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AGUS76 KRSA 021559
HMDRSA

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).


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



Osborne

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