866
FXUS65 KPSR 281745
AFDPSR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
1045 AM MST FRI AUG 28 2026
UPDATE
18Z AVIATION DISCUSSION
KEY MESSAGES
- EXTREME HEAT WARNINGS REMAIN IN EFFECT THROUGH SATURDAY WITH
AREAS OF MAJOR TO EXTREME HEAT RISK, DESPITE TEMPERATURES
SLOWLY DECREASING.
- TODAY WILL BRING LOW END CHANCES FOR SHOWERS AND ISOLATED
THUNDERSTORMS WITH INCREASING CHANCES BEGINNING SATURDAY.
- AN APPROACHING LOW PRESSURE SYSTEM WILL BRING MUCH BETTER
CHANCES FOR RAIN, INCLUDING A CHANCE OF STRONG TO SEVERE STORMS
ACROSS SOUTHERN ARIZONA MAINLY ON SUNDAY AND MONDAY.
SHORT TERM /TODAY THROUGH SATURDAY/
CURRENT OBJECTIVE ANALYSIS SHOWS THE SUBTROPICAL HIGH CENTER ALONG
THE ARIZONA/NEW MEXICO STATE LINE WHILE A SLUG OF DECENT MID AND
UPPER LEVEL MOISTURE STREAMS NORTHEASTWARD THROUGH CALIFORNIA INTO
THE GREAT BASIN. SOME OF THIS MOISTURE DID MAKE ITS WAY INTO
ARIZONA EARLIER ON THURSDAY, BUT A POCKET OF DRIER AIR IS ALREADY
MOVING INTO THE STATE FROM THE SOUTH AROUND THE HIGH CENTER. THE
RIDGE IS ALSO IN THE FIRST STAGES OF WEAKENING WHILE SLOWLY
STARTING TO SHIFT FARTHER TO THE EAST. THE DRIER AIR SHOULD LIMIT
CONVECTIVE POTENTIAL TODAY, BUT CAMS ARE AT LEAST SHOWING SOME
POTENTIAL FOCUSED OVER THE EASTERN ARIZONA HIGH TERRAIN AND OVER
SOUTHEAST CALIFORNIA. OVERALL, WE ARE NOT ANTICIPATING MUCH WITH
THIS ACTIVITY, BUT GIVEN THE DRY BOUNDARY LAYER WE CAN'T RULE OUT
SOME STRONG GUSTY WINDS WITH ANY MODEST THUNDERSTORMS THAT MAY
DEVELOP. THIS WIND THREAT WILL MOSTLY COVER IMPERIAL COUNTY WHERE
THE HIGHEST INSTABILITY IS EXPECTED. TEMPERATURES TODAY ARE
FORECAST TO BE VERY SIMILAR TO YESTERDAY'S HIGHS OF 110-114
DEGREES, BUT CLOUDS MAY HOLD TEMPERATURES A COUPLE DEGREES COOLER
IN SOME AREAS.
AS THE RIDGE SHIFTS MORE INTO NEW MEXICO AND TEXAS TONIGHT INTO
SATURDAY, IT WILL BE THE START OF A SIGNIFICANT PATTERN SHIFT. A
LARGE PACIFIC TROUGH OFF THE NORTHWEST U.S. COAST WILL GET
REINFORCED AND SLIDE FARTHER TO THE SOUTH AND EVENTUALLY TO THE
EAST. DURING THIS TRANSITION THIS WEEKEND, OUR REGION WILL SEE
MODEST TO STRONG MOISTURE ADVECTION WITH LOW LEVEL MIXING RATIOS
GRADUALLY IMPROVING FROM THE CURRENT 7-8 G/KG TO 10-11 G/KG LATE
SATURDAY BEFORE PEAKING ON SUNDAY AND MONDAY AT A RESPECTABLE
11-12 G/KG. GUIDANCE SUGGESTS SOME POTENTIAL FOR ELEVATED SHOWERS
AND WEAK THUNDERSTORMS FRIDAY NIGHT WITH THE FIRST BIG PUSH OF
MOISTURE. AS OF NOW, THE BEST CHANCE FOR THIS RAIN SHOULD BE FROM
PHOENIX TO JUST TO THE EAST OF PHOENIX.
