191
FXUS65 KPSR 262107
AFDPSR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
207 PM MST WED AUG 26 2026
KEY MESSAGES
- EXTREME HEAT WARNINGS REMAIN IN EFFECT THROUGH SATURDAY ACROSS
MUCH OF THE AREA.
- LOWER DESERT HIGHS IN EXCESS OF 110 DEGREES AND OVERNIGHT LOWS
IN THE 80S TO LOWER 90S WILL BE COMMON THIS WEEK, RESULTING IN
MAJOR TO EXTREME HEAT RISK.
- MONSOON STORM ACTIVITY WILL REMAIN ISOLATED IN COVERAGE THROUGH
FRIDAY BEFORE A SIGNIFICANT INCREASE IN MOISTURE ARRIVES THIS
WEEKEND, PROMOTING COOLER TEMPERATURES AND BETTER OVERALL RAIN
CHANCES.
SHORT TERM /TODAY THROUGH THURSDAY/
CURRENT GOES WV IMAGERY AND 500 MB STREAMLINE ANALYSIS REVEALS AN
UNSEASONABLY STRONG RIDGE OF HIGH PRESSURE SITUATED OVER THE AZ/NM
BORDER. 500 MB HGHTS ARE NOW UP TO 598 DAM WHICH IS AT THE
CLIMATOLOGICAL MAXIMUM FOR LATE AUGUST. LATEST ACARS SOUNDINGS
PRESENT A WELL MIXED BOUNDARY LAYER (UP TO 600 MB) UNDER FULL
SUNSHINE ACROSS SOUTHCENTRAL AZ WHICH IS CAUSING TEMPERATURES TO
SOAR ABOVE 110 DEGREES IN MOST DESERT LOCALES. TEMPERATURES WILL
PEAK AROUND 113-117 DEGREES ACROSS THE LOWER DESERTS THIS
AFTERNOON. IF SKY HARBOR REACHES THE FORECAST HIGH OF 117 DEGREES,
IT WOULD TIE THE RECORD HIGH FOR TODAY'S DATE LAST SET IN 2011.
FARTHER WEST ACROSS SE CALIFORNIA AND SW ARIZONA, CLOUD COVER LEFT
OVER FROM EARLIER SHOWER ACTIVITY HAS STUNTED WARMING SLIGHTLY,
BUT HIGH TEMPERATURES ARE STILL EXPECTED TO REACH AROUND 110-116
LATER THIS AFTERNOON. STORM CHANCES WILL REMAIN MINIMAL THROUGH
THE REST OF TODAY AND TONIGHT WITH ONLY AROUND A 10% CHANCE OF AN
ISOLATED STORM OR TWO IN S GILA COUNTY AND FAR SW IMPERIAL COUNTY.
SOME MID-LVL MOISTURE FROM THE E PACIFIC IS BEGINNING TO ADVECT
INTO THE REGION WHICH WILL CAUSE CLOUD COVER TO INCREASE TONIGHT
AND INTO THURSDAY MORNING. IF CLOUDS ARE THICK ENOUGH TO PREVENT
AMPLE RADIATIONAL COOLING, THEN PHOENIX MAY SET A NEW RECORD WARM
LOW (CURRENT RECORD IS 91 DEGREES).
ON THURSDAY, THE ROBUST SUBTROPICAL HIGH WILL STILL BE STATIONED
OVER THE AZ/NM BORDER WITH ONLY A SLIGHT DECREASE IN 500 MB HGHTS
TO AROUND 595-596 DAM. THIS WILL ALLOW TEMPERATURES TO DECREASE
BY A FEW DEGREES, BUT MOST LOWER DESERT COMMUNITIES WILL STILL SEE
HIGHS AROUND 108-116 DEGREES, OR NEAR RECORD LEVELS. MOISTURE
LEVELS WILL REMAIN QUITE LOW ON THURSDAY AFTERNOON WITH PWAT
VALUES RANGING FROM 1.2-1.4" AND MIXING RATIOS AROUND 6-8 G/KG.
