452
FXUS65 KPSR 082039
AFDPSR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
139 PM MST SAT AUG 8 2026
KEY MESSAGES
- EXTREME HEAT WARNINGS REMAIN IN EFFECT THROUGH SUNDAY EVENING AS
AFTERNOON HIGHS AND MORNING LOWS HOVER SEVERAL DEGREES ABOVE
NORMAL WHILE HUMIDITY VALUES REMAIN HIGHER THAN NORMAL,
RESULTING IN AREAS OF MAJOR HEATRISK.
- SHOWER AND THUNDERSTORM ACTIVITY THROUGHOUT THE WEEKEND WILL
LARGELY REMAIN CONFINED TO THE HIGHER TERRAIN AREAS WITH GUSTY
OUTFLOW WINDS AND AREAS OF BLOWING DUST THE MOST LIKELY IMPACTS
FOR THE LOWER DESERTS.
- DEEPER MOISTURE WILL PROVIDE A BETTER OPPORTUNITY FOR MORE
WIDESPREAD SHOWER AND THUNDERSTORM ACTIVITY, INCLUDING THE LOWER
DESERTS, ALONG WITH COOLING TEMPERATURES BY EARLY NEXT WEEK.
SHORT TERM /TODAY THROUGH SUNDAY/
CURRENT GOES MID-LVL WV IMAGERY AND 500 MB STREAMLINE ANALYSIS
REVEALS AN UNSEASONABLY STRONG SUBTROPICAL HIGH CENTERED NEAR THE
4-CORNERS REGION WITH HEIGHT FIELDS APPROACHING 596-598 DAM.
HEIGHTS OF THIS MAGNITUDE ARE ABOVE THE 98TH PERCENTILE OF
CLIMATOLOGY FOR EARLY AUGUST. DUE TO THE OVERALL STRENGTH OF THIS
RIDGE, AND RESPONDING LOW-LVL THERMAL PROVIDE, TEMPERATURES WILL
ONCE AGAIN TOP OUT WELL ABOVE NORMAL (5-8 DEGREES) THIS AFTERNOON.
MOST LOWER DESERT COMMUNITIES WILL SEE HIGHS IN THE 110-115
DEGREE RANGE, RESULTING IN A WIDESPREAD MAJOR HEATRISK. THE
EXTREME HEAT WARNING REMAINS IN EFFECT TODAY ACROSS THE LOWER
DESERTS OF AZ AND SOUTHEAST CA, THUS IT IS IMPORTANT TO CONTINUE
PRACTICING SMART HEAT SAFETY. THE CENTER OF THE SUBTROPICAL HIGH
WILL BEGIN TO SLOWLY SHIFT EWD ON SUNDAY WHICH WILL ALLOW 500 MB
HEIGHT FIELDS TO LOWER EVER SO SLIGHTLY ACROSS THE DESERT SOUTHWEST.
THIS WILL CAUSE TEMPERATURES TO TICK DOWN A COUPLE OF DEGREES,
BUT STILL REMAINING IN A WELL ABOVE NORMAL RANGE SUNDAY AFTERNOON
WITH LOWER DESERT HIGHS REACHING 108-112 DEGREES. GIVEN THE
AFTERNOON HIGHS EXCEEDING 110 DEGREES ALONG WITH EARLY MORNING
LOWS BOTTOMING OUT IN THE MIDDLE 80S TO LOWER 90S, THE EXTREME
HEAT WARNINGS WILL REMAIN IN EFFECT ACROSS ALL OF THE LOWER
DESERTS THROUGH SUNDAY EVENING.
SIMILAR TO THE LAST SEVERAL DAYS, THUNDERSTORM ACTIVITY IS EXPECTED
TO DEVELOP ACROSS THE HIGHER TERRAIN AREAS TO THE NORTH AND EAST OF
PHOENIX THIS AFTERNOON AND MIGRATE WESTWARD BUT LIKELY WEAKENING AS
THE ACTIVITY APPROACHES THE LOWER DESERTS DURING THE EARLY EVENING
HOURS. FORECAST SOUNDINGS FOR THE LOWER DESERTS INDICATE A STRONG
INVERSION IN THE 700-600 MB LAYER. LATEST RAP ANALYSIS ALSO SHOWS
MLCIN VALUES APPROACHING -90 TO -110 J/KG ACROSS MARICOPA COUNTY
WHICH WILL LIKELY LIMIT STORM ACTIVITY ACROSS THE LOWER DESERTS.