WHAT OCCURS SATURDAY AFTERNOON/EVENING IS STILL QUITE UNCERTAIN AS
IT WILL BE MORE OF A CONDITIONAL TYPE ENVIRONMENT FOR STORM
DEVELOPMENT. MOISTURE IS EXPECTED TO HAVE INCREASED ENOUGH TO
BRING MUCAPES UP TO AROUND 1000 J/KG INTO SOUTH-CENTRAL ARIZONA,
BUT NOT ENOUGH TO ERASE ALL OF THE CIN. THE QUESTION IS WHERE
EXACTLY WILL SHOWERS AND STORMS DEVELOP SATURDAY AFTERNOON AND IF
A LARGE ENOUGH CLUSTER CAN DEVELOP TO FORCE A STRONG OR MULTIPLE
OUTFLOWS INTO THE LOWER DESERTS. IT IS LOOKING MORE ENCOURAGING
FOR STORM POTENTIAL AS THE AMOUNT OF CIN DOES NOT LOOK TOO HIGH
AND ANY DECENT OUTFLOW SHOULD OVERCOME IT. WE WILL ALSO START TO
SEE SOME UPPER LEVEL SUPPORT FROM THE INCOMING TROUGH. THE LATEST
06Z HRRR HINTS AT A CLUSTER OF STORMS FIRING ACROSS PIMA COUNTY
LATE SATURDAY AFTERNOON AND THEN PROGRESSING NORTHWARD OR AT LEAST
ADDITIONAL STORMS DEVELOPING ALONG A NORTHWARD PROGRESSING
OUTFLOW DURING THE EVENING. WITH A HIGH DCAPE ENVIRONMENT
EXPECTED, STRONG GUSTY WINDS ARE VERY POSSIBLE ACROSS MARICOPA AND
PINAL COUNTY SATURDAY EVENING. SATURDAY SHOULD ALSO BE THE LAST
OF THE EXTREME HEAT WITH FORECAST HIGHS DROPPING TO 107-111
DEGREES BEFORE A MUCH MORE NOTICEABLE COOL DOWN BEGINS SUNDAY.
LONG TERM /SUNDAY THROUGH THURSDAY/
SUNDAY AND/OR MONDAY ARE STILL LOOKING QUITE INTERESTING FOR
THUNDERSTORM POTENTIAL WITH THE ENVIRONMENT POTENTIALLY SUPPORTING
SOME SEVERE STORMS. SOME INGREDIENTS FOR STRONG TO SEVERE STORMS
ARE EXPECTED TO BE PRESENT, LIKE UPPER LEVEL SUPPORT AND
SUFFICIENT INSTABILITY, BUT WIND SHEAR WILL BE SOMEWHAT LACKING.
MOISTURE IS FORECAST TO IMPROVE ENOUGH TO SUPPORT A NEARLY
UNCAPPED ENVIRONMENT ACROSS SOUTH-CENTRAL ARIZONA SUNDAY AND
POTENTIALLY AGAIN MONDAY AFTERNOON WITH MUCAPES AS HIGH AS
1500-1800 J/KG. BOTH DAYS HAVE THE POTENTIAL TO BRING SCATTERED
TO NUMEROUS SHOWERS AND THUNDERSTORMS ACROSS SOUTH-CENTRAL AND
EASTERN ARIZONA. STRONG TO LOCALIZED SEVERE WIND GUSTS, BLOWING
DUST, HEAVY RAINFALL, AND FLOODING ALL LOOK POSSIBLE, BUT AS
STATED ABOVE THE THREAT MAY BE LOCALIZED DUE TO THE FAIRLY WEAK
SHEAR WHICH IS OFTENTIMES NEEDED TO SUSTAIN STRONG STORMS OR
CLUSTERS OF STORMS. WE SHOULD HAVE A BETTER IDEA ON HOW THIS
STRONG TO SEVERE STORM THREAT MAY EVOLVE BY SATURDAY/SATURDAY
NIGHT. GUIDANCE THEN SUGGESTS SOME DRYING WILL OCCUR BY TUESDAY
WHICH SHOULD DECREASE RAIN CHANCES SUBSTANTIALLY THROUGH THE
MIDDLE OF NEXT WEEK.
TEMPERATURES WILL DROP INTO OR EVEN JUST BELOW NORMAL EARLY NEXT
WEEK, BUT HIGHS ARE STILL FORECAST TO TOP 100 DEGREES EACH DAY
ACROSS THE LOWER DESERTS. ONCE THE DRIER AIR MOVES INTO THE REGION
BY THE MIDDLE OF NEXT WEEK, WE EXPECT TEMPERATURES TO QUICKLY WARM
TO A FEW DEGREES ABOVE NORMAL BUT WITH LITTLE CHANCE OF REACHING
110 DEGREES AGAIN.
AVIATION
UPDATED AT 1735Z.
