Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 251010
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
310 AM PDT Wed Apr 25 2018

.SYNOPSIS...
Mainly dry and warm this week except for a chance of a few
afternoon showers or thunderstorms near the Sierra Crest. Cooler
weather Friday into the weekend with increasing chances for
mountain showers and thunderstorms.

&&

.DISCUSSION...
Skies are clearing out as the initial band of high clouds shifts
east. Current temperatures range from the mid 30s to lower 40s in
the mountain valleys to the 50s to lower 60s across the Central
Valley.

Ridge will remain over the area over the next 24 hours as the
offshore low remains quasi-stationary off the coast. Temperatures
will remain warm inland today, but some cooling will begin near
the Delta as onshore flow increases. Cap may weaken enough by late
this afternoon to allow for isolated thunderstorm development
along the Sierra crest.

Low is forecast to shift closer to the coast Thursday and Friday
before moving inland Saturday. Temperatures will cool to average
or below by Friday and Saturday and chances for mainly mountain
showers and thunderstorms will increase.

&&

.EXTENDED DISCUSSION (Sunday THROUGH Wednesday)
Extended models keep upper low over the Pacific Northwest and
Norcal as the prominent weather feature on Sunday. Still enough
instability indicated for isolated thunderstorms in the afternoon.
Upper trough axis should have shifted east of the state by Sunday
so shower and thunderstorm threat should remain confined to the
northeastern half of the forecast area. Cooler air ushered into
the region will keep daytime highs just a bit below normal. Models
differ going into early next week but a slight shower threat
continues at this time over the Sierra Cascade range in the
western most portion of the cyclonic flow of the low. Most areas
should see northerly flow on Monday as upper ridging begins to
build over the eastern Pacific. This should bring up daytime highs
Monday to a few degrees above normal. As usual with upper lows
models struggle with progression of this one. Have left a slight
chance of showers over the northern Sierra on Tuesday but the rest
of the forecast area remains dry. Airmass continues to warm with
highs by Tuesday pushing to more than 10 degrees above normal.
Upper ridging will bring more warming on Wednesday with northerly
flow and subsidence bringing and end to any precipitation threat
over the Sierra.

&&

.AVIATION...
VFR conditions at the TAF sites the next 24 hours. Winds
generally 10 kts or less.

&&

.STO WATCHES/WARNINGS/ADVISORIES...None.

&&

$$


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