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AGUS76 KRSA 291940

HMDRSA



Hydrometeorological Discussion

National Weather Service / California Nevada RFC / Sacramento CA

1240 PM PDT Fri Mar 29 2024



...A LARGE SURFACE/UPPER LOW WILL TRAVEL ALONG THE COAST TODAY INTO 

THE WEEKEND BRINGING WIDESPREAD PRECIP AND ISOLATED TSTORMS WITH 

LINGERING SHOWERS PERSISTING INTO MON AM...

...HIGH PRESSURE WILL DRY CONDITIONS OUT EARLY NEXT WEEK BEFORE 

ANOTHER SYSTEM RETURNS PRECIP CHANCES MID WEEK...



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



The two upper lows have become one and now a surface/upper low is 

currently spinning offshore to the sw of Cape Mendocino. Radar 

imagery shows the low sending precip into the Bay Area/central coast 

and through the valley into the Sierra. The low is also drawing 

moisture towards the southern CA coast. Observations report about 

0.25-0.50" of precip over the past 6 hours with locally higher/lower 

amounts around the Bay Area. Not much has changed regarding the 

overall pattern and forecast the next few days since this morning. 

The low will continue to travel southward offshore the rest of today 

and tonight sending moisture into coastal soCal and refocusing 

moderate/heavy precip along the coastal mountains from Monterey to 

Ventura counties. Precip will continue throughout Saturday, though 

diminishing across soCal some by the afternoon as the moisture plume 

exits to the south. It is worth noting that the 12z run of the ECMWF 

is showing a heavier band of precip just offshore of srn CA Saturday 

night into Sunday morning as the core of the low moves by. Six hour 

QPF in that heavy band is on the order of 0.75-1.50" in each time 

block from 00z-18z. Meaning even a subtle shift in the position of 

the low closer to the coast around that time could more than double 

the amount of precip than what is currently in the forecast. 



A secondary low is still anticipated to form Saturday evening over 

NV progressing into UT Sunday morning resulting in another surge of 

precip over NV. This as the offshore low passes by Point Conception 

and continues to bring precip to coastal soCal. The rest of Sunday, 

the area will be situated under a long positively tilted trough 

stretching from offshore of Baja all the way to MT/WY. This will 

keep scattered showers and isolated thunderstorms possible the rest 

of the near term. Thunderstorms possible along the central coast/Bay 

Area this afternoon/evening as well with more widespread chances for 

Saturday/Sunday.



The afternoon forecast was a combination of the previous forecast 

and the latest WPC guidance. This resulted in changes generally 

between a few hundredths and 0.30" across the region. The exception 

being a decrease of 0.50-1" over the Big Sur coast, particularly in 

the late afternoon evening period of tonight likely due to drier 

trends in the higher res models that carry precip out of that area a 

bit quicker than before. QPF through 12z Mon: 2-4.50" Big Sur Coast, 

2.50-5.25" Transverse Range, 0.75-2.50" Sierra, 1.50-2.50" coastal 

soCal, 0.50-1.75" Bay Area/central coast, 1-2" NV mountains, 0.25-1" 

down the valleys lower elev areas of NV (higher Sierra foothills), 

and 0.10-0.50" for ne/se CA.



Freezing levels generally 3.5-6.5 kft north of Point Conception rest 

of today becoming 4.5-6.5 kft over the weekend. Levels will begin to 

rise nw to se into Monday as high pressure moves in. Freezing levels 

along nrn/cntrl coastal CA 6.5-10 kft lowering inland to 5-6 kft 

across NV and interior CA.





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

A few showers will linger across southern CA as the base of a 

positively tilted upr trof moves out of the area on Monday. An 

offshore upr ridge will nudge from the eastern Pacific toward the 

Pacific Northwest to northern CA...generating dry north to northeast 

flow across the region for later Monday into Tuesday. But this 

feature will be short-lived as it gets pushed downstream of the west 

coast as a disturbance moves over the northeast Pacific on its way 

to the Pacific Northwest and northern CA on Wednesday. Light precip 

will fall along the CA/OR border area and far northern NV...along 

with near the crest of the northern/central Sierra. Freezing levels 

down near 5000- to 6000-feet will start to increase as the upr ridge 

moves overhead...peaking later Tuesday from 10000- to 12500-feet. 

Then as the cooler airmass moves in with the s/wv trof...these will 

fall to 2500- to 6000-feet across northern CA...but still be in the 

range of 7000- to 11500-feet ahead of the cold front on early 

Thursday across much of NV and central/southern CA.





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







AS/Kozlowski



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