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AGUS76 KRSA 081544
HMDRSA

Hydrometeorological Discussion
National Weather Service / California Nevada RFC / Sacramento CA
745 AM PST Fri Nov 8 2024

...MAINLY DRY THROUGH SATURDAY...
...OPPORTUNITIES FOR PRECIP RETURN NEXT WEEK...

.METEOROLOGICAL CONDITIONS (SHORT TERM: FRI AM - MON AM)...

A deep upr low is spinning in the vicinity of the 4-Corners this
morning...while broad cyclonic flow exists over the eastern Pacific.
In between...a narrow wavelength upr ridge extends north-northeast
from near 30N/130W into northern CA and the Pacific Northwest. This
overall pattern will bring another day of dry conditions to the
region.

By Saturday...a s/wv trof moving through the cyclonic flow over the
eastern Pacific will sharpen as it moves over the coastal waters and
then shows signs of splitting along the west coast. This will limit
any precip mainly to the immediate coast from about Cape Mendocino
northward with a few hundredths of an inch at best. However...this
system will open the door to a more impressive disturbance making
its way toward the west coast later Sunday into Monday. Right
now...precip looks to spread across northwest CA and southwest OR
late in the forecast period with the majority falling after Mon 12Z.


.METEOROLOGICAL CONDITIONS (LONG TERM: MON AM - THU AM)...

Periods of precipitation possible early-mid next week, especially
over Srn OR and Nrn CA as a couple systems move through. Models
continue to vary on how far south the trough will dig on Monday (EC
farther south than GFS) leading to uncertainty in the southern
extent of precipitation. PW plume around 1.1 inches, ahead of the
cold front,  along the Nrn CA coast Sunday night/early Monday
morning and drops south to around the Bay Area by around noon and
weakens off the Central CA coast in the afternoon. The GFS dominated
Cluster (total 41% of ensemble members- Canadian 35%, GFS 77% of
members, EC 22% of members) on the 24 hr QPF 50th Percentile
Clusters ending 00Z Tuesday keep precip mainly around the I-80
corridor and north and highest amount around 2.5 inches for Smith
Basin and up to an inch for the Shasta Mtns and Nrn Sierra. A third
of the Ensemble members (50% Canadian- 20% GFS and Ec 34%) shows
higher precip amounts and precip spreading south down along the
Central CA coast and through the Central Sierra and portion of Srn
Sierra with up to 4 inches for the Smith Basin and around Cape Mendo
and up to 2 inches for the Shasta Mtns and the Nrn Sierra. The
forecast is mainly a mix of NBM and WPC which spreads precip along
the Central CA coast and into the Central and  Srn Sierra with
precip amounts around 2 inches for the Smith Basin and 0.5-1 inch
for Shasta Basin and Nrn Sierra through 00Z Tuesday. Showers
possible over Srn OR and Nrn and Central CA and Nrn NV Monday night.
 The trough moves into the Rockies/ Great Basin on Tuesday leaving
the region in between systems for generally dry conditions except
mainly light precip possible over the far north. The next system
drops out of the Gulf of Alaska and along the BC/Pac NW coast on
Wednesday bringing the next chance of precip, mainly to Srn OR and
Nrn CA (mainly along the NW CA coast and into the Shasta Basin) on
Wednesday. The forecast uses a mix of the latest NBM and WPC for
precip amounts around 1.25-2.25 inches for the Smith Basin and 0.3-
0.65 for the Shasta Basin and a third of an inch or less for the nrn
Sierra and Russian Basin.

Freezing levels near the ORCA border around 5500 ft Monday morning
and around 5000 ft in the afternoon. Freezing levels above 9000ft
over the Sierra then drop to 6000-7000ft over the Nrn Sierra  and
7000-8000ft over the Central Sierra Monday afternoon and 5500-6500ft
for the North and 7000-8000ft for Central Sierra Monday evening.
Freezing levels around 5000ft near ORCA border and 5000-7000ft over
Nrn sierra and over Nrn and Central NV on Tuesday morning then
rising to around 7000ft and higher  near the ORCA border and above
8000ft and higher over the Sierra Tuesday night into Wednesday.
Freezing levels drop to around 7000ft bear ORCA border and around
8000-10000ft over nrn Sierra Thursday morning.


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



Kozlowski/Osborne

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