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CNRFC Hydrometeorological Discussion

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Hydrometeorological Discussion
National Weather Service / California Nevada RFC / Sacramento CA
130 PM PST Mon Nov 28 2022

...COOLER WITH SHOWERS POSSIBLE OVER SRN OR AND FAR NRN CA AND ALONG 
THE NORTHERN SIERRA AND EAST INTO NRN AND CENTRAL NV INTO TONIGHT 
WITH A FEW SHOWERS POSSIBLE OVER SRN CA MTNS TONIGHT INTO TUESDAY 
MORNING...

...A WETTER SYSTEM BRINGS PRECIP TO SRN OR AND NW CA ON WEDNESDAY 
WITH PRECIP SPREADING SOUTH INTO CENTRAL CA AND EAST INTO NV 
WEDNESDAY NIGHT INTO THURSDAY AND INTO SRN CA LATER THURSDAY INTO 
FRIDAY...

...ANOTHER SYSTEM WILL BRING MORE PRECIP TO MOST OF THE REGION 
OVER THE WEEKEND...

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

Little change to the forecast for tonight into early Tuesday as a 
trough digs over the Great Basin/Western U.S.  Showers with the cold 
front over NE NV and a few showers behind the front near the ORCA 
border continue this afternoon.  Showers are expected to taper off 
tonight into early Tuesday as the trough moves off to the east.  A 
few showers are possible over San Bernardino Mtns and south to San 
Diego Cty mtns with moist onshore flow tonight into Tuesday morning. 
Cooler temperatures are expected into Tuesday with max temperatures 
generally dropping down to near to around 15 degrees below normal 
and up to 25 degrees below normal for NE NV on Tuesday. Freezing 
levels over Nrn NV lowering to around 1000-2000 ft overnight. 
Freezing levels along the Sierra and Central NV lowering to around 
3000-5000 ft tonight. Freezing levels above 8000 ft for the Srn CA 
Mtns tonight into Tuesday morning.

A wetter system drops south along the B.C./ Pac NW coast with the 
associated trough digging out over the Ern Pacific on Wednesday and 
moving inland Thursday into Friday. This system taps into a good 
moisture plume over the Eastern Pacific. Precip begins over the far 
NW CA coast and Srn OR Cascades Wednesday morning and increases and 
spreads south and east across Nrn CA during the day and into 
Wednesday night. Increased amounts along the Nrn CA coast for 
Wednesday for this forecast, especially in Smith and Eel Basins. 
Freezing levels around 4500 ft lower to around 2500 ft over Srn 
Cascades and near ORCA border Wednesday night and 4000-6000 ft over 
the Northern Sierra Wednesday night. Max temperatures near to around 
10 degrees below normal for Wednesday. 

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

Still expecting the initial system to impact the region to swing 
across the region Thursday into Friday with the heaviest precip 
moving across northern CA to start the period before shifting inland 
and southward over the area...while a moisture plume entrained into 
the system ahead of the cold front with PW values near or just above 
1.00-inch intersects the coast. Finally into Friday...the s/wv trof 
will swing inland with the better forcing dissipating across 
southern CA and the highest moisture content air moving south of the 
CA/MX border. 

The next system to move toward the region will arrive from the Gulf 
of Alaska and form a broad system over the northeast Pacific on 
Saturday. This will bring the next round of precip toward the 
region...promising another system with widespread impacts. There is 
less moisture entrained into this system with PW values hovering 
near 0.75-inch along the coast...however...models are varying with 
how the system will interact with a potential secondary higher 
moisture content plume advecting toward central/southern CA. 28/12Z 
GFS is most bullish with this occurring across central CA...while 
the EC is a bit weaker and across southern CA. The CMC really isn/t 
showing this feature at all across the CA coast. Definitely lower 
confidence with this weekend system at this point.