Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 201601

Area Forecast Discussion
National Weather Service Sacramento CA
901 AM PDT Tue Jun 20 2017

Extended heat wave continues with widespread highs over 100
degrees and warm nights. Isolated afternoon thunderstorms possible
over the mountains into mid-week.


Made some changes this morning to some of our warning/advisory
products. First, we`ve extended the Heat Advisory and Excessive
Heat Warning for interior NorCal through Friday. Even though our
region will undergo slight cooling on Friday, highs will still be
very hot with little relief from this heat wave. Second, we
upgraded the Fire Weather Watch to a Red Flag Warning. JBB

.Previous Discussion...Clear skies across interior NorCal early
this morning. Current temperatures are running around 3-6 degrees
cooler compared to 24 hours ago and generally range from the upper
40s and 50s in the mountain valleys to the 60s and 70s elsewhere
except for some lower 80s in warmer portions of the Central

Delta breeze has made a very modest return with the marine layer
now around 1K ft deep. This will help keep valley readings close
to Monday`s with Delta perhaps a few degrees cooler.

Very weak trough along with lingering mid/upper level moisture
combined with daytime heating over the higher terrain will lead to
more isolated late-day thunderstorms over the NorCal mountains
today and Wednesday.

High pressure strengthens again Wednesday into Thursday and will
suppress the Delta Breeze leading to warmer temperatures. It will
also likely limit thunderstorms to the Sierra south of Tahoe. In
addition, north winds will set up in the valley, especially on the
western side on Wednesday and Thursday. Those winds, coupled with
dry conditions will enhance fire weather concerns.

Some record highs are listed below.
Record Highs...........Tuesday....Wednesday..Thursday....Friday
Redding City...........109(1961)..108(1961)..109(1970)..109(1925)
Redding Apt............107(2001)..110(1992)..107(2006)..111(2006)
Red Bluff..............110(1970)..110(1962)..111(1970)..112(2006)
Sacramento Exec........109(1961)..111(1961)..106(1968)..105(2006)



A NW to SE orientated long wave ridge in place over NorCal
through the weekend with a weak short wave trough that passes
through on Sunday which may bring instability to the area. At the
least, temperatures will cool as a Delta breeze looks to develop
late this weekend. Monday and Tuesday continue the cooling trend
and onshore flow as the longwave ridge shifts into the Great Basin
and a longwave trough works its way closer to the coast. JClapp



VFR conditions expected at the TAF sites the next 24 hours. SW
gusts 15 to 25 kts in the Delta. Potential isolated thunderstorms
over Coastal Range in Glenn county this afternoon. JClapp


Heat Advisory until 11 PM PDT Friday 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 from 1 PM Wednesday to 11 PM PDT Thursday 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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