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Hydrometeorological Discussion
National Weather Service / California Nevada RFC / Sacramento CA
830 AM PST Sat Dec 27 2025

...RETURN TO DRY PATTERN AS ANOMALOUS RIDGE BUILDS ACROSS THE WEST...
...POTENTIAL FOR PRECIPITATION RETURN LATER IN THE WEEK AS MULTIPLE 
SYSTEMS APPROACH THE COAST...

.METEOROLOGICAL CONDITIONS (SAT AM - FRI AM)...

A return to a dry pattern is anticipated over the weekend with 
remnant light shower activity over the next several hours. Any 
shower activity is expected to be light and spotty. An anomalous 
ridge will begin building across the West as the current system 
continues exiting the region forming a surface high off the coast of 
Oregon and NorCal bringing several days of dry weather across the 
region. 

This ridge aloft and surface high will begin to weaken around 
Wednesday and multiple systems will begin approaching the forecast 
area. As the ridge weakens, a system off the coast of the Baja 
Peninsula begins to approach from the south as another frontal 
system off the PNW coast begins to dig southward. Guidance currently 
disagrees quite substantially on the phasing of these two systems 
which creates considerable uncertainty in the resulting precipitation 
over California beginning Wednesday. Precipitation over southern 
California may begin as early as Wednesday as the northward 
propagating low begins extending a plume of higher PWAT values 
inland across the southern California Bight. This precipitation may 
begin spreading northward as the low continues shifting to the north 
and interacts with the frontal system moving inland off the PNW and 
NorCal coast, increasing precipitation chances across California 
through Friday.

Morning forecasts generally followed guidance from the NBM and WPC, 
spreading over an inch of accumulation over the Transverse mountains 
and Big Sur coast in the 3-day window ending 12Z Friday. 
Accumulations further north are currently lighter with 0.5 to 1.0 
inch forecast for the higher elevations of the Sierra and Cape 
Mendocino. Generally <.25 inches over lower elevations throughout 
the Central Valley. Expect accumulations to be adjusted as guidance 
is updated and the event approaches. 

Freezing levels are expected to rise substantially over the coming 
days under the anomalous ridge to >12k feet before lower under the 
uncertain pattern change beginning Wednesday. 

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.