854
FXUS65 KPSR 100511
AFDPSR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
1011 PM MST WED SEP 9 2026
UPDATE
06Z AVIATION DISCUSSION.
KEY MESSAGES
- ABOVE NORMAL TEMPERATURES WILL PREVAIL THROUGH THE REST OF THE
WEEK, RESULTING IN WIDESPREAD MODERATE HEAT RISK AND AREAS OF
MAJOR HEAT RISK.
- EXTREME HEAT WARNINGS WILL REMAIN IN EFFECT FOR PORTIONS OF THE
LOWER DESERTS THROUGH THE END OF THE WEEK.
- THUNDERSTORMS CHANCES WILL CONTINUE TO FOCUS OVER SOUTHEASTERN
ARIZONA AND THE EASTERN ARIZONA HIGH TERRAIN, WITH LOW CHANCES
FOR LOWER DESERT STORMS BEGINNING THURSDAY AND SLIGHTLY BETTER
FRIDAY.
- A PATTERN SHIFT BY THE WEEKEND WILL RESULT IN DECREASING
TEMPERATURES AND EVENTUALLY DRYING CONDITIONS FROM WEST TO EAST
ACROSS THE FORECAST AREA.
SHORT TERM /TODAY THROUGH THURSDAY/
SOUTHEASTERLY FLOW ALOFT CONTINUES OVER THE REGION AS THE
SUBTROPICAL HIGH IS NOW CENTERED OVER ARIZONA. THE HIGH WILL PEAK
TODAY WITH HEIGHTS RANGING BETWEEN 594-597 DAM, CONTINUING TO BE
NEAR TO AT THE MAX OF NAEFS CLIMATOLOGICAL PERCENTILE. H5 HEIGHTS
WILL CONTINUE TO BE UNSEASONABLY HIGH, HOWEVER THE POSITIONING OF
THE HIGH WILL CONTINUE TO RETROGRADE FURTHER TO THE SOUTHWEST, AND
WEAKEN/FLATTEN SLIGHTLY BY THE END OF THE WEEK. DESPITE THE
POSITIONING OF THE HIGH, AFTERNOON TEMPERATURES WILL CONTINUE TO
BE 3-7 DEGREES ABOVE NORMAL FOR MID SEPTEMBER. MORNING LOW
TEMPERATURES ARE ALSO BEING AFFECTED AND ARE EXPECTED TO REMAIN
8-10 DEGREES ABOVE NORMAL THROUGH AT LEAST THE END OF THE WEEK,
PROVIDING VERY LITTLE RELIEF FROM THE HEAT DURING THE DAY. A GULF
SURGE LAST NIGHT BROUGHT AN INCREASE IN MOISTURE INTO THE LOWER
DESERTS. THIS CAN ESPECIALLY BE SEEN ON THIS MORNING'S 12Z
SOUNDING WHERE COMPARED TO 24 HOURS AGO PWATS INCREASED FROM 1.47"
TO 1.79" AND MEAN MIXING RATIOS INCREASED FROM 8.5 G/KG TO 13.6
G/KG. THIS INCREASE IS ALSO NOTABLE IN THE MORNING DEW POINTS,
WHERE SC AZ HAD DEW POINTS IN THE MID TO UPPER 60 AND THE WESTERN
LOWER DESERTS WERE EVEN HIGHER IN THE MID TO UPPER 70S. THIS
MOISTURE AND THICK OVERNIGHT CLOUD COVERAGE, KEPT LOWS WELL ABOVE
NORMAL, EVEN SETTING NEW RECORD WARM LOWS BY 3F-6F AT ALL THREE
OF THE CLIMATE CITES (PHOENIX, YUMA, AND EL CENTRO). WITH THE
ABOVE NORMAL HIGH AND LOW TEMPERATURES, IN CONJUNCTION WITH MORE
HUMID CONDITIONS, WIDESPREAD MODERATE TO MAJOR HEATRISK REMAIN
OVER THE REGION, ESPECIALLY OVER THE LOWER DESERT AREAS. DUE TO
THIS THE EXTREME HEAT WARNING REMAINS IN PLACE FOR PORTIONS OF THE
LOWER DESERTS THROUGH THE END OF THE WEEK. SINCE THE REGION HAS
MORE MOISTURE IN PLACE/ HIGHER DEW POINTS THE HEAT WILL BE LESS
MANAGEABLE AND INDIVIDUALS SHOULD TAKE EXTRA CARE WHEN SPENDING
TIME OUTDOORS, AS APPARENT TEMPERATURES WILL BE CLOSER TO
108F-117F, WITH THE HIGH RANGE MOST COMMON ACROSS SW AZ AND SE CA.
