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Hydrometeorological Discussion
National Weather Service / California Nevada RFC / Sacramento CA
830 AM PDT Thu May 2 2024

...LIGHT PRECIP POSSIBLE NEAR ORCA BORDER AND NRN NV TODAY AND AGAIN 
ON MONDAY INTO TUESDAY AS DISTURBANCES BRUSH THE FAR NORTHERN 
PORTION OF THE REGION...

...COOLER WITH MORE WIDESPREAD PRECIP OVER SRN OR AND NRN CA FRIDAY 
AFTERNOON/NIGHT AND SPREADING SOUTH AND EAST SATURDAY WITH SHOWERS 
POSSIBLE SUNDAY MAINLY OVER THE SIERRA AND OVER NV AS AN UPPER 
LEVEL LOW PRESSURE SYSTEM MOVES THROUGH THE REGION...

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

Upper level trough over the North west U.S. with a disturbance 
moving through Pac NW and into the Great Basin and weak ridging off 
the west coast ahead of a low pressure system coming down from the 
Gulf of Alaska today. Precipitable water plume aimed near the ORCA 
border this morning with about an inch PW off far NW CA coast (12Z 
MFR sounding 0.78 inches, above normal for this time of year). Light 
precip near the ORCA border and over far Nrn NV this morning will 
continue today and taper off overnight as the disturbance shifts to 
the east and weak ridging moves over the region. Precip amounts 
generally around a third of an inch or less but local amounts up to 
half an inch possible. Freezing levels around 5500-7000 ft over the 
far north and above 7000 ft elsewhere today into tonight. 

The low pressure system moving down from the Gulf of Alaska 
approaches the Pac NW and Nrn CA coast on Friday with the cold front 
moving southeast through the region Friday night into early Sunday 
and the moving onshore near the ORCA border Saturday night and east 
into UT/ID region Sunday night.  This system will bring cooler 
temperatures along with widespread precip to Srn OR and Nrn and 
Central CA and most of NV along with a slight chance of 
thunderstorms. Moisture plume around 1.1 inches along the NRn CA 
coast Friday afternoon/evening drops to around the Bay area Saturday 
morning and around Point Conception Saturday afternoon/evening and 
down into Baja Sunday morning. Increased precip amounts (generally a 
tenth to around a half an inch) over Nrn and Central CA and NV for 
Friday night into Saturday night. Precip will start over the NW CA 
coast and Srn OR Cascades Friday afternoon (although light precip 
possible NW CA coast Friday morning) and increase and spread south 
and east into Nrn NV and Central CA Friday night into Saturday as 
the front moves through the region with some showers possible over 
Srn CA and NV Saturday night into early Sunday. Precip tapers off 
Saturday night into Sunday as the moisture plume and front shift out 
of the region and low moves through the Great Basin. Precip amounts 
for Friday night through Sunday night around 2-3 inches for the NW 
CA coast and 1.5-2.5 inches for the Nrn and Central Sierra and 1-2 
inches for the Srn OR Cascades and Shasta Basin and over higher 
terrain of Nrn NV including the Ruby Mountains and 0.5-1.5 inches 
for the Srn Sierra and  0.5-1 inch for the Russian Basin and into 
Central CA coast and 0.3-1.25 inches for the Sacramento Valley and a 
few hundredths to around a half of an inch for SJ Valley. Freezing 
levels around 7000 ft and higher Friday afternoon then drop to 3000-
5000 ft over Nrn and Central CA behind the front Saturday into 
Saturday evening and 4000-6000ft over Nrn and Central NV Saturday 
night.  Freezing levels rising to around 4000-6000 ft over Nrn CA 
and 6000-8000 ft over Central CA and NV on Sunday. A shortwave 
trough moves into the Pac NW and brushes the far north portion of 
the region on Monday into Tuesday for a chance of light precip over 
the far north. Precip amounts expected to be generally a quarter of 
an inch or less on Monday and a tenth of an inch or less on Tuesday.
Freezing levels generally around 7000 ft and higher on except around 
4000-6000ft for the far north Monday and Tuesday. 

Max temperatures generally around normal today and Friday. Max 
temperatures cool to below normal (up to 20 degrees) over most of CA 
and western NV on Saturday behind the cold front and temperatures 
stay near normal to a few degrees above over NE NV and SE CA. Max 
temperatures generally 10 to 25 degrees below normal across the 
entire region on Sunday. Max temps warm up to near normal to 15 
degrees below normal on Monday and Tuesday (with the coolest temps 
in the far north).