Area Forecast Discussion
Issued by NWS Sacramento, CA

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000
FXUS66 KSTO 221727
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
1027 AM PDT Thu Jun 22 2017

.SYNOPSIS...
Extended heat wave with widespread highs over 100 degrees and
warm nights through the end of the week. Isolated afternoon
thunderstorms possible over the mountains. Not as hot next week.

&&

.DISCUSSION...
As of 10 am, much of the valley has already warmed into the 90s!
Today will be the hottest day of this heatwave so please find a
way to take care of each other, stay cool and hydrated. No
significant changes to the forecast package this morning, but
aviation discussion was updated.  JBB

.Previous Discussion...Clear skies across interior
NorCal early this morning. Strengthening high pressure and
northerly surface flow has weakened the Delta Breeze and is
resulting in warmer temperatures through much of the Sacramento
Valley.

Breezy northerly flow increases across the area today shutting
off the flow from the Delta by mid to late morning. The strongest
winds will be over the north and west side of the valley. Hotter
temperatures will be the result with record heat again and highs
most likely the hottest of the year for a number of locations. The
high heat, low relative humidity and increased winds will continue
high fire danger for a number of areas.

Thunderstorm chances likely to be limited to the Sierra south of
Lake Tahoe over the next few days.

Hot weather continues across the northern half of the Sacramento
Valley and in the mountains late this week while cooler weather
gradually returns to the Delta and southern Sacramento Valley as
the Delta Breeze returns.

&&
.EXTENDED DISCUSSION (Monday THROUGH Thursday)

Cooling trend continues Monday as the upper level ridge axis
shifts eastward into the Great Basin and an upper trough moves
into the eastern Pacific. Even with signficant cooling, daytime
max temperatures are still expected to come in a few to several
degrees above normal. Stable southwest flow aloft will keep skies
fair over the CWA while a moderate onshore surface gradient brings
an increasing delta breeze. Weak upper trough moves over the west
coast on Tuesday bringing more cooling. Although models differ a
bit, all models keep norcal under stable dry conditions. Extended
models show another weak upper low dropping into the eastern
Pacific around the middle of next week. Under this scenario, there
should be some amplification of high pressure over the western
U.S. and a weakening delta flow. This would bring a slight warming
trend towards the end of the extended period.


&&

.AVIATION...

VFR conditions expected at the TAF sites the next 24 hours.
Isolated thunderstorms possible over the northern Sierra crest in
the afternoon. Northerly winds 15 to 30 kt northern Sacramento
valley and coast range through 6z Friday. Southwest winds 15 to 25
kt through the delta...otherwise winds generally below 15 kt.

&&

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

Red Flag Warning until 11 PM PDT this evening for Central
Sacramento Valley in Glenn, Colusa, Yuba, Northern Sutter, and
Butte County Below 1000 Ft-Eastern Mendocino NF-Eastern Portion
of Shasta/Trinity NF-Lake County Portion of Lake-Napa-Sonoma
Unit-Northern Sacramento Valley to Southern Tehama County Line
Below 1000 Ft-Northern Sierra Foothills from 1000 to 3000 Ft.
Includes portions of Shasta-Trinity and Butte Units-Southeast
Edge Shasta-Trinity NF and Western Portions of Tehama-Glenn Unit-
Southern Sacramento Valley in Yolo-Sacramento Far Western
Placer, southern Sutter and Solano County Below 1000 Ft.

Excessive Heat Warning until 11 PM PDT Friday for Carquinez
Strait and Delta-Central Sacramento Valley-Northern Sacramento
Valley-Northern San Joaquin Valley-Southern Sacramento Valley.

&&

$$


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