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Hydrometeorological Discussion
National Weather Service / California Nevada RFC / Sacramento CA
830 AM PDT Wed Sep 27 2023

...LIGHT PRECIP OVER NW CA AND SRN OR DURING THE DAY TODAY AS A WEAK 
FRONT MOVES THROUGH...
...AN UPPER TROUGH AND LOW MOVING INTO THE REGION THIS WEEKEND WILL 
BRING SHOWERS FRIDAY INTO MONDAY AND MAX TEMPS BELOW NORMAL BY 10-20 
DEG F OVER THE WEEKEND...

.METEOROLOGICAL CONDITIONS (WED AM - TUE AM)...

A low moving into the PAC NW this morning with trailing end of weak 
front on the NW CA coast this morning. This will bring some light 
precip to NW CA (around Cape Mendocino and north) and Srn Cascades 
this morning. Precipitation will taper off this afternoon. Dry 
conditions expected tonight into the day Thursday with a trough over 
the Western U.S..  

A disturbance approaches the ORCA border Thursday night and deepens 
the trough over the region as the main low moves south into the Pac 
NW on Friday.  The trough continues to deepen over the region on 
Saturday with a closed low forming Saturday night and over the 
region Sunday and shifting to the southeast on Monday as high 
pressure builds into the northern region from the Eastern Pacific. 
Precipitation may start as early as Thursday night over NW CA coast 
(around Cape Mendocino north) and along the Srn Or Cascades. Showers 
spread south and east over Srn Or, Nrn CA and NV Friday afternoon 
into night and spreading south into Central CA and along Srn CA 
coast and mountains and over most of NV on Saturday. Isolated 
thunderstorms are possible. Showers mainly along the Sierra and east 
over Nevada on Sunday and decreasing Monday. Light precip possible 
along Srn CA coast and into the mtns on Sunday. Freezing levels 
dropping to around 7000 ft near the ORCA border and around 8000-9000 
ft for the Sierra Saturday and around 7000-8000 ft for the NE 
Plateau and Nrn Sierra and into Wrn NV Sunday.  Highest 
precipitation amounts generally expected along NW CA coast and along 
the Sierra and over higher terrain of NV with 0.5-1.5 inches. The 
trough will also bring cooler temperatures with max temperatures 
generally dropping to 10 to 25 degrees below normal and min temps 
near normal to 10 degrees below normal over the weekend. Nevada and 
Srn CA will still be around 10 to 20 degrees below normal on Monday 
but Nrn and Central CA will warm up to near normal to 10 degrees 
below normal as high pressure builds in. 


Please Note: This product may NOT be routinely updated Friday
through Sunday between Jun 1 and Oct 1. Please refer to
www.cnrfc.noaa.gov/dailyBriefing.php for a graphical summary of
weather and hydrologic conditions.