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Area Forecast Discussion
Issued by NWS San Joaquin Valley, CA

000
FXUS66 KHNX 200810
AFDHNX

Area Forecast Discussion
National Weather Service Hanford CA
110 AM PDT Sat Apr 20 2024


&&

.KEY MESSAGES...
1. High temperatures remain above average through Monday

2. There is a 10 to 15 percent chance of thunderstorms over the
Sierra Nevada in Tulare and Fresno Counties this afternoon.

3. Cooling trend expected Tuesday through Friday

&&

.DISCUSSION...

We have a ridge of high pressure just off the Pacific coast with a
weak shortwave trough which brought some thunderstorms to the SIerra
Nevada on Friday afternoon sliding southeast and dissipating.
However, the trough impacts can still be seen later today with
the potential of thunderstorms over the Sierra Nevada again this
afternoon. Latest model ensembles are in agreement that the
ridge will move onshore and strengthen a bit over our area while
flattening to our north due to a trough that is going to slide
along the U.S.-Canada border. This ridge has helped warm
temperatures and will continue warming through the weekend until
Monday.

Thunderstorm probability for this afternoon is at about 10 to
15 percent in the Tulare and Fresno county portions of the
Sierra Nevada with CAPE values peaking around 1000 J/kg. Lapse
rates between 500 and 700 mb over the SIerra Nevada are around 7
to 8 C/km which indicates a heavy lean towards instability.
The surface based lifted index is peaking around -5 to -6 C
which is not common for the Sierra Nevada. These parameters
along with the warming temperatures and leftover moisture make
thunderstorms favorable for this afternoon.

Monday is expected to be the warmest day with the best probabilities
for our first 90 degree day of the year. Most locations in the
Valley south of Madera and Merced have a 35 to 50 percent
probability of a high of at least 90 degrees on Monday with the
exception of Reedley. Kern County locations including Delano and
Bakersfield have the highest probability between 45 and 50
percent of a high of at least 90.

However, things change on Tuesday as the ridge moves east and a
trough slides in from the Pacific coast bringing cooler
temperatures. Model ensembles are in agreement that this trough will
weaken before being absorbed by a second trough that will move
across the Pacific Northwest Thursday into Friday which will
strengthen the trough. By Friday, there will only be a 20 to 45
percent probability of high temperatures of at least 75 degrees
across the San Joaquin Valley and foothills.

&&


.AVIATION...
Kern County Desert may have less than VFR conditions until 12Z this
morning due to blowing dust. Thunderstorms are possible between
18Z today and 3Z Sunday mainly in the Tulare and Fresno County
portions of the SIerra Nevada. Otherwise, VFR conditions will
prevail for 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.html for additional information
and/or to provide feedback.

&&

.HNX WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 4 AM PDT early this morning for CAZ338.
&&

$$

JPK

weather.gov/hanford