Herndon, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

999
FXUS66 KHNX 290506
AFDHNX

Area Forecast Discussion
National Weather Service Hanford CA
1006 PM PDT Wed May 28 2025

.UPDATE...
Updated aviation section.

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.KEY MESSAGES...
1. A Heat Advisory is in effect for the San Joaquin Valley,
Kern River Valley, lower Sierra Foothills, and West Side Hills
valid from 11 AM Friday through 7 AM Sunday.

2. Widespread Moderate to Major Heat Risk is expected across
the lower elevations of the region.

3. Relative humidity will gradually decrease through the week as
temperatures warm. Widespread 15 to 20 percent minimum RH is
expected across the San Joaquin Valley, and as low as 5 to 10
percent for the Kern County Desert and Mountains.

4. Mountain thunderstorms are possible Wednesday afternoon,
with potential for additional storms on Sunday.

&&

.DISCUSSION...
Ridge pattern over the west today as temperatures approach the
90s this Wednesday. While a weak trough will slow down the warm-
up, the Central California Interior is on track to reach the
century mark by the end of the week. In the meanwhile, enough
weak instability exist across the Sierra Nevada and extending
down toward Yosemite that afternoon convection will once again
pop-up across the mountains. A Heat Advisory is in effect for
Friday and Saturday before a cool-down occurs next week.

While a trough will flatten the current ridge pattern over the
west, its effect over the region will be minimal. The next
trough pattern on Thursday will only support a slow-down of
temperatures as minimal change will occur from Wednesday to
Thursday. Probability of Exceedance (PoE) of reaching 90 degrees
today sits between 50% and 80% across the San Joaquin Valley.
On Thursday, PoE of 90 degrees drops slightly with values
between 45% to 80% before a significant jump occurs on Friday.
At that time the 50% to 80% PoE values now represent the
occurrence of 100 degrees. Even then, PoE values increase
further on Saturday as the range sits between 70% and 95% for
100 degrees. A Heat Advisory in effect for conditions of 105
degree as PoE for those values sits at 20%-40%. Another
disturbance knocks-down temperatures next week as values drop to
or below seasonal normals.

Ensemble mean instability continues to show the Yosemite area
with good values (best mean instability exist over NorCal) down
to just north of Fresno County. Probability of Thunderstorm sits
between 5% and 15% today ahead of the heat wave this weekend.
With a transition to a more westerly wind on Thursday,
Probability of Thunder drops to near zero on Thursday and
remains low during the Friday and Saturday time frame. With a
return to southeast flow aloft on Sunday, ensemble mean
instability returns as Probability of Thunder will once again
see values of 5% to 15% across the Sierra Nevada. By Monday, a
more significant cool-down (and westerly flow) may once again
inhibit convective development across as the district returns to
near normal conditions.

&&


.AVIATION...
06Z Update:

VFR conditions will prevail for the next 24 hours across the
Central California Interior.

&&

.AIR QUALITY ISSUES...
ISSUED:  05/28/2025 14:31
EXPIRES: 05/29/2025 23:59
None.



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.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
and/or to provide feedback.

&&

.HNX WATCHES/WARNINGS/ADVISORIES...
Heat Advisory from 11 AM Friday to 7 AM PDT Sunday for
CAZ300>321-324-332.
&&

$$

public...Molina
aviation....EW

weather.gov/hanford