287
FXUS65 KPSR 282300
AFDPSR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
400 PM MST TUE JUL 28 2026
UPDATE
UPDATED AVIATION
KEY MESSAGES
- HIGH PRESSURE WILL CENTER ITSELF OVER ARIZONA AND STRENGTHEN LATE
THIS WEEK RESULTING IN HOTTER TEMPERATURES AND WIDESPREAD MAJOR TO
EXTREME HEAT RISK.
- EXTREME HEAT WARNINGS HAVE BEEN EXPANDED TO COVER THE ENTIRE
FORECAST AREA STARTING THURSDAY, AND CONTINUING THROUGH THE WEEKEND.
- DAILY CHANCES FOR SHOWERS AND THUNDERSTORMS WILL CONTINUE OVER
EASTERN ARIZONA HIGH TERRAIN, BUT WILL DECREASE CONSIDERABLY AND
BECOME ALMOST ENTIRELY CONFINED TO THE MOST PROMINENT TERRAIN
FEATURES THE REMAINDER OF THE WEEK.
SHORT TERM /TODAY THROUGH WEDNESDAY/
A COUPLE MCVS TRACKED NORTHWARD THROUGH GILA/PINAL/MARICOPA COUNTIES
THIS MORNING PROVIDING FORCING FOR SHOWERS AND RELEASING ELEVATED
INSTABILITY OF UP TO 1000-1500 J/KG (BACKED UP BY EARLIER RAP
ANALYSIS AND THE 12Z PSR SOUNDING) TO PRODUCE ISOLATED THUNDERSTORMS
AND LOCALLY HEAVY RAINFALL FOR SOME. WHILE NOT ALL SAW RAINFALL,
PORTIONS OF THE EAST VALLEY RECEIVED ANYWHERE FROM A FEW HUNDREDTHS
OF AN INCH UP TO AROUND 0.3" FROM THIS MORNING'S ACTIVITY. FURTHER
EAST IN SOUTHERN GILA COUNTY, AUTOMATED GAUGES THAT WERE LUCKY
ENOUGH TO HAVE CONVECTIVE CELLS TRACK OVERHEAD RECORDED UPWARDS OF
0.25" TO AS MUCH AS 1.0" IN SOME SPOTS. RAIN-COOLED, HUMID AIR
OVERSPREAD MUCH OF SOUTH-CENTRAL AZ THIS MORNING, DROPPING MORNING
LOWS TO A FEW DEGREES BELOW THE DAILY NORMALS, RANGING FROM THE
UPPER 70S TO MIDDLE 80S AND INCREASING DEWPOINT TEMPERATURES TO
BETWEEN THE MIDDLE 60S AND LOWER 70S. WITH COOLER TEMPERATURES TO
START THE DAY AND DELAYED SURFACE HEATING, EXPECT DAYTIME HIGHS
SEVERAL DEGREES COOLER THAN ORIGINALLY FORECAST, LIKELY REACHING
NEAR NORMAL VALUES (105F-107F IN THE PHOENIX METRO) ACROSS SOUTH-
CENTRAL AZ AND A PORTION OF SOUTHWEST AZ, WHEREAS TEMPERATURES WILL
REMAIN SEVERAL DEGREES ABOVE NORMAL FOR THE WESTERN DESERTS.
