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AGUS76 KRSA 091936

HMDRSA



Hydrometeorological Discussion

National Weather Service / California Nevada RFC / Sacramento CA

1235 PM PDT Tue Apr 9 2024



...WARM AND DRY TRANSITIONING TO COOLER AND UNSETTLED FRI-MON...



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



High pressure will move across the region over the next few days 

with dry conditions and warming temperatures above average...peaking 

about plus 5- to plus 15-degF over seasonal norms. As the pattern 

evolves on Thursday with the high pressure moving downstream and a 

system dropping out of the Gulf of Alaska down the west coast along 

with a weak disturbance moving along 30N within 130W...the models 

are hinting at a few showers developing across the crest of the 

southern Sierra and above Shasta Dam. The bigger impacts from the 

approaching system will be expected during the long term beyond 

Friday morning.





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



Models continue to struggle with the timing and track of an upper 

low expected to bring precip to CA Friday and into the weekend. The 

12z GFS has not changed too much since the 06z run still further 

offshore than the ECMWF as it approaches before traveling south into 

the weekend and passing Point Conception just off the coast into 

Sunday evening. The 12z ECMWF has changed quite a bit, picking up 

the speed of the low and carrying it inland around Monterey County 

late Saturday into Sunday and already moving into NV Sunday morning. 

Now, at 00z Monday the 12z GFS has the core of the low just nw of 

Point Conception while the ECMWF has the low over NV and beginning 

to move into UT. For what it's worth, the 12z CMC is closer to the 

ECMWF solution. This is leading to some very different QPF out of 

the two models. For the 24 hrs ending 00z Monday, the GFS has 1-

1.50+" over Santa Barbara/Ventura counties while the ECMWF has 0.10-

0.25". The faster timing of the ECMWF is also leading to big 

differences early on. The 24 hr QPF ending 00z Sunday has a few 

hundredths to 0.30" across the Sierra in the GFS solution vs 1-2" in 

the ECMWF. The ensembles have not come any closer together either 

with spreads in initial precip arrival still between Friday morning 

and Saturday afternoon in both the GFS and ECMWF members. The 

ensembles vary in the track of the low as well. All this to say, 

there is still a great deal of uncertainty in the QPF for the 

extended.



Given the continued uncertainty, did not make any major changes to 

the morning forecast. The afternoon update consisted mainly of 

previous forecast and blended in the 12z ECMWF/GFS in some 

instances. This resulted in QPF changes on the order of 0.10-0.25" 

over the three day period. Amounts went down across the central 

coast and up in a narrow area from Point Conception northeastward 

through the Sierra. QPF 12z Fri-12z Mon: 0.75-1.50" central coast (1-

2" mountains), 0.50-1.50" Sierra, 0.30-0.80" north coast/valleys, 

0.75-1.25" for coastal Santa Barbara/Ventura counties, and 0.10-

0.30" for the rest of southern coastal CA. Little to no precip over 

se CA.



Freezing levels will lower Friday from nw to se down to 5.5-9 kft 

north of I-80 and 8-11 kft to the south in the afternoon. Lower 

freezing levels will spread along the coast as the low passes down 

to 4.5-6.5 kft west of I-5 and 6.5-10.5 kft to the east Saturday 

morning. These levels will also progress inland the rest of Saturday 

with most of CA down to 4-7 kft Sunday morning and up to 7-10 kft 

towards far nrn/srn CA. By the end of the period the region is 

expected to see freezing levels between 5.5-8.5 kft.





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







Kozlowski/AS



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