875
FXUS65 KPSR 210531
AFDPSR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
1031 PM MST SAT DEC 20 2025
UPDATE
UPDATED AVIATION DISCUSSION
KEY MESSAGES
- DRY AND TRANQUIL WEATHER CONDITIONS WITH WELL-ABOVE NORMAL
TEMPERATURES WILL PREVAIL ACROSS THE REGION INTO EARLY NEXT
WEEK.
- AN UNSETTLED WEATHER PATTERN IS EXPECTED MID AND LATE NEXT WEEK
WITH INCREASED RAIN CHANCES AND SLIGHTLY COOLER TEMPERATURES.
SHORT TERM /TODAY THROUGH MONDAY/
DRY AND TRANQUIL CONDITIONS, WITH ABOVE NORMAL TEMPERATURES (10-15
DEGREES), WILL CONTINUE THROUGH THE START OF THE COMING WORKWEEK,
AS HIGH PRESSURE REMAINS SITUATED JUST TO THE SOUTH. THE MAIN
WEATHER-RELATED TALKING POINT FOR THE NEXT FEW DAYS WILL BE THE
POTENTIAL FOR DAILY RECORD HIGH TEMPERATURES. MOST LOWER DESERT
LOCATIONS ARE FORECAST TO REACH THE UPPER-70S TO LOWER 80S AND BE
WITHIN A FEW DEGREES OF DAILY RECORDS THROUGH MONDAY. PHOENIX
CURRENTLY HAS THE HIGHEST PROBABILITIES OF EXPERIENCING RECORD
HIGHS WITH AROUND 70-90% CHANCE SUNDAY AND MONDAY. MORNING LOW
TEMPERATURES WILL REMAIN COOL, BUT ALSO UP TO 10 DEGREES ABOVE
NORMAL, WITH URBAN AREAS IN THE LOW 50S AND RURAL AND VALLEY
AREAS IN THE MID TO UPPER 40S.
LONG TERM /TUESDAY THROUGH FRIDAY/
TUESDAY IS LIKELY TO BE A TRANSITION DAY INTO WHAT IS EXPECTED TO
BECOME AN UNSETTLED WEATHER PATTERN AROUND THE CHRISTMAS HOLIDAY
AND FOLLOWING WEEKEND. THE RIDGE OF HIGH PRESSURE, WHICH HAS LED
TO THE PROLONGED PERIOD OF ABOVE NORMAL TEMPERATURES, IS EXPECTED
TO MIGRATE INTO TEXAS WHILE A DEEP TROUGH DEVELOPS OFF THE WEST
COAST. AFTERNOON HIGH TEMPERATURES ON TUESDAY WILL CONTINUE TO
REMAIN UNSEASONABLY WARM AS AFTERNOON HIGHS TOP OUT IN THE MID TO
UPPER 70S ACROSS THE LOWER DESERTS. PHOENIX MAY EVEN SEE ANOTHER
DAILY RECORD HIGH, WITH A FORECAST HIGH OF 79 DEGREES AND THE
RECORD BEING 79.
ENSEMBLES SHOW A RAPID MOISTURE INCREASE TUESDAY WITH BOTH THE
EPS AND GEFS SHOWING BELOW NORMAL PWATS IN THE MORNING AND THEN
QUICKLY REACHING 200-300% OF NORMAL BY MIDNIGHT. MODELS ALSO SHOW
A WEAK SUBTROPICAL SHORTWAVE MOVING INTO ARIZONA WITH THE
MOISTURE FLUX TUESDAY EVENING INTO EARLY WEDNESDAY, WHICH MAY
SPARK AT LEAST SOME LIGHT SHOWERS. THIS SHORTWAVE LOOKS TO MOVE
THROUGH RATHER QUICKLY, WITH SOME MID-LEVEL DRYING AND SUBSIDENCE
ON THE BACK SIDE THAT COULD PROVIDE A BRIEF LAPSE IN RAIN CHANCES
ACROSS THE LOWER DESERTS BEFORE THE NEXT WAVE.
A NEGATIVELY TILTED SHORTWAVE ROUNDING THE BASE OF THE LONGWAVE
COASTAL TROUGH LATE WEDNESDAY MORNING INTO WEDNESDAY AFTERNOON
WILL GUIDE A MODERATE AR (IVT UP TO 500-700KG/MS) INTO SOCAL AND
HELP DRIVE WHAT LOOKS TO DRIVE THE HEAVIEST PRECIPITATION OF THE
FORECAST FOR THE WINDWARD SIDE OF THE CALIFORNIA MOUNTAINS. GLOBAL
MODELS SHOW GOOD AGREEMENT IN TRACKING THE PRIMARY FORCING WITH
THIS WAVE, AND THE AXIS OF THE HIGHEST IVT VALUES, ACROSS SOCAL
AND UP THROUGH SOUTHERN NV AND NORTHWEST AZ. THIS TRACK IS NOT
FAVORABLE FOR WIDESPREAD RAIN ACROSS THE INTERIOR DESERTS AND
RAIN-SHADOWING WILL LIKELY LIMIT THE PRECIPITATION CHANCES IN
SOUTHEAST CA. HOWEVER, RAIN CHANCES STILL GO UP LATER WEDNESDAY
INTO THURSDAY (CHRISTMAS DAY) AS THE MAIN IVT AXIS SHIFTS FURTHER
EAST INTO AZ. THE PERSISTENT FLUX OF MOISTURE INTO THE REGION
SHOULD ALLOW FOR AREAS OF SCATTERED SHOWERS TO DEVELOP, WITH BEST
RAIN CHANCES FAVORING SOUTH AND SOUTHWEST-FACING SLOPES OF CENTRAL
AND WESTERN AZ.
