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AGUS76 KRSA 041443

HMDRSA



Hydrometeorological Discussion

National Weather Service / California Nevada RFC / Sacramento CA

745 AM PDT Thu Apr 4 2024



...COLD CORE SYSTEM MOVING ACROSS THE AREA TO END THE WEEK...

...TURNING DRIER AND WARMER BY MON INTO TUE...



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



Satellite imagery shows the core of the polar system dropping down 

the west coast is currently located just west of Point Arena this 

morning. Plenty of cold air entrained into the system indicated by 

the cellular clouds diving southward on the backside of the system 

behind the cold front. There is one line of precip associated with 

an initial boundary that is aligned from north-central NV back 

through the southern Sierra...while a secondary boundary that will 

usher in the much cooler airmass is bringing a line of precip to the 

region that arcs from the Eel/Russian River basins back across the 

SF Bay Area down to the Santa Cruz mountains and Big Sur coast. 

Through Thursday...the core of the system will move inland across 

northern/central CA with the best precip focused on an area bounded 

by a line of Cape Mendocino to Alturas to the north...and Point 

Conception to Tehachapi on the southern end. Also...the models 

continue to show the band of precip on the downstream side of the 

upr trof axis across north-central NV back toward west-central NV. 

Overall totals in these areas should be in the range of 0.25- to 

0.75-inch with some localized amounts closer to 1.00-inch (Big Sur 

coast and southern Sierra from the Tuolumne River basin to the Kings 

River basin).



Into Friday...the upr trof axis will swing inland across the region 

while the base of the system crosses coastal southern CA. Best 

totals will be near the southern extent of the system with 0.10- to 

0.33-inch local to 0.50-inch amounts for the central CA coast inland 

toward the southern Sierra...and then coastal southern CA. By the 

evening and overnight hours...the system will move downstream of the 

area across the Rocky Mountain states with a transitory s/wv ridge 

and west to northwest flow aloft moving across the region. This will 

result in drying conditions for much of Saturday. By the end of the 

period...a weak s/wv trof will move through this flow...possibly 

bringing some scattered light precip to areas near the CA/OR border.



Freezing levels this morning have already dropped across the upper 

Klamath River basin and much of northern CA...down to about 2500- to 

3500-feet. Ahead of the system...where the cooler airmass hasn/t 

started to settle in yet...these are still between 6500- to almost 

12000-feet for eastern/southern areas. Once the polar airmass moves 

overhead with the core of the system on early Friday...look for 

freezing levels to bottom out between 2000- and 5000-feet from 

northwest to southeast. Finally...as the s/wv ridge traverses the 

region on Saturday...there will be some rebound of the freezing 

levels from 4000- to 8000-feet across the region.





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



Shower activity, primarily over the mountains of California and 

Nevada is possible on Sunday and into Monday as a s/wv is forecast 

to dig southward over the Forecast area over the weekend. Guidance 

continues to disagree on the exact characteristics of the s/wv, but 

precipitation accumulations are relatively light (<0.10 inches). 

Ridging will then build over the eastern Pacific as the s/wv shifts 

inland on Monday leading to dryer and warmer conditions across the 

forecast region on Tuesday. 





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







Kozlowski/CH



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