THE OVERALL LOWER MOISTURE CONTENT WILL KEEP CONVECTION ISOLATED
AND MAINLY CONFINED TO THE AZ HIGH TERRAIN, ALTHOUGH HIGH-RES
MODELS DO INDICATE A SLIGHT UPTICK IN SHOWER/STORM ACTIVITY ACROSS
E AND SE AZ THURSDAY AFTERNOON. IF ENOUGH CONVECTION DEVELOPS
OVER THE HIGHER TERRAIN, THERE MAY BE A MORE WELL DEFINED OUTFLOW
THAT DESCENDS INTO THE LOWER DESERTS. LATEST HREF PROBABILITIES
FOR WINDS GREATER THAN 35 MPH IS AROUND 10-30% IN MARICOPA COUNTY
AND 30-50% IN PINAL COUNTY. OTHER THAN A POTENTIAL OUTFLOW, THE
CHANCES FOR ANY ADDITIONAL STORM ACTIVITY IN THE LOWER DESERTS
WILL BE VERY LOW (10% OR LESS).
LONG TERM /FRIDAY THROUGH TUESDAY/
THE SUBTROPICAL RIDGE IS STILL EXPECTED TO WEAKEN AND SHIFT BACK
EASTWARDS BY FRIDAY ACCORDING TO ENSEMBLES. THIS IS DUE TO A
TROUGHING PATTERN PUSHING INTO THE NW CONUS AND ALONG THE WEST
COAST. AS THE TROUGH PUSHES EASTWARD, PWATS WILL BEGIN TO IMPROVE,
REACHING NEAR 1.5"-1.7" BY SATURDAY AND LASTING THROUGH AT LEAST THE
WEEKEND. MIXING RATIOS WILL ALSO SIGNIFICANTLY IMPROVE GOING FROM
MID WEEK'S 6-8 G/KG TO 10-12 G/KG BY THIS WEEKEND, GENERATING BETTER
SUPPORT FOR STORM FORMATION IN THE LOWER DESERTS. WITH THAT BEING
SAID NBM/WPC CONTINUE TO SHOW POPS OVER THE WEEKEND BETWEEN 20-35%
ACROSS SOUTH-CENTRAL AZ, AND NOW EVEN UP TO 50% IN THE EASTERN HIGH
TERRAIN. WITH THESE POPS THE NBM/WPC QPE TOTALS OVER THE WEEKEND ARE
FORECASTED BETWEEN 0.10"-0.25" TO LOCALLY HIGHER IN THE HIGHER
TERRAIN AREAS. CONTINUED MONITORING OF THIS SYSTEM WILL BE NEEDED
BUT MODELS CONTINUE TO SHOW SUPPORT FOR ACTIVITY DEVELOPING THIS
WEEKEND. IN OTHER GOOD NEWS, TEMPERATURES ARE FORECAST TO DROP
CLOSER TO LATE AUGUST NORMALS BY SUNDAY AND INTO EARLY NEXT WEEK AS
FALLING MIDLEVEL HEIGHTS AND AN INCREASE IN MOISTURE/CLOUD COVER
OVER THE EASTERN CWA SUPPORT A COOLING TREND (MORE PRONOUNCED ACROSS
SOUTH-CENTRAL AZ).
AVIATION
UPDATED AT 1740Z.
SOUTH CENTRAL ARIZONA INCLUDING KPHX, KIWA, KSDL, AND KDVT:
NO MAJOR AVIATION WEATHER CONCERNS UNDER FEW-SCT MID/HIGH CLOUD
DECKS CAN BE EXPECTED THROUGHOUT THE TAF PERIOD. WINDS THROUGH
TONIGHT WILL FOLLOW TYPICAL DIURNAL TENDENCIES, WITH A WESTERLY
SWITCH ANTICIPATED WITHIN THE NEXT 2-3 HOURS. THIS EVENING,
FORECAST CONFIDENCE IN THE WINDS DECREASES CONSIDERABLY, AS THERE
IS A POTENTIAL FOR DISTANT TS OUTFLOWS TO REACH THE TERMINALS FROM
THE NE OR SE. TIMING WOULD LIKELY BE EARLY TO MID EVENING, NO
EARLIER THAN 01Z AND NO LATER THAN 04Z. REGARDLESS, CONFIDENCE IS
MODERATE THAT WINDS WILL EVENTUALLY SETTLE OUT OF AN EASTERLY
DIRECTION OR RELAX TO AOB 5 KTS OVERNIGHT. SPOTTY VIRGA AND/OR
LIGHT, ELEVATED SHOWERS CANNOT BE RULED OUT DURING THE OVERNIGHT
HOURS TONIGHT, BUT CONFIDENCE AND POTENTIAL IMPACTS ARE TOO LOW
FOR MENTION IN THE TAFS. THEN, AN EARLIER THAN USUAL SW/W WIND
SHIFT IS ANTICIPATED THURSDAY MORNING.