SOUTH CENTRAL ARIZONA INCLUDING KPHX, KIWA, KSDL, AND KDVT:
A GUSTY SOUTHERLY OUTFLOW WITH SOME LOFTED HAZE THIS EVENING WILL
BE THE PRIMARY AVIATION WEATHER ISSUE DURING THE NEXT 24 HOURS.
IN THE MEANTIME, WINDS WILL GRADUALLY SHIFT OUT OF THE WEST BY THE
EARLY TO MID-AFTERNOON HOURS WITH A PERIOD OF SOUTHERLY WINDS
BEFORE THE EVENTUAL WESTERLY SHIFT. OVERALL SPEEDS THROUGH THIS
AFTERNOON ARE FORECAST TO REMAIN AOB 10 KTS. THEREAFTER, GUIDANCE
CONTINUES TO SHOW A SOUTHERLY OUTFLOW FROM CONVECTIVE ACTIVITY IN
SOUTHEAST AZ PROPAGATING INTO THE AREA, SOMETIME BETWEEN 03-06Z,
WITH SOME GUSTY WINDS POTENTIALLY UPWARDS OF 25-30 KTS AS WELL AS
SOME REDUCED VIS DUE TO LOFTED HZ/BLDU. AFTER THE OUTFLOW PASSAGE
LATER THIS EVENING, VCSH IS POSSIBLE DURING THE OVERNIGHT PERIOD,
MAINLY BETWEEN 06-12Z, WITH MINIMAL OPERATIONAL IMPACTS EXPECTED.
SCT TO AT TIMES BKN MID/HIGH CLOUD DECKS WILL BE COMMON THROUGH
THE PERIOD.
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:
ISOLATED TS ACTIVITY, ESPECIALLY AT KIPL, THIS AFTERNOON WILL BE
THE PRIMARY AVIATION WEATHER ISSUE DURING THE NEXT 24 HOURS.
WINDS WILL FLUCTUATE BETWEEN THE SOUTHEAST TO WEST AT KIPL AND
SOUTH TO SOUTHWEST AT KBLH. HEADING INTO THIS AFTERNOON, TS
ACTIVITY OVER THE BAJA SPINE MAY DRIFT INTO THE IMPERIAL VALLEY,
AFFECTING KIPL, HOWEVER, THERE CONTINUES TO BE UNCERTAINTY IN THE
OVERALL COVERAGE AND INTENSITY OF THE TS ACTIVITY AND THUS A
PROB30 REMAINS IN THE LATEST TAF PACKAGE. IF A TS WOULD TO
MATERIALIZE, GUSTY WINDS AND REDUCED VIS DUE TO HZ/BLDU WILL BE
THE MAIN IMPACTS. KBLH MAY SEE AN OUTFLOW FROM THE ACTIVITY TO
THE SOUTHWEST, BUT CONFIDENCE REMAINS TOO LOW FOR INCLUSION IN
THE LATEST TAF PACKAGE. FEW-SCT MID/HIGH CLOUD DECKS WILL BE
COMMON THROUGHOUT THE PERIOD, WITH OCCASIONAL BKN DECKS WITH ANY
CONVECTIVE ACTIVITY.
FIRE WEATHER
HOT AND RELATIVELY DRY CONDITIONS WILL CONTINUE INTO THIS WEEKEND,
BUT WITH SLIGHT CHANCES FOR ISOLATED SHOWERS AND THUNDERSTORMS.
CHANCES THEN INCREASE CONSIDERABLY BY SUNDAY, ESPECIALLY ACROSS
SOUTHERN AND CENTRAL ARIZONA. AFTERNOON MINIMUM HUMIDITIES WILL
IMPROVE SLIGHTLY TO 15-20% TODAY AND THEN 17-25% SATURDAY. WINDS
WILL BE RELATIVELY LIGHT AND FOLLOW DIURNAL TENDENCIES TODAY
BEFORE SOUTH TO SOUTHWESTERLY WINDS INCREASE SATURDAY,
PARTICULARLY ACROSS THE WESTERN DESERTS, WHERE AFTERNOON GUSTS
INCREASE UP TO 20-30 MPH.
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 THIS EVENING 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 THIS EVENING FOR CAZ561-563-
564-568.
SHORT TERM...KUHLMAN
LONG TERM...KUHLMAN
AVIATION...LOJERO
FIRE WEATHER...KUHLMAN
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