406
FXUS65 KPSR 240010
AFDPSR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
510 PM MST SAT AUG 23 2025
UPDATE
UPDATED AVIATION DISCUSSION.
KEY MESSAGES
- ABOVE NORMAL TEMPERATURES PERSIST THIS WEEKEND RESULTING IN
FAIRLY WIDESPREAD MAJOR HEAT RISK, AND SO EXTREME HEAT WARNINGS
REMAIN IN EFFECT FOR MUCH OF THE LOWER DESERTS THROUGH SUNDAY.
- FOR THE REMAINDER OF TODAY, THERE WILL BE SLIGHT CHANCES FOR
SHOWERS AND STORMS MOSTLY OVER PROMINENT TERRAIN FEATURES OF
SOUTHWEST ARIZONA AND THE HIGH TERRAIN NORTH AND EAST OF
PHOENIX.
- CHANCES FOR SHOWERS AND STORMS GENERALLY INCREASE AND BECOME
MORE WIDESPREAD EACH DAY AS WE HEAD THROUGH THE FIRST HALF OF
THE UPCOMING WORK WEEK.
- TEMPERATURES COOL TO BELOW NORMAL DURING THE MIDDLE OF THE
UPCOMING WORK WEEK.
SHORT TERM /TODAY THROUGH SUNDAY/
A HIGH AMPLITUDE RIDGE IS SITUATED OVER THE WESTERN US, WITH A
MIDLEVEL ANTICYCLONE CENTERED ALONG NORTHERN AZ. MIDLEVEL WV
IMAGERY SHOWS THAT EASTERLY FLOW OVER THE FORECAST AREA HAS
BROUGHT IN ABUNDANT DRY AIR ALOFT, WHICH SHOULD ACT TO INHIBIT
CONVECTIVE POTENTIAL FOR THE REST OF THE DAY. A LAYER OF DRY AIR
BETWEEN 650 MB AND 400 MB IS QUITE APPARENT IN THE 12Z KPSR
SOUNDING AS WELL, REINFORCING THE INTERPRETATION OF THE SATELLITE
IMAGERY - THAT DRY AIR ALOFT HAS "PUNCHED" INTO THE REGION FROM
THE EAST. IN ADDITION TO THIS DRY AIR ALOFT, IT APPEARS AN
EASTERLY WAVE HAS PASSED THROUGH THE WESTERN CWA AND INTO SOCAL
THIS MORNING, AND SO AN AREA OF SUBSIDENCE IS LIKELY INHIBITING
ANY FURTHER CONVECTIVE DEVELOPMENT FOR SOUTHEASTERN CA FOR THE
REST OF THE DAY. ALL THIS IS NOT TO SAY THAT WE WILL NOT SEE
CONVECTION OVER THE CWA TODAY; SPC MESOANALYSIS STILL DEPICTS
ABUNDANT LOW-LEVEL MOISTURE, WITH MIXING RATIOS IN EXCESS OF
10-12 G/KG ACROSS MUCH OF THE AREA. RAP ANALYSIS ALSO SHOWS A FAIR
AMOUNT OF SFC AND 100 MB MIXED LAYER INSTABILITY, CERTAINLY
SUFFICIENT FOR SUPPORTING DEEP MOIST CONVECTION. HOWEVER, THE
COMBINATION OF A DEEP LAYER OF DRY AIR ALOFT AND
SUBSIDENCE/CAPPING OUT WEST TOWARDS SOUTHEAST CA MEANS THAT
CONVECTIVE POTENTIAL IS MUCH LESS THAN RAP ANALYZED CAPE WOULD
SUGGEST. LATEST CAMS SHOW MOST CONVECTION TODAY BEING CONFINED TO
THE KOFA AND HARCUVAR MOUNTAINS IN LA PAZ COUNTY, THE FOUR PEAKS,
MAZATZALS, AND PINAL MOUNTAINS EAST OF PHOENIX, AND POTENTIALLY
SOME ACTIVITY FROM PIMA COUNTY MAKING ITS WAY INTO SOUTHWESTERN
MARICOPA COUNTY LATER THIS AFTERNOON.
