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AGUS76 KRSA 072108

HMDRSA



Hydrometeorological Discussion

National Weather Service / California Nevada RFC / Sacramento CA

110 PM PST Thu Mar 7 2024



...DRYING OUT INTO FRIDAY...

...A FEW DISTURBANCES AFFECT THE AREA THROUGH EARLY NEXT WEEK...



.METEOROLOGICAL CONDITIONS (SHORT TERM: THU PM - SUN AM)...



General troffing is shifting inland as a positively tilted upr ridge 

noses across the Pacific Northwest. This is generating drier 

northerly flow that should bring an end to the scattered precip 

affecting the region this afternoon. Dry conditions are still 

expected on Friday with a weak system traversing northern areas from 

about I-80 northward on Saturday. Thinking pretty much remains the 

same with minimal changes to the afternoon forecast.





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



A pair of systems are still on track to bring precip to the northern 

portion of the region late this weekend and early/mid next week. The 

first as a surface/upper low from the Gulf of Alaska that will open 

up into a trough Sunday passing across the region west to east 

through Monday morning. The 12z GFS has come better into alignment 

with the arrival timing of precip being early Sunday morning along 

the north coast before spreading inland across nrn CA and southward 

into central CA. There are still differences on the depth of the 

trough with the GFS showing a deeper system compared to the ECMWF. 

The deeper GFS spreads a bit more precip into the Bay Area, but the 

QPF differences are not extreme. The main source of uncertainty for 

this first system is represented in the ensembles. The QPF clusters 

ending 12z Monday are divided into 5 groups showing QPF along the 

north coast ranging from 0.50-1.50" to 1.5-3" in the wettest cluster 

(number 5). 



The second system is expected to bring precip to the north coast 

first Monday evening into Tuesday as another low moves into the Gulf 

of Alaska sending a front towards the PacNW and nrn CA. The upper 

trough will then begin to swing through Tuesday morning exiting into 

the Four Corners in the evening and overnight. The ECMWF remains the 

wetter model for the second system, this is reflected in both the 

12z det run and the ensembles. Looking at the 12z 24 hr QPF 

clusters, the wettest 2 are populated by the ECMWF and CMC 

containing none of the GFS ensembles. The differences in QPF come 

out to 0.25-0.50" along the north coast vs 1.50-3". Given the 

continued uncertainty, stuck mainly with a blend of WPC guidance and 

the latest NBM. Blended in some of the 12z GFS/ECMWF in overlapping 

areas of agreement.



For the total three days, QPF went up by about 0.10-0.30" and 

locally up to 0.50". Highest precip amounts still expected along the 

north coast, over Shasta, and across the northern Sierra. QPF 12z 

Sun-12z Weds: 2-3.50" north coast (3-5.50" Smith Basin/Kings Range), 

1.50-3.50" Shasta, 1-2.50" srn OR Cascades/northern Sierra, 0.50-

1.25" central Sierra, 0.10-0.75" Bay Area/valleys, and a few 

hundredths to 0.30" for much of the rest of nrn CA. 



Freezing levels 4-6.5 kft north of I-80 Sunday morning lowering into 

Monday down to 3-4.5 kft before rising again in the afternoon to 4-6 

kft. Some fluctuation early next week but generally 3.5-6.5 kft 

north of I-80 and 5.5-9.5 kft to the south.







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







Kozlowski/AS



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