Area Forecast Discussion
Issued by NWS San Joaquin Valley, CA

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868
FXUS66 KHNX 202137
AFDHNX

Area Forecast Discussion
National Weather Service San Joaquin Valley - Hanford CA
237 PM PDT Sun Aug 20 2017

.SYNOPSIS...
An area of low pressure will remain anchored off the southern
California coast through Wednesday and bring a chance of mainly
afternoon showers and thunderstorms to the Sierra each day with a
slight chance in the Kern mountains and desert Monday. A dry
westerly flow aloft will return by Thursday.

&&

.DISCUSSION...
Showers and thunderstorms once again developing over the Sierra
Nevada this afternoon as a low pressure system remains along the
southern California coast. The flow aloft is from the east-
southeast. This will bring a slight chance of a shower or a
thunderstorm drifting into the foothills early this evening
before they dissipate. Also cannot rule out storms developing
over the Kern mountains this afternoon and early evening as well.
Debris clouds from the storms will once again move out over the
San Joaquin Valley tonight.

Temperatures this afternoon are running a few degrees cooler than
yesterday thanks to a 2500 foot deep marine layer that allowed
a little cooler air to spill in last night. Temperatures are
expected to be near normal through at least mid week.

Models are in agreement that the trough will remain off the
coast through Tuesday, maintaining an east to southeast mid level
flow. However, the monsoonal moisture that was expected to come up
from the south now is forecast to stay a bit farther east. This
means that it will not make it into the Kern county mountains and
desert tonight, so have removed pops. The moisture will advect
north on Monday, but will only add a little additional moisture to
the Sierra Nevada. Expect the continuation of afternoon showers
and thunderstorms over the Sierra Monday with only a slight
chance in Kern county mountains and desert.

Models indicate a continuation of the southeast flow Monday night
and Tuesday as the low closes off point conception. However, they
also bring drier air into the southern part of the district. This
will keep the threat of thunderstorms to only the Sierra Nevada
through Wednesday.

The models forecast the trough to weaken as it moves onshore over
southern California Wednesday and another trough of low pressure
moves across the Pacific Northwest. A westerly flow aloft should
bring drier and stable conditions Thursday. A slight warming and
drying trend is expected as we go into next weekend as an upper
level ridge builds northwestward from Texas.


&&

.AVIATION...
Isolated to scattered thunderstorms in the mountains until 03z this
evening with a recurrence in the mountains and possibly the Kern
county desert after 20z Monday. Otherwise VFR conditions can be
expected over much of the central CA interior during the next 24
hours.

&&

.AIR QUALITY ISSUES...
Please see SFOAQAHNX for an Air Quality Alert

On Sunday August 20 2017... Unhealthy for sensitive groups in
Fresno... Kern... Kings 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 medium.
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...
NONE.
&&

$$

public...Bean
avn/fw...Durfee
synopsis...Bean

weather.gov/hanford



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