637
FXUS66 KHNX 211858
AFDHNX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HANFORD CA
1158 AM PDT TUE JUL 21 2026
KEY MESSAGES
1. ANOTHER ROUND OF MONSOONAL MOISTURE WILL BRING CHANCES FOR
THUNDERSTORMS ACROSS THE SIERRA NEVADA CREST THROUGH THE MIDDLE
OF THE WEEK.
2. EXTREME HEAT WATCH ISSUED FOR THE MOJAVE DESERT AND INDIAN
WELLS VALLEY THURSDAY THROUGH MONDAY. MAJOR HEATRISK EXPECTED
WITH AFTERNOON HIGHS 108 TO 112 EACH DAY.
3. HIGH PRESSURE OVER THE REGION WILL MAINTAIN TEMPERATURES
NEAR SEASON AVERAGES FOR THE REMAINDER OF CENTRAL CALIFORNIA FOR
MOST OF THE WEEK.
DISCUSSION
HIGH PRESSURE REMAINS THE DRIVING FORCE BEHIND THE WEATHER
PATTERN AFFECTING CENTRAL CALIFORNIA FOR THE FORESEEABLE FUTURE.
TODAY, THE HIGH IS LOCATED OVER THE GREAT BASIN/FOUR CORNERS
REGION, LEADING TO SOUTHERLY FLOW ACROSS OUR AREA AS WINDS
ROTATE ANTICYCLONICALLY AROUND THE SYSTEM. THIS FLOW ALOFT IS
DRIVING MOISTURE INTO CALIFORNIA FROM THE WARMER TROPICAL
REGIONS, PARTICULARLY FROM THE GULF OF CALIFORNIA. AS THE
MOISTURE ENCOUNTERS THE LOCAL TERRAIN IN THE SIERRA NEVADA, IT
WILL CONDENSE AS IT RISES, RESULTING IN INCREASED CLOUD COVER
OVER THE MOUNTAINS. WARM AIR FROM THE SAN JOAQUIN VALLEY WILL BE
UPSLOPING INTO THE SIERRA DURING THE AFTERNOON, PUSHING THE
MOISTURE HIGHER INTO THE ATMOSPHERE, AND CREATING SHOWERS AND
THUNDERSTORMS ACROSS THE HIGHER ELEVATIONS. FOR TODAY, THERE IS
A 30 TO 40 PERCENT PROBABILITY FOR THUNDERSTORMS TO OCCUR
ACROSS THE SIERRA NEVADA, WITH THESE BEING THE GREATEST
PROBABILITIES OF THE WEEK. GUSTY AND ERRATIC WINDS, LOCALLY
INTENSE RAINFALL RATES, SMALL HAIL, AND CLOUD-TO-GROUND
LIGHTNING ARE ALL THREATS WITH CONVECTIVE DEVELOPMENT. TO THE
SECOND POINT LISTED, THESE STORMS WILL BE ON THE WETTER SIDE,
WITH ENSEMBLE GUIDANCE FROM THE NATIONAL BLEND OF MODELS
EXPRESSING AN 80 TO 90 PERCENT PROBABILITY FOR RAINFALL TO
EXCEED 0.10" THROUGH 5 AM WED. WHILE THE PATTERN WILL REMAIN
MOSTLY UNCHANGED FOR TOMORROW, THUNDERSTORM PROBABILITIES FALL
TO AROUND 20 TO 30 PERCENT.
LATER THIS WEEK, THE RIDGE WILL BEGIN TO SLIDE SOUTHWARD,
CENTERING ITSELF OVER WESTERN TEXAS AND EASTERN NEW MEXICO,
STRENGTHENING OVER CENTRAL CALIFORNIA AND TURNING THE FLOW OUT
OF THE SOUTHWEST. THIS WILL CAUSE WARMER TEMPERATURES TO DEVELOP
ACROSS THE AREA, PARTICULARLY OVER THE MOJAVE DESERT. BEGINNING
THURSDAY, HIGH TEMPERATURES IN THIS AREA WILL BE APPROACHING
110 DEGREES EACH AFTERNOON THROUGH AT LEAST NEXT MONDAY, WITH
MINIMUM TEMEPRATURES PROVIDING LITTLE RELIEF FROM THE HEAT AT
75 TO 80 DEGREES EACH MORNING. BECAUSE OF THIS, AN EXTREME HEAT
WATCH HAS BEEN ISSUED FOR A PORTION OF THE MOJAVE DESERT AND
INDIAN WELLS VALLEY.
IN THE SAN JOAQUIN VALLEY, THE HIGH PRESSURE WILL NOT HAVE AS
LARGE AN IMPACT, WITH AFTERNOON HIGHS REMAINING NEAR SEASON
AVERAGES FOR THIS TIME OF YEAR. EACH AFTERNOON THROUGH MONDAY,
THERE IS A 50 TO 60 PERCENT PROBABILITY FOR TEMPERATURES TO
EXCEED 100 DEGREES IN THE VALLEY AREAS, ALBEIT ON THURSDAY WHEN
THERE IS A 20 TO 30 PERCENT PROBABILITY.
AVIATION
25 TO 50 PERCENT CHANCE OF THUNDERSTORMS OVER THE SIERRA NEVADA
BEGINNING AROUND 17Z AND WILL BE A PROBLEM THROUGH AT LEAST 6Z
WEDNESDAY. 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
EXTREME HEAT WATCH FROM THURSDAY MORNING THROUGH MONDAY
EVENING FOR CAZ337-339.
PUBLIC/AVIATION...MCCOY
WEATHER.GOV/HANFORD
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