THE OVERALL SYNOPTIC PATTERN SHIFTS SLIGHTLY SUNDAY, WITH THE
ANTICYCLONE ADVERTISED TO MOVE SOUTHEASTWARD TOWARDS THE AZ/NM
BORDER AND MIDLEVEL STEERING FLOW TURNING MORE SOUTHEASTERLY.
LATEST HREF ADVERTISES BETTER COVERAGE OF THUNDERSTORMS ACROSS
SOUTHWEST AZ TOMORROW, PERHAPS AIDED BY THE RETURN OF MOISTER AIR
IN THE MIDLEVELS AND ANOTHER EASTERLY WAVE ROTATING AROUND THE
ANTICYCLONE AND THROUGH THE REGION. NEIGHBORHOOD PROBABILITIES FOR
WIND GUSTS >58 MPH HAVE ALSO INCREASED TO 10-30% OVER SOUTHWEST
AZ, HOWEVER, ENVIRONMENTAL CHARACTERISTICS ARE NOT TOO DISSIMILAR
TO THAT OF TODAY. HREF PROBABILITIES MAY BE PICKING UP ON A FEW
STRONGER STORMS FORMING OVER PIMA COUNTY AND NORTHERN SONORA THEN
BEING PUSHED INTO YUMA AND SOUTHWESTERN MARICOPA COUNTIES, WHERE
DCAPES ARE HIGHER, LEADING TO THE HIGHER PROBABILITIES FOR SEVERE
WIND GUSTS.
TEMPERATURES WILL REMAIN AROUND 5F ABOVE NORMAL THROUGH THE
REMAINDER OF THE WEEKEND, SUPPORTED BY ENSEMBLE MEAN H5 HEIGHTS IN
A 592-594 DAM RANGE. WITH THE AFOREMENTIONED LOW-LEVEL MOISTURE
IN PLACE, OVERNIGHT LOWS ARE ALSO NOT COOLING AS MUCH AS THEY
OTHERWISE WOULD, LEADING TO CONTINUED NEAR RECORD WARM VALUES. AS
SUCH, AREAS OF MAJOR HEATRISK PERSIST, AND EXTREME HEAT WARNINGS
WILL REMAIN IN PLACE THROUGH 8 PM MST/PDT SUNDAY EVENING.
LONG TERM /MONDAY THROUGH FRIDAY/
FOR THE FIRST HALF OF NEXT WEEK THE OVERALL SYNOPTIC PATTERN WILL
SHIFT, WITH THE SUBTROPICAL HIGH WEAKENING AND SHIFTING TO THE
SOUTH AND EAST. ENSEMBLES CONTINUE TO BE IN GOOD AGREEMENT THAT BY
THE BEGINNING OF NEXT WEEK THE OVERALL SYNOPTIC PATTERN WILL
SHIFT, WITH THE SUBTROPICAL HIGH WEAKENING AND SHIFTING TO THE
SOUTH AND EAST. THIS SHIFT WILL OCCUR DUE TO TWO TROUGHS, ONE
DIGGING INTO THE EAST/NORTH EAST PORTION OF THE US AND ANOTHER
TROUGH DIGGING OFF THE PACIFIC COAST. THIS WILL DO A COUPLE THINGS
FOR OUR REGION. ONE IT WILL SHIFT THE STEERING FLOW TO BE OUT OF
THE SOUTH/SOUTHEAST, WHICH WILL PROMOTE BETTER MOISTURE INTO OUR
REGION AND THUS AN INCREASE IN SHOWER AND STORM ACTIVITY. AND TWO,
THE WEAKENING OF THE HIGH WILL LEAD TO COOLING TEMPERATURES.
GLOBAL ENSEMBLES CONTINUE TO DISAGREE ON THE AMOUNT OF MOISTURE,
WITH A DIFFERENCE OF ABOUT 0.2" BETWEEN THE GEFS AND ECMWF ENSEMBLE.