HEADING INTO FRIDAY AND SATURDAY, GLOBAL MODELS SHOW A SLOW TREND
DOWN IN MOISTURE LEVELS, WITH SOME MID-LEVEL DRYING SHOWING UP IN
FORECAST SOUNDINGS. THERE ARE ALSO HINTS THAT WEAK SHORTWAVE
RIDGING WILL BRIEFLY DEVELOP OVER THE AREA, DOWNSTREAM OF THE
STILL PRESENT COASTAL TROUGH, AND HELP STABILIZE THINGS. FOR THESE
REASONS, POPS WERE LOWERED FROM THE BASE NBM. EVENTUALLY THE
COASTAL TROUGH SHOULD SLIDE ACROSS THE REGION, PROBABLY TOWARD THE
END OF NEXT WEEKEND, BUT GLOBAL MODEL SOLUTIONS DIVERGE
SIGNIFICANTLY BY NEXT WEEKEND, SO CONFIDENCE IS LOW.
OVERALL, THERE CONTINUES TO BE A GREAT DEAL OF UNCERTAINTY IN THE
RAINFALL FORECAST, ESPECIALLY FOR THE LOWER DESERTS. LATEST WPC
QPF HAS WIDESPREAD 0.5-1.0" STORM TOTAL AMOUNTS, WED-SAT, WITH
LOCALLY HIGHER AMOUNTS IN TERRAIN FAVORED AREAS OF SOUTHEAST CA
AND SOUTHERN AZ. SOME OF THESE HIGHER RAINFALL AMOUNTS IN THE
LOWER DESERTS ARE LIKELY A RESULT OF THE COARSER GLOBAL MODELS
BLEEDING OUT FROM THE HIGHER TERRAIN. WOULD NOT BE SURPRISED TO
SEE RAINFALL AMOUNTS CONSIDERABLY LOWER OVER THE NEXT SEVERAL
DAYS. FOR AZ, GLOBAL ENSEMBLES SUPPORT YAVAPAI AND MOHAVE COUNTIES
RECEIVING THE MOST RAINFALL, WITH 50-70% CHANCES OF EXCEEDING 1".
BEST CHANCES FOR HIGHER END RAINFALL AMOUNTS IN SOUTHEAST CA WILL
BE IN JOSHUA TREE NP.
TEMPERATURES THROUGH THIS PERIOD OF UNSETTLED WEATHER WILL COOL,
BUT NOT DRAMATICALLY, GIVEN THE MAIN TROUGH STAYS TO THE WEST. THE
NBM EVEN HAS TEMPERATURES STAY ABOVE NORMAL. THE EXTRA CLOUDS,
SOME RAIN-COOLED AIR, AND LOWERED HEIGHTS WILL NOT BE ENOUGH TO
DROP THINGS BACK TO NORMAL. AFTERNOON HIGHS WILL REMAIN MOSTLY IN
THE 70S. LOW TEMPERATURES WILL ACTUALLY COME UP A BIT, DUE TO THE
EXTRA INSULATION AND MOISTURE. PHOENIX IS FORECAST TO BREAK A FEW
RECORD WARM LOWS DURING THE SECOND HALF OF NEXT WEEK. A MORE
SIGNIFICANT COOLDOWN WILL LIKELY NOT HAPPEN UNTIL THE COASTAL
TROUGH FULLY MOVES THROUGH.
AVIATION
UPDATED AT 0530Z.
SOUTH CENTRAL ARIZONA INCLUDING KPHX, KIWA, KSDL, AND KDVT; AND
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:
NO AVIATION CONCERNS ARE EXPECTED FOR MOST SITES DURING THE TAF
PERIOD UNDER SCT-BKN HIGH CIRRUS DECKS. THE ONE EXCEPTION TO THIS
WILL BE AT KIPL WHERE POTENTIAL FG/BR DEVELOPMENT IS POSSIBLE
EARLY SUNDAY MORNING. HOWEVER, CONFIDENCE REGARDING THESE
CONDITIONS IS LOW AND THEREFORE DIRECT IMPACTS AT THE TAF SITE
HAVE BEEN LEFT OUT OF THE FORECAST FOR NOW. A VCFG GROUP HAS BEEN
ADDED AT THIS TIME BUT FUTURE ADJUSTMENTS MAY BE NEEDED THROUGH
THE NIGHT IF VIS BEGINS TO DETERIORATE. WINDS WILL CONTINUE TO BE
LIGHT WITH SUBTLE DIRECTIONAL SHIFTS. VRB TO CALM CONDITIONS WILL
BE COMMON THROUGH SUNDAY.
FIRE WEATHER
HIGH PRESSURE ACROSS THE REGION WILL CONTINUE TO PROMOTE DRY AND
TRANQUIL WEATHER, AS WELL AS UNSEASONABLY WARM TEMPERATURES UP TO
10 TO 15 DEGREES ABOVE NORMAL THROUGH EARLY NEXT WEEK. WINDS WILL
GENERALLY BE LIGHT UNDER 15 MPH AND TEND TO FOLLOW TYPICAL DIURNAL
TRENDS. AFTERNOON MINRHS WILL RANGE BETWEEN 20-35% WITH GOOD
OVERNIGHT RECOVERIES OF 40-70%. A TRANSITION TO A MORE UNSETTLED
WEATHER PATTERN WITH HIGHER MOISTURE, INCREASED RAIN CHANCES AND
COOLER TEMPERATURES IS LIKELY MID AND LATE NEXT WEEK.
PSR WATCHES/WARNINGS/ADVISORIES
AZ...NONE.
CA...NONE.
SHORT TERM...BENEDICT
LONG TERM...BENEDICT
AVIATION...RW
FIRE WEATHER...LOJERO/BENEDICT
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