Version:  Current  |  Back 1  |  Back 2  |  Back 3  |  Back 4  |  Back 5  |
Hydrometeorological Discussion
National Weather Service / California Nevada RFC / Sacramento CA
830 AM PST Sun Dec 28 2025

...DRY WEATHER THROUGH MID-WEEK UNDER ANOMALOUS RIDGE...
...RETURN TO WETTER PATTERN ON WEDNESDAY AS TROUGH APPROACHES FROM 
NORTH AND CUTOFF APPROACHES FROM SOUTH...

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

Ridging has continued to build over the Eastern Pacific driving dry 
conditions across the forecast area. This ridge is forecast to 
persist into mid-week before weakening and shifting east on 
Wednesday, keeping the forecast dry for a few days. 

As the ridge weakens on Wednesday, an upper level-level trough is 
forecast to approach northern California from the Gulf of Alaska and 
interact with a slow moving cutoff approaching from the south. 
Models are struggling to agree on the exact phasing and interaction 
between these two systems and, therefore, the onset and magnitude of 
precipitation over California. Currently, light precipitation is 
forecast to begin spreading northward over southern California on 
Wednesday morning before making its way to northern California on 
Thursday morning. Persistent troughing and shortwave activity from 
the Gulf of Alaska may keep the pattern relatively wet through the 6-
day forecast window. 

Current forecasts primarily followed guidance from the NBM and WPC 
placing the heaviest accumulations of >2 inches over the southern CA 
coast, northern Sierra, Cape Mendocino, and Big Sur coast. A 
majority of the Sierra, outside of the Yuba and Feather Basins, are 
forecast to receive .5 to 1 inch through the end of the forecast 
period. Light precipitation (<.5 inches) is expected throughout the 
Central Valley. 

Freezing levels will remain above 12k feet underneath the ridge 
across much of the forecast area before lowering to ~5k feet across 
the north, ~7k feet across the southern Sierra, and 9k feet across 
the south during the active pattern. 

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.