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Hydrometeorological Discussion
National Weather Service / California Nevada RFC / Sacramento CA
720 AM PST Mon Jan 5 2026

...OFFSHORE LOW WILL BRING SCATTERED PRECIP TO NRN/CNTRL CA THROUGH 
TUES AM WITH LINGERING SHOWERS ALONG THE COST THE REST OF TUES...
...WEDS/THURS ADDITIONAL SHOWERS OVER NRN CA/NV AS A TROUGH DIGS IN 
BEFORE DRY CONDITIONS RETURN AS HIGH PRESSURE BUILDS OFFSHORE...

.METEOROLOGICAL CONDITIONS (MON AM - SUN AM)...

A surface low sits offshore this morning west of Mendocino as an 
upper trough resides above gradually forming itself into a low. This 
has allowed for continued shower activity across much of 
northern/central CA after yesterdays heavier band moved through. 
Observations overnight report another 0.25-1" or so across much of 
the region and 1-2.25" over the mountains. Already seeing some 
lightning offshore west of Point Reyes this morning. The upper 
trough will close off into a low some time late this afternoon into 
the evening as the surface low continues to rotate precip into nrn 
CA. Thunderstorms possible over parts of the nrn CA coast today. 

The system will move to the southwest this evening and overnight 
tonight both shifting precip into the central coast and pulling it 
westward. Models continue to have the low far enough away from the 
coast on Tuesday that only light isolated coastal showers are 
anticipated. However, the possibility that the low follows a path 
closer to shore remains. At this point, only about 24% of the ECMWF 
ensemble members are showing the scenario discussed in previous days 
that would result in heavy precip across the western Transverse 
later today/early Tuesday while the GEFS and CMC do not have any 
members showing this solution. Just under half of the ensembles 
overall favor focusing precip over the Big Sur coastal mountains, 
while the rest show lighter amounts from Cape Mendocino through 
Monterey County. Rainfall rates overall should be lighter than the 
past couple days with only about a 10-30% chance of 0.50+"/hr rates 
along the coast and over Shasta from this system.

The low will cease its southerly trajectory tomorrow evening once 
most of it has crossed the southern CA border and shift east towards 
Baja. At the same time, a trough will begin to dig into nrn CA 
bringing additional light showers to that area. This will continue 
through Thursday morning as the trough expands over the region. 
There is some chance of precip along the srn CA borer as the low 
moves through Baja, but for now it looks to be far enough away to 
avoid that. The upper trough arriving from up north will swing 
eastward through the region the rest of Thursday exiting in the late 
afternoon/evening leaving only lingering showers over NV. High 
pressure will also build over the eastern Pacific at the same time. 
This will allow for the return of dry conditions starting Friday and 
lasting at least through the weekend. Longer range outlooks favor 
below normal precipitation for at least another week or so.

Majority of the remaining QPF is expected within the next 24 hours. 
This was the main focus of the morning forecast. Blended in the 12z 
HRRR, the latest NBM, and morning WPC guidance in with the previous 
forecast. As expected, models have indeed continued to underestimate 
precip over srn CA particularly around San Diego county. The main 
difference from yesterday has been the steepening of the slope of 
the more moderate precip band expected later today. This pulled some 
precip out of the central coast/South Bay and the nrn Sierra while 
moving into the Russian basin. Again, if the low tracks closer to 
the coast than models predict that could shift higher precip amounts 
further along the coast and further inland. QPF for the rest of this 
system (through tomorrow morning): 1-3" Russian Basin/Shasta, 0.75-
1.75" Santa Cruz/Big Sur mountains, 0.50-2" nrn Sierra, 0.25-0.75" 
north coast (locally >1" possible), 0.25-0.50" San Diego area, and 
generally 0.10-0.50" elsewhere over nrn/cntrl CA. Lighter showers 
along coastal srn CA. For the rest of the period (late Tues/Thurs 
trough): 0.50-1" north coast, 1-2+" srn OR Cascades, 0.10-0.50" nrn 
Sierra, and generally a tenth of an inch or less scattered across 
the rest of the region.

Freezing levels 4.5-6.5 kft north of I-80 and 6-7.5 kft from I-80 to 
the southern Sierra later this morning hovering around there through 
mid-week. Levels will lower into Thursday as the trough digs in to 
3.5-4.5 kft north of I-80 before coming up again west to east into 
Friday as the trough exits and the ridge builds in.


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.