490
FXUS65 KPSR 261128
AFDPSR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
428 AM MST MON OCT 26 2026
UPDATE
UPDATED 12Z AVIATION DISCUSSION.
KEY MESSAGES
- TEMPERATURES WILL REMAIN WITHIN THE NORMAL RANGE THROUGH
THURSDAY WITH LOWER DESERT HIGHS MOSTLY IN THE EIGHTIES.
- DRY AND TRANQUIL WEATHER CONDITIONS WILL LAST THROUGH THE MIDDLE
OF WEEK WITH INCREASING CLOUDS STARTING WEDNESDAY.
- AN UNSETTLED WEATHER PATTERN WILL RETURN LATE WEEK AND LAST
THROUGH THE WEEKEND WITH THE BEST RAIN CHANCES ON FRIDAY AND
SUNDAY.
SHORT TERM /TODAY THROUGH WEDNESDAY/
QUIET WEATHER CONDITIONS HAVE SETTLED INTO THE REGION UNDER
QUASI-ZONAL WESTERLY FLOW ALOFT. A DRY AIR MASS NOW IN PLACE WILL
KEEP SKIES CLEAR TO MOSTLY CLEAR THROUGH TUESDAY, WHILE
TEMPERATURES RISE A BIT UNDER THE MODESTLY HIGHER HEIGHTS ALOFT.
DAYTIME HIGHS ARE EXPECTED TO REACH INTO THE MID 80S ACROSS THE
LOWER DESERTS STARTING TODAY AND LAST THROUGH THE MIDDLE PART OF
THE WEEK DESPITE INCREASING CLOUDS STARTING WEDNESDAY. OVERNIGHT
LOWS WILL ALSO FALL WITHIN THE NORMAL RANGE THROUGH WEDNESDAY WITH
LOWER DESERT READINGS MOSTLY BETWEEN 55-60 DEGREES.
LONG TERM /THURSDAY THROUGH SUNDAY/
THE WEATHER PATTERN IS EXPECTED TO SHIFT LATE THIS WEEK WITH A
DEEP TROUGH GETTING CARVED OUT OVER THE PACIFIC NORTHWEST AND
SOUTHWESTWARD TO OFF THE COAST OF CALIFORNIA BY THURSDAY. THE
POLAR JET ASSOCIATED WITH THE NORTHERN STREAM SYSTEM IS EXPECTED
TO DIP FARTHER SOUTHWARD OFF THE WEST COAST, WHILE A STRONGER
SUBTROPICAL JET ACROSS THE CENTRAL PACIFIC SHIFTS EASTWARD TOWARD
BAJA. ALTHOUGH THESE JET BRANCHES ARE NOT EXPECTED TO PHASE
TOGETHER GOING INTO FRIDAY, THERE IS LIKELY TO BE SOME COMBINED
ENERGY REACHING THE WESTERN U.S.
AS THE TROUGH SETS UP TO OUR WEST ON WEDNESDAY INTO THURSDAY, HIGH
LEVEL MOISTURE WILL STREAM INTO OUR REGION, FOLLOWED BY INCREASING
SOUTHERLY MOIST FLOW IN THE LOWER LEVELS THURSDAY NIGHT INTO
FRIDAY. GUIDANCE IS IN VERY GOOD AGREEMENT SOUTHERLY LOW LEVEL
MOIST ADVECTION WILL COMBINE WITH SOME TOP-DOWN SATURATION IN THE
UPPER LEVELS ON FRIDAY ACROSS SOUTHERN AND CENTRAL ARIZONA. PWATS
ARE SHOWN TO QUICKLY RISE TO JUST ABOVE 200% OF NORMAL BY FRIDAY
MORNING, WHILE LOW LEVEL MIXING RATIOS RISE TO A RESPECTABLE 8-9
G/KG. THIS DECENT MOISTURE IS ALSO EXPECTED TO COINCIDE WITH
MODEST LOW LEVEL UPSLOPE FORCING AND QUITE STRONG MID AND UPPER
LEVEL ASCENT WITHIN THE LEFT EXIT REGION OF THE SUBTROPICAL JET.
ALTHOUGH WE ARE STILL FOUR DAYS OUT, CONFIDENCE IS QUITE GOOD IN
SHOWER ACTIVITY BLOSSOMING AT SOME POINT THURSDAY NIGHT/FRIDAY
MORNING ACROSS SOUTH-CENTRAL ARIZONA AND LASTING THROUGH MUCH OF
FRIDAY. GUIDANCE ALSO SHOWS MODEST MUCAPE OF 250-500 J/KG ON
FRIDAY WHICH SHOULD ALLOW FOR SOME ISOLATED TO SCATTERED WEAK
THUNDERSTORMS. SHEAR VALUES LOOK TO BE ON THE LOW SIDE, SO AT THIS
POINT WE ARE NOT ANTICIPATING ANY STRONG STORMS. FORECAST QPF
FROM THURSDAY NIGHT THROUGH FRIDAY NIGHT CURRENTLY AVERAGES AROUND
0.50" ACROSS THE PHOENIX AREA TO UPWARDS OF 0.75-1.00" IN THE
HIGHER TERRAIN NORTH OF PHOENIX. THE HIGHER END OF GUIDANCE IS AT
LEAST DOUBLE THAT, SO IT'S NOT OUT OF THE QUESTION TO HAVE TO
WORRY ABOUT SOME MINOR FLOODING ISSUES FRIDAY. WPC HAS ALSO
INCLUDED THIS AREA IN A SLIGHT RISK ON THEIR DAY 5 ERO.
