Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 250410

Area Forecast Discussion
National Weather Service Sacramento CA
910 PM PDT Mon Jul 24 2017

Slight chance of afternoon and evening showers or thunderstorms
across higher elevations of the interior mountains through
Tuesday. Continued cooler Tuesday with near normal temperatures,
then warmer for the remainder of the week.


Temperatures have been running about 5 to 10 degrees cooler this
evening when compared to last night. The breeze through the Delta
is not overly strong this evening but will at least be persistent
overnight. Thunderstorm activity continue`s to remain to the
northeast and east of the crest and forecast area. Have continued
the slight chance in the Burney Basin for the overnight hours with
activity currently along the county border with Lassen.

Low pressure area over northwest part of California will linger
there for another day or so before slowly moving inland on
Wednesday. Not much change in the weather is expected for Tuesday
with temperatures slightly cooler than todays highs for most
locations. Thunderstorm chances look the greatest north and east
of the CWA but the best chances within the CWA look to be over
Plumas and Shasta Counties.

580 DM upper low approaching the NW CA coast will be main weather
feature for Interior NorCal over the next 48 hours. Satellite
imagery showing much of the CU/TCU that developed over the higher
terrain earlier has dissipated or lead to development east of the
Sierra crest. Marine layer has continued to deepen under
influence of low and flow through the Strait continues at a
moderate strength. Afternoon temperatures are running cooler at
all locations with greatest cooling in Delta influenced areas of
about 7 to 15 degrees.

GFS/NAM/EC similar in keeping upper low quasistationary invof of
the coast Tuesday, filling it slightly. Greater cooling expected
over the forecast area tomorrow with high temperatures forecast
near seasonal normal. Elevated instability progs suggest only a
slight chance for deep moist convection over the higher elevations
of the Coastal range, Shasta, Western Plumas, and Sierra Nevada
in the afternoon/early evening.

Upper low progged to slowly progress inland Tuesday night into
Wednesday, weakening to trough Wednesday night as it pushes ENE of
the forecast area. Potential for any mountain shower/thunderstorm
activity over our CWA looks less likely Wednesday. Temperatures
rebound a few degrees Wednesday as upper low weakens.

Heights increase over the area Thursday as upper ridging from the
Desert SW expands NW towards NorCal. Dry weather expected Thursday
as triple digit heat returns across much of the Central Valley.



High pressure centered over the southwest four corners region
continues to build northwest through the extended period. High
temperatures across the area will be 5-10 degrees above seasonal
normal with valley temperatures hovering near the century mark
through at least Monday. Toward the end of the forecast period,
models disagree on the location of the high pressure center. The
Euro has the high pressure centered over CA and NV whereas the GFS
and Canadian have it centered further east. The latter models
bring some monsoonal convection over the high Sierra Sunday and
Monday, but with model uncertainty I have left precipitation out
of the forecast for now.




VFR conditions the next 24 hours across interior NorCal. Winds
up to 15 kt in the area, except gusts to 30 kt near the Delta and
over higher terrain.



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