686
FXUS65 KPSR 201110
AFDPSR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
410 AM MST SAT DEC 20 2025
UPDATE...UPDATED 12Z AVIATION DISCUSSION
KEY MESSAGES
- DRY AND TRANQUIL WEATHER CONDITIONS WITH WELL-ABOVE NORMAL TEMPERATURES
WILL CONTINUE TO PREVAIL ACROSS THE REGION INTO EARLY NEXT
WEEK.
- AN UNSETTLED WEATHER PATTERN IS EXPECTED MID AND LATE NEXT WEEK
WITH INCREASED RAIN CHANCES AND COOLER TEMPERATURES.
SHORT TERM /TODAY THROUGH MONDAY/
AN UPPER-LEVEL RIDGE CURRENTLY SITUATED JUST WEST OF THE BAJA
PENINSULA WILL CONTINUE TO INFLUENCE THE WEATHER PATTERN ACROSS
THE DESERT SOUTHWEST HEADING INTO EARLY NEXT WEEK AS IT SLOWLY
MIGRATES EASTWARD. AS IT HAS BEEN THE CASE FOR THE PAST SEVERAL
DAYS, THE RIDGE WILL CONTINUE TO PROMOTE DRY AND TRANQUIL WEATHER
WITH UNSEASONABLY WARM TEMPERATURES OF AROUND 10-15 DEGREES ABOVE
NORMAL. AFTERNOON HIGH TEMPERATURES TODAY WILL BE SLIGHTLY COOLER
COMPARED TO YESTERDAY, TOPPING OUT IN THE MID TO UPPER 70S ACROSS
THE LOWER DESERTS. FOR SUNDAY AND MONDAY, TEMPERATURES WILL BE
SLIGHTLY WARMER, IN THE UPPER 70S TO AROUND 80 DEGREES ACROSS THE
LOWER DESERTS. DAILY RECORD HIGHS ARE LIKELY TO BE TIED/BROKEN
BOTH SUNDAY AND MONDAY AT PHOENIX SKY HARBOR, WITH THE LATEST NBM
SHOWING A GREATER THAN 70% CHANCE OF OCCURRENCE.
LONG TERM /TUESDAY THROUGH FRIDAY/
TUESDAY IS LIKELY TO BE A TRANSITION DAY OF WHAT IS EXPECTED TO
BECOME AN UNSETTLED WEATHER PATTERN HEADING TOWARDS THE CHRISTMAS
HOLIDAY PERIOD. THE RIDGE OF HIGH PRESSURE 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 HIGH TOP OUT IN THE MID TO UPPER
70S ACROSS THE LOWER DESERTS.
ENSEMBLES SHOW MOISTURE INCREASING QUITE RAPIDLY BETWEEN LATE
TUESDAY THROUGH WEDNESDAY WITH BOTH THE EPS AND GEFS SHOWING PWATS
REACHING 200-300% OF NORMAL. MODELS SHOW A WEAK SUBTROPICAL
SHORTWAVE MOVING ARIZONA TUESDAY EVENING INTO EARLY WEDNESDAY AND
MAY SPARK SOME LIGHT ISOLATED SHOWERS. A STRONGER SHORTWAVE OUT
AHEAD OF THE MAIN PARENT TROUGH THAT WILL STILL BE CENTERED OFF
THE WEST COAST WILL MIGRATE FROM SOUTHWEST TO NORTHEAST TOWARDS
THE GREAT BASIN. THIS SHORTWAVE IN COMBINATION WITH THE AVAILABLE
MOISTURE THAT WILL BE IN PLACE WILL LIKELY GENERATE WIDESPREAD
SHOWER ACTIVITY LATER WEDNESDAY INTO THURSDAY. THERE CONTINUES TO
BE A GOOD DEAL OF UNCERTAINTY IN THE OVERALL RAIN AMOUNTS AS IT
WILL ALL BE DEPENDENT ON WHERE THIS SHORTWAVE TRACKS WITH THE
UPSLOPE REGIONS FAVORED TO RECEIVE THE HIGHEST RAINFALL AMOUNTS AT
THIS TIME GIVEN THAT THE FORCING MAY BE A BIT TOO FAR TO THE
NORTHWEST FOR THE LOWER DESERTS TO RECEIVE SIGNIFICANT RAINFALL.
HOWEVER, IF THE SHORTWAVE DOES TRACK A BIT FURTHER EAST THAN
CURRENTLY PROJECTED, THEN THE LOWER DESERTS WILL HAVE A HIGHER
CHANCE OF RECEIVING MORE SIGNIFICANT RAINFALL.
AFTER THE AFOREMENTIONED SHORTWAVE MOVES THROUGH, THERE MAY BE A
BREAK IN THE RAINFALL ACTIVITY BEFORE THE MAIN PARENT TROUGH MOVES
INLAND SOMETIME LATE NEXT WEEK INTO NEXT WEEKEND AND LIKELY
GENERATES MORE SHOWER ACTIVITY. HOWEVER, THIS PART OF THE FORECAST
IS OF HIGH UNCERTAINTY GIVEN THAT BOTH THE DETERMINISTIC AND
ENSEMBLE MODEL GUIDANCE DIFFER ON THE POSITIONING, STRENGTH AND
TIMING OF THE TROUGH AS IT MIGRATES INLAND. TEMPERATURES TOWARDS
THE LATTER HALF OF NEXT WEEK WILL GRADUALLY COOL DOWN BY ABOUT
5-10 DEGREES FROM THE READINGS EARLIER IN THE WEEK, BUT STILL
REMAIN ABOVE NORMAL.
AVIATION
UPDATED AT 1110Z.
SOUTH CENTRAL ARIZONA INCLUDING KPHX, KIWA, KSDL, AND KDVT; AND
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:
NO AVIATION WEATHER CONCERNS UNDER PERIODS OF THICKER CIRRUS
CLOUD DECKS CAN BE EXPECTED DURING THE NEXT 24 HOURS. WINDS WILL
REMAIN LIGHT WITH ONLY SUBTLE DIURNAL DIRECTIONAL SHIFTS. EXTENDED
PERIODS OF VARIABLE TO EVEN CALM CONDITIONS WILL BE COMMON.
FIRE WEATHER
HIGH PRESSURE ACROSS THE REGION WILL CONTINUE TO PROMOTE DRY AND
TRANQUIL WEATHER AS WELL AS UNSEASONABLY WARM TEMPERATURES, 10 TO 15
DEGREES ABOVE NORMAL, INTO EARLY NEXT WEEK. WINDS WILL GENERALLY BE
LIGHT UNDER 15 MPH. AFTERNOON MINRHS WILL RANGE BETWEEN 20-35% WITH
GOOD OVERNIGHT RECOVERIES OF 40-70%. A TRANSITION TO A MORE
UNSETTLED WEATHER PATTERN WITH INCREASING RAIN CHANCES AND COOLER
TEMPERATURES IS LIKELY MID AND LATE NEXT WEEK.
PSR WATCHES/WARNINGS/ADVISORIES
AZ...NONE.
CA...NONE.
SHORT TERM...LOJERO
LONG TERM...LOJERO
AVIATION...LOJERO/18
FIRE WEATHER...LOJERO
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