BOTH SHOW PWATS PEAKING ON TUESDAY. THE GEFS SHOWS PWATS PEAKING
AROUND 1.4-1.7", WHEREAS THE ECMWF ENSEMBLE SHOWS PWATS PEAKING
AROUND 1.6-1.9". EITHER WAY, THE FIRST HALF OF NEXT WEEK LOOKS TO BE
RATHER ACTIVE. MONDAY MAY END UP BEING MORE OF A TRANSITION DAY,
WITH BETTER CHANCES ON TUESDAY AND WEDNESDAY, WITH TUESDAY CURRENTLY
LOOKING THE BEST. WITH THE COMBINATION OF LOWERING HEIGHTS ALOFT AND
INCREASED CLOUD COVER, FROM THE INCREASED POPS, TEMPERATURES ARE
EXPECTED TO COOL THROUGH THE MIDDLE OF NEXT WEEK. AFTERNOON HIGH
TEMPERATURES ARE FORECASTED TO COOL TO NEAR TO SLIGHTLY ABOVE NORMAL
ON MONDAY (104-108 DEGREES ACROSS THE LOWER DESERTS) AND FALL BELOW
NORMAL TUESDAY AND WEDNESDAY (FORECASTED HIGHS OF 98-103 DEGREES
ACROSS THE LOWER DESERTS). MORNING LOWS WILL ALSO BE COOLING NEXT
WEEK, WITH MORNING LOWS FORECASTED TO FALL INTO THE MID 70S TO MID
80S ACROSS THE LOWER DESERTS BY THE MIDDLE OF NEXT WEEK. DEPENDING
ON THE EXACT TIMING AND COVERAGE OF SHOWERS AND STORMS NEXT WEEK,
TEMPERATURES COULD BE EVEN COOLER THAN CURRENTLY FORECASTED.
BY THE END OF THE WORKWEEK, FLOW OVERHEAD WILL BECOME MORE
SW'RLY/W'RLY, WHICH WILL IN TURN CAUSE US TO SEE DRYING CONDITIONS.
OVERALL, ENSEMBLES SHOW PWATS GENERALLY IN THE 1.2-1.4" RANGE BY
THURSDAY AND IN THE 0.8-1.1" RANGE ON FRIDAY. WITH THE DRYING
CONDITIONS AND NO FORCING, OUR SHOWER AND STORM CHANCES WILL BE
COMING TO AN END ACROSS THE CWA. WHILE, HEIGHTS ALOFT WON'T CHANGE
TOO MUCH TO END THE WEEK, WITH THE DECREASING SHOWER AND STORM
CHANCES WE WILL SEE A RETURN OF MOSTLY CLEAR SKIES. THIS WILL RESULT
IN TEMPERATURES WARMING A FEW DEGREES. CURRENT FORECASTED AFTERNOON
HIGH TEMPERATURES ARE IN THE 98-104 DEGREE RANGE ACROSS THE LOWER
DESERTS FOR THURSDAY AND FRIDAY, WHICH ARE STILL A FEW DEGREES SHY
OF THE DAILY NORMALS FOR THIS TIME OF YEAR.
AVIATION
UPDATED AT 0010Z.
SOUTH CENTRAL ARIZONA INCLUDING KPHX, KIWA, KSDL, AND KDVT:
WINDS WILL MOSTLY FOLLOW TYPICAL DIURNAL TENDENCIES THROUGH
TOMORROW MORNING WITH SPEEDS MAINLY AOB 10 KT. A SLOW WESTERLY
SHIFT IS EXPECTED TOMORROW AFTERNOON, WITH LIGHT VARIABILITY
DURING THE TRANSITION. ODDS ARE HIGHER FOR THUNDERSTORM OUTFLOW
IMPACTS TOMORROW AFTERNOON AND EVENING. THERE IS GOOD CONFIDENCE
OF AN OUTFLOW FROM THE SOUTHWEST, AND AN OUTFLOW MAY ALSO ARRIVE
FROM THE NORTH. THERE IS UNCERTAINTY IN EXACT TIMING OF OUTFLOWS
AND WHICH DIRECTION WILL ARRIVE FIRST, BUT THEY WILL MOSTLY
LIKELY OCCUR AFTER 00Z. THERE IS CURRENTLY LOW CONFIDENCE IN VCTS
AT TERMINALS TOMORROW AFTERNOON AND EVENING, BUT THERE IS AT LEAST
A SLIGHT CHANCE (10-20%) FOR CONVECTION IN THE PHOENIX AREA
BEGINNING AS EARLY AS 22-23Z. FEW TO SCT MID AND HIGH CLOUDS WILL
PERSIST WITH DECKS AOA 10K FT AGL.
