Fresno, California Weather Forecast Discussion

891
FXUS66 KHNX 290906
AFDHNX
Area Forecast Discussion
National Weather Service Hanford CA
206 AM PDT Mon Sep 29 2025
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.KEY MESSAGES...
1. Thunderstorms are once again possible this afternoon in the
Sierra Nevada, with a 15-35% chance for development. These
probabilities will be mainly north of Tulare County, and the
highest chances in Mariposa County and Yosemite National Park.
2. A small area of Marginal Risk (at lest 5%) of excessive
rainfall remains today in the mountainous region of Mariposa
County and into Madera County.
3. The next week is expected to be dominated by below normal
temperatures, with the Valley likely seeing highs in the mid to
lower 80`s through this weekend.
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.DISCUSSION...
As of current models, today is the last day with strong chances
for mountain thunderstorms, with a probability of 15 to 35% for
development this afternoon. This is due to an incoming trough
from the Pacific, which will bring in enough energy along the
Sierra Nevada to uplift the remaining moisture into becoming
thunderstorm cells. These cells are most likely to form along
the Sierra Nevada crest north of Kern County from 11am through
8pm. The area with the greatest chance for development this
afternoon is expected in the mountainous portion of Mariposa
County and around Yosemite National Park. This area also has a
Marginal Risk (at least 5%) of excessive rainfall due to this
possibility.
Tomorrow afternoon sees these chances fall off a cliff below
10%, with similar chances on Wednesday, which is due to the
passage of the main front of the trough and the cooler air
behind it will limit uplifting of moisture. Another trough may
come close to our CWA by Thursday, but it is likely to only
clip Yosemite, which will keep thunderstorm chances low. Model
ensembles begin to deviate more by Friday. One ensemble shows a
trough directly over our CWA, which would lead to stronger
chances for thunderstorms, but another ensemble has that trough
further north, which would not affect our CWA nearly as much in
the aspect.
In either case, however, the effect on temperatures will be a
consistent pattern of below normal temperatures throughout the
week, though the actual numbers may fluctuate by a few degrees
over time. This will be caused by consistent troughing through
the week.
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.AVIATION...
12Z Update:
A 15-35 percent chance of thunderstorms from 18Z Monday through
03Z Tuesday will exist across the Sierra Nevada. Ceilings lower
to around 10k feet in spots around 18Z Monday. Otherwise, VFR
conditions expected for the next 24 hours.
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.AIR QUALITY ISSUES...
None.
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.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.
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.HNX WATCHES/WARNINGS/ADVISORIES...
None.
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$$
EW
weather.gov/hanford

NWS HNX Office Area Forecast Discussion