Area Forecast Discussion
Issued by NWS San Joaquin Valley, CA

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FXUS66 KHNX 201107

Area Forecast Discussion
National Weather Service San Joaquin Valley - Hanford CA
407 AM PDT Sun May 20 2018

.SYNOPSIS...Scattered showers and isolated thunderstorms
can be expected over the higher elevations of the Sierra
each day through Thursday. The threat of isolated showers
or thunderstorms will include the Sierra foothills and the
San Joaquin Valley from Fresno county northward Monday and
Tuesday. Temperatures will trend cooler through Monday then
warm to slightly above normal by midweek.


.DISCUSSION...The weather pattern across central California
will become more complicated during the next 48 hours as some
atmospheric energy feeds into an upper level trough and forms
a closed low over our CWA by late tonight. This low will be
a slow mover and it is not forecast to exit into southern Nevada
until midday Tuesday at the earliest. Until its arrival, today`s
weather will be much like yesterday across the central California
interior with mostly sunny skies, seasonable afternoon temps and
little more than a few pop up thunderstorms over the Sierra.
Otherwise, an onshore flow will continue to bring marine air into
the San Joaquin Valley through this evening. Showers might
continue to develop over the Sierra tonight as the upper level
low approaches from the northwest. Elsewhere, a good deal of mid
level cloudiness will invade the central California interior.

The atmosphere will become increasingly unstable Monday in the
vicinity of this cold core low. In turn, this means there will
likely be an uptick of showers and thunderstorms over the higher
terrain Monday through Tuesday. This not only includes the Sierra,
but also the Kern county mountains and desert and the foothill
regions surrounding the San Joaquin Valley. On the north side of
this closed low, northeast to east winds aloft may steer a few of
these showers and thunderstorms into the San Joaquin Valley
by Monday afternoon and evening, especially north of Tulare
county and Kings county. Even as the center of this low exits
east of our CWA Tuesday, wraparound moisture could still show up
as some light showers or sprinkles in the San Joaquin Valley
through early Tuesday evening.

The models agree on lifting this closed low out of the Great
Basin and into the northern Rockies during midweek with some
short wave ridging aloft moving over central California Wednesday
through Thursday. Dry weather will prevail during this period
with little more than isolated afternoon thunderstorms over the
higher elevations of the Sierra. There is better model agreement
now in the 5 to 7 day period. Both the ECM and GFS now forecast
another rather deep closed low to remain offshore later next week
with an eventual track toward the Pacific Northwest Memorial Day
weekend. This would leave central California under a prevailing
southwest flow aloft (ECM) or continued upper level ridging (GFS).
Both solutions suggest we will remain in a dry weather pattern
during this time.

Temperatures will continue their May zig zagging during the next
7 days. After another seasonably warm day today, high temperatures
will cool sevaral degrees below normal Monday. Tuesday through
Thursday will bring another warming trend with temperatures ending
up a few degrees above normal by Wednesday. Thursday through the
Memorial Day weekend will likely average slightly above normal.
In the warmest locations of the San Joaquin Valley and the Kern
county desert, thermometer readings could top the 90-degree mark
as early as Wednesday.


Isolated thunderstorms with local MVFR/IFR conditions will occur
over the higher elevations of the Southern Sierra Nevada between 19Z
today and 03Z Monday. Otherwise...VFR conditions will prevail across
the Central CA Interior during the next 24 hours.





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 for additional information
an/or to provide feedback.


.HNX Watches/Warnings/Advisories...


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