WHILE HEAT IS CURRENTLY A DOMINATING TALKING POINT, THUNDERSTORM
CHANCES ARE ALSO WORTH MENTIONING. AS MENTIONED ABOVE, WE HAVE
PLENTY OF MOISTURE IN PLACE OVER THE REGION, AND GFS FORECAST
SOUNDINGS SHOW MUCAPE VALUES BETWEEN 500-750 J/KG LATE TONIGHT
INTO THE OVERNIGHT PERIOD. DURING THAT WINDOW THOUGH CIN WILL
ALSO BE QUITE HIGH (BETWEEN -100 TO -150 J/KG) SO DEVELOPMENT IN
THE LOWER DESERTS REMAINS UNFAVORABLE. THE LATEST CAMS ARE STILL
SHOWING GOOD SIGNAL FOR DEVELOPMENT IN SOUTHEASTERN AZ, AND ARE
TRYING TO SHOW ISOLATED SHOWERS DEVELOPING IN PINAL COUNTY LATE
TONIGHT, ALTHOUGH LIKE THE PAST FEW NIGHTS THIS WILL REMAIN
CONDITIONAL. IN ADDITION, THE HREF SHOWS BETWEEN A 10-30% CHANCE
OF THUNDERSTORMS MOSTLY CONFINED TO THE FAR EASTERN HIGH TERRAIN,
WHILE THE BEST CHANCES REMAIN IN SOUTHEASTERN AZ OUTSIDE OF OUR
CWA, BOTH TONIGHT AND AGAIN THURSDAY NIGHT.
LONG TERM /FRIDAY THROUGH TUESDAY/
THE UPPER LEVEL PATTERN WILL BEGIN TO SHIFT FRIDAY, AS TROUGHING
ENTERS THE NORTHWEST US AND DISPLACES THE SUBTROPICAL HIGH EAST OF
THE REGION THIS WEEKEND. FLOW ALOFT WILL TRANSITION BACK OUT OF
THE SOUTHWEST, ENDING THE BRIEF, MORE TYPICAL MONSOON FLOW PATTERN
EXPERIENCED DURING THE MIDDLE OF THE WORK WEEK TO SOMETHING MORE
AKIN TO A TRANSITION SEASON SETUP. HOWEVER, BEFORE MORE PRONOUNCED
SOUTHWESTERLY DRYING BEGINS IN EARNEST THIS WEEKEND, WEAKER FLOW
ALOFT AND PERHAPS THE BEST MOISTURE PROFILES OF THE WEEK OVER
SOUTH- CENTRAL AZ (NEAR-SURFACE MIXING RATIOS 11-12 G/KG) WILL
PRESENT AN OPPORTUNITY FOR AT LEAST ONE ACTIVE MONSOON
THUNDERSTORM DAY ACROSS THE LOWER DESERTS (IF THE HIGHLY
CONDITIONAL THREAT IS NOT REALIZED ON THURSDAY). KPHX GFS BUFR
SOUNDINGS, WHICH ADMITTEDLY HAVE BEEN VERY SENSITIVE TO SUBTLE
CHANGES IN LOW LEVEL MOISTURE, INDICATE A BALANCE OF CAPE/DCAPE
AROUND 1500 J/KG LATE FRIDAY AFTERNOON INTO THE EARLY EVENING,
WITH WEAK (GREATER THAN -50 J/KG) CIN FOR SEVERAL HOURS. ON
SATURDAY, THERMODYNAMICS ALSO LOOK SIMILARLY FAVORABLE, WITH THE
CAP ALMOST COMPLETELY DISAPPEARING. BOTH DAYS, THE THREAT IS ONCE
AGAIN HIGHLY CONDITIONAL, AS THERE IS NO OBVIOUS UPPER LEVEL
ASCENT MECHANISM.
ENSEMBLES CONTINUE TO DISAGREE ON HOW FAR SOUTH THE JET WILL DIP
WITH THE INCOMING NORTHWEST US TROUGHING THIS WEEKEND, HOWEVER, IT
WILL LIKELY REMAIN FAR ENOUGH REMOVED THAT JET DYNAMICS DO NOT
COME INTO PLAY TO INFLUENCE THUNDERSTORM CHANCES LOCALLY.