THE FORECAST AREA REMAINS UNDER EASTERLY TO SOUTHEASTERLY FLOW ALOFT
ON THE WESTERN PERIPHERY OF A NOW WEAKER SUBTROPICAL HIGH CENTERED
APPROXIMATELY OVER NORTHERN NM AT THIS HOUR. CURRENT 500 MB RAP
ANALYSIS AND MIDLEVEL WATER VAPOR IMAGERY SUGGESTS A SUBTLE EASTERLY
WAVE AND YET ANOTHER VORT MAX OR MCV FEATURE JUST EAST OF THE
NORTHERN TIP OF THE GULF OF CALIFORNIA. THESE WILL PASS INTO WESTERN
AZ AND BE PULLED NORTHWARD TODAY THANKS TO THE ANTICYCLONIC FLOW
ABOUT THE SUBTROPICAL HIGH. AS WE ARE NOW ON THE BACKSIDE OF A FEW
MCVS AND THE AFOREMENTIONED EASTERLY WAVE, SUBSIDENCE SEEMS TO BE
FAVORED OVER THE REGION AND AT THE VERY LEAST OVER SOUTH- CENTRAL
AZ. LATEST GFS BUFR SOUNDINGS FOR KPHX DISPLAY A MIDLEVEL INVERSION
THIS AFTERNOON, INDICATIVE OF THIS SUBSIDENCE, AND POOR 850-700 MB
LAPSE RATES CAN BE SEEN IN EARLY AFTERNOON PHX ACARS SOUNDINGS,
PUTTING A CONSIDERABLE CAP ON THE LOCAL ENVIRONMENT. HOWEVER, THIS
CAP WILL ERODE THROUGH THE REMAINDER OF THE AFTERNOON, AND CAMS DO
INDICATE THE POTENTIAL FOR THUNDERSTORMS TO FORM OVER SOME OF THE
TYPICALLY FAVORED TERRAIN SUCH AS THE TABLETOP MOUNTAIN WILDERNESS
AND THE RIM/FAR EASTERN GILA COUNTY. THESE COULD PRODUCE LOCALLY
GUSTY WINDS AND HEAVY RAINFALL. WIND SHEAR IS ALSO STILL PRESENT,
WITH BULK EFFECTIVE SHEAR UPWARDS OF 25-35 KTS OVER THE SOUTHEASTERN
THIRD OF THE STATE. WHILE STORM COVERAGE IS VERY UNCERTAIN AND
LIKELY TO BE QUITE LOW BASED ON LATEST CAMS, ANY THAT DO FORM COULD
DEVELOP ROTATING UPDRAFTS AND BE CAPABLE OF SEVERE WIND GUSTS. HREF
CONSENSUS IS THAT THE THREAT IS GREATER TOWARDS THE AZ/NM BORDER IN
THE SOUTHEASTERN CORNER OF THE STATE, WHERE THE CAP WILL ERODE
QUICKER AND ALLOW SURFACE BASED CONVECTION TO DEVELOP LATE THIS
AFTERNOON. A FEW SEVERE- WARNED CELLS HAVE ALREADY DEVELOPED OVER
THE WHITE MOUNTAINS.
THIS EVENING/OVERNIGHT TONIGHT, LESS EVIDENCE EXISTS THAT AN
UPSTREAM MCV WILL FORM AND TRACK NORTHWARD OVER THE FORECAST AREA,
HOWEVER, THE POSSIBILITY CANNOT BE ENTIRELY RULED OUT. IT IS HIGHLY
DEPENDENT ON THUNDERSTORM COVERAGE AND INTENSITY UPSTREAM OVER
SONORA OR THE SOUTHEASTERN CORNER OF THE STATE. CAMS DO SEEM TO BE
PICKING UP ON THE INFLUENCE OF ANOTHER AXIS OF VORTICITY BEING
PULLED NORTHWARD AROUND THE ANTICYCLONE AND PROVIDING ENOUGH LIFT
AHEAD OF IT TO PRODUCE SHOWERS OR EVEN AN ISOLATED STORM OVER
SOUTHWEST AZ TONIGHT. ON WEDNESDAY, ENSEMBLES REMAIN IN GOOD
AGREEMENT THAT FLOW ALOFT WILL SHIFT SOUTHERLY TO EVEN A SLIGHTLY
SOUTHWESTERLY ORIENTATION, STARTING A W-E DRYING TREND. BY LATE
WEDNESDAY, LOWER DESERT NEAR-SURFACE MIXING RATIOS DROP BELOW 10
G/KG, ESSENTIALLY ENDING LOWER DESERT STORM CHANCES. DAILY
THUNDERSTORM ACTIVITY ACROSS THE REGION WILL DIMINISH AND REMAIN
DIMINISHED HEADING THROUGH THE REST OF THE WORK WEEK. ENSEMBLE MEAN
H5 HEIGHTS WILL CONTINUE IN A 594-596 DAM RANGE, BETWEEN THE 90TH
AND 95TH PERCENTILE OF CFSR CLIMATOLOGY, SUPPORTING ABOVE NORMAL
HIGHS AROUND 109F-113F FOR THE TYPICALLY HOTTER SPOTS WEDNESDAY.
