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Area forecast discussion
National Weather Service Sacramento California
330 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...
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. Current temperatures range
from the upper 40s and 50s in the mountain valleys with 70s to
lower 80s elsewhere, except current temperatures remain around 90
across the northern 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 County Warning Area 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 25 kt northern Sacramento
Valley and Coast Range. 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

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