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AGUS76 KRSA 251654

HMDRSA



Hydrometeorological Discussion

National Weather Service / California Nevada RFC / Sacramento CA

955 AM PDT Mon Mar 25 2024



...MAINLY DRY CONDITIONS TO START THE WEEK...

...COOLER AND UNSETTLED WEATHER RETURNS TO END THE WEEK...



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



The upr troffing along the west coast this past weekend has shifted 

inland with its axis now generally aligned along the Rocky Mountain 

states. Offshore over the eastern Pacific along 145W or so...an upr 

ridge has built and is nudging its way slowly toward the west coast. 

Across CA and NV...the flow aloft is northwesterly with PW values 

ranging from about 0.25-inch over the Great Basin and 0.50-inch 

along the immediate coast. Weak disturbances moving through this 

flow the 24 to 36 hours will provide just enough forcing to squeeze 

out some scattered showers mainly from the crest of the Cascades and 

Sierra along with points east over NV. Then later Tuesday into 

Wednesday...the upr ridge will slide across the area ahead of the 

next s/wv trof making its way toward the northeast Pacific with a 

moisture plume of approx 1.00-inch PW entrained into the system. 

Precip will start to move onshore along the north coast during the 

morning hours on Wednesday before spreading across much of northern 

CA as the cold front gets pushed southward and inland across the 

area...and the mid-level disturbance moves rotates through the 

cyclonic flow across northern CA before making its way toward the 

interior of the Pacific Northwest and eventually the northern 

Rockies. Best precip amounts on Wednesday will fall from the Eel 

River basin northward to the Smith River basin and then inland from 

the Shasta Lake drainage down across the northern/central Sierra 

with 1.00- to 2.00-inches. Lesser amounts are expected south toward 

central CA as the cold front weakens...the moisture plume 

narrows...and the best mid-level forcing remains to the north. 

Freezing levels on Wednesday will start from 5500- to 8000-feet 

across areas near and north of I-80 with the lowest being across 

northwest CA. After the cold front moves across the region...look for 

these to fall to 3500-feet northwest to 5000-feet along I-80 across 

CA.





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



Expect some lingering light showers across the central CA coast, 

into the Sierra and NE NV along a dissipating front Thu morning, 

while additional post-frontal showers continue further to the north 

associated with weak disturbances and north or NE of an upper jet 

max.  Expect showers to generally decrease through at least Thu 

evening.  Model agreement is decent during this time frame.  Expect 

freezing levels around 3000-4000 ft on the north coast and 4000-6000 

ft in the northern half of the Sierra.



Model agreement is much less regarding the next system expected to 

affect the region to close out the week.  Expect a fairly stacked 

low pressure system to deepen and drop south off the CA coast Fri-

Sat while a front and associated moisture plume bring precip across 

the region.  Models vary widely regarding how much precip remain 

offshore or move inland, as well as with how quickly the main precip 

band will push across the region.  Some deterministic and ensemble 

solutions show a slow progression of fairly heavy precipitation 

across the transverse ranges of southern CA late in the week, while 

others push the band more quickly into SW CA and out of the region. 

The NBM seemed like a reasonable compromise and was used, although 

the potential for higher amounts exists.  Expect freezing levels 

4000-6000 ft in the northern half of the region and 6000-10000 ft in 

the southern half.





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







Kozlowski/Lerman



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