Area Forecast Discussion
Issued by NWS San Joaquin Valley, CA

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FXUS66 KHNX 202107
AFDHNX

Area Forecast Discussion
National Weather Service San Joaquin Valley - Hanford CA
207 PM PDT Sat May 20 2017

.SYNOPSIS...A ridge of high pressure along the coast will
bring dry weather and Summerlike afternoon temperatures to the
district 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...A profound warming trend is taking place across
the central California interior this afternoon, and it`s only
a preview of what`s to come during the next few days. High
temperatures will be well into the 90s in the San Joaquin Valley,
lower foothills and the Kern county desert Sunday, Monday and
Tuesday. In the hottest locations, thermometer readings will
top the century mark early next week.  If Fresno makes it to
100 degrees in this toasty spell, it will be the first time
since September 19th.

Our Summerlike warmth can be blamed on a strong upper level
ridge of High pressure currently centered over the Eastern
Pacific. The ridge axis will shift westward a bit during the
next 24 hours and allow a weak short wave trough to slip
southward from Idaho into the Great Basin. Although there isn`t
much moisture associated with this feature, it will provide
enough lift for the development of isolated thunderstorms near
the Sierra crest tomorrow afternoon into tomorrow evening.
Once this short wave feature moves into northern Arizona
tomorrow night, the EPAC ridge will build in behind it and
settle over the Golden State early next week. Atmospheric
subsidence associated with this upper level ridge will probably
suppress afternoon convection over the Sierra, but there might
still be enough moisture available from melting snow for
cumulus buildups over the crest Monday and Tuesday. The models
forecast just enough CAPE and 700 mb to 500 mb moisture along
the Sierra crest both afternoons to keep a slight chance of
thunderstorms in the forecast. All in all, dry weather will
prevail under this high pressure ridge.

Additionally, rapidly melting snow over the high Sierra during
the next few days will bring an increase in water levels and
flows on many rivers over the higher terrain. The Merced river
that runs through Yosemite National Park is forecast to crest
just above flood stage late Monday night and again the following
two nights. Folks that might think rivers would be a cool and
inviting escape from Summerlike heat will put themselves in
potential danger as the snow-fed waters will be icy cold and
swift.

The models forecast a collapse of the upper level ridge by
the middle of next week as a closed low develops over the Pacific
Northwest. An onshore flow will become established across central
California Wednesday and will strengthen somewhat during the
latter part of next week as the upper level trough settles
southward into Northern California. Westerly winds will probably
become gusty again through and below the mountain passes of Kern
county and along the west side of the San Joaquin Valley Thursday
through Friday. Otherwise, Wednesday through Friday will be dry
with a refreshing change to seasonably cooler weather.

Memorial Day weekend should be dry with a modest warming trend
as the trough exits into the Great Basin and a short wave ridge
builds into central California.

&&

.AVIATION...
Isolated thunderstorms are possible along the Sierra crest
Sunday afternoon. Othewise, VFR conditions will prevail across
the central CA interior during 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.php for additional information
an/or to provide feedback.

&&

.HNX Watches/Warnings/Advisories...
NONE.
&&

$$

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

weather.gov/hanford


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