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AGUS76 KRSA 011528

HMDRSA



Hydrometeorological Discussion

National Weather Service / California Nevada RFC / Sacramento CA

830 AM PDT Wed May 1 2024



...LIGHT PRECIP POSSIBLE OVER FAR NORTH TONIGHT INTO THURSDAY AND 

AGAIN ON MONDAY AS DISTURBANCES BRUSH BY TO THE NORTH...



...PRECIP POSSIBLE OVER SRN OR AND NRN CA FRIDAY AFTERNOON/NIGHT AND 

SPREADING SOUTH AND EAST SATURDAY WITH SHOWERS POSSIBLE SUNDAY 

MAINLY OVER THE SIERRA INTO NV...



.METEOROLOGICAL CONDITIONS (WED AM - TUE AM)...



Upper level ridge over the Central Eastern Pacific (centered around 

145W) with a trough over the NW U.S. with disturbances moving 

through. A disturbance enters the Pac NW tonight and into the Great 

Basin Thursday brushing by the far north portion of the region for 

periods of light precip possible over the Srn OR Cascades and near 

ORCA border and Nrn NV tonight into Thursday. Moisture plume around 

1.1 inches across the Eastern Pacific and along the Nrn CA coast on 

Thursday. Precip amounts expected to be generally up to a quarter of 

an inch except around half an inch to an inch along far NW CA coast 

and Srn OR Cascades and local amounts in higher terrain of Nrn NV. 

Freezing levels generally around around 7000 ft and higher this 

afternoon and dropping to around 5500-7000 ft over the far north 

tonight into Thursday morning.



Weak ridging over the region Thursday night into early Friday in 

between systems as the trough over Nrn Great Basin shifts to the 

east and an upper level low pressure system approaches the NW Coast. 

This low pressure system is expected to drop down the west coast to 

off the Oregon/ Nrn CA coast Saturday afternoon and then inland 

Saturday night and into the Great Basin on Sunday. Moisture plume 

around 1.1 inches along the Nrn Ca coast Friday shifts south to 

around the Bay Area Saturday morning and around Point Conception 

Saturday afternoon/evening and weakens as it moves south along Srn 

CA Coast Saturday night into Sunday morning. Models are in a little 

better agreement (det GFS farther north than yesterday and EC a 

little farther south and timing a little quicker) than yesterday but 

still variability with the timing and track and strength for lower 

confidence in precip amounts and coverage and timing.  The 24 hr QPF 

50th percentile clusters ending 00Z Sunday show precip over Srn Or 

and Nrn CA but vary in amounts and extent with 2 clusters ( cluster 

1 41 % of members and cluster 2 32% of members) showing precip down 

to around Monterey Bay Area and into Central Sierra with amounts 1.5 

-3 inches along NW CA coast and 1-2 inches over Shasta and into Nrn 

Sierra and Cluster 3 27% of the ensemble members (canadian 30% and 

GFS 27% and EC 26%) keeping precip farther north along the Coast 

from around Pt Arena and north and over higher terrain of Nrn CA and 

into far Nrn NV and lower amounts.  For 24 hr QPF 50th percentile 

clusters ending 00Z Monday around a quarter (23 %) of ensemble 

members have precip mainly confined over Nrn NV and the other 

ensemble members (around 77%) generally having precip along the 

Sierra and east over Nevada and near ORCA border. The forecast 

mainly uses a combination of the latest NBM and WPC with some of the 

previous forecast for Friday into the weekend. Precip may start as 

early as Friday afternoon over the NW CA coast and Srn OR Cascades 

and increase and spread south and east into Nrn NV and possibly 

Central CA Friday night into Saturday as the front moves through the 

region. Precip tapers off Saturday night into Sunday as the moisture 

plume and front shift out of the region and low moves through the 

Great Basin. Highest precip amounts around 1.5-2.5 inches expected 

over the NW CA coast and 1-2 inches over the Srn OR Cascades and 

Shasta Basin and into the Nrn and Central Sierra and Ruby Mtns. 

Freezing levels currently forecast to be around 7000 ft and higher 

Friday afternoon then drop to 3000-5000 ft over Nrn CA Saturday and 

around 5000-7000 ft over Central CA Saturday afternoon and 3000-5000 

ft over Nrn and Central CA and 4000-6000ft over Nrn and Central NV 

Saturday night and rising to around 4000-6000 ft over Nrn CA and 

6000-8000 ft over Central CA and NV on Sunday. Another disturbance 

moves into the Pac NW and brushes the far north portion of the 

region on Monday for a chance of light precip over the far north. 

Freezing levels generally around 7000 ft and higher on Monday except 

around 4000-6000ft for the far north. 



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







Osborne



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