034
FXUS65 KPSR 131000
AFDPSR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
300 AM MST THU AUG 13 2026
UPDATE
UPDATED AVIATION DISCUSSION.
KEY MESSAGES
- ISOLATED SHOWERS AND THUNDERSTORMS WILL REMAIN POSSIBLE MAINLY
DURING THE AFTERNOON HOURS TODAY AND FRIDAY WITH THE BEST
CHANCES ACROSS THE LOWER COLORADO RIVER VALLEY.
- NEAR TO BELOW NORMAL TEMPERATURES ARE FORECAST THROUGH FRIDAY
BEFORE HEATING BACK UP OVER THE WEEKEND INTO EARLY NEXT WEEK.
- AN EXTREME HEAT WATCH HAS BEEN ISSUED FOR THE PHOENIX METRO FOR
NEXT MONDAY THROUGH WEDNESDAY.
SHORT TERM /TODAY THROUGH FRIDAY/
SHOWERS CONTINUE TO WIND DOWN ACROSS EASTERN PORTIONS OF ARIZONA
AS DRIER AIR SLOWLY WORKS NORTHEASTWARD INTO SOUTHWEST AND SOUTH-
CENTRAL ARIZONA. THIS ACTIVITY IS EXPECTED TO END JUST BEFORE
SUNRISE WITH LITTLE TO NO ADDITIONAL RAIN CHANCES THE REST OF THE
MORNING. THE MAIN CULPRIT FOR THE WIDESPREAD STORM COVERAGE
YESTERDAY WAS A PACIFIC TROUGH MOVING INTO CALIFORNIA. THE TROUGH
HAS EVEN BRIEFLY FORMED A CLOSED LOW JUST SOUTH OF SAN FRANCISCO,
BUT IT IS ANTICIPATED TO OPEN UP AS IT MOVES NORTHEASTWARD INTO
NEVADA LATER TODAY. THE BROADER UPPER LEVEL TROUGH IS FORECAST TO
REMAIN STATIONARY THROUGH FRIDAY WITH THE MAIN TROUGH AXIS ALONG
AND JUST WEST OF THE CALIFORNIA COAST. THIS WILL KEEP MUCH OF THE
DESERT SOUTHWEST UNDER THE EAST SIDE OF THE TROUGH ALLOWING FOR
THE BELOW NORMAL TEMPERATURES TO PERSIST WITH HIGHS FROM THE UPPER
90S TO THE LOW 100S ACROSS THE LOWER DESERTS.
DESPITE THE DRIER AIR ALREADY STARTING TO WORK IN FROM THE
SOUTHWEST, GUIDANCE SHOWS ENOUGH LINGERING MOISTURE FOR ANOTHER
ROUND OF AFTERNOON ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS
TODAY. A MOSTLY WORKED OVER ATMOSPHERE WILL MAKE IT A BIT
DIFFICULT FOR STORMS TO FIRE THIS AFTERNOON, BUT WITH A DECENT
AMOUNT OF SUNSHINE, SOME RECOVERY IS ANTICIPATED. HREF GUIDANCE
DOES SHOW A NARROW STRIP OF 1000 J/KG OF MUCAPE THIS AFTERNOON
ACROSS THE LOWER CO RIVER VALLEY INTO THE CENTRAL ARIZONA HIGH
TERRAIN WHICH COULD PROVIDE ENOUGH ENERGY FOR A FEW STRONGER
STORMS TO DEVELOP. ALSO CAN'T RULE OUT SOME ISOLATED LATE
AFTERNOON SHOWERS AND WEAK STORMS NEAR OR WITHIN THE PHOENIX METRO
TODAY.
ADDITIONAL DRY AIR IS FORECAST TO MOVE IN ON FRIDAY WITH LOW LEVEL
MIXING RATIOS DROPPING TO 8-10 G/KG ACROSS THE AREA. THE LACK OF
MOISTURE SHOWS IN THE FORECAST MUCAPE DROPPING TO 250-500 J/KG
OVER MUCH OF THE AREA TO AT MOST 500-750 J/KG ACROSS THE LOWER CO
RIVER VALLEY. AS OF RIGHT NOW, WE ARE ONLY EXPECTING A FEW WIDELY
ISOLATED SHOWERS OR WEAK STORMS AROUND THE LOWER CO RIVER VALLEY
AND OVER THE AZ HIGH TERRAIN ON FRIDAY.
LONG TERM /SATURDAY THROUGH WEDNESDAY/
THE WEATHER PATTERN WILL SHIFT OVER THE WEEKEND INTO EARLY NEXT
WEEK AS THE SUBTROPICAL RIDGE ONCE AGAIN BECOMES THE DOMINANT
WEATHER FEATURE ACROSS THE SOUTHWESTERN U.S. THE PACIFIC TROUGH
WILL SOMEWHAT STICK AROUND INTO SATURDAY, BUT IT IS SHOWN TO
QUICKLY LIFT TO THE NORTH BY SUNDAY AS THE RIDGE MOVES BACK IN
FROM THE EAST. FORECAST H5 HEIGHTS RISE FROM 588-590DM ON FRIDAY
TO 591-594DM SATURDAY BEFORE PEAKING AROUND 594-596DM DURING THE
FIRST HALF OF NEXT WEEK.
