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Hydrometeorological Discussion
National Weather Service / California Nevada RFC / Sacramento CA
830 AM PDT Thu Apr 25 2024

...COOL WITH PERIODS OF SHOWERS AND ISOLATED THUNDERSTORMS POSSIBLE, 
ESPECIALLY OVER THE HIGHER TERRAIN THROUGH FRIDAY... 

...MAINLY DRY AND WARMER OVER THE WEEKEND INTO TUESDAY...

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

Upper level trough continues to move east into the four corners 
region this morning as another shortwave trough and associated front 
approach the Pac NW and Nrn Ca coast.  The trough deepens over the 
region this afternoon into Friday. Two main areas of showers this 
morning with one ahead of the front and shortwave trough along the 
NW CA coast and into Srn Oregon and another group over North Central 
NV. Also, a few showers over Srn Ca and Srn NV with light rain. 
Showers will increase over Srn OR and Nrn CA (mainly along the coast 
and higher terrain) and into NE NV during the day into tonight. Best 
chance of thunderstorms is over Eastern NV today. Precip amounts 
will be variable due to convective nature of showers. Precip amounts 
generally around 0.75-1.25 over far NW CA coast and west slope of 
the Srn OR Cascades and around 0.25-0.75 inches over Nrn NV and 0.1-
0.5 inches over the Nrn Sierra and generally a tenth of inch or less 
along the CA coast and over Srn Sierra and Srn NV and Srn Ca 
mountains. Precip amounts for Friday generally around a quarter of 
an inch or less except locally to around a half an inch mainly in 
the Nrn Mtns including the Srn OR Cascades and Ruby Mtns and along 
the NW CA coast and along the Sierra. Precipitation stretches south 
along the Sierra and into Srn NV and possible a few showers over the 
transverse mtns and into San Diego County Mtns Friday. Thunderstorms 
possible over the Sacramento Valley and Shasta region and alog the 
Sierra and east over Nevada. The trough shifts to the east Friday 
night into the weekend with weak ridging over the region and 
shortwaves to the north approaching the B.C./ Pac NW coast. This 
will bring warmer and mainly dry conditions to the region except 
some light precip possible over the far NW CA coast and west slope 
of Srn OR Cascades over the weekend. More of the ensemble members 
and deterministic GFS and EC keeping the shortwaves farther north 
than yesterdays runs. Although there are a few GFS and EC members 
(16% of total members, 27% GFS and 16% EC) that show a deeper trough 
into the northern part of the region starting Tuesday with others 
delaying it into Wednesday or Thursday. 

Max temperatures near normal to 15 degrees below normal across the 
region this afternoon and similar Friday afternoon. Temperatures 
warm up to near normal for most of the region except around 10 
degrees below normal along NW CA coast Sunday afternoon and warming 
to near normal to 10 degrees above normal over the region on 
Tuesday. Overnight temperatures near normal to around 10 degrees 
above normal tonight decrease to around normal Friday night then 
warming to near normal to 10 degrees above normal Sunday night 
and above normal up to 15 degrees Tuesday night. 

Freezing levels around 5000-7000 ft over Nrn CA and 8000-10000 ft 
for Central and Srn CA and NV this morning and around 4000-6000 ft 
over Nrn CA and 6000-8000 ft elsewhere Friday and rising to around 
6000-8000ft over Nrn CA and 8000 ft and higher elsewhere Saturday 
and 4000-6000ft over far NW CA coast and Srn OR and 7000 ft and 
higher for the rest of the region Sunday into Monday and rising to 
8000 ft and higher across the region Tuesday.