425
FXUS66 KHNX 072030
AFDHNX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HANFORD CA
130 PM PDT MON SEP 7 2026
KEY MESSAGES
1. HEAT ADVISORY ISSUED FOR THE SAN JOAQUIN VALLEY, SIERRA
FOOTHILLS AND WEST SIDE HILLS ALONG THE COASTAL RANGE.
2. MEDIUM TO HIGH PROBABILITY (70 TO 80 PERCENT) FOR TRIPLE-
DIGIT HIGHS IN THE SAN JOAQUIN VALLEY THURSDAY.
3. DECREASING CONFIDENCE IN PRECIPITATION WEDNESDAY. MEDIUM
PROBABILITY (40 TO 50 PERCENT) FOR MEASURABLE RAINFALL IN THE
SIERRA NEVADA.
DISCUSSION
A GRADUAL WARM-UP BEGINS TODAY ACROSS CENTRAL CALIFORNIA IN THE
WAKE OF A CUT-OFF LOW PRESSURE SYSTEM. THE CENTER OF THIS SYSTEM
IS CURRENTLY LOCATED OVER WESTERN MONTANA AND WILL CONTINUE TO
TRACK EASTWARD OVER THE NORTHERN GREAT PLAINS OVER THE NEXT FEW
DAYS, ALLOWING A HIGH PRESSURE RIDGE TO BUILD IN OVER THE
WESTERN UNITED STATES IN ITS PLACE. AS WITH MOST AREAS OF HIGH
PRESSURE, THIS SYSTEM IS DRIVING THE WARMING TREND THE LOCAL
AREAWILL EXPERIENCE THROUGH MIDWEEK. BY WEDNESDAY, WIDESPREAD
MODERATE HEAT RISK WILL ENCOMPASS THE SAN JOAQUIN VALLEY, SIERRA
FOOTHILLS, AND WEST SIDE HILLS ALONG THE COASTAL RANGE; NBM
ENSEMBLE GUIDANCE GIVES A 50 TO 60 PERCENT PROBABILITY FOR HIGHS
TO EXCEED 100 DEGREES. TEMPERATURES WILL PEAK ON THURSDAY, WITH
PROBABILITIES FOR TRIPLE-DIGITS PUSHING TO 70 TO 80 PERCENT IN
THE VALLEY AREAS. MEANWHILE, THERE IS A 60 TO 70 PERCENT
PROBABILITY FOR VALLEY LOWS TO EXCEED 70 DEGREES, AND SIMILAR
PROBS FOR GREATER THAN 75 DEGREES IN THE FOOTHILLS, PROVIDING
LESS RELIEF AT NIGHT. A HEAT ADVISORY HAS BEEN ISSUED FOR THE
LOWER ELEVATIONS OF THE CENTRAL VALLEY AS A RESULT, VALID FROM
10 AM WEDNESDAY, SEPTEMBER 9TH THROUGH 10 PM THURSDAY, SEPTEMBER
10TH.
PREVIOUS ITERATIONS OF THE FORECAST HIGHLIGHTED THE POTENTIAL
FOR TROPICAL MOISTURE TO TRACK OVER CENTRAL CALIFORNIA FROM THE
REMNANTS OF TROPICAL STORM MARIE. HOWEVER, MORE CONFIDENCE IS
BEING PLACED IN THE HIGH PRESSURE BUILDING FURTHER WEST,
RESULTING IN THE AFOREMENTIONED MOISTURE LARGELY REMAINING OFF
THE COAST. THERE REMAINS A 40 TO 50 PERCENT PROBABILITY FOR
MEASURABLE RAINFALL (>0.01"), AND 30 TO 40 PERCENT FOR A WETTING
RAIN (>0.10") IN THE SIERRA NEVADA AROUND MOUNT WHITNEY AND NEAR
MOUNT PINOS. HOWEVER, ALL OTHER LOCATIONS OF CENTRAL CALIFORNIA
HAVE LESS THAN A 10 PERCENT PROBABILITY FOR ANY PRECIPITATION.
IN THE LATTER PORTION OF THE WEEK AND INTO THE WEEKEND, ENSEMBLE
CLUSTER ANALYSIS SUGGESTS A ROBUST TROUGH WILL SCRAPE NORTHERN
CALIFORNIA, RESULTING IN COOLER WESTERLY FLOW ACROSS CENTRAL
CALIFORNIA. THIS PATTERN WILL BRING TEMPERATURES SIMILAR TO
THIS PAST WEEKEND, WITH JUST A 30 TO 40 PERCENT PROBABILITY TO
EXCEED 90 DEGREES NEXT SUNDAY IN THE SAN JOAQUIN VALLEY.
AVIATION
VFR CONDITIONS EXPECTED 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
HEAT ADVISORY FROM 10 AM WEDNESDAY TO 10 PM PDT THURSDAY FOR
CAZ300>317-319-321.
PUBLIC/AVIATION...MCCOY
WEATHER.GOV/HANFORD
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