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Hydrometeorological Discussion
National Weather Service / California Nevada RFC / Sacramento CA
830 AM PST Fri Feb 7 2025

...LINGERING SHOWERS TODAY MAINLY ALONG THE SIERRA AND OVER NW CA 
AND SRN CA AND NRN AND ERN NV THEN MAINLY DRY AND COOL OVER THE 
WEEKEND INTO MONDAY EXCEPT LIGHT PRECIP POSSIBLE OVER NW CA AND SRN 
OR CASCADES SATURDAY...

...MORE WIDESPREAD PRECIP POSSIBLE MID-LATE NEXT WEEK...

.METEOROLOGICAL CONDITIONS (SHORT TERM: FRI AM - MON AM)...

Upper level shortwave trough moves through the region today. 
Scattered showers possible through the day then diminishing 
overnight. Highest precip amounts generally expected along the 
Sierra and over Srn CA (San Gabriel and San Bernardino Mtns and 
south) and NE CA plateau and over higher terrain of Ern NV with 0.15-
0.6 inches except locally around an inch for the San Bernardino 
Mtns. Another shortwave trough moves through the Pac NW and brushes 
far Nrn CA and Nrn NV on Saturday. Light precipitation around a tenth 
of an inch or less is possible along the NW CA coast and Srn OR 
Cascades and possibly into NE NV higher terrain on Saturday. 
Freezing levels around 2000-3000 ft near ORCA border and around 3500-
4500 ft for Nrn Sierra and 4500-5500 ft Central Sierra and 5500-7500 
ft for Srn Sierra and 9000-12000 ft over Srn CA and around 4000-9000 
(N-S) over Nevada today and fluctuate near similar levels on 
Saturday.  A weak baggy trough digs into the region on Sunday with 
dry conditions expected.  Freezing levels rising to around 3000-4000 
ft near the ORCA border and 4500-6500 ft for the Nrn Sierra and 5500-
7000 ft for Central Sierra and 7000-9000 ft for the Srn Sierra.  


Max temperatures near to around 10 degrees below normal 
over most of the region except up to 10 degrees above normal over SE 
CA and Srn NV. On Saturday, max temperatures generally below normal 
up to 15 degrees except near normal SE CA and far Srn NV . Min 
temperatures 5 to 15 degrees below normal over Nrn CA and near normal 
to 10 degrees below normal for Central CA and most of NV near normal 
to 10 degrees above normal for Srn CA (especially SE). Max 
temperatures generally near normal to 20 degrees below normal for the 
region on Sunday. Min temperatures 5 to around 20 degrees below 
normal over Nrn CA and 5 to 15 degrees below normal for Central CA 
and NW NV and near normal to 10 degrees below normal for Srn 
CA (except far SE CA) and Srn and Eastern NV. 


.METEOROLOGICAL CONDITIONS (LONG TERM: MON AM - THU AM)...

The work week will begin with dry west to northwest flow across the 
region as general troffing exists along the west coast. A weak 
disturbance will move toward northern Baja with little to no impact 
in precip across southern CA on Monday as it moves eastward to the 
south of the CA/MX border. At the same time...a s/wv trof moving 
southward from western Canada toward the Pacific Northwest will 
bring a polar continental airmass to the region on Tuesday. There 
are some model differences in the trajectory of the system as it 
eventually swings across the region from the north and then curves 
east...but the overall trend was to keep precip rather scattered and 
light mainly over coastal locations of northern/central CA and the 
higher terrain between the southern Cascades down the Sierra. 
Overall totals will remain from about 0.10-inch or less. Freezing 
levels will crash with the cooler airmass advecting in from the 
north and bottom out late Tuesday into early Wednesday generally at 
the surface across NV...500- to 2500-feet over the Sierra...1000- to 
3000-feet for the rest of northern CA and much of central CA...and 
4000- to 6000-feet for southern CA.

Bigger differences in the models with an approaching system for the 
middle of the week as a s/wv trof rides eastward along 40N and a 
moisture plume from the lower latitudes advects northeast toward the 
CA coast. This is looking to bring another round of widespread 
precip to the region. For now...used a blend of the latest WPC QPF 
with the 07/13Z NBM and the 07/00Z GFS and EC. Freezing levels will 
moderate as the warmer airmass begins to move in from the southwest 
and by the end of the forecast period range from 2500- to 5000-feet 
for NV...2000- to 6000-feet for northern CA...5500- to 8000-feet for 
central CA...and 7000- to 8500-feet for southern CA.