Area Forecast Discussion
Issued by NWS San Joaquin Valley, CA

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FXUS66 KHNX 231130
AFDHNX

Area Forecast Discussion
National Weather Service San Joaquin Valley - Hanford CA
427 AM PDT Mon Apr 23 2018

.SYNOPSIS...Dry weather and unseasonably warm afternoon
temperatures can be expected across the central California
interior through midweek. Thursday through Saturday will
trend cooler with an increasing chance of showers and
thunderstorms over the Sierra.

&&

.DISCUSSION...If you live in the San Joaquin Valley, lower
foothills or the Kern county desert, you`ll likely hear the
sound of your air conditioner or swamp cooler turning on
during the next few afternoons. Thermometers will top the ninety
degree mark throughout much of these regions today, tomorrow and
Wednesday. It will also be our longest stretch of 90-degree
weather since late September. In the warmest locations, high
temperatures will be in the mid 90s. By July standards, that
might seem almost refreshing. Normal highs in the San Joaquin
Valley this time of year should only be in the mid to upper 70s.
If it`s any consolation, today, historically, is the earliest
day of triple digit heat in the record books for Fresno and
Bakersfield. That occurred in 1910. Nonetheless, today, as well
as tomorrow and Wednesday will be rather toasty- more typical
of mid June rather than late April. Additionally, our unseasonably
warm weather during the next few days will accelerate snowmelt
over the high Sierra and cause diurnal water rises on streams
and rivers over the higher terrain.

If you`re looking for cooling relief, we advise not venturing
into these rivers as the waters are icy cold and the currents
are dangerously swift. A safer place to cool off would be over
the higher elevations, but even there temperatures will average
well above normal through midweek. Blame it on an upper level
ridge of high pressure. It`s going to amplify over central
California during the next 48 hours before shifting eastward into
the Great Basin Wednesday. Other than some cirrus clouds at times,
skies will be generally clear. Although an isolated thunderstorm
or two could pop up near the Sierra crest Wednesday afternoon, dry
weather will rule.

A cooling trend will begin Thursday and continue into the weekend
as an onshore flow becomes established across central California.
This onshore flow will bring ocean cooled air into the San Joaquin
Valley and lower foothills by Thursday evening/night. Additional
marine pushes should follow Friday through Saturday as a storm
system over the Eastern Pacific inches toward the coast. The
higher terrain will also become cooler during this period while
gusty westerly winds blow through and below the mountain passes.

Otherwise, temperatures will finally cool to seasonable levels
Friday and remain close to normal through the weekend. This is the
only part of the 4-7 day forecast we`re very confident of. The
past several model runs have been inconsistent with the track of
the storm system over the Eastern Pacific later this week.
Yesterday, the GFS was agressively moving this low inland over
central California this weekend while the ECM kept it anchored off
the northern California coast. Today, the models have flip-
flopped. Now the ECM forecasts this closed low to move inland
over central California this weekend while the GFS weakens it and
tracks it into the Pacific Northwest. The GFS eventually develops
a second closed low near the San Francisco Bay area Sunday night
and tracks this low down the California coast next Monday. The
ensembles are leaning toward the ECM solution at this time.

So what does it all mean? Well, if the ECM is right, our weather
will become unsettled Friday into the weekend with a chance of
showers or isolated thunderstorms, especially over the mountains.
This is the scenario we`re favoring now, but it could change if
the models continue to diverge. Otherwise, we should expect a much
cooler change in the pattern in the 4 to 7 day period.


&&

.AVIATION...
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...BSO
synopsis...Durfee

weather.gov/hanford



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