632
FXUS66 KHNX 121815
AFDHNX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HANFORD CA
1115 AM PDT WED AUG 12 2026
KEY MESSAGES
1. CHANGING WEATHER PATTERNS BRINGING COOLER WEATHER AND THE
NEXT REGIONAL CHANCES FOR RAIN.
2. POTENTIAL FOR THUNDERSTORMS ACROSS THE AREA TODAY, RANGING
FROM 10-15% IN THE SAN JOAQUIN VALLEY UP TO 40% ALONG THE
SIERRA NEVADA CREST.
3. THREAT OF DAMAGING WIND FROM STRONG THUNDERSTORMS ALONG THE
SAN JOAQUIN VALLEY AND SIERRA NEVADAS.
DISCUSSION
A RATHER UNPLEASANT MORNING ALARM GREETED MANY IN VISALIA AND
GREATER FRESNO WITH ISOLATED THUNDERSTORMS THIS MORNING. WE'VE
RECEIVED MULTIPLE PUBLIC REPORTS OF HEAVY RAINFALL,
PARTICULARLY ALONG THE CA-99 CORRIDOR BETWEEN TULARE AND THE
MADERA COUNTY LINE. PRECIPITATION GAUGE DATA CURRENTLY SHOWS
MULTIPLE STATIONS REPORTING SEVERAL HUNDRETHS AN INCH, WITH
GAUGES IN CLOVIS AND TULARE APPROACHING A DECENT WETTING
RAINFALL OF A TENTH AN INCH, AND SEVERAL FOOTHILL GAUGES
BETWEEN FRESNO AND MARIPOSA COUNTY INDICATING SEVERAL TENTHS AN
INCH RAINFALL ALREADY.
THIS AREA OF ISOLATED THUNDERSTORMS HAS SINCE TRACKED OUT THE
VALLEY AND INTO THE FOOTHILLS AND PEAKS OF THE SIERRA NEVADA
ALONG FRESNO COUNTY AND NORTHWARD. NONETHELESS, LATEST
PROBABILISTIC FORECASTING DATA STILL PLACES THE SAN JOAQUIN
VALLEY UNDER A 10-15% PROBABILITY FOR THUNDERSTORMS, WITH BEST
CHANCES BETWEEN BAKERSFIELD AND MADERA. CURRENT ATMOSPHERIC
PARAMETERS ARE INDICATIVE OF TYPICAL MONSOON-LIKE RAINFALL
(ISOLATED, BRIEF THUNDERSTORMS) FOR THE SAN JOAQUIN VALLEY AND
MOJAVE DESERT, WITH MORE WIDESPREAD PROBABILITY FOR
THUNDERSTORMS (30-40%) ABOVE 6,000 FEET AND ALONG THE SIERRA
CREST. WETTING RAINFALL PROBABILITIES, MEANWHILE, ARE STILL
READING BELOW 5% FOR MUCH OF THE FORECAST AREA OUTSIDE THE
SIERRA NEVADA ABOVE 6,000 FEET, WHERE PROBABILITIES ARE AS HIGH
AS 70% THIS AFTERNOON ALONG THE CREST.
WHILE THUNDERSTORM ACTIVITY HAS YET TO INITIATE IN THE MOJAVE
DESERT, CONDITIONS ARE FAVORABLE FOR ISOLATED THUNDERSTORMS,
INCLUDING THE MOJAVE SLOPES. THIS AREA CURRENTLY HAS A 15-20%
PROBABILITY FOR THUNDERSTORMS, WITH DEVELOPMENT STARTING IN THE
AFTERNOON HOURS.
THROUGHOUT THE REGION, DAMAGING WIND GUSTS APPEAR TO BE THE
MOST LIKELY THREAT ASSOCIATED WITH STRONG THUNDERSTORMS. LOWER
LEVEL AIR IS STILL RATHER DRY, EVEN IN PLACES THAT RECEIVED
RAINFALL THIS MORNING. COMBINED WITH IMPRESSIVE MID-ATMOSPHERE
MOISTURE AND DECENT DOWNDRAFT SPEED, ANY STRONG THUNDERSTORMS
THAT DO DEVELOP ARE IN AN IDEAL ENVIRONMENT FOR DRY DOWNBURSTS.
AND FURTHER GIVEN HOW DRY SOILS ARE THIS FAR IN THE SUMMER, ANY
DOWNBURSTS THAT ARE GENERATED IN THE SAN JOAQUIN VALLEY OR
MOJAVE DESERT ARE CAPABLE OF PRODUCING AREAS OF HEAVY BLOWING
DUST, WITH VISIBILITY BELOW ONE-QUARTER MILE. BECAUSE OF THIS
POTENTIAL THREAT, OUR RADAR OPERATIONS WILL BE PAYING KEEN
ATTENTION TO ANY SIGNATURES OF AN IMMINENT WIND THREAT
THROUGHOUT THE AFTERNOON.
AS A SILVER LINING TO TODAY'S INCREASED THUNDERSTORM THREAT,
THE ATMOSPHERE OVER THE FORECAST AREA IS NOT FAVORABLE FOR
TORNADOS OR SEVERE HAIL. REGARDING THE FORMER, LOCAL AND STORM
PREDICTION CENTER GUIDANCE INDICATE POOR CONVECTIVE UPDRAFT
POTENTIAL AND INSUFFICIENT DIRECTIONAL AND SPEED SHEARING OF
WIND ABOVE GROUND FOR DEVELOPMENT OF TORNADIC THUNDERSTORMS.
NEAR GROUND AIR IS ALSO TOO WARM FOR ANY SEVERE SIZED HAIL THAT
MAY FORM TO MAKE IT TO THE GROUND WITHOUT EXPERIENCE
SIGNIFICANT MELTING, ESPECIALLY WHEN COMBINED WITH POOR UPDRAFT
SPEED TO SUPPORT GROWTH OF LARGE HAIL.
AVIATION
VFR CONDITIONS WILL PREVAIL FOR THE NEXT 24 HOURS, THOUGH WITH
SCATTERED TO BROKEN CLOUD COVER ABOVE 10,000 FEET. REGIONWIDE THREAT
OF THUNDERSTORMS, WITH GREATEST PROBABILITY (35-40%) ALONG THE
SIERRA NEVADA CREST UNTIL 03Z THURSDAY. LOWER (10-15%)
PROBABILITIES IN THE MOJAVE DESERT AND SAN JOAQUIN VALLEY. MVFR
TO HIGH-END IFR CONDITIONS POSSIBLE WITHIN THUNDERSTORMS FROM
DECREASED VISIBILITY AND LOWER CLOUD COVER.
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...ND
WEATHER.GOV/HANFORD
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