####018004554####
AGUS76 KRSA 111433

HMDRSA



Hydrometeorological Discussion

National Weather Service / California Nevada RFC / Sacramento CA

730 AM PDT Mon Mar 11 2024



...A PAIR OF TROUGHS TO BRING PRECIPITATION TO NRN/CNTRL CA AND NRN 

NV THRU TUES...

...BUILDING HIGH PRESSURE TO RETURN DRY CONDITIONS TO THE REGION MID-

WEEK THRU THE REST OF THE PERIOD...



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



An upper trough that moved through much of CA yesterday is currently 

making its way into NV as a front weakens across nrn/cntrl CA. Over 

the past 24 hours the nrn/central CA coasts and Shasta have seen 

about 0.50-1" of precip with locally over 1" around the Smith Basin 

and up to 1.50" near the Kings Range. Lesser amounts were observed 

away from coastal areas. Radar is showing some light scattered 

showers this morning over nrn CA/NV and around the central coast. 

These showers will continue the rest of the morning as the trough 

heads eastward beginning to exit the area this afternoon. Meanwhile 

another surface/upper low will move into the Gulf of Alaska sending 

an additional round of more moderate precip towards nrn CA and srn 

OR. Initial showers are expected to reach the north coast this 

afternoon spreading inland across nrn CA into the evening as the low 

travels south offshore of BC. The system's trough will begin to head 

inland across the PacNW and nrn CA tonight allowing showers to move 

into nrn NV. The trough will continue to travel eastward across the 

area on Tuesday with slight chances of some thunderstorms over ne NV 

as the trough passes by.



Into Wednesday, the trough will dig itself into an upper low moving 

to the south into ne NV by the afternoon. The low will continue to 

deepen as it heads south through eastern NV settling near srn NV/se 

CA/w AZ by the end of the short term. The system may drop some 

showers across part of NV as it moves through the area. As this 

occurs, a strong upper ridge will be building in over the eastern 

Pacific attempting to shift into the west coast. This will act to 

dry out the rest of the region and rise temperatures/freezing levels 

for much of CA.



Official QPF was a blend of the morning WPC guidance and the latest 

NBM. Best chances of precip still north of I-80 and particularly 

along the north coast over the Smith Basin/Kings Range. Majority of 

the precip is expected in the next 48 hrs. QPF for the short term: 

0.50-1" nrn CA coast Sonoma northward (1-2" Smith Basin/Kings 

Range), 0.75-1.50" Shasta/northern Sierra, 0.10-0.75" central 

Sierra, 0.10-0.50" Bay Area, and a few hundredths to 0.25" or so 

down the valleys.



Freezing levels this morning 3.5-5.5 kft north of I-80 and 5.5-10 

kft to the south fluctuating between 3.5-6.5 kft through tomorrow. 

Higher freezing levels then expected to develop along the CA coast 

as high pressure builds offshore up to 8-11 kft from Cape Mendocino 

southward mid Weds morning. Levels will decrease further inland as 

the low digs across the region the rest of the short term down to 3-

5.5 kft E to W from NV through much of the Sierra and 6-10 kft E to 

W to the coast early Thursday.





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



The overall pattern to end the week will show little movement as the 

flow remains rather amplified across the central/eastern Pacific 

along with the western US. Across CA and NV...an upr ridge will 

reside generally along or just off the west coast stretching 

northward into western Canada...while an upr low spins in the 

vicinity of the lower Colorado River basin. This will generate dry 

north to northeast flow across much of the region with PW values 

near or less than 0.25-inch except over portions of southern CA near 

the upr low that may entrain moisture in upwards of 0.50-inch PW. 

Currently...it looks like any scattered showers that do develop with 

this upr low...will primarily be over the Desert Southwest...but 

there may be a stray shower that moves over far southern NV and the 

southeast CA deserts...amounting to a few hundredths at best. 

Freezing levels will show a sharp gradient across the area from as 

high as 11500-feet northwest to about 6000-feet southeast...with 

some fluctuations up and down depending on the overall position of 

the upr ridge and upr low.





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







AS/Kozlowski



$$