132
FXUS65 KPSR 122320
AFDPSR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
420 PM MST MON OCT 12 2026
UPDATE
UPDATED 00Z AVIATION DISCUSSION.
KEY MESSAGES
- PERIODS OF ISOLATED TO SCATTERED SHOWERS WILL CONTINUE TODAY
THROUGH TUESDAY MORNING.
- TEMPERATURES WILL CONTINUE TO COOL THROUGH THE FIRST HALF OF THE
WEEK WITH HIGHS DIPPING INTO THE SEVENTIES, WHILE OVERNIGHT
LOWS EASILY REACH INTO THE FIFTIES FOR TUESDAY AND WEDNESDAY.
- DRY WEATHER WILL SETTLE IN BY WEDNESDAY BEFORE BREEZY TO WINDY
CONDITIONS RETURN LATER IN THE WEEK AND TEMPERATURES SLOWLY
RETURN TO NEAR NORMAL.
SHORT TERM /TODAY THROUGH WEDNESDAY/
THE LOCAL AREA REMAINS DOWNSTREAM OF A LARGE WESTERN CONUS TROUGH
AND UNDER A PERSISTENT STRONG SSW FLOW. ISOLATED TO SCATTERED
SHOWERS CONTINUE TO DEVELOP ACROSS PORTIONS OF SOUTH-CENTRAL AZ.
MESOANALYSIS SHOWS THIS IS A HIGH SHEAR - LOW CAPE ENVIRONMENT AND
WITH WARM SOUTHERLY FLOW AND A LOT OF DRY AIR ALOFT, ABOVE 700MB,
THERE HAS HARDLY BEEN ANY LIGHTNING WITH THE ACTIVITY SO FAR TODAY.
REGARDLESS, THE SHOWERS HAVE BEEN STRONG ENOUGH AT TIMES TO PRODUCE
HIGH RAIN-RATES, WITH SOME INSTANTANEOUS RATES OBSERVED UP TO 1-
2"/HR. UNFORTUNATELY THE SHOWERS ARE ZOOMIN', MOVING NE AT ROUGHLY
30 KTS (35 MPH). THIS HAS INHIBITED THE POTENTIAL OF RECEIVING ANY
SIGNIFICANT RAINFALL FROM ANY ONE SHOWER. HOWEVER, WITH THE
UNIFORM SHEAR, SEVERAL SHOWERS HAVE FORMED INTO LINEAR SEGMENTS OR
HAVE DEVELOPED ALONG CONVERGENT CLOUD STREETS AND THIS ALLOWED
FOR A FEW AREAS TO PICK UP A QUICK 0.25-0.50". SHOWER CHANCES ARE
EXPECTED TO CONTINUE THROUGH THIS AFTERNOON AND EVENING, BUT THEY
WILL MAY BECOME MORE ISOLATED ACROSS THE LOWER DESERTS AND
FOCUSED MOSTLY OVER THE AZ HIGH TERRAIN TO THE NORTH, AS MODEL
SOUNDINGS SHOW LCLS LIFTING (DECREASING THE CLOUD DEPTH) AND DRY
AIR CONTINUING TO SLOWLY FILTER IN.
HEADING INTO TONIGHT A SHORTWAVE TROUGH AT THE BASE OF THE LARGER
WESTERN CONUS TROUGH IS EXPECTED TO SWING THROUGH THE AREA WITH A
WEAK SURFACE FRONTAL BOUNDARY. POPS GO UP AGAIN IN RESPONSE TO THIS,
UP TO 40-70% BETWEEN 10 PM AND 5 PM - WITH THE LATEST NBM -
ACROSS MARICOPA AND PINAL COUNTIES. SHOWERS SHOULD THEN SHIFT
COMPLETELY EAST OF THE PHOENIX AREA BY THE AFTERNOON TOMORROW AS
EVEN MORE DRY AIR FILTERS IN ALOFT. DESPITE THE SHORTWAVE AND
FRONT, RAINFALL IS EXPECTED TO REMAIN ON THE LIGHT SIDE,
ESPECIALLY WITH SHOWERS STILL MOVING VERY FAST. MOST AREAS ARE
LIKELY TO RECEIVE LESS THAN 0.25" (THIS INCLUDES RECEIVING NOTHING
AT ALL), WITH LATEST HREF ONLY SHOWING AROUND A 10% CHANCE OF
RECEIVING >0.25" ACROSS THE LOWER DESERTS WITH TONIGHT'S ACTIVITY.
