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AGUS76 KRSA 241516
HMDRSA

Hydrometeorological Discussion
National Weather Service / California Nevada RFC / Sacramento CA
715 AM PST Mon Nov 24 2025

...A SYSTEM MOVING IN TO THE PACNW ON THURS MAY BRING LIGHT
SHOWERS TO THE NORTH COAST...
...OTHERWISE DRY CONDITIONS THROUGH THANKSGIVING BEFORE POTENTIAL
FOR ADDITIONAL PRECIP NEXT WEEKEND, LOW CONFIDENCE...

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

A few showers along the north coast this morning as a front sits
across northern CA. Dry conditions for the rest of the region under
an upper ridge. This ridging will dominate the pattern for the
majority of the forecast period steering a couple of approaching
systems to our north into the PacNW. The tail end of a surface low
headed into BC/WA on Thursday is expected to just scrape the nrn CA
border sending light showers into the north coast. Right now looking
at about a tenth of an inch or less. Some uncertainty beyond that.
The GFS has a trough dropping in from the Gulf of Alaska late Friday
forming a closed low west of OR/WA Saturday. This would drop
widespread showers across CA over the weekend. The ECMWF has a much
stronger ridge over the eastern Pacific and a weak embedded shortwave
just offshore of CA riding the eastern edge of the ridge. The ECMWF
solution would keep the region dry. The det CMC is also dry. There
are ensemble members of each model that do have this system for the
weekend. The QPF range at Arcata for Saturday is 0 to 1" out of the
GEFS and 0 to 2" from the ECMWF AIFS. About half of the ECMWF AIFS
members have some precip while the rest are dry. More of the GEFS
members predict precip but overall are showing lower amounts.
Ensemble 500 mb height clusters all have some degree of troughing
but in different relative positions and to varying strengths. All
this to say, confidence in the forecast decreases greatly beyond
Thanksgiving.

Given that enough of the ensembles predict at least something over
the weekend in addition to the det GFS, precip is present in the
latest run of the NBM for Saturday. Blended this in with WPC which
was dry for the morning issuance to show at least a little QPF. The
QPF right now is a tenth of an inch or so across the Sierra and less
than a tenth for the north coast and parts of coastal srn CA. Expect
these amounts to change over the coming days as hopefully the models
will converge on a solution.


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.

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



AS

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