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Hydrometeorological Discussion
National Weather Service / California-Nevada RFC / Sacramento CA
100 PM PST Thu Nov 12 2026

...DRY CONDITIONS THROUGH THIS EVENING AS HIGH PRESSURE REMAINS IN 
THE AREA...
...CHANCES FOR HEAVIER MORE WIDESPREAD PRECIP FRIDAY THROUGH EARLY 
NEXT WEEK AS A PAIR OF SYSTEMS MOVE THROUGH...

.METEOROLOGICAL CONDITIONS (SHORT TERM: THU PM - WED AM)...

Forecast overall remains on track for a series of upper lows and 
associated cold fronts to bring widespread precip to the region over 
the next six days. An upper low continues to form offshore of 
central CA and will head towards soCal/Baja the rest of today 
bringing some showers to the srn CA coast tonight. The main upper 
low and cold front approaching from the northwest will also bring 
initial showers to the north coast tonight before the main system 
moves through Friday into Saturday. No big changes on this first 
system since this morning, the GFS remains lagging behind the ECMWF 
by a few hours. The upper trough will move through west to east 
across nrn CA and NV later Friday into Saturday. Scattered showers 
Saturday as the region sits between systems.

The second cold front will arrive some time Sunday morning bringing 
the next round of precip to nrn CA. The trough should deepen just 
offshore of CA before moving through the region on Monday/Tuesday. 
The models have come closer together compared to earlier runs on 
this trough, the GFS has deepened the system a bit while the ECMWF 
has shifted it northward. The result was relatively minor changes up 
or down 0.10-0.25" for this second system.

The biggest change came in the final approaching cold front and 
upper low at the end of the forecast window. Both the GFS and the 
ECMWF have moved up the arrival timing of the next front, 
unfortunately while maintaining the timing difference of about 6 
hours or so between themselves. The GFS now brings showers into the 
north coast Tuesday afternoon while the ECMWF brings them in Tuesday 
evening. This brought QPF up across nw CA and the north SF Bay by 
0.10-0.50".

To summarize, a series of cold fronts and associated upper 
troughs/lows will bring rounds of widespread precipitation to the 
region over the next six days. The first Friday/Saturday, the second 
Sunday/Monday, and the third later Tuesday/Wednesday. QPF through 
12z Weds: 2.25-4.50" Sonoma County northward along the coast (4-
5.50" Smith Basin/King Range), 3-6" Shasta, 1.50-4.75" Sierra, 0.75-
1.75" Bay Area, 0.50-1.25" central coast (up to 2" Santa Cruz 
mountains and Big Sur coast), 0.25-1.50" down the valleys (up to 2" 
closer to the foothills), and 0.50-1.50" coastal soCal.


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.