LONG TERM /THURSDAY THROUGH MONDAY/
ENSEMBLES REMAIN IN GOOD AGREEMENT THAT THE SUBTROPICAL HIGH OVER NM
WILL RETROGRADE INTO AZ AND STRENGTHEN, ESPECIALLY BY FRIDAY-
SATURDAY, WITH MEAN H5 HEIGHTS BUILDING TO A 599-601 DAM RANGE, NEAR
OR JUST ABOVE CFSR CLIMATOLOGICAL MAXIMUM VALUES. NAEFS/ENS MEAN 850
MB TEMPERATURES WILL ALSO APPROACH CLIMATOLOGICAL MAXIMUM VALUES
AROUND 32C-35C. UNDER DRIER CONDITIONS, MUCH CLEARER SKIES THANKS TO
REDUCED THUNDERSTORM ACTIVITY, AND STRONG ANTICYCLONIC SUBSIDENCE,
HEIGHTS/TEMPERATURES ALOFT IN THIS RANGE WILL SUPPORT AFTERNOON
SURFACE TEMPERATURES PEAKING BETWEEN 115F-120F, WITH VALUES ON THE
HIGHER END OF THAT RANGE FAVORED IN SOUTHEAST CA. SATURDAY IS
SHAPING UP TO BE THE HOTTEST DAY, WITH NBM ADVERTISING 25-40%
PROBABILITIES OF REACHING 120+F IN SOME OF THE HOTTEST SPOTS ACROSS
SOUTHEAST CA AND ALONG THE LOWER COLORADO RIVER VALLEY. OVERNIGHT
LOWS ARE ALSO FORECAST TO WARM INTO THE UPPER 80S TO LOWER 90S,
PROVIDING VERY LITTLE RELIEF FROM THE HEAT. COVERAGE OF MAJOR
HEATRISK BUILDS STARTING THURSDAY AND IS WIDESPREAD FRIDAY-SUNDAY,
WITH AREAS OF EXTREME HEATRISK INDICATED IN THOSE AREAS WHERE
OVERNIGHT LOWS DO NOT COOL BELOW 90F. AS SUCH, WIDESPREAD EXTREME
HEAT WARNINGS GO INTO EFFECT FOR THE ENTIRE FORECAST AREA THURSDAY
AND WILL CONTINUE THROUGH THE WEEKEND.
LONG RANGE GLOBAL GUIDANCE CONTINUES TO INDICATE MOISTURE INCREASING
ACROSS THE AREA AS THE SUBTROPICAL HIGH WEAKENS LATE THIS WEEKEND
INTO THE FOLLOWING WEEK. HOWEVER, DETAILS ARE VERY UNCERTAIN THIS
FAR OUT. CURRENT CONSENSUS OF THE GEFS AND ENS IS FOR THE NORTHERN
STREAM TO IMPINGE FURTHER SOUTH, FLATTENING THE SUBTROPICAL RIDGE.
MEANWHILE, FLOW ALOFT ON THE SOUTHERN PERIPHERY OF THE SUBTROPICAL
ANTICYCLONE STRENGTHENS AND TURNS EASTERLY TO NORTHEASTERLY,
EXPOSING THE REGION TO THE POSSIBILITY OF EASTERLY WAVES AND BETTER
SHEAR/STEERING FLOW TO CARRY STORMS OFF EASTERN/SOUTHEASTERN AZ
TERRAIN FEATURES. REGARDLESS OF THE EVENTUAL INCREASE IN MOISTURE
AND THUNDERSTORM ACTIVITY, THIS WILL ALSO HELP END THE EXTENDED
PERIOD OF EXTREME HEAT CONDITIONS BY EARLY NEXT WEEK.
AVIATION
UPDATED AT 2300Z.
