Area Forecast Discussion
Issued by NWS San Joaquin Valley, CA

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FXUS66 KHNX 211119

Area Forecast Discussion
National Weather Service San Joaquin Valley - Hanford CA
419 AM PDT Sun May 21 2017

.SYNOPSIS...A ridge of high pressure along the coast will
maintain our dry weather and summerlike afternoon temperatures
through Tuesday. Isolated afternoon thunderstorms are possible
each day near the Sierra crest. An onshore flow during mid to late
week will cool temperatures to near normal.


.DISCUSSION...Satellite loops show a weak shortwave trough
tracking through the Great Basin area as it drops down the
frontside of the high pressure ridge located over the northeast
Pacific. This passing trough will have little impact on our
weather other than helping to fire off a few thunderstorms over
the high Sierra zones this afternoon. A significant warming trend
will continue for the next few days as the ridge builds in behind
the trough. This will result in afternoon highs around 10 to 15
degrees above climo, with many locations reaching triple digits by
Monday and Tuesday. Dry conditions will continue with the
exception of the possibility for isolated convection near the
Sierra crest each afternoon.

By Wednesday there will be a break from the unseasonable heat, as
models swing a low pressure system through the Pacific Northwest
and flatten the ridge over us. As heights and thickness decrease
and onshore surface pressure gradients increase, temperatures will
trend downward back to around seasonal averages by the end of the
week. This pattern will also bring increased gusty winds, especially
for the mountain and desert zones of Kern County. We could see
additional thunderstorm development over the Sierra Wednesday with
the developing low pressure system, but otherwise continued dry
through the period.

The warming temperatures for the next few days will cause increased
snow melt in the Sierra and rivers will be running fast and frigid.
We continue to urge people to use caution around the water as these
are dangerous conditions. The latest forecast for the Merced River
at Pohono bridge in Yosemite calls for the river to go above flood
stage of 10 feet by early Tuesday morning and again each morning
through at least Thursday.


Local IFR possible over the Sierra Nevada crest due to mountain
obscurations from isolated thunderstorms during this afternoon and
early evening. VFR conditions are otherwise expected across the
central CA interior during the next 24 hours.


On Sunday May 21 2017... Unhealthy for sensitive groups in
Fresno... Kern... Kings... Madera and Tulare Counties.
Further information is available at



The level of certainty for days 1 and 2 is high.
The level of certainty for days 3 through 7 is medium.

Certainty levels include low...medium...and high. Please visit for additional information
an/or to provide feedback.


.HNX Watches/Warnings/Advisories...


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