Area Forecast Discussion
Issued by NWS San Joaquin Valley, CA

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FXUS66 KHNX 221925
AFDHNX

Area Forecast Discussion
National Weather Service Hanford CA
1225 PM PDT Tue Jun 22 2021

.SYNOPSIS...Temperatures will average close to normal over
much of the district through Friday. There is a slight chance
of afternoon thunderstorms in the mountains and desert Wednesday.
Isolated afternoon thunderstorms are possible over the high
Sierra again Thursday and Friday. Hot weather will return this
weekend and continue through at least next Tuesday.

&&

.DISCUSSION...A noticeably cooler air mass settled into the
central California interior last night. For the first time in
nearly a week, thermometer readings bottomed out in the 50s
prior to daybreak in several locations of the San Joaquin Valley.
This morning`s low temperature of 64 degrees in Fresno was the
lowest minimum temperature at the airport since June 12th. This
morning was the first time since June 15th that the temperature
fell below 70 degrees at Meadows Field airport in Bakersfield.
Temperatures are on track to dip a bit lower in most locations
tonight. High temperatures will trend similarly over the CWA
Wednesday and Thursday.

We can thank a low pressure system that is centered a few hundred
miles west of the San Francisco Bay area for the cool change in
our weather. The models forecast this system to remain anchored
where it is through at least Thursday. During this time, an onshore
flow will keep marine air flowing into the  district. This morning,
that marine layer was nearly 4,000 feet deep at Fort Ord and that`s
not likely to change much during the next 48 hours. What will change,
however, is the wind direction aloft. They are currently southwest,
but will veer to a southerly or southeasterly direction late tonight
and remain southerly through Thursday as the offshore low pivots over
the coastal waters. Some mid level subtropical moisture that is
embedded in the southwesterly flow aloft is currently flowing into
southeastern California. As these high altitude winds veer slightly
during the next 24 hours, we can expect this moisture to be steered
into Kern County and up the spine of the Sierra Wednesday. Although
this moisture is rather shallow, its presence could aid in the
development of a few high based thunderstorms in the mountains and
desert, primarily during the afternoon and evening hours Wednesday.
The focus of afternoon convection will shift out of Kern county
Thursday as the offshore low continues to pivot and forces mid level
moisture northward into the higher elevations of the Sierra. Although
thunderstorms will be very isolated during mid to late week, few if
any will bring measurable rain and instead a threat of dry lightning.
When you consider how extremely dry fuels currently are, any cloud to
ground lightning strike could easily ignite a fire over the higher
terrain. While the chance is slim that this will occur, it`s still
worth mentioning.

On Friday, the offshore low is forecast to weaken, move inland and
become rather diffuse as an upper level ridge begins to build back
over California. By then, our refreshing onshore flow will be shut
off, and the air mass over the central California interior will
start warming up again. The ensembles forecast the high pressure
ridge to strengthen over the Golden State in the 4 to 7 day period.
This will lead to a major warm up and unfortunately a return of
widespread triple digit heat in the San Joaquin Valley, lower
foothills and the Kern County desert. We`ll notice it as early as
Saturday. The heat will really get turned up Sunday and Monday and
continue through next Tuesday, during which time Excessive Heat
Warnings are a good possibility. The table below this discussion
shows the probability that the temperature will reach 105 degrees
in the Sunday through Tuesday period for select airport sites.
Inyokern has at least a 60 percent chance of reaching 110 degrees
each of these days!  So enjoy the cool change while it`s here. The
heat will come back with a vengeance this weekend.

            PROBABILITY OF MAX TEMPERATURE OF 105 DEGREES

             AIRPORT       JUN 27     JUN 28     JUN 29
               MCE           28%        35%        31%
               MAE           33%        44%        39%
               FAT           43%        60%        54%
               HJO           42%        56%        48%
               BFL           42%        55%        50%

&&


.AVIATION...
VFR conditions can be expected throughout the central CA interior
for at least the next 24 hours.

&&

.AIR QUALITY ISSUES...
None.


&&

.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.html for additional information
an/or to provide feedback.

&&

.HNX WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

synopsis...Durfee
public/aviation/fw...Durfee
PIO/IDSS...BS

weather.gov/hanford


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