HIGHEST RAINFALL POTENTIAL WILL BE ACROSS THE HIGHER TERRAIN
AREAS EAST AND NORTHEAST OF PHOENIX. A FEW ISOLATED SPOTS OF UP TO
1" OR MORE WILL STILL BE POSSIBLE WHERE STRONGER SHOWERS TRAIN
OVER THE SAME AREA.
A MUCH STRONGER COLD FRONT WILL SWEEP THROUGH THE AREA TOMORROW
NIGHT THROUGH WEDNESDAY MORNING AS THE DEEP LOW PRESSURE AT THE
CENTER OF THE LARGE WESTERN CONUS TROUGH DIGS THROUGH THE NORTHERN
HALF OF AZ. THIS WILL BE A DRY FRONT THAT WILL CLEAN OUT MUCH OF THE
LINGERING LOW LEVEL MOISTURE. DEW POINT TEMPERATURES ARE FORECAST TO
GO FROM THE MID TO UPPER 50S TUESDAY AFTERNOON IN THE PHOENIX AREA
TO DIPPING BELOW 50 DEGREES BY WEDNESDAY AFTERNOON. MEAN MIXING
RATIOS WILL ALSO DROP TO 3-5 G/KG ACROSS THE AREA BY WEDNESDAY
AFTERNOON. SO, NO ADDITIONAL SHOWERS ARE EXPECTED HEADING INTO
WEDNESDAY AS THE DRY AIR SURGES IN. IN ADDITION TO THE DRYING
CONDITIONS MIDWEEK, THE LOW WEDNESDAY WILL LEAD TO THE DEVELOPMENT
OF A N-S PRESSURE GRADIENT LEADING TO INCREASING NORTHERLY WINDS
ACROSS SOUTHEAST CALIFORNIA AND FAR WESTERN ARIZONA EARLY WEDNESDAY
LIKELY PEAKING LATE WEDNESDAY MORNING BEFORE THE GRADIENT RELAXES.
WIND GUSTS OF 25-30 MPH CAN BE EXPECTED ACROSS MUCH OF THE LOWER CO
RIVER VALLEY WEDNESDAY MORNING INTO THE AFTERNOON.
TEMPERATURES TODAY WILL NOT GET MUCH WARMER THAN THEY CURRENTLY ARE
EARLY THIS AFTERNOON. MOST LOWER DESERTS ARE IN THE 70S TO LOW-80S.
WITH THE SHORTWAVE TROUGH TONIGHT AND THEN STRONGER UPPER LOW MOVING
THROUGH TOMORROW NIGHT, THE NEXT COUPLE DAYS ARE FORECAST TO BE
COOLER. THE LATEST NBM FORECAST HAS JUST ABOUT ALL LOWER DESERT
LOCATIONS FAILING TO REACH 80 DEGREES TOMORROW AND AGAIN FOR
WEDNESDAY ACROSS SOUTH-CENTRAL AZ. PERHAPS MORE NOTABLE WILL BE THE
MUCH COOLER LOW TEMPERATURES. MORNING LOW TEMPERATURES WILL BE
DIPPING INTO THE 50S ACROSS THE LOWER DESERTS; COOLEST ON WEDNESDAY.
SOME AREAS WILL EVEN DIP INTO THE 40S, LIKE UP AROUND WICKENBURG,
AND PORTIONS OF JOSHUA TREE NP WILL FALL INTO THE 30S. THIS WILL BE
THE COLDEST PUSH OF AIR SINCE THE SPRING. THE LAST TIME PHOENIX SKY
HARBOR REPORTED A LOW BELOW 60 DEGREES WAS MARCH 11. DON'T LET THE
SNOWBIRDS KNOW!
