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AGUS76 KRSA 042117
HMDRSA

Hydrometeorological Discussion
National Weather Service / California Nevada RFC / Sacramento CA
130 PM PST Tue Nov 4 2025

...UNSETTLED PATTERN BRINGING PERIODS OF WET WEATHER TO NORTHERN
PORTIONS OF FORECAST REGION OVER NEXT FEW DAYS...
...PRECIPITATION WILL INTENSIFY OVERNIGHT TONIGHT AND INTO TOMORROW
AS A BROADER TROF AND STRONGER ATMOSPHERIC RIVER MOVES ONSHORE...

.METEOROLOGICAL CONDITIONS (TUE PM - MON AM)...

Afternoon forecasts have adjusted QPF slightly throughout the next
three days with pockets of increases of 0.25 to 1.5 inches over the
North Coast and Shasta Drainage where onshore moisture flux
associated with the strong atmospheric river through the next 48 to
72 hours will be strongest. Most of the increases over the Shasta
Basin were done so using the NBM and other higher-resolution
guidance that favors strong southerly flow within the northern
Sacramento Valley that would favor orographic ascent over the
northern portions of the Valley.

Decreases were made over the northern Sierra (Feather Basin) where
the NBM has been relatively high compared to the consistently lower
EC and GFS. Adjustments will be made across the forecast area as new
guidance is updated.

Additional atmospheric river activity is forecast to bring lighter
precipitation to locations across the north with relatively modest
precipitation accumulations and shower activity throughout the rest
of the week beginning on Thursday. Most of this shower activity is
confined to the North Coast though a few hundredths to a couple
tenths could spread as far south as Sonoma County along the Coast
and Donner Pass along the Sierra on Friday into Saturday morning.


Freezing levels will remain between 9k and 12k feet across the north
today before lowering to 7k and 10k feet by Thursday morning under
the digging trough.


QPF graphics are available at www.cnrfc.noaa.gov/qpf.php



CH

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