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AGUS76 KRSA 301515

HMDRSA



Hydrometeorological Discussion

National Weather Service / California Nevada RFC / Sacramento CA

830 AM PDT Tue Apr 30 2024



...LIGHT PRECIP POSSIBLE OVER FAR NORTH INTO THURSDAY AS SYSTEMS 

BRUSH BY TO THE NORTH...



...PRECIP POSSIBLE LATER FRIDAY INTO THE WEEKEND BUT UNCERTAINTY IN 

DETAILS ESPECIALLY THE SRN EXTENT OF PRECIP...  



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



Upper level ridge over the Central Eastern Pacific (centered around 

150W) with a trough over the NW U.S.. A disturbance moving into the 

Pac NW this morning then digging into the Great Basin tonight into 

Wednesday morning and another disturbance entering the Pac NW 

Wednesday night and into the Great Basin Thursday.  These 

disturbances will brush by the far north portion of the region for 

periods of light precip possible over the Srn OR Cascades and far NW 

CA coast and Nrn NV today through Thursday.  Precip amounts expected 

to be generally around a tenth of an inch or less each day but up to 

around a quarter of an inch possible over the Srn OR Cascades and 

Wednesday and Thursday. Freezing levels generally around 3000-5000 

ft over Srn OR and far NW CA and around 5500-7500 ft over Nrn NV 

today rising to around 7000 ft and higher Wednesday afternoon and 

dropping to around 5500 ft over Srn OR Cascades on Thursday morning.



Weak ridging over the region 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.  There is model and 

ensemble member variability with the timing track and strength of 

this system for lower confidence in precip amounts and areas 

(especially the southern extent of precip) and timing for late 

Friday into the weekend. The det 06Z GFS is farther south with the 

low off the Nrn CA coast Saturday morning and moving through Central 

CA and into Srn NV Sunday. The det 00z EC has the low off the Pac NW 

coast Saturday morning and brings it inland through the Pac NW and 

Nrn CA Saturday afternoon into Sunday. The 24 hr QPF 50th percentile 

clusters ending 00Z Sunday show a range of solutions from cluster 3 

22% of members (Canadian 5% and GFS 17% and EC 32%) showing only 

light precip over NW CA coast and Srn OR Cascades to Cluster 4 21% 

of the members (canadian 35%, GFS 20% and EC 16%) to precip spread 

across Srn OR and Nrn CA and even into the South Bay Area with 

amount up 1-2 inches along the Nrn CA coast and 0.75-1.5 inches for 

the Shasta Basin and Nrn Sierra and Srn OR Cascades.  The forecast 

mainly uses a combination of the NBM and WPC 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. 

Precip tapers off Saturday night into Sunday. Highest precip amounts 

(around 1-1.75 inches) expected over the NW CA coast and Srn OR 

Cascades and Nrn Sierra.  Freezing levels will vary with the exact 

track of the low and are currently forecast to drop to 3000-5000 ft 

over Nrn CA Saturday and around 5000-7000 ft over Central CA and Nrn 

NV Saturday night and rising on Sunday. 





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







Osborne



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