396
FXUS65 KPSR 220927
AFDPSR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
227 AM MST MON DEC 22 2025
KEY MESSAGES
- QUIET WEATHER WITH WELL-ABOVE NORMAL TEMPERATURES WILL CONTINUE
TODAY ACROSS THE REGION.
- AN UNSETTLED WEATHER PATTERN IS EXPECTED BEGINNING LATE TUESDAY
AND PERSISTING THROUGH LATE WEEK WITH INCREASED RAIN CHANCES AND
COOLING TEMPERATURES.
SHORT TERM /TODAY THROUGH TUESDAY/
AN UPPER-LEVEL RIDGE OF HIGH PRESSURE SITUATED OVER NORTHERN
MEXICO WILL CONTINUE TO PROVIDE ONE MORE FULL DAY OF DRY, TRANQUIL
WEATHER CONDITIONS. WELL-ABOVE NORMAL TEMPERATURES WILL CONTINUE
WITH AFTERNOON HIGHS ACROSS THE LOWER DESERTS TOPPING OUT IN THE
MID TO UPPER 70S ACROSS SOUTHEAST CA AND SOUTHWEST AZ TO LOW 80S
ACROSS SOUTH-CENTRAL AZ, INCLUDING THE PHOENIX METRO. IN FACT, IT
IS LIKELY (~80% CHANCE) OF PHOENIX ONCE AGAIN BREAKING ANOTHER
DAILY RECORD HIGH.
HEADING INTO TUESDAY, THE OVERALL PATTERN WILL GO INTO A
TRANSITIONAL STATE AS THE UPPER-LEVEL RIDGE MIGRATES EASTWARD
TOWARDS THE GULF COAST STATES, ALLOWING A DEEP TROUGH TO SETTLE OVER
THE EASTERN PACIFIC JUST OFF THE WEST COAST. THIS PATTERN
CONFIGURATION WILL PUT THE DESERT SOUTHWEST UNDER SOUTHWESTERLY
FLOW, WITH A STRONG PUSH OF MOISTURE FROM THE SUBTROPICS MOVING IN.
PWATS ARE PROJECTED TO QUICKLY RISE FROM 0.3-0.5" EARLY TUESDAY
MORNING TO AS HIGH 1.2-1.4" (300-350% OF NORMAL) BY LATE IN THE
EVENING. A WEAK SUBTROPICAL SHORTWAVE MOVING UP WITH THIS PUSH OF
MOISTURE IS LIKELY TO INSTIGATE SCATTERED LIGHT SHOWERS STARTING OUT
WEST OVER SOUTHWEST AZ TUESDAY AFTERNOON AND MOVING INTO SOUTH-
CENTRAL AZ BY TUESDAY EVENING AND PERSISTING INTO THE OVERNIGHT
HOURS. ONLY VERY MINOR RAINFALL ACCUMULATIONS, RANGING BETWEEN A
FEW HUNDREDTHS TO AS MUCH AS A TENTH OF AN INCH IS ANTICIPATED
WITH THIS INITIAL WAVE.
AFTERNOON HIGH TEMPERATURES WILL BE SLIGHTLY COOLER, WITH READINGS
RANGING FROM THE LOW TO MID 70S ACROSS THE WESTERN DESERTS WHERE
THICKER CLOUDS WILL LIMIT THE AMOUNT OF INSOLATION TO UPPER 70S
IN SOUTH-CENTRAL AZ. THERE IS EVEN THE POTENTIAL THAT PHOENIX MAY
ONCE AGAIN SEE ANOTHER DAILY RECORD HIGH, GIVEN THAT CURRENTLY THE
FORECAST HIGH IS 79 DEGREES WITH THE RECORD BEING 79.
LONG TERM /WEDNESDAY THROUGH NEXT WEEKEND/
ANY SHOWER ACTIVITY ACROSS SOUTH-CENTRAL AZ SHOULD QUICKLY COME TO
AN END EARLY WEDNESDAY MORNING AS THE SHORTWAVE QUICKLY LIFTS TO THE
NORTHEAST WITH SOME SUBSIDENCE AND MID-LEVEL DRYING OCCURRING ON ITS
WAKE. ATTENTION WILL THEN TURN TO A MUCH STRONGER SHORTWAVE THAT IS
PROJECTED TO MOVE OUT AHEAD OF THE MAIN TROUGH AND WILL MIGRATE FROM
SOUTHWEST TO NORTHEAST FROM SOUTHERN CA THROUGH THE GREAT BASIN.