WHAT IS MORE LIKELY WILL BE AN OUTFLOW BOUNDARY ASSOCIATED WITH A
DECAYING COMPLEX OF STORMS OVER THE FOOTHILLS NE OF PHOENIX WHICH
COULD BRING STRONG, GUSTY WINDS INTO PORTIONS OF MARICOPA COUNTY.
WINDS COULD GUST BETWEEN 25-35 MPH FOR A COUPLE HOURS AS THE
OUTFLOW SWEEPS THROUGH. PATCHY BLOWING DUST WILL ALSO BE POSSIBLE,
ESPECIALLY FOR AREAS SOUTH AND WEST OF THE PHOENIX METRO. VERY
SIMILAR CONDITIONS ARE ANTICIPATED ON SUNDAY IN TERMS OF AREAL
COVERAGE OF THUNDERSTORMS WITH NBM POPS RANGING FROM 10-25% ACROSS
THE LOWER DESERTS OF SOUTHCENTRAL AZ. AGAIN THE MAIN IMPACTS FROM
ANY STORMS WILL BE GUSTY OUTFLOW WINDS IN EXCESS OF 30 MPH.
LONG TERM /MONDAY THROUGH FRIDAY/
THE OVERALL PATTERN HEADING INTO THE FIRST HALF OF NEXT WEEK IS
LIKELY TO BECOME MORE FAVORABLE FOR MORE WIDESPREAD CONVECTIVE
ACTIVITY ACROSS THE REGION, INCLUDING FOR THE LOWER DESERTS. THE
SUBTROPICAL HIGH IS PROJECTED TO WEAKEN EVEN FURTHER AND MIGRATE
MORE TOWARDS THE FOUR CORNERS REGION, RESULTING IN THE OVERALL
FLOW TO SHIFT MORE OUT OF THE SOUTHEAST. THIS WILL CAUSE MOISTURE
VALUES TO INCREASE WITH THE LATEST EPS AND GEFS INDICATING PWATS
SETTLING AROUND 1.5-1.8" AND LOW-LEVEL MIXING RATIOS EXCEEDING
11-12 G/KG. THIS INCREASE IN MOISTURE WILL RESULT IN BETTER
INSTABILITY AND WEAKER CONVECTIVE INHIBITION, MAKING THE
ENVIRONMENT MORE FAVORABLE FOR STORMS THAT DO DEVELOP ACROSS THE
TYPICAL HIGHER TERRAIN AREAS TO SURVIVE INTO THE LOWER DESERTS.
THIS MORE FAVORABLE ENVIRONMENTAL SETUP IS DEPICTED IN THE LATEST
FORECAST FROM THE NBM, WHICH SHOWS POPS ABOVE 40% ACROSS THE
SOUTH-CENTRAL AZ LOWER DESERTS STARTING ON MONDAY WITH ELEVATED
CHANCES CONTINUING THROUGH THE MIDDLE OF THE WEEK. WHICH DAY EARLY
NEXT WEEK COULD BE THE MOST ACTIVE IS DIFFICULT TO PINPOINT AT
THIS TIME AS IT WILL BE DICTATED BY MESOSCALE PROCESSES THAT ARE
DIFFICULT TO PREDICT THIS FAR OUT.
HEADING TOWARDS THE LATTER HALF OF THE WEEK, LATEST GUIDANCE
INDICATES THE SUBTROPICAL HIGH MIGRATING FURTHER EASTWARD TOWARDS
TEXAS WHILE AN UPPER-LEVEL LOW SETS UP OFF THE CALIFORNIA COAST.
THIS OVERALL SETUP IS LIKELY TO SHIFT THE FLOW MORE OUT OF THE
SOUTHWEST, BRINGING IN SOME DRIER AIR AS PWATS DROP UNDER 1.5".
AS A RESULT, AN OVERALL DOWNTREND IN STORM ACTIVITY IS LIKELY BY
THE END OF THE WEEK.
WITH THE WEAKENING OF THE SUBTROPICAL HIGH AND IN INCREASE IN
CONVECTIVE ACTIVITY AND CLOUD COVER, TEMPERATURES NEXT WEEK ARE
EXPECTED TO GRADUALLY COOL WITH AFTERNOON HIGHS EXPECTED TO FALL TO
NEAR SEASONAL LEVELS BY TUESDAY WITH AFTERNOON HIGHS OF 102-108
DEGREES ACROSS THE LOWER DESERTS. THE NBM IS EVEN SHOWING
TEMPERATURES POTENTIALLY COOLING EVEN FURTHER THROUGH THE END OF THE
WEEK AS IT SHOWS AFTERNOON HIGHS OF 100-106 DEGREES, WHICH IF IT
MATERIALIZES, WOULD BE SLIGHTLY BELOW NORMAL FOR THE MIDDLE OF
AUGUST.