REGARDLESS, MOISTURE WILL NOT BE ENTIRELY SCOURED OUT OF
EASTERN/SOUTHEASTERN AZ, AND DAILY MONSOON THUNDERSTORM ACTIVITY
WILL BE MAINTAINED OVER PROMINENT TERRAIN FEATURES OF EASTERN AZ,
SOUTHEASTERN AZ, AND SONORA INTO NEXT WEEK. EVENTUALLY, IF THE
SUBTROPICAL HIGH CAN REASSERT ITSELF EAST OF THE REGION AND/OR
TROUGHING WEAKENS AND RETREATS NORTH, DAILY CONVECTION TO OUR
SOUTH COULD PUSH BETTER MOISTURE INTO SOUTH-CENTRAL AZ AND ONCE
AGAIN GIVE OUR AREA A SHOT AT MORE WIDESPREAD THUNDERSTORM CHANCES
BY THE MIDDLE OF NEXT WEEK. ANTICIPATE TEMPERATURES TO DECREASE
BACK INTO A NEAR NORMAL RANGE OVER THE WEEKEND AS A RESULT OF THE
PATTERN SHIFT, AND POSSIBLY SLIGHTLY BELOW NORMAL NEXT WEEK.
AVIATION
UPDATED AT 0510Z.
SOUTH CENTRAL ARIZONA INCLUDING KPHX, KIWA, KSDL, AND KDVT:
NO MAJOR AVIATION WEATHER CONCERNS WILL EXIST THROUGH THE FORECAST
PERIOD UNDER OCCASIONAL PASSING MID TO HIGH LEVEL CLOUDS. AREA
RADARS CURRENTLY SHOW A WEAK OUTFLOW BOUNDARY PROGRESSING NW
THROUGH PINAL COUNTY. THIS MAY CAUSE AN EARLIER E-SE WIND SHIFT AT
KIWA AND KPHX TONIGHT, MAINLY BETWEEN 07Z-08Z. THE BOUNDARY ITSELF
WILL NOT BE STRONG ENOUGH TO GENERATE ANY ADDITIONAL SHOWER
ACTIVITY IN THE PHOENIX METRO OVERNIGHT. WINDS SHOULD RETURN OUT
OF THE SW LATE TOMORROW MORNING WITH SPEEDS REMAINING GENERALLY
AROUND 8 KTS OR LESS.
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:
NO MAJOR WEATHER CONCERNS WILL EXIST THROUGH THE TAF PERIOD WITH
INTERMITTENT PERIODS OF PASSING MID TO HIGH CLOUDS. WINDS SHOULD
FOLLOW TYPICAL DIURNAL PATTERNS AT BOTH TERMINALS WITH SPEEDS
REMAINING AOB 8KTS ALONG WITH EXTENDED PERIODS OF NEARLY CALM
CONDITIONS DURING THE OVERNIGHT AND EARLY MORNING HOURS.
FIRE WEATHER
ABOVE NORMAL TEMPERATURES WILL PREVAIL THROUGH THE END OF THE WORK
WEEK, THEN TEMPERATURES ARE LIKELY TO DECREASE CLOSER TO NORMAL OVER
THE WEEKEND. AFTERNOON MINIMUM HUMIDITIES WILL GENERALLY RANGE
BETWEEN 18-30% AREAWIDE THROUGH MUCH OF THE WEEK FOLLOWING FAIR TO
GOOD OVERNIGHT RECOVERIES BETWEEN 35-70%. FAIRLY TYPICAL DIURNAL
WINDS WITH OCCASIONAL AFTERNOON UPSLOPE BREEZINESS CAN BE EXPECTED
THROUGH THURSDAY, FOLLOWED BY AN INCREASE IN SOUTHERLY TO
SOUTHWESTERLY WINDS FRIDAY INTO THIS WEEKEND. RAIN AND THUNDERSTORM
CHANCES WILL REMAIN LOW AND MOSTLY LIMITED TO THE EASTERN ARIZONA
HIGH TERRAIN THROUGH MIDWEEK BEFORE SLIGHT CHANCES BECOME INTRODUCED
TO THE LOWER DESERTS OF AT LEAST THE EASTERN DISTRICTS LATE WEEK.
PSR WATCHES/WARNINGS/ADVISORIES
AZ...EXTREME HEAT WARNING UNTIL 8 PM MST FRIDAY FOR AZZ530-532-533.
EXTREME HEAT WARNING UNTIL 8 PM MST THURSDAY FOR AZZ531-535>544-
546-548>551-559.
CA...EXTREME HEAT WARNING UNTIL 8 PM PDT FRIDAY FOR CAZ562-566-567-
569-570.
SHORT TERM...RYAN
LONG TERM...WHITTOCK
AVIATION...SALERNO
FIRE WEATHER...WHITTOCK
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