THE DRY AIR AND INCREASING SUBSIDENCE THIS WEEKEND SHOULD KEEP ALL
BUT A FEW EASTERN ARIZONA HIGH TERRAIN SHOWERS AND STORMS FROM
DEVELOPING. TEMPERATURES WILL WARM UP QUICKLY OVER THE WEEKEND
WITH THE EXPANSION OF THE RIDGE WITH NBM FORECAST HIGHS REACHING
103-106 DEGREES SATURDAY AND 106-109 DEGREES SUNDAY. THE DROP IN
MOISTURE WILL AT LEAST PUSH SURFACE DEW POINTS WELL INTO THE 50S
THIS WEEKEND TO AS LOW AS THE UPPER 40S EARLY NEXT WEEK. THIS WILL
HELP TO KEEP OVERNIGHT LOWS CLOSE TO NORMALS THROUGH THE WEEKEND
BEFORE WE HEAT UP FURTHER NEXT WEEK. ENSEMBLES EVENTUALLY SHOW
THE RIDGE CENTER SHIFTING DIRECTLY OVER ARIZONA BY AROUND MONDAY,
LIKELY STAYING IN PLACE FOR A FEW DAYS. THE INCREASED SUBSIDENCE
FROM THE RIDGE WITH NO MEANINGFUL MOISTURE RETURN HAPPENING EARLY
NEXT WEEK SHOULD KEEP LOWER DESERT POPS BELOW 10% TO AT MOST
10-20% OVER THE FAR EASTERN ARIZONA HIGH TERRAIN.
AS THE MODESTLY STRONG (90-97TH PERCENTILE OF CLIMATOLOGY) RIDGE
SETTLES OVER ARIZONA DURING THE FIRST HALF OF NEXT WEEK,
TEMPERATURES ARE LIKELY TO HEAT UP ENOUGH TO RESULT IN MAJOR
HEATRISK ACROSS PORTIONS OF THE LOWER DESERTS. THE HIGHEST
LIKELIHOOD FOR MAJOR HEATRISK LOOKS TO IMPACT THE PHOENIX METRO
WITH DAYTIME HIGHS AROUND 110 DEGREES AND LOWS AROUND 90 DEGREES
STARTING MONDAY. MORE RURAL LOWER DESERT AREAS SHOULD BENEFIT FROM
OVERNIGHT LOWS WITHIN A COUPLE DEGREES OF NORMALS, BUT WITH
SIMILAR DAYTIME HIGHS. DUE TO THE HIGHER CONFIDENCE, WE HAVE
ISSUED AN EXTREME HEAT WATCH FOR THE PHOENIX METRO, VALID FROM
MONDAY THROUGH WEDNESDAY.
AVIATION
UPDATED AT 1000Z.
SOUTH CENTRAL ARIZONA INCLUDING KPHX, KIWA, KSDL, AND KDVT:
THE MAIN AVIATION CONCERN WILL BE THE POTENTIAL FOR ISOLATED
CONVECTION THIS AFTERNOON INTO THE EARLY EVENING. VCSH, WITH
PERHAPS ISOLATED VCTS, MAY POP ONCE AGAIN BY 21-22Z THIS
AFTERNOON, BUT CHANCES TO SEE ANYTHING AT THE TERMINALS IS ONLY
AROUND 20%, SO NOTHING MORE THAN A MENTION OF VCSH IN THE TAFS
FELT WARRANTED AT THIS TIME. OUTSIDE OF ANY REMAINING RAINFALL
INFLUENCES, AND PERIODS OF VRB CONDITIONS OVERNIGHT, WINDS ARE
EXPECTED TO FOLLOW FAMILIAR DIURNAL TRENDS WITH PERHAPS AN EARLIER
THAN USUAL SOUTHEASTERLY SWITCH THIS EVENING.
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:
NO MAJOR AVIATION CONCERNS ARE EXPECTED OVER THE NEXT 24 HOURS.
OUTSIDE OF PERIODS OF VRB CONDITIONS, WINDS WILL FOLLOW FAMILIAR
DIURNAL TRENDS. SOME ISOLATED CONVECTION MAY POP AROUND THE REGION
THIS AFTERNOON, BUT NO DIRECT IMPACTS ARE ANTICIPATED AT OR IN
THE VICINITY OF THE TERMINALS AT THIS TIME. BKN TO EVEN OVC SKIES
WILL BE COMMON THROUGH MUCH OF THE PERIOD.
FIRE WEATHER
ELEVATED HUMIDITY LEVELS, BELOW NORMAL TEMPERATURES, AND
LINGERING CHANCES FOR SHOWERS AND A FEW THUNDERSTORMS ARE
EXPECTED TODAY BEFORE MUCH DRIER AIR FILTERS INTO THE REGION
FRIDAY INTO THE WEEKEND. AFTERNOON MINRHS OF 30-50% TODAY WILL
DROP TO 20-30% BY SATURDAY AND INTO THE TEENS ACROSS THE LOWER
DESERTS STARTING SUNDAY. OVERNIGHT RECOVERIES WILL REMAIN GOOD TO
EXCELLENT. WINDS WILL REMAIN PREDOMINATELY OUT OF THE SOUTH
SOUTHWEST MUCH OF THE PERIOD WITH OVERNIGHT LIGHT EASTERLY
DOWNSLOPING WINDS OVER THE EASTERN DISTRICTS. TEMPERATURES WILL
WARM BACK TO NORMAL BY SATURDAY AND THEN ABOVE NORMAL STARTING
SUNDAY.
PSR WATCHES/WARNINGS/ADVISORIES
AZ...EXTREME HEAT WATCH FROM MONDAY MORNING THROUGH WEDNESDAY EVENING
FOR AZZ537-540-542>544-546-548-550-551.
CA...NONE.
SHORT TERM...KUHLMAN
LONG TERM...KUHLMAN
AVIATION...WHITTOCK/RW
FIRE WEATHER...KUHLMAN
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