213
AGUS76 KRSA 220809
HMDRSA

Hydrometeorological Discussion
National Weather Service / California Nevada RFC / Sacramento CA
1200 AM PST Fri Nov 22 2024

...MODERATE TO HEAVY PRECIP CONTINUES OVER NORTHERN CA...
...COLD FRONT SWEEPS ACROSS THE AREA FRI INTO SAT...

.METEOROLOGICAL CONDITIONS (SHORT TERM: THU PM - SAT PM)...

Heavier precip has lifted northward as expected with the deluge of
the lower Russian/Napa now at a pause. Radar imagery shows heavier
precip focusing futher northward over the northern Sierra and across
the Eel/Mad basins. IR imagery shows a robust moisture plume moving
into the nrthrn CA coast with heavier echos on the radar now moving
onshore. TPW imagery shows about 1.50" PW of moisture being funneled
into the nrn CA coast. This came in a bit later than expected,
meaning the 00z-06z QPF over the north coast was overestimated.
Expecting this heavier precipitation to be falling in that area
overnight tonight with 0.75-1.50"+ over the next 6 hours. HREF
exceedance probabilities over nw CA overnight show about a 30-60%
chance of 0.50"+/hr rain rates. Precip will shift back to the south
early Friday morning as the cold front starts to move to the
southeast along with the moisture plume. This will return heavier
precip into Napa/Sonoma County and the northern Sierra while pulling
away from the north coast. The front and moisture plume will focus
precip across the Bay Area/central coast in the afternoon while
still funneling into the northern Sierra throughout the day. The
front and moisture plume will begin to move into srn CA late Friday
night and Saturday morning while diminishing in strength. The
moisture will head out of the area by Saturday evening with
lingering showers across the region as the upper trough pushes
inland.

The overnight update was mainly focused on the next 24 hrs, but QPF
was updated with new data through 00z Sunday. This was a blend of
the previous forecast, the new WPC Guidance, the HRRR, and the
latest NBM. QPF overnight is forecast at about 1-2.50" across the
Eel/Mad/Smith basins, Shasta, and the northern Sierra, another 0.10-
0.30" across the lower Russian/Napa, and 0.50-1" for northern Sonoma
through mid Mendocino County.


QPF graphics are available at www.cnrfc.noaa.gov/qpf.php



Kozlowski/Osborne

$$