Area Forecast Discussion
Issued by NWS San Joaquin Valley, CA

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FXUS66 KHNX 210030 AAA

Area Forecast Discussion
National Weather Service San Joaquin Valley - Hanford CA
530 PM PDT Fri Jul 20 2018

...updated air quality section...

High pressure continues to move eastward and will cool
temperatures slightly to around normal. Afternoon and early
evening thunderstorms will be possible for the Sierra crest areas
over the next several days. The slight cooling will continue over
the weekend, but by next week high pressure will once again move
into the region and bring a return to much above normal


Air quality in the Yosemite National Park areas and thunderstorms
over the Sierra crest this afternoon and early evening are the
main short term concerns. Spoiler Alert: Longer term concern however,
is the strong ridge retrograding back into our region early next
week and raising temperatures across the region to much above
normal. Back to the short term, scattered showers and
thunderstorms are beginning to develop as of 1 PM courtesy of the
most recent satellite and radar imagery. The thunderstorms will
primarily stay over the crest areas as we have a southerly to
slightly southwesterly flow, due to being sandwiched between the
weak low pressure to the west and the high pressure to the east,
that will direct developing storms north to northeastward. The
main threats from these thunderstorms will be dangerous lightning,
heavy downpours and gusty erratic winds. Some localized flooding
will be possible due to the training of thunderstorms and weak
storm movement. Campers and hikers in these areas should be
vigilant and take adequate shelter if storms approach. Be
cautious of falling tree limbs or branches as winds can suddenly
knock these down onto tents and campers. As the high pressure
moves further east the inversion levels have been slightly
increasing however air quality in many parts of the Yosemite N.P.
and close proximity to the Ferguson fire will continue to suffer
as the inversion will not completely dissipate. As long as the
fire continues to burn, air quality will continue to be an issue.
Once the high pressure builds back in early next week it would
seem likely that conditions would further deteriorate, provided
the source of the smoke is still present. This is definitely not
good for ideally viewing all of the wonderful topographic
treasures that Yosemite has to offer.

As the high pressure once again builds into the region early next
week we will see significant synoptic heating take place and bring
some locations high temperatures well over the century mark. We
have elected to continue the Excessive Heat Watch for the Kern
County desert areas and expanded it to include the SJV,
surrounding foothills and Kern County Mountain areas from Tuesday
until Thursday evening. This will give people several days to
make sure their cooling devices are working well and take
precautions for their work week. Hot temperatures can be deadly.
Now would be a good time to just remind people to never leave
anyone or animals in an enclosed car as temperatures inside a
vehicle can become deadly in just minutes. Also, remember to stay
hydrated and take more breaks from work. (As if many of us
actually needed heat as a reason to do that.) These safety tips
could save your life!


Areas of MVFR visibility in smoke will continue in the vicinity of
the Ferguson Fire in Mariposa County for at least the next 24 hours.
A chance of thunderstorms will be possible over the Sierra Nevada
between 19z today and 04z Saturday. Otherwise, VFR conditions will
prevail over the central California interior during the next 24


Please see SFOAQAHNX for an Air Quality Alert

On Saturday July 21 2018... Unhealthy for sensitive groups in
Fresno, Kern 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 high.

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


.HNX Watches/Warnings/Advisories...
Excessive Heat Watch from Tuesday afternoon through Thursday
evening CAZ089>095-098-099.



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