Area Forecast Discussion
Issued by NWS San Joaquin Valley, CA

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874
FXUS66 KHNX 222224 AAA
AFDHNX

Area Forecast Discussion...UPDATED
National Weather Service San Joaquin Valley - Hanford CA
324 PM PDT Thu Jun 22 2017

...UPDATED AIR QUALITY SECTION...

.SYNOPSIS...Above normal temperatures will continue across the
area into early next week. Thunderstorms will be possible over the
Southern Sierra Nevada each afternoon and evening through the
weekend.

&&

.DISCUSSION...Large upper ridge centered over AZ continues to
keep much above normal temperatures across our area. Temperatures
are trending 2-5 DEG F higher than yday at this time and are on
track to reach their highest values recorded this year with
temperatures at most locations in the San Joaquin Valley, Southern
Sierra Foothills and Kern County Deserts expected to max out
between 105 and 112 DEG F later this afternoon and approach or set
new daily records. Visible imagery is already indicating
scattered cumulus buildups near and along the crest of the
Southern Sierra Nevada. 18Z WRF indicating CAPES between 2000 and
3000 J/KG and LI`s between -5 and -3 DEG C later this afternoon
near the southern Sierra crest where melting snow will provide a
moisture source for thunderstorm development this afternoon and
early this evening. The upper flow over the southern Sierra Nevada
is expected to be a light offshore flow through early this
evening which could push some of the thunderstorms west toward the
valley facing slopes. One concern is that with light steering
currents today any thunderstorms which do form in the Southern
Sierras will be slow movers and could have the potential to
produce flash flooding. Instability each afternoon and evening
near and along the crest of the Southern Sierra Nevada will
provide for a slight chance of thunderstorms each afternoon and
evening through the weekend and this will be a concern for those
who are hiking or camping in the Southern Sierra Nevada while
escaping the heat over the lower elevations.

The ridge is progged to weaken slightly on Friday which will
allow for a slight cooling trend to take place through Saturday
although temperatures remain well above normal. The ridge then
strengthens on over the weekend which will result in temperatures
climbing back upward some by Sunday. Little change in temperatures
is expected is expected in the Kern County Deserts where the hot
airmass will remain in place and the excessive heat warning will
continue through Sunday in the Kern County Deserts.

Take extra precautions, if you work or spend time outside.
Shelter yourself from the hot sun if possible and schedule
strenuous physical work outside to the early morning or evening
hours. Wear light colored, loose fitting clothing if possible.
Remain hydrated and drink plenty of water. Know the signs and
symptoms of heat exhaustion and heat stroke.

Young children and pets should never be left unattended in
vehicles under any circumstances. Look before you lock! The
temperature inside of a car on a hot day can climb to lethal
levels in a matter of minutes.

With continued well above normal temperatures...significant
Sierra Nevada snow melt will be occuring. This will result in
swift...cold...and very dangerous rivers. Even through it is warm
outside...do not cool off in the river...it is not worth it. Do
not become a statistic.

Beyond this weekend, the medium range models continue to indicate
an upper trough pushing through the PAC NW early next week which
will bring a more pronounced onshore flow and a cooling trend to
our area. However, the models are trending toward the ridge not
flattening as much as advertised earlier. Height/thickness falls
will allow for temperatures to cool to near seasonal normals by
Tuesday.

&&

.AVIATION...Isolated thunderstorms are possible over the higher
elevations of the Southern Sierra Nevada through around 06Z Friday
and are expected to redevelop by 21Z Friday. Otherwise, VFR
conditions will prevail across the central CA interior during the
next 24 hours.

&&

.AIR QUALITY ISSUES...On Friday June 23 2017... Unhealthy for
sensitive groups in Fresno...Kern...Madera and Tulare Counties and
Sequoia National Park and Forest. Further information is
available at Valleyair.org

&&

.CERTAINTY...

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
www.weather.gov/hnx/certainty.php for additional information
an/or to provide feedback.

&&

.HNX Watches/Warnings/Advisories...
Excessive Heat Warning until 11 PM PDT Friday CAZ089>095.

Excessive Heat Warning until 9 PM PDT Sunday CAZ098-099.

&&

$$

public...DS
avn/fw...BSO
synopsis...DS

weather.gov/hanford



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