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AGUS76 KRSA 272028

HMDRSA



Hydrometeorological Discussion

National Weather Service / California Nevada RFC / Sacramento CA

130 PM PDT Wed Mar 27 2024



...A COLD FRONT WILL BRING PRECIPITATION TO NRN/CNTRL CA TODAY/THURS 

ALONG WITH ISOLATED THUNDERSTORMS...

...A SURFACE/UPPER LOW TO THEN TRAVEL ALONG THE CA COAST FRI/SAT 

SPREADING PRECIP ACROSS THE REGION BEFORE MOVING INLAND LATER THIS 

WEEKEND...



.METEOROLOGICAL CONDITIONS (SHORT TERM: WED PM - SAT AM)...



A cold front is moving onshore this afternoon as radar imagery shows 

precip spreading inland past I-5 and to the south across parts of 

the northern Sierra. The surface/upper low offshore continues to 

approach the coast displacing an upper ridge inland. TPW imagery 

also continues to show a 0.75-1" PW moisture plume surrounding the 

front across the nrn CA coast and stretching back near HI. Another 

0.50-1.25" have fallen across the nrn CA coast since early this 

morning with 0.25-0.75" inland to Shasta. The front will continue to 

traverse CA from nw to se the rest of today spreading precip into 

central CA and resulting in mountain snow. Isolated thunderstorms 

for nrn CA and the nrn/cntrl Sierra also remain a possibility.

 

Models have the surface/upper low just west of WA/BC Thursday 

morning as another surface low and upper trough develop off the back 

side of the main system. This second shortwave will combine with the 

current low as it heads for nrn CA arriving Friday morning. The 

result will be another surge of precipitation, this time more 

focused along the central and soCal coasts as the low moves south 

just offshore of CA. The low will also drag additional moisture 

northward sending it towards coastal soCal Friday into Saturday. Not 

much has changed in the forecast pattern wise since this morning, 

but models have trended a little wetter along parts of the 

central/soCal coast and through to the valleys/Sierra for the short 

term. These fluctuations may continue as models dial in on the exact 

track of the system and how close it gets to the coastline. 



The afternoon forecast was a combination of WPC guidance, the 

previous forecast, and the 12z GFS/ECMWF in areas of agreement. QPF 

increased by about 0.10-0.50" in generally with locally higher/lower 

amounts. Highest QPF in the short term expected along nrn/cntrl CA 

coast, Shasta, and across the Sierra. QPF rest of today through 12z 

Saturday: 1-4" Sierra, 1-3.50" Shasta, 1-2.50" CA coast from Ventura 

County northward (2.50-4" Smith Basin), 0.40-1.50" down the valleys, 

and a few hundredths to 0.75" rest of coastal soCal (locally higher 

over mountains).



Freezing levels 4.5-6.5 kft this afternoon north of I-80 and 6-11 

kft to the south. Freezing levels will gradually lower from n to s 

the rest of the week with lower levels spreading across CA/NV. 

Friday morning expecting 3.5-4.5 kft north of I-80 and 4.5-9.5 kft 

to the south. By the end of the short term, forecasting 4-5.5 kft 

for most of the region north of Point Conception and 5.5-9 kft to 

the south (nw to se).





.METEOROLOGICAL CONDITIONS (LONG TERM: SAT AM - TUE AM)...



Still expecting an area of low pressure off the central CA coast and 

another over west-central NV near Tonopah to be the focal points for 

precip as a moisture plume ahead of a sfc cold front moves across 

coastal southern CA. The one area of low pressure off the coast will 

drop southeast past Point Conception and then swing east across the 

CA/MX border area. The other low will move northeast and move out of 

the area near Wendover as the feature weakens. Best precip will be 

on Saturday into early Sunday for coastal southern CA between Los 

Angeles and San Diego (1.00- to 4.00-inches with highest over San 

Bernardino mountains)...and then over much of NV as the "Tonopah 

Low" moves across the state...especially in a deformation axis on 

the north side of the area of low pressure (0.25- to 1.00-inch best 

in vicinity of I-80 over the higher terrain). Freezing levels will 

be from 4000- to 7000-feet from north to southeast on Saturday and 

Sunday. Then as conditions dry out on Monday...high pressure will 

nose toward the Pacific Northwest and northern CA as the upr trof 

moves off toward the east...and freezing levels will rebound to 9000-

to 11000-feet over north and west locations. 





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







AS/Kozlowski



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