THE FRIDAY WEATHER EVENT WILL NOT BE THE LAST PERIOD OF RAIN
EXPECTED OVER THE NEXT WEEK AS ANOTHER LIKELY EVEN STRONGER SYSTEM
IS FORECAST TO TRACK EAST NORTHEASTWARD TOWARD SOUTHERN CALIFORNIA
AND NORTHERN BAJA ON SATURDAY BEFORE MOVING THROUGH OUR REGION
ON SUNDAY. THERE IS MUCH MORE UNCERTAINTY WITH THIS SECOND
WEATHER SYSTEM COMPARED TO THE FIRST AS THERE ARE NOTABLE TIMING
AND EVOLUTION DIFFERENCES. THERE ARE ALSO SOME DIFFERENCES WITH
THE POTENTIAL PHASING OF THE POLAR AND SUBTROPICAL JET STREAMS
WHICH IF IT OCCURS WOULD LIKELY RESULT IN A DECENT LOW PRESSURE
SYSTEM DEVELOPING WITHIN THE BASE OF THE LARGE SCALE TROUGH.
MODELS AT LEAST AGREE THAT THERE WILL BE AS MUCH IF NOT BETTER
MOISTURE THEN THE FRIDAY SYSTEM AND STRONGER MID-LEVEL AND FRONTAL
ASCENT. GIVEN THE UNCERTAINTY, QPF AMOUNTS ARE STILL QUITE
VOLATILE TO ANY BIG CHANGES IN THE STRENGTH OF THE SYSTEM AND
TRACK. HOWEVER, SO FAR ENSEMBLE MEAN QPF AMOUNTS INDICATE OVERALL
HIGHER AVERAGE AMOUNTS COMPARED TO FRIDAY'S EVENT, AS WELL AS MORE
WIDESPREAD COVERAGE. RAIN CHANCES COULD ALSO EXTEND INTO MONDAY,
ESPECIALLY ACROSS EASTERN PORTIONS OF ARIZONA.
TEMPERATURES WILL TAKE A HIT LATER THIS WEEK AND THROUGH THE
WEEKEND WITH NBM FORECAST HIGHS DROPPING INTO A 75-80 DEGREE RANGE
FRIDAY AND SATURDAY AND EVEN LOWER STARTING SUNDAY. THE COOLEST
AIR SO FAR THIS FALL SHOULD MOVE IN WITH THE SUNDAY WEATHER
SYSTEM AS HIGHS MAY FALL TO AS THE UPPER 60S TO LOWER 70S FOR
SUNDAY AND MONDAY.
AVIATION
UPDATED AT 1127Z.
SOUTH CENTRAL ARIZONA INCLUDING KPHX, KIWA, KSDL, AND KDVT:
NO AVIATION WEATHER CONCERNS EXPECTED THROUGH THE TAF PERIOD
UNDER FEW HIGH CIRRUS. THE OVERALL WIND PATTERN WILL CONTINUE TO
FOLLOW TYPICAL DIURNAL TENDENCIES, BUT WITH WIND SPEEDS MOSTLY
UNDER 6 KTS. THERE WILL ALSO BE EXTENDED PERIODS OF LIGHT
VARIABILITY TO CALM CONDITIONS.
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:
NO AVIATION WEATHER CONCERNS EXPECTED THROUGH THE TAF PERIOD UNDER
MOSTLY CLEAR SKIES. WIND SPEEDS WILL MOSTLY STAY BELOW 6 KTS WITH
A WESTERLY COMPONENT FAVORED AT KIPL AND PREDOMINANTLY VARIABLE AT
KBLH. EXTENDED PERIODS OF LIGHT VARIABILITY TO CALM CONDITIONS CAN
BE EXPECTED AT KIPL AS WELL.
FIRE WEATHER
WEAK HIGH PRESSURE WILL REMAIN OVER THE REGION EARLY THIS WEEK
ALLOWING FOR GRADUAL DRYING AND TEMPERATURES WITHIN THE NORMAL
RANGE. MINIMUM HUMIDITY LEVELS WILL CONTINUE TO FALL, REACHING
20-35% TODAY AND 15-30% TUESDAY. OVERNIGHT RECOVERIES WILL REMAIN
GOOD AT 40-65%. WINDS WILL REMAIN LIGHT EACH DAY FAVORING TYPICAL
DIURNAL PATTERNS. A SHIFT IN THE WEATHER PATTERN LATE THIS WEEK
AND INTO NEXT WEEKEND SHOULD BRING ABOUT COOLER, WETTER, AND
BREEZIER CONDITIONS.
PSR WATCHES/WARNINGS/ADVISORIES
AZ...NONE.
CA...NONE.
SHORT TERM...KUHLMAN
LONG TERM...KUHLMAN
AVIATION...BENEDICT/LOJERO
FIRE WEATHER...KUHLMAN
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