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AGUS76 KRSA 230441
HMDRSA

Hydrometeorological Discussion
National Weather Service / California Nevada RFC / Sacramento CA
730 PM PST Fri Nov 22 2024

...MAIN BAND OF PRECIP AROUND I-80 CORRIDOR AND SOUTH THIS EVENING...
...COLD FRONT CONTINUES MOVING THROUGH CENTRAL CA TOMORROW...
...NEXT ROUND OF PRECIP MONDAY INTO TUESDAY...

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

Updated forcast for tonight into Saturday morning.

Main band of precip ahead of the cold front around the Bay Area and
through Sacramento area and into the Feather and Yuba Basins around
00Z with areas of 1-2.5 inches 18z-00z. Scattered showers behind the
front with precip amounts generally a third of an inch or less 18Z-
00Z. Main band has shifted south to around the South Bay area and
into Big Sur Coast and stretching into the Yuba and American Basins
around 03z. 00Z-03Z precip amounts around 0.2-0.6 with local amounts
up to an inch.  Increased amounts up to 0.75 inches over the South
Bay Area and into the Santa Cruz Mountains and around a tenth for
the Big Sur Coast and stretched precip down into Santa Barbara
County for 00z-06Z.  Front and moisture plume will continue to
shifts south overnight. For 06z-12Z increased amounts up to around
an inch for the Big Sur Coast and over the Srn Sierra (mainly
Tuolumne and SJ Basins). Weakening front and moisture plume
continues to shift south into Srn CA during the day Saturday.
Increased amounts up to a half an inch over the Srn Sierra and up to
about a tenth of an inch over the Santa Ynez and Santa Monica and
San Rafael Mtns from 12Z-18Z.

Snow levels around 4800 ft at Happy Camp and around 6800 ft at
Shasta Dam and on the S-band Snow Level Radar. Freezing levels
falling behind the front to around 4500-5500 ft near the ORCA border
and around 7000-8000 ft in the Nrn Sierra this evening and will drop
to around 3500-5500 ft over Nrn CA and around 6000-8000ft over
Central CA by Saturday morning and 3500-6000ft over Nrn and Central
CA and 6000-12000 ft over Srn CA by Sunday morning.

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

Expect an upper low off the Pac NW coast with a moisture plume off
the central CA coast at the beginning of the period.  As moisture
transport increases on Mon, expect precip rates to increase central
CA.  An uptick in precip rates is expected in far NW CA as well
closer to mid-level forcing combined with onshore (but not as moist
as further south) flow.  Model spread is fairly high in terms of
placement and intensity of precipitation associated with this
system.  Some ensemble members show some heavy amounts still, and a
couple show heavy precip lingering in nearly the same location in
the southern Sierra for an extended period of time. Models show the
plume exiting the region by midweek for the most part, with lots of
spread in this time frame too.  Followed NBM through Mon evening to
try to match the latest guidance, especially with WPC being wetter
on the north coast.  Followed WPC beyond Mon evening.  Overall
changes were slightly drier in the northern Sierra by generally 0.3"
or less and wetter on the central coast and San Joaquin Valley (up
to 0.2") and southern Sierra (0.6-1.0"). Freezing levels are
forecast to range from 4000-6000 ft in far northern CA/NV, 6000-9000
ft central (area of highest precip amounts), and over 10,000 ft
further south.  Little change in freezing level was noted.


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



Osborne/Lerman

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