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:
WESTERLY WINDS NOW AT KIPL WILL TREND BACK TO A S/SE COMPONENT
LATER THIS EVENING/TONIGHT AND PERSIST THOUGH THE EARLY AFTERNOON
TOMORROW, WHILE KBLH WILL CONTINUE TO FAVOR A SOUTHERLY COMPONENT.
THERE WILL BE SLIGHT CHANCES (10-20%) FOR AN AFTERNOON/EVENING
SHOWER OR STORM TOMORROW AT BOTH TERMINALS, WITH MOST OF THE
ACTIVITY REMAINING WEST OF KIPL AND EAST TO NORTH OF KBLH. OUTFLOW
WINDS FROM STORMS WILL BE CAPABLE OF PRODUCING SUDDEN WIND SHIFTS
AND THERE WILL BE AROUND A 50% CHANCE FOR WIND GUSTS >30 KT FROM
ANY VCTS. FEW TO SCT MID AND HIGH CLOUDS WILL BE COMMON THROUGH
THE TAF PERIOD WITH LOWEST BASES AOA 10K FT AGL.
FIRE WEATHER
TEMPERATURES WILL REMAIN AROUND 5 DEGREES ABOVE NORMAL THROUGH
THE WEEKEND. DAILY THUNDERSTORM CHANCES WILL CONTINUE THROUGH THE
WEEKEND WITH MONSOONAL ACTIVITY EXPECTED TO EXPAND TO INCLUDE THE
WESTERN DISTRICTS. BEST CHANCES FOR STORMS THIS WEEKEND WILL BE
ACROSS THE WESTERN DISTRICTS. LIGHTNING, LOCALLY HEAVY RAINFALL,
AND GUSTY ERRATIC OUTFLOW WINDS WILL BE THE PRIMARY THREATS WITH
THUNDERSTORMS. MINRHS WILL BE AROUND 15-25% THROUGH THE WEEKEND,
WHILE MAX RHS WILL BE AROUND 40-50% FOR MOST AREAS. SHOWER AND
STORM CHANCES INCREASE FURTHER DURING THE FIRST HALF OF NEXT
WEEK. MINRHS IMPROVE TO 20-40% DURING THE FIRST PART OF NEXT WEEK,
WITH OVERNIGHT RECOVERIES IMPROVING TO 50-70% FOR THE FIRST HALF
OF NEXT WEEK. BY THE END OF NEXT WEEK WE WILL START DRYING OUT
AGAIN, SEEING STORM CHANCES COME TO AN END ALONG WITH RHS
DECREASING (MINRHS: 15-35% AND MAXRHS: 30-60% FOR THURSDAY AND
FRIDAY, WITH THE HIGHEST RHS ACROSS THE EASTERN DISTRICTS).
PSR WATCHES/WARNINGS/ADVISORIES
AZ...EXTREME HEAT WARNING UNTIL 8 PM MST SUNDAY FOR AZZ530>555-559.
CA...EXTREME HEAT WARNING UNTIL 8 PM PDT SUNDAY FOR CAZ560>570.
SHORT TERM...WHITTOCK
LONG TERM...BERISLAVICH
AVIATION...BENEDICT
FIRE WEATHER...WHITTOCK/BERISLAVICH
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