LONG TERM /THURSDAY THROUGH SUNDAY/
MODELS ARE FINALLY COMING INTO BETTER AGREEMENT FOR LATE THIS WEEK
INTO THE WEEKEND SHOWING SHORTWAVE ENERGY AND AN UPPER LEVEL JET MAX
DIVING SOUTHWESTWARD THROUGH THE REGION ON THURSDAY. AT THE SAME
TIME A STRONG UPPER LEVEL RIDGE JUST OFF THE WEST COAST WILL MOVE
INLAND. FOR NOW, IT SEEMS THIS SET UP WILL RESULT IN A WEAK CUT-OFF
LOW FORMING SOMEWHERE TO OUR SOUTHWEST BY FRIDAY WITH RIDGING
SETTLING IN JUST TO OUR NORTH. TO COMPLICATE THINGS EVEN MORE, A
POLAR AIR MASS WILL QUICKLY DIVE THROUGH THE PLAINS STATES THURSDAY
POTENTIALLY BRINGING A BACK-DOOR COOL FRONT INTO EASTERN ARIZONA
FRIDAY MORNING. EVEN THOUGH THIS IS A COMPLEX PATTERN, IT REALLY
WON'T AMOUNT TO MUCH FOR OUR AREA AS DRY AIR WILL REMAIN ENTRENCHED
ENOUGH TO KEEP RAIN CHANCES BELOW 10%.
HOWEVER, IT IS LOOKING INCREASINGLY LIKELY A STRONG PRESSURE
GRADIENT WILL DEVELOP ACROSS ARIZONA BY FRIDAY LEADING TO BREEZY TO
LOCALLY WINDY EASTERLY WINDS DEVELOPING THURSDAY NIGHT INTO FRIDAY
MORNING. NBM GUIDANCE DOES SHOW THE POTENTIAL FOR ADVISORY LEVEL
WINDS, BUT FROM PAST EXPERIENCE THESE WINDS TEND TO BE OVERDONE. WE
SHOULD AT LEAST EXPECT OCCASIONAL WIND GUSTS OF 25-35 MPH TO MAYBE
SOME 35-40 MPH POSSIBLE ACROSS FAR SOUTHERN GILA COUNTY, PINAL
COUNTY, INTO SOUTHERN MARICOPA COUNTY. THESE GUSTY EASTERLY WINDS
WILL BE MORE PRONOUNCED DURING THE LATTER HALF OF THE MORNING BEFORE
DIMINISHING SOME DURING THE AFTERNOON. GUIDANCE SUGGESTS A REPEAT OF
THESE GUSTY WINDS ON SATURDAY BEFORE THE GRADIENT BEGINS TO RELAX
INTO SUNDAY. MODERATING TEMPERATURES ARE FORECAST FOR LATE WEEK WITH
HIGHS WARMING INTO THE 80S BY THURSDAY AND LIKELY STAYING AT OR JUST
BELOW NORMAL THROUGH NEXT WEEKEND.
AVIATION
UPDATED AT 2320Z.
SOUTH CENTRAL ARIZONA INCLUDING KPHX, KIWA, KSDL, AND KDVT:
GUSTY WINDS, PERIODS OF VFR CIGS BETWEEN 5-7K FT AGL, AND PERIODS
OF VCSH/SHRA WILL BE THE MAIN AVIATION WEATHER CONCERNS THROUGH
TOMORROW MORNING. A BAND OF SHOWERS IS MOVING THROUGH THE EAST
VALLEY NOW WITH NO LIGHTNING, BRIEF HEAVY RAINFALL, GUSTY WINDS,
AND LOWER CIGS (AROUND 4-5 KFT). THIS SHOULD BE EXITING THE
AIRSPACE WITHIN THE NEXT HOUR, WITH SOME LINGERING SHOWERS BEHIND
IT. PERIODIC PERIODS OF SHOWERS CANNOT BE RULED OUT THROUGH THE
EVENING SO VCSH HAS BEEN ADDED THROUGH THE OVERNIGHT HOURS.
