 6500-feet will cover northern into central CA and portions of northern NV...while remaining near or above 10000-feet for southern CA into extreme southern NV. These will recover into Thursday and Friday as the system moves downstream of the area with 9000- to 12500-feet the norm. Then by the weekend with the next system arriving...look for a broad area of 6000- to 9000-feet for freezing levels. 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. |