690
FXUS65 KPSR 161053
AFDPSR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
353 AM MST WED SEP 16 2026
KEY MESSAGES
- SCATTERED TO WIDESPREAD SHOWERS AND STORMS ARE FORECAST TO
DEVELOP TODAY ACROSS ARIZONA, WITH POTENTIAL FOR AREAS OF HIGH
RAINFALL AMOUNTS LEADING TO FLASH FLOODING.
- A FLOOD WATCH IS IN EFFECT THROUGH EARLY TONIGHT ACROSS MUCH OF
SOUTHERN ARIZONA.
- SHOWER AND THUNDERSTORM CHANCES WILL GREATLY DIMINISH BY
THURSDAY AND COME TO AN END STARTING FRIDAY WITH MUCH DRIER
AIR MOVING IN AND LASTING THROUGH AT LEAST THIS WEEKEND.
- BELOW NORMAL TEMPERATURES ARE EXPECTED TODAY ACROSS SOUTH-
CENTRAL ARIZONA, BEFORE WARMING BACK TO TO SLIGHTLY ABOVE
NORMAL LEVELS BY THE WEEKEND.
SHORT TERM /TODAY THROUGH FRIDAY/
THERE IS POTENTIAL FOR A VERY ACTIVE AND HIGHLY IMPACTFUL WEATHER
DAY ACROSS MUCH OF ARIZONA TODAY. CONSIDERABLE AND POTENTIALLY
DEADLY FLASH FLOODING IS IN THE CARDS FOR TODAY. HI- RES MODELING
CONTINUE TO SHOW SCATTERED TO WIDESPREAD SHOWERS AND
THUNDERSTORMS EVENTUALLY DEVELOPING TODAY ACROSS THE REGION AND
LEADING TO MANY AREAS RECEIVING 1-3 INCHES OF RAIN WHICH WILL
LIKELY RESULT IN FLASH FLOODING. WHERE THESE HI-RES CAMS HAVE
STRUGGLED SO FAR IS TIMING OUT INITIAL CONVECTIVE DEVELOPMENT.
PREVIOUS MODEL RUNS SUGGESTED TUESDAY AFTERNOON WAS GOING TO BE
VERY ACTIVE ACROSS SOUTH-CENTRAL AZ, AS WELL AS EARLY THIS
MORNING, WHICH HAS NOT QUITE COME TO FRUITION. WHILE OBJECTIVE
ANALYSIS SHOWS MOISTURE AND INSTABILITY HAVE BEEN FAVORABLE AND
CONTINUE TO BE FAVORABLE THIS MORNING, THERE HAS NOT BEEN MUCH IN
THE WAY OF FORCING/LIFT. THIS IS EXPECTED TO CHANGE TODAY THOUGH.
A WELL DEFINED LOW PRESSURE CIRCULATION IS SEEN ON SATELLITE ALONG
THE WEST COAST OF SONORA, MX. THIS FEATURE IS FORECAST TO MOVE
STRAIGHT NORTH UP THROUGH AZ LIKELY THIS AFTERNOON THROUGH TONIGHT
AND HELP PROVIDE THE LIFT THAT HAS BEEN SOMEWHAT LACKING. THERE
WILL ALSO BE INCREASED JET SUPPORT WITH A STRENGTHENING OF THE
200MB JET AND ENTRANCE REGION OF THE JET SETTING UP OVER SOUTH-
CENTRAL AZ. SO, THE INGREDIENTS WILL ALL BE THERE FOR STRONG
SHOWERS AND STORMS TO DEVELOP, BUT THERE HAS STILL BEEN A LITTLE
BIT OF UNCERTAINTY WITH TIMING OF GREATEST COVERAGE AND IMPACT OF
SHOWERS AND STORMS. LATEST NBM POPS ARE HIGHEST IN THE 5AM-11AM
TIMEFRAME FOR THE PHOENIX AREA AND THE 00Z HI-RES MODELS SHOW
HIGHEST QPF IN THIS TIMEFRAME AS WELL, BUT CONCEPTUALLY, BASED ON
THE SETUP, THE BEST TIMING FOR SOUTH- CENTRAL AZ LOOKS TO BE MORE
FROM MIDDAY THROUGH THIS EVENING.
A FLOOD WATCH IS CURRENTLY IN EFFECT FOR SOUTH-CENTRAL AZ AND
WILL CONTINUE THROUGH 11 PM MST TONIGHT. THE WATCH WAS ISSUED
LARGELY DUE