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AGUS76 KRSA 021533

HMDRSA



Hydrometeorological Discussion

National Weather Service / California Nevada RFC / Sacramento CA

830 AM PDT Tue Apr 2 2024



...HIGH PRESSURE DOMINATES TODAY...

...COOLER AND UNSETTLED WEATHER FOR THE LATTER HALF OF THE WEEK...



.METEOROLOGICAL CONDITIONS (SHORT TERM: TUE AM - FRI AM)...



Dry conditions on tap for much of today as a positively tilted upr 

ridge extends from off the CA coast to northeast across the interior 

of the Pacific Northwest up into west-central Canada. A polar system 

has crossed the northern Pacific and is now located over the Gulf of 

Alaska...and is expected to dig along the west coast for the latter 

half of the week...promising to bring cooler temperatures and precip 

to much of the region...as the high pressure gets displaced 

downstream.



By this evening and overnight...models are hinting at some scattered 

showers developing above Shasta Dam well ahead of the system with 

light amounts possible. Then into Thursday...as the s/wv trof carves 

out cyclonic flow aloft along the west coast...an area of diffluence 

on the downstream side of the system and a mid-level vort max moving 

through the flow will generate widespread precip in a band generally 

over portions of the upper Klamath River basin...eastern portion of 

the Shasta Lake drainage...and the northeast CA Plateau with totals 

from 0.25- to 0.75-inch (local to 1.00-inch). Also...southwest flow 

in the low to mid levels over the northern/central Sierra will bring 

anywhere from 0.10- to 0.50-inch along the west slope down to about 

the Merced River basin. 



Then for Thursday into early Friday...the system will continue to 

dig southward with the core of the coolest air moving overhead 

across central CA with the best precip focused on the Santa Cruz 

mountains and Big Sur coast along with areas inland over the Sierra 

between the Tuolumne and Kings River basins where totals between 

0.25- and 0.75-inch (local to 1.00-inch) are expected. Also...a band 

of precip on the downstream side of the s/wv trof looks to set up 

over north-central NV back toward the west-central portion of the 

state with 0.25- to 0.50-inch (local to 0.75-inch) possible.



Freezing levels will be elevated today with the high pressure across 

the region...peaking this afternoon from 10000- to 12000-feet ahead 

of the cooler polar airmass expected to encompass the entire region 

later Thursday into early Friday. As the core of the cold air moves 

over the west coast...look for freezing levels to bottom out 

anywhere from 2000- to 5000-feet from northwest to southeast.



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



Upper level trough over the region on Friday and shifting east on 

Friday night with another system along the Pac NW Coast Saturday and 

trough/low moving over Nrn/Central CA Sunday and into Srn Ca Sunday 

night. The trough will bring showers to the region Friday especially 

over Srn Ca and over NV and along the Sierra. Precip tapers off 

Friday night into Saturday between systems and then showers spread 

across the region sunday into Sunday night with the next system. 

There are differences in the models and ensemble members in the 

details including the timing of these systems. The majority of the 

GFS ensemble members still faster in moving the system to the east 

and a little stronger with the next system on Sunday. Enter 

Discussion Here Precip amounts generally around 0.1-0.5 over Srn Ca 

with 0.25-0.75 with local amounts around an inch in the San Gabriel 

Mtns and into San Bernardino Mtns and South into San Diego County 

Mtns and 0.25-0.5 inches over Srn Sierra and 0.1-0.5 with local 

amounts up to .75 inches over Nevada on Friday. Precip amounts 

generally around a tenth of an inch or less with local amounts up to 

a third of an inch over the Smith Basin and Ruby Mtns on Saturday. 

Precip amounts to around a tenth of an inch over Nrn and Central CA 

and NV on Sunday with a few hundredths over Srn CA Sunday night. 



Freezing levels around 2000-3500 ft over CA and around 3000-6000 ft 

(W-E) over NV Friday morning then rising to 3000-4500ft over CA and 

around 4000-5500ft over NV in the afternoon and around 2500-4500ft 

overnight then around 3000-5000 ft over Nrn and Central CA and 4000-

7000 (N-S) over NV and around 6000-8000+ over Srn CA Saturday then 

dropping to around 4000-6000 ft over Srn Ca and NV Sunday night.





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







Kozlowski/Osborne



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