Onyx, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

240
FXUS66 KHNX 042317
AFDHNX

Area Forecast Discussion
National Weather Service Hanford CA
417 PM PDT Sun May 4 2025

.UPDATE...
Updated Aviation Section.

&&

.KEY MESSAGES...
1. Isolated to scattered showers and thunderstorms will
develop this afternoon and last into the early evening hours,
although mainly over the mountains.

2. Drying and warming return by the middle of next week with well
above normal temperatures. Widespread Valley temperatures reaching
90 degrees expected by Friday.

&&

.DISCUSSION...
Upper low continues to track across Central/Southern California
as ensemble mean upper-air analysis has it over Yuma, AZ early
this evening. Until then, wrap around energy will allow for the
development of convective showers across a good portion of the
Central California Interior. Ensembles are placing the best
instability across the Sierra Nevada (from near Noon to around 6
PM PDT) and taper off probability of thunder to less than 10%
over the lower foothills. The San Joaquin Valley has the lowest
probability of thunder today, but, the easterly flow may allow a
storm to reach into the eastern portion of the valley near the
Highway-99 corridor. In addition to the unsettled conditions,
the upper low is also keeping temperatures below seasonal normal
as Probability of Exceedance (PoE) of reaching 79 degrees is
below 40% outside of Merced. Therefore, will expect cool
conditions ahead of the next ridge pattern.

Monday will be a transition period as lingering effects from the
traveling upper low will still affect Central California.
Ensemble mean upper-air analysis places the upper low near the
Four Corners area on Monday with minimal instability able to
reach the Southern Sierra Nevada Monday afternoon. At that
point, ensemble instability over the San Joaquin Valley is near
zero with Probability of Thunder between 10%-15% across the
Sierra Crest from Kern to Fresno Counties during the afternoon
hours. By Tuesday, the upper low is across the Mid-west and
ridging will than take hold of the West Coast. A warming trend
this week with lead toward max temperatures reaching the 90s by
Friday. With each passing day, PoE of reaching 90 degrees goes
up by 20% and reaches 80%-90% on Friday. Therefore, confidence
is high in having the first widespread 90 degree day on Friday,
May 9th. Snow-melt from warm temperatures will allow for cloud
development during the ridge pattern as PoE of measurable
precipitation remains below 10% each day. By next Sunday, with
high uncertainty, ensemble hint toward another disturbance
entering the region for another round of unsettled conditions.

&&

.AVIATION...
00Z Update:
Thunderstorm activity expected through 03Z Monday over the
higher terrain of the Sierra Nevada. A 5%-10% chance of
thunderstorms reaching the eastern side of the San Joaquin
Valley during the same time exist. Otherwise, VFR conditions are
expected for the next 24 hours in much of the San Joaquin
Valley. Areas of mountain obscuration IFR as scattered showers
with high elevation snow expected over the Sierra through 06Z
Monday.

&&

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

&&

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

&&

$$

Public/Aviation....Molina

weather.gov/hanford