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:
FOR THE NEXT FEW HOURS, WIDELY SCATTERED -SHRA AND SOME ISOLATED
TS WILL STREAM NORTHWARD, ALREADY OBSERVED WITHIN THE VICINITY OF
KIPL. OPTED FOR VCSH AT KIPL THROUGH 19Z, AS THE LIGHTNING
ACTIVITY IS VERY LOW AND DIRECT IMPACTS AT THE TERMINAL ARE
UNLIKELY. VCSH MAY BE AMENDED TO THE CURRENT KBLH IF NECESSARY,
BUT THE DRY ENVIRONMENT WILL MEAN THAT MOST OF THE ACTIVITY
TRANSITIONS TO VIRGA BY THE TIME IT REACHES THAT FAR NORTH.
OTHERWISE, WINDS WILL OSCILLATE BETWEEN SE TODAY TO SW LATER THIS
AFTERNOON AND THIS EVENING AT KIPL. A DISTANT TS OUTFLOW COULD
PRODUCE GUSTS TO AROUND 25 KTS AT KIPL LATE THIS AFTERNOON INTO
THE EVENING. WINDS AT KBLH WILL VARY BETWEEN S AND WSW WITH SPEEDS
8-12 KTS AND OCCASIONAL HIGHER GUSTS INTO THE UPPER TEENS. CLOUD
DECKS WILL REMAIN RATHER HIGH, MOSTLY ABOVE 12 KFT AGL, WITH SCT
TO AT TIMES BKN COVERAGE.
FIRE WEATHER
UNSEASONABLY HOT TEMPERATURES WILL CONTINUE THROUGH THE REMAINDER
OF THIS WEEK WITH SOME RELIEF IN STORE BY THIS WEEKEND. OVERALL
TEMPERATURES WILL REMAIN WELL ABOVE NORMAL THROUGH SATURDAY UNTIL
FALLING TO MORE SEASONAL LEVELS BY SUNDAY. ISOLATED SHOWERS AND
STORMS WILL BE CONFINED TO THE AZ HIGH TERRAIN THROUGH THE END OF
THIS WEEK WITH A MUCH BETTER INFLUX IN MOISTURE AND RAIN CHANCES
ANTICIPATED AREA-WIDE BY THIS WEEKEND. HUMIDITY LEVELS WILL BOTTOM
OUT AROUND 10-15% TODAY AND INCREASE TO ABOVE 15% ON THURSDAY.
OVERNIGHT RECOVERIES WILL BE POOR TO FAIR, INCREASING TO GOOD
ACROSS THE EASTERN DISTRICTS ON FRIDAY NIGHT. OUTSIDE OF DISTANT
THUNDERSTORM OUTFLOWS, EXPECT OVERALL LIGHT WINDS (BELOW 15 MPH)
FOLLOWING TYPICAL DIURNAL TENDENCIES WITH SOME MODEST AFTERNOON
UPSLOPE GUSTINESS.
CLIMATE
RECORD HIGHS:
DATE PHOENIX YUMA EL CENTRO
---- ------- ---- ---------
AUG 26 117 IN 2011 115 IN 2020 115 IN 1981
AUG 27 114 IN 2023 120 IN 1981 117 IN 1981
AUG 28 117 IN 2023 118 IN 2023 117 IN 2009
AUG 29 116 IN 2023 117 IN 1954 117 IN 2005
PSR WATCHES/WARNINGS/ADVISORIES
AZ...EXTREME HEAT WARNING UNTIL 8 PM MST SATURDAY FOR AZZ530>555-559-
560.
EXTREME HEAT WARNING UNTIL 8 PM MST FRIDAY FOR AZZ556-561-562.
CA...EXTREME HEAT WARNING UNTIL 8 PM PDT SATURDAY FOR CAZ562-565>567-
569-570.
EXTREME HEAT WARNING UNTIL 8 PM PDT FRIDAY FOR CAZ561-563-564-
568.
SHORT TERM...SALERNO
LONG TERM...WHITTOCK/RYAN
AVIATION...WHITTOCK
FIRE WEATHER...SALERNO
CLIMATE...18/KUHLMAN
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