THIS WAVE WILL DRIVE A MODERATE TO STRONG AR EVENT (IVT VALUES IN
EXCESS OF 500 KG/MS), AFFECTING MUCH OF CA AND THE SOUTHERN GREAT
BASIN REGION WITH HEAVY PRECIPITATION THROUGHOUT THE DAY. OVER
OUR REGION, THE IVT PLUME AND ASSOCIATED FORCING FROM THE
SHORTWAVE WILL DRIVE AN AREA OF RAINFALL FROM WEST TO EAST,
AFFECTING SOUTHEAST CA AND SOUTHWEST AZ DURING THE AFTERNOON AND
EVENING HOURS AND THEN AFFECTING SOUTH-CENTRAL AZ HEADING INTO THE
OVERNIGHT AND MORNING HOURS ON THURSDAY. THE HIGHEST RAINFALL
TOTALS ARE PROJECTED ACROSS THE UPSLOPE AREAS AND MOUNTAINS WHERE
OROGRAPHIC LIFT WILL BE MAXIMIZED. THE LATEST QPF FROM WPC HAS
RAINFALL TOTALS RANGING FROM OVER 1" ACROSS THE FOOTHILLS NORTH
OF PHOENIX AND IN WESTERN JOSHUA TREE NATIONAL PARK TO BETWEEN
0.50-1.00" IN THE PHOENIX AREA AND BETWEEN 0.10-0.50" ACROSS THE
REST OF THE LOWER DESERTS.
RAIN CHANCES WILL GRADUALLY DECLINE THURSDAY AFTERNOON THROUGH
FRIDAY AS SUBSIDENCE AND DRYING BEHIND THE SHORTWAVE MOVES
OVERHEAD. THE FORECAST THEN BECOMES HIGHLY UNCERTAIN HEADING INTO
THE WEEKEND AS BOTH THE DETERMINISTIC AND ENSEMBLE MODEL SUITE
CONTINUE TO DIVERGE ON THE OVERALL STRENGTH, TIMING, AND
TRAJECTORY OF THE MAIN TROUGH AS IT MIGRATES INLAND TOWARDS
REGION WITH SOLUTIONS RANGING FROM A MORE PROGRESSIVE TROUGH
PASSAGE (EPS AND GEPS SUITE) BY NEXT SATURDAY TO SHOWING THE
TROUGH HANGING BACK JUST OFFSHORE AND NOT MOVING THE FEATURE
THROUGH THE REGION UNTIL EARLY NEXT WEEK (GEFS AND THE AI SUITE).
THE OVERALL STRENGTH AND TRAJECTORY OF THE TROUGH WILL ALSO
DETERMINE IF THE AREA SEES ANOTHER ROUND OF PRECIPITATION.
WITH THE UNSETTLED PATTERN EVOLVING MID TO LATE WEEK, TEMPERATURES
ARE EXPECTED TO GRADUALLY COOL, BUT WILL REMAIN ABOVE NORMAL AS
AFTERNOON HIGHS WILL TOP IN THE LOW TO MID 70S. WITH THE ABUNDANT
MOISTURE AND CLOUD COVER THAT WILL BE IN PLACE, OVERNIGHT LOW
TEMPERATURES BETWEEN THE WEDNESDAY THROUGH FRIDAY TIME FRAME WILL BE
QUITE WARM FOR LATE DECEMBER, IN THE UPPER 50S TO AROUND 60 DEGREES
AND POTENTIALLY BREAKING RECORD WARM LOWS ACROSS ALL THREE CLIMATE
SITES (PHOENIX, YUMA, AND EL CENTRO). EVEN MORE OF A COOL DOWN TO
MORE SEASONAL LEVELS IS LIKELY ONCE THE MAIN TROUGH MOVES THROUGH,
HOWEVER, WHEN THAT EXACTLY OCCURS IS UNKNOWN AT THIS TIME GIVEN
THE LARGE UNCERTAINTIES IN THE TROUGH EVOLUTION HEADING INTO NEXT
WEEKEND.
AVIATION
UPDATED AT 0515Z.
SOUTH CENTRAL ARIZONA INCLUDING KPHX, KIWA, KSDL, AND KDVT; AND
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:
NO WEATHER CONCERNS WILL EXIST THROUGH MONDAY NIGHT UNDER GRADUALLY
INCREASING THICKER HIGH CIRRUS DECKS. WIND SPEEDS AND DIRECTIONS
WILL BE NEARLY IDENTICAL TO THE PAST 24 HOURS WITH PROLONGED PERIODS
OF NEARLY CALM CONDITIONS.
FIRE WEATHER
HIGH PRESSURE ACROSS THE REGION WILL CONTINUE TO PROMOTE DRY AND
TRANQUIL WEATHER TODAY ALONG WITH UNSEASONABLY WARM TEMPERATURES
AS AFTERNOON HIGHS TOP OUT IN THE UPPER 70S TO LOW 80S ACROSS THE
LOWER DESERTS. 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 50-75%. A
WEATHER SYSTEM IS EXPECTED TO AFFECT THE REGION MID AND LATE WEEK
BRINGING HIGHER MOISTURE, INCREASED RAIN CHANCES, AND COOLER
TEMPERATURES. THE INITIAL STRONG PUSH OF MOISTURE WILL COME
DURING THE DAY TUESDAY, WITH AFTERNOON MINRHS RANGING BETWEEN
20-50% AND MAXRH VALUES TUESDAY NIGHT JUMPING TO 75-100%. IN THE
FOLLOWING DAYS, MINRHS WILL BE IN THE 45-70% RANGE.
PSR WATCHES/WARNINGS/ADVISORIES
AZ...NONE.
CA...NONE.
SHORT TERM...BENEDICT
LONG TERM...BENEDICT
AVIATION...18
FIRE WEATHER...LOJERO/BENEDICT
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