Area Forecast Discussion
Issued by NWS Sacramento, CA

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000
FXUS66 KSTO 232200
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
300 PM PDT Fri Jun 23 2017



.SYNOPSIS...
Hot again Saturday except some cooling in the Delta, southern
half of the Sacramento Valley, and Northern San Joaquin Valley.
More significant cooling for the remainder of Interior NorCal
expected Sunday into early next week. Isolated afternoon/evening
thunderstorms possible over the mountains through Sunday.

&&

.DISCUSSION...
Strong high pressure ridging continues over the West Coast keeping
the heat wave going over Interior NorCal. Moderate flow through
the Carquinez Strait with marine layer around 1200 feet has
resulted in some minor cooling in the Central Sacramento and
Northern San Joaquin Valleys, with more significant cooling in the
Delta and Southern Sacramento Valley. Afternoon temperatures
around the Delta and into the Sacramento area running upwards of
5 to 15 degrees cooler and thus will be dropping heat related
products for these areas. Satellite imagery showing some cu/tcu
beginning to develop over southern portions of our Sierra Nevada
attm and may lead to an isolated shower or thunderstorm late in
the day.

Delta breeze expected to continue moderate to strong overnight
into Saturday bringing additional cooling to areas influenced by
it. Remainder of Interior NorCal expected to see similar
temperatures Saturday with excessive heat warning likely to
continue for the Northern and Central Sacramento Valley. High
pressure from the Desert SW builds NE towards the EPAC high,
turning mid level flow more SEly on Saturday. This could extend
the threat of afternoon thunderstorms from the Sierra Nevada to
also include the Coastal Range.

Upper ridging weakens over NorCal Sunday and shifts east as closed
upper low off the CA coast deepens and approaches. This should
help deepen the marine layer and strengthen onshore flow. Some
synoptic cooling will also result and expect around a 3 to 8
degree drop in max temperatures. Threat of isolated afternoon
thunderstorms continues over the Sierra Nevada Sunday and possibly
along the coastal range as some models hint at vort max lifting
across that area in southerly flow aloft.

Cooling continues on Monday as weakening upper troughing shifts
inland over NorCal. Main dynamics look to remain northwest and
north of our CWA for any potential deep moist convection threat.
High temps on Monday forecast to be back in the 90s throughout
the Central Valley.

PCH

&&

.EXTENDED DISCUSSION (Tuesday THROUGH Friday)

Additional cooling expected on Tuesday as weak trough moves
across the area. From Wednesday into Thursday, our CWA will sit
between the trough to our east and high pressure over the Pacific.
With no significant changes in the weather pattern, high
temperatures will range within a few degrees of normal in the
extended forecast. Valley highs will be in the 90s, Delta region
in the 80s, higher terrain in the 70s and 80s. JBB

&&

.AVIATION...

VFR conditions expected at the TAF sites the next 24 hours.
Isolated thunderstorms possible over Sierra this afternoon near
Yosemite. Southwest winds up to 20 kt through the delta...
otherwise winds generally around 6-12 kts for TAF sites.


&&

.STO WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 11 PM PDT Saturday for Central Sacramento
Valley-Clear Lake/Southern Lake County-Motherlode-Mountains
Southwestern Shasta County to Northern Lake County-Northeast
Foothills/Sacramento Valley-Northern San Joaquin Valley-Shasta
Lake Area / Northern Shasta County-West Slope Northern Sierra
Nevada-Western Plumas County/Lassen Park.

Excessive Heat Warning until 11 PM PDT this evening for Central
Sacramento Valley-Northern Sacramento Valley.

&&

$$



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