National Weather Service California Nevada River Forecast Center Department of Commerce National Oceanic and Atmospheric Administration National Weather Service

Printer Version
CNRFC Hydrometeorological Discussion

Version:  Current  |  Back 1  |  Back 2  |  Back 3  |  Back 4  |  Back 5  |
Hydrometeorological Discussion
National Weather Service / California Nevada RFC / Sacramento CA
130 PM 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 PM - SUN AM)...

Increased amounts (up to 0.25 inches) in the Nrn and Central Sierra 
and along the transverse range for this evening and about a tenth of 
an inch or less for San Gabriel and San Bernardino into San Diego 
Mtns Friday morning.  Decreased amounts a little for Friday during 
the day. 

An upper level low/shortwave trough positively tilted off the Pac NW 
coast and a sfc low approaching the Central CA moves onshore this 
afternoon/evening and the upper level shortwave trough moving 
through the region tonight into Friday. PW plume about 1.05 inches 
from around Pt Arena to the Bay area around to Point Conception to 
around LA County and inland this afternoon then focused on the Srn 
CA coast tonight into Friday morning and dropping south into Mexico 
in the afternoon. This is bring precipitation to Srn OR and most of 
CA (except SE) and much of NV into tonight with showers tapering off 
during the day of Friday as the shortwave trough moves off to the 
east.  Isolated thunderstorms possible over Nrn CA and along the 
Sierra today. 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 and 6000-7500ft over the 
Nrn and Central Sierra and 7500-8500ft for the Srn Sierra and 6000-
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.