ALTHOUGH, NOT MUCH ACTIVITY IS EXPECTED UNTIL 9-14Z OVERNIGHT WHEN
A MORE DEFINED AREA OF SHOWERS IS EXPECTED TO DEVELOP AND MOVE
THROUGH THE PHOENIX METRO. A PROB30 LINE REMAINS IN THE TAFS WITH
SHRA BR, REDUCED VIS, AND CIGS LOWERING TO 5 KFT. SHOWERS MAY
LINGER THROUGH 16Z BEFORE FULLY CLEARING THE AREA. WIND SPEEDS
WILL GENERALLY BE AOB 12 KT THROUGH THE PERIOD, WITH THE
EXCEPTION OF SOME STRONG 25-35 KT GUSTS POSSIBLE WITH SOME OF THE
SHOWER/STORM ACTIVITY AND SOME OCCASIONAL GUSTS IN THE UPPER
TEENS TOMORROW AFTERNOON. WIND DIRECTIONS WILL GENERALLY FAVOR A
TYPICAL DIURNAL PATTERN, BUT MAY FAVOR MORE OF A SOUTHERLY
DIRECTION THAN SOUTHEASTERLY OVERNIGHT/TOMORROW MORNING. VFR CIGS
WILL BEGIN TO CLEAR THE AIRSPACE LATE TUESDAY MORNING INTO THE
AFTERNOON.
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:
GUSTY WINDS WILL BE THE AVIATION CONCERN THROUGH THE TAF PERIOD.
WINDS WILL MAINLY BE OUT OF THE WEST AT KIPL AND OUT OF THE SW AT
KBLH THROUGH MOST OF TOMORROW MORNING. BY LATE TOMORROW
MORNING/EARLY TOMORROW AFTERNOON WINDS WILL GO MORE NW'RLY AT BOTH
SITES. CURRENT GUSTS UP AROUND 25 KT WILL CONTINUE AT KIPL
THROUGH MOST OF THE OVERNIGHT BEFORE TAPERING OFF. HOWEVER, THE
GUSTS AT KBLH WILL TAPER OFF OVER THE NEXT COUPLE OF HOURS WITH
GUSTS UP AROUND 20 KT RETURNING TOMORROW AFTERNOON. FEW-SCT DECKS
AOA 7 KFT WILL GRADUALLY CLEAR THROUGH THE EVENING BECOMING MOSTLY
CLEAR BY DURING THE OVERNIGHT HOURS.
FIRE WEATHER
PERIODS OF ISOLATED TO SCATTERED SHOWERS ARE EXPECTED THROUGH
TONIGHT BEFORE A WEAK COLD FRONT MOVES THROUGH AND DRIER AIR
BEGINS TO FILTER IN TOMORROW. A STRONGER AND DRIER FRONT WILL
FOLLOW TOMORROW NIGHT INTO WEDNESDAY. ELEVATED MOISTURE LEVELS
WILL KEEP MINRHS MOSTLY ABOVE 40% THROUGH TOMORROW BEFORE
LOWERING DOWN TO 20-35% WEDNESDAY AND THURSDAY. BREEZY CONDITIONS
ARE EXPECTED JUST ABOUT EVERY DAY. A NORTHERLY GRADIENT WIND WILL
DEVELOP ACROSS SOUTHEAST CA AND SOUTHWEST AZ TOMORROW AND
STRENGTHEN EACH DAY THROUGH THE MIDDLE OF THE WEEK, WITH MORNING
AND AFTERNOON GUSTS UP TO 20-30 MPH. STRONGER BREEZES WILL SPREAD
TO THE REST OF AZ BY FRIDAY WITH BREEZY TO WINDY EASTERLIES
DEVELOPING. BELOW NORMAL TEMPERATURES ARE EXPECTED THROUGH AT
LEAST THE MIDDLE OF THE WEEK. MOISTURE RETURN LATE WEEK INTO THE
WEEKEND MAY BRING A RETURN OF RAIN CHANCES.
PSR WATCHES/WARNINGS/ADVISORIES
AZ...NONE.
CA...NONE.
SHORT TERM...BENEDICT
LONG TERM...KUHLMAN
AVIATION...BERISLAVICH
FIRE WEATHER...BENEDICT/KUHLMAN
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