CNRFC Hydrometeorological Discussion
Hydrometeorological Discussion
National Weather Service / California Nevada RFC / Sacramento CA
830 AM PST Thu Feb 6 2025
...A SYSTEM MOVES THROUGH TODAY INTO FRIDAY BRINGING PRECIP TO MOST
OF THE REGION....
...MAINLY DRY OVER THE WEEKEND INTO MONDAY EXCEPT LIGHT PRECIP
POSSIBLE OVER NW CA AND SRN OR CASCADES THEN MORE WIDESPREAD PRECIP
POSSIBLE MID-WEEK NEXT WEEK...
.METEOROLOGICAL CONDITIONS (SHORT TERM: THU AM - SUN AM)...
An upper level low/shortwave trough positively tilted off the Pac NW
coast and a sfc low approaching the Central CA coast this morning
and sfc low moves onshore this afternoon/evening and the upper level
shortwave trough moving through the region tonight into Friday. PW
plume about 1.05 inches aimed at the Central CA coast this morning
spreads from the Bay area around Point Conception to around LA
County and inland in the afternoon then focused on the Srn CA coast
tonight into Friday morning and dropping south into Mexico in the
afternoon. This will bring precipitation to Srn OR and most of CA
(except SE) and much of NV today and tonight with showers tapering
off during the day of Friday as the shortwave trough moves off to
the east. Precip has started over the Bay area and Central CA coast
and spreading inland into the Nrn Sierra this morning. Slight chance
of thunderstorms over Nrn CA and along the Sierra today. The
forecast is generally a blend of NBM and WPC with some of the latest
forecast and in some locations mixed with the HRRR resulting in a
generally increase in amounts for today into tonight especially
along the Central CA coast and the sierra and over the transverse
mtns compared to yesterday afternoons forecast. Precipitation totals
for today into tonight generally around 1.5-3.5 inches for the
Sierra and Central CA coast and 1-2.5 inches for the transverse mtns
and 0.5-2 inches along Nrn Ca coast and Shasta Basin and 0.5-1.5
inches for the Sac Valley and generally a half an inch or less over
Nevada and SJ valley. Precipitation amounts for Friday generally
nothing up to a half an inch except locally up to an inch possible
over the San Gabriel and San Bernardino Mtns and in the Srn Sierra
on Friday. Freezing levels around 3000-4000 ft near the ORCA border
to around 4500-6500 ft for the Nrn and Central Sierra and Nrn NV and
6500-8500 ft for Srn Sierra and 7000-10000 ft over Srn NV this
morning then around 2500-3500 ft near the ORCA border and 6000-
7500ft over the Nrn and Central Sierra and 7500-8500ft for the Srn
Sierra and 7000-9500 ft over NV and 8000-12000 ft over Srn CA this
afternoon. Freezing levels drop Friday morning to around 2000-4000
ft over Nrn CA and around 4000-7000 ft over Srn Sierra and around
7000-12000 ft over Srn CA and around 5000-9000ft (NW-SE) over NV.
Another weak shortwave trough moves into the Pac NW and brushes Nrn
CA on Saturday. Not much moisture with this system with PW less than
half an inch. A chance of light precipitation to NW CA and the Srn
OR Cascades on Saturday with amounts generally a tenth of an inch or
less on Saturday. Freezing levels around 2000-3000 ft near the ORCA
border on Saturday.
.METEOROLOGICAL CONDITIONS (LONG TERM: SUN AM - WED AM)...
A weak disturbance will be exiting the area from southern CA toward
AZ to start the weekend with a west-to-east aligned s/wv trof
dropping south from western Canada toward the Pacific Northwest on
the downstream side of a narrow wavelength upr ridge situated along
140W. Model spread is a bit tighter this morning as compared to
yesterday with the general pattern of dropping the s/wv trof across
the region on Sunday into Monday. The GFS has trended closer to what
the EC and CMC was previously showing...which has increased
confidence in widespread light to locally moderate precip. Best
totals look to fall along the length of the Sierra and the coastal
mountains of southern CA from Point Conception to the CA/MX border
(0.50- to 1.00-inch). Also...given the trajectory of this
system...this will usher in a cooler airmass across the region.
Freezing levels early Saturday will start from near 2500-feet north
and east to 9000- to 10000-feet south and west. By Monday...as the
cold air settles in across the area...freezing levels will bottom
out from near sea-level north to 4000-feet far south.
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