Porterville, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

665
FXUS66 KHNX 131818
AFDHNX

Area Forecast Discussion
National Weather Service Hanford CA
1118 AM PDT Wed Aug 13 2025


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.KEY MESSAGES...

1. As temperatures across the region cool, the Major Heat Risk
in the Mojave Desert will reduce to Moderate today and tomorrow,
before becoming a Minor Risk by this Friday.

2. There is a slight (10-15%) chance for isolated thunderstorms
along the Sierra Nevada crest this afternoon, with the dry
conditions near the ground leading to little rainfall and the
possibility for dry lightning to occur.

3. Minor fire risk with widespread minimum relative humidity
between 15 and 25 percent for the non-desert areas. Minimum
relative humidity expected to be less than 10 percent in the
Mojave Desert with breezy winds in the afternoon to evening.

&&

.DISCUSSION...
The ridge that had been above California for the last few days
has now begun to weaken in earnest as the trough from Canada
makes its way south. This will lead to slightly reduced
temperatures across the region, with the Mojave Desert coming
out of Major Heat Risk and into a Moderate Risk today and into
tomorrow. The Valley can expect mostly a Minor Heat Risk with
some pockets of Moderate mainly around the coastal mountains and
southern Valley. As the trough moves further south, Heat Risk
for much of the region will become Minor as the Valley will see
highs in the mid 90`s with probabilities for triple digits less
than 10%. This trend is expected to continue through the weekend
and into early next week, though a ridge may retrograde west and
cause increasing temperatures once again. This movement may be
influenced by an incoming tropical system in the Atlantic
pushing the ridge west.

Along with the cooling temperatures caused by the weaking ridge
and incoming trough, a small amount of mid-level moisture may
lead to the formation of isolated thunderstorms this afternoon,
with the chances of cell development at 10 to 15% along the
Sierra Nevada crest as well as to the lee of the mountain
range. Due to the low relative humidity over the Sierras this
afternoon, any rain that might fall may then evaporate before it
reaches the ground, which creates the possibility for dry
lightning to strike in any cell that forms. And due to the dry
fuels and low moisture levels, new fire starts are a concern
with any thunderstorm that develops.

There is also a continued minor fire risk for the Valley as low
RH`s of 15 to 25 percent remain consistent in the Valley today.
The deserts will also continue to see low RH`s in the single
digits as well as elevated winds along the slopes. RH`s for the
Valley are likely to improve this Friday and over the weekend as
temperatures cool, though winds are expected to become slightly
breezier as the trough passes through California. Then with the
possible ridge intrusion next week, RH`s are likely to return
to similar values as we will see this afternoon.

&&

.AVIATION...
18Z Update:

VFR conditions are expected in the San Joaquin Valley for the next
24 hours. There is a 10 to 15 percent chance for mountain
obscuring thunderstorms to form this afternoon along the Sierra
Nevada crest from 19Z Wednesday thru 03Z Thursday.

&&

.AIR QUALITY ISSUES...
None

&&

.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.html for additional information
and/or to provide feedback.

&&

.HNX WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

Public/Aviation/Fire Weather....EW
DSS/PIO.........................McCoy

weather.gov/hanford