SOUTH CENTRAL ARIZONA INCLUDING KPHX, KIWA, KSDL, AND KDVT:
NO MAJOR WEATHER ISSUES WILL EXIST THROUGH WEDNESDAY EVENING UNDER A
FEW PASSING MID/HIGH CLOUD DECKS. THERE IS UNCERTAINTY IN TIMING AND
DURATION OF THE TYPICAL EASTERLY WIND SHIFT LATE TONIGHT, WITH THE
MAJORITY OF GUIDANCE SUGGESTING A VERY LATE SWITCH AND ONLY A FEW
HOURS IN DURATION. THERE IS A LOW PROBABILITY THAT WINDS NEVER MAKE
THE EASTERLY SWITCH AT KPHX. OTHERWISE, CONFIDENCE IS GOOD THAT TS
WILL REMAIN RELEGATED TO MOUNTAINS WITH VERY LOW CHANCES OF DISTANT
OUTFLOWS SURVIVING INTO LOWER ELEVATIONS.
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:
NO MAJOR WEATHER ISSUES WILL EXIST THROUGH WEDNESDAY EVENING UNDER
OCCASIONAL PASSING MID/HIGH CLOUDS. TRENDS IN WINDS WILL BE SIMILAR
TO THE PAST 24 HOURS FAVORING A SOUTHERLY COMPONENT AT KBLH, AND
VARYING BETWEEN SE AND SW AT KIPL. A FEW GUSTS 15-20KT WILL BE
COMMON LATE AFTERNOON/EARLY EVENING. WHILE A FEW SHRA MAY PASS
THROUGH THE AREA OVERNIGHT, CHANCES FOR DIRECT IMPACT TO ANY
TERMINAL IS TOO LOW TO MENTION IN THIS TAF PACKAGE.
FIRE WEATHER
FAIRLY TYPICAL MONSOON CONDITIONS REMAIN IN PLACE THROUGH TONIGHT
BEFORE MORE NOTABLE DRYING OCCURS FROM WEST TO EAST ON WEDNESDAY.
LOW CHANCES (10-20% AT MOST) FOR SCATTERED SHOWERS AND EVEN SOME
ISOLATED STORMS REMAIN POSSIBLE THIS EVENING AND OVERNIGHT FOR
PORTIONS OF SOUTHWEST AND SOUTH-CENTRAL AZ, WITH GUSTY, ERRATIC
WINDS AND LOCALLY HEAVY RAINFALL THE MAIN CONCERNS. NEAR TO SLIGHTLY
ABOVE NORMAL TEMPERATURES WILL CONTINUE THROUGH MID WEEK BEFORE EVEN
HOTTER TEMPERATURES ARRIVE LATE WEEK INTO THE WEEKEND. HUMIDITIES
WILL DECREASE THROUGH THE REST OF THE WEEK, WITH AFTERNOON MINIMUMS
DROPPING INTO A 7-15% RANGE ACROSS THE WESTERN DISTRICTS AND 12-20%
RANGE ACROSS THE EASTERN DISTRICTS, FOLLOWING POOR TO FAIR OVERNIGHT
RECOVERIES STARTING WEDNESDAY NIGHT. WINDS OUTSIDE OF THUNDERSTORM
OUTFLOWS WILL FOLLOW FAIRLY TYPICAL TRENDS WITH UPSLOPE/UPVALLEY
AFTERNOON AND EARLY EVENING GUSTS INTO A 20-25 MPH RANGE COMMON. AS
THE DRYING OCCURS DURING THE LATTER HALF OF THE WEEK, LOCALLY
ELEVATED FIRE WEATHER CONDITIONS ARE LIKELY TO DEVELOP, WITH LOW
AFTERNOON HUMIDITIES AND THE TYPICAL UPSLOPE/UPVALLEY BREEZINESS.
PSR WATCHES/WARNINGS/ADVISORIES
AZ...EXTREME HEAT WARNING UNTIL 8 PM MST SUNDAY FOR AZZ530-532-537-
540-542>544-546-548-550-551.
EXTREME HEAT WARNING FROM 10 AM THURSDAY TO 8 PM MST SUNDAY FOR
AZZ531-533>536-538-539-541-545-547-549-552>563.
CA...EXTREME HEAT WARNING UNTIL 8 PM PDT SUNDAY FOR CAZ567-569-570.
EXTREME HEAT WARNING FROM 10 AM THURSDAY TO 8 PM PDT SUNDAY FOR
CAZ560>566-568.
SHORT TERM...WHITTOCK
LONG TERM...WHITTOCK
AVIATION...18
FIRE WEATHER...WHITTOCK
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