AVIATION
UPDATED AT 1750Z.
SOUTH CENTRAL ARIZONA INCLUDING KPHX, KIWA, KSDL, AND KDVT:
THE MAIN AVIATION CONCERN WILL CONTINUE TO BE GUSTY WINDS DUE TO
AN OUTFLOW EXPECTED LATER THIS EVENING. CURRENT MODELS HAVE PUSHED
THE OUTFLOW A TAD EARLIER, NOW REFLECTING A START TIME OF NEAR
00-01Z, WITH GUST SPEEDS BETWEEN 15-25KTS OUT OF THE NE. AFTER THE
OUTFLOW PASSES WINDS WILL BE VRB BEFORE EVENTUALLY RETURNING OUT
OF THE SE FOR THE LATER MORNING HOURS. IN THE MEANTIME, WINDS ARE
EXPECTED TO FOLLOW DIURNAL TRENDS INTO THE AFTERNOON HOURS, THOUGH
THE SWITCH TO THE WEST MAY TAKE LONGER THAN USUAL AS SEVERAL
HOURS OF SOUTHERLY FLOW IS BEING SUGGESTED. SCT TO BKN CLOUD DECKS
WILL BE COMMON OVER THE REGION DURING THE FORECAST WINDOW.
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:
NO MAJOR AVIATION CONCERNS ARE EXPECTED DURING THE NEXT 24 HOURS.
FAMILIAR DIURNAL TRENDS WILL PREVAIL AT EACH TERMINAL, WITH SE'RLY
WINDS SWITCH OUT OF THE W AT KIPL, AND S/SW'RLY FLOW BEING COMMON
AT KBLH. THERE IS A LOW END CHANCE (~10%) OF AN OUTFLOW FROM
DISTANT CONVECTION MOVING THROUGH KBLH LATER IN THE PERIOD, BUT
CONFIDENCE IS TOO LOW TO WARRANT MENTION IN THE TAF AT THIS TIME.
FEW- SCT HIGH CLOUDS WILL BE PRESENT THROUGH MUCH OF THE FORECAST
WINDOW BEFORE MID-LEVEL DECKS MOVE IN EARLY TONIGHT.
FIRE WEATHER
ABOVE NORMAL TEMPERATURES WILL PREVAIL THROUGH THIS WEEKEND BEFORE
GRADUALLY COOLING TO MORE SEASONAL LEVELS BY EARLY NEXT WEEK.
AFTERNOON MINRHS WILL BOTTOM OUT BETWEEN 15-25% TODAY AND INCREASE
SLIGHTLY ON SUNDAY CLOSER TO 20-25% AREAWIDE. LOW-LEVEL MOISTURE
WILL CONTINUE TO RISE THROUGH EARLY NEXT WHICH WILL PROMOTE MUCH
BETTER OVERNIGHT RECOVERY. SHOWER AND THUNDERSTORMS WILL BE MAINLY
CONFINED TO THE HIGHER TERRAIN AREAS TO THE NORTH AND EAST OF
PHOENIX AS WELL AS SOUTHEASTERN ARIZONA THROUGHOUT THE WEEKEND WITH
MORE WIDESPREAD ACTIVITY, INCLUDING THE LOWER DESERTS ARRIVING BY
EARLY NEXT WEEK. CHANCES OF WETTING RAINFALL WILL ALSO INCREASE
SIGNIFICANTLY EARLY NEXT WEEK. OUTSIDE OF GUSTY AND ERRATIC WINDS
DUE TO THUNDERSTORMS, WINDS WILL FOLLOW THE FAMILIAR DIURNAL
TRENDS, WITH TYPICAL AFTERNOON UPSLOPE BREEZINESS AROUND 20 MPH.
PSR WATCHES/WARNINGS/ADVISORIES
AZ...EXTREME HEAT WARNING UNTIL 8 PM MST SUNDAY FOR AZZ530>544-546-
548>551-553>555-559.
CA...EXTREME HEAT WARNING UNTIL 8 PM PDT SUNDAY FOR CAZ560>570.
SHORT TERM...SALERNO
LONG TERM...LOJERO
AVIATION...RYAN
FIRE WEATHER...LOJERO/SALERNO
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