National Weather Service California Nevada River Forecast Center Department of Commerce National Oceanic and Atmospheric Administration National Weather Service

Printer Version
CNRFC Hydrometeorological Discussion

AGUS76 KRSA 282004
HMDRSA

Hydrometeorological Discussion
National Weather Service / California Nevada RFC / Sacramento CA
100 PM PDT Thu Mar 28 2024

...LINGERING SHOWERS AND ISOLATED TSTORMS TODAY AS A COLD FRONT 
CONTINUES TO MOVE THROUGH CA/NV...
...A LARGE SURFACE/UPPER LOW WILL TRAVEL ALONG THE COAST FRIDAY INTO 
THE WEEKEND BRINGING WIDESPREAD PRECIP AND ISOLATED TSTORMS...

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

Radar imagery continues to show scattered showers across the region 
this afternoon along with some thunderstorms as a cold front passes 
through soCal/NV and troughing takes over the west coast. The 
surface/upper low continue to inch closer to the coast as well while 
the next system develops offshore. Another 0.25-0.75" has fallen 
over the Sierra the past 6 hours with 0.10-0.50" along the north 
coast and through to Shasta. Forecast overall remains on track for a 
surface/upper low to approach the CA coast tonight arriving Friday 
morning. The system will draw in some moisture from the southwest 
funneling into soCal as the low travels south along the coast into 
the weekend. This is expected to produce widespread precipitation 
and isolated thunderstorms Friday/Saturday with the heaviest amounts 
along the central/srn coastal CA mountains, across coastal soCal, 
and over the Sierra. A secondary low is still expected to develop 
over NV/UT late Saturday into Sunday producing additional precip 
over NV.

There haven't been many changes in the 12z model runs compared to 
this morning aside from some subtle shifts in timing/positioning of 
the low. QPF change from this morning over the three day period has 
generally between 0.10-0.50" up or down depending on location. 
Exceptions have been 0.50-1" increase along the Big Sur coastal 
mountains. Ensemble spread is just as wide across coastal soCal as 
this morning with 24 hr QPF ending Sunday morning at San Diego 
ranging between <0.50" to over 3" between the GFS and ECMWF. 

The official forecast was a blend of the latest WPC guidance and the 
12z GFS/ECMWF along with the previous forecast. QPF through 12z Sun: 
1-2.50" CA coast from Sonoma to San Diego, 2-4" Transverse Range, 2-
4.50" central coast mountains, 1.50-3" Sierra, 0.50-1.50" most of 
the rest of nrn CA, 0.25-1" down the valleys, and 0.10-0.50" for 
ne/se CA.

Freezing levels 3.5-5 kft north of I-80 and 4-11 kft to the south 
today with lower freezing levels spreading across the region into 
Friday. Mid Friday morning, expecting freezing levels 3.5-6.5 kft 
north of Point Conception and 5.5-10.5 kft to the south. Most of the 
region will be below 6 kft by Saturday morning with the entire 
region down to 4.5-6.5 kft at the end of the period as the low takes 
over.


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

Minor changes to the afternoon forecast issuance after incorporating 
the latest WPC QPF and NBM as two areas of low pressure move out of 
the area...one over northeast NV and the other crossing the CA/MX 
border area. These two features will be the focal points of the 
precip on Sunday before tapering off. Coastal southern CA and 
northern NV near the I-80 corridor will see the best precip with 
0.25- to 0.75-inch. Freezing levels will range from 4000- to about 
6000-feet from north to south. After the upr trof moves a bit more 
inland...an upr ridge building over the eastern Pacific will nudge 
across the Pacific Northwest and northern CA...which will generate 
dry north to northeast flow aloft. Freezing levels will bump up to 
10000- to 12000-feet. 



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



AS/Kozlowski

$$