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AGUS76 KRSA 052045

HMDRSA



Hydrometeorological Discussion

National Weather Service / California Nevada RFC / Sacramento CA

1245 PM PST Tue Mar 5 2024



...PRECIP FOCUSES NEAR THE CA/OR BORDER TODAY...

...INCREASING OPPORTUNITY FOR PRECIP ACROSS SOCAL TOMORROW...

...STILL ANTICIPATING A NORTHERN CA SYSTEM THIS WEEKEND...



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



Best precip continues to fall along the north coast where a nearly 

stationary frontal boundary is situated...primarily along the CA/OR 

border stretching eastward. This is associated with a s/wv trof off 

the west coast that is approaching 130W...and broad upr troffing 

extending from a circulation over southern Alberta...with individual 

disturbances moving through the flow. Through the rest of 

today...this boundary will be the focal point for precip with the 

best totals across portions of northern CA and the upper Klamath 

River basin.



Then into tomorrow...the offshore s/wv trof will make its way 

southeast toward Point Conception and eventually the area between 

Los Angeles and San Diego. Models continue to hint at totals from 

0.25- to 0.75-inch along the transverse mountains and then down 

toward the CA/MX border mainly during the afternoon and evening 

hours on Wednesday. 



Finally into Thursday...a positively tilted upr ridge will nose 

across the Pacific Northwest...allowing for conditions to dry out 

with northerly flow setting up across the area.





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



Forecast remains on track with no big changes in the afternoon 

update. Dry conditions expected Friday as a ridge sets up over much 

of the western U.S. Chances of precip then return for the weekend 

thanks to two systems. The first as an upper trough arriving 

Saturday morning bringing showers into the north coast. The trough 

will then move through northern CA/NV the rest of the day as the 

next system approaches. A surface and upper low looks to travel down 

the BC coast into Sunday. There are still timing differences between 

models on when precip will start. The ECMWF remains the faster model 

bringing precip into the north coast Sunday morning while the GFS 

holds off until the afternoon (quicker than the 06z run but still 

behind). The upper trough will then begin to swing inland later 

Sunday and into Monday across the PacNW/nrn CA. The depth of the 

trough is also an area of disagreement with the GFS showing a deeper 

system as it moves inland compared to the ECMWF. The result being the 

ECMWF predicting heavier precip initially Sunday and then the GFS 

predicting heavier precip later on.



For the afternoon package, stuck with a blend of WPC guidance and 

the latest NBM. This amounted to minor changes plus or minus 0.10" 

for the nrn CA coast and about a 0.10-0.20" decrease over the 

northern Sierra. The highest precip amounts still expected along the 

north coast. QPF for the extended: 1-2.50" north coast, 0.50-1.25" 

Shasta, 0.25-0.50" northern Sierra, and a few hundredths to a couple 

tenths for the rest of nrn CA. Freezing levels lowering into 

Saturday with the first system to 4-7 kft north of I-80 and 7-9.5 

kft to the south. Levels to lower further throughout Saturday 

reaching 3.5-6 kft north of I-80 in the evening. Freezing levels 

then generally 3.5-6.5 kft north of I-80 the rest of the extended 

and 5.5-10 kft to the south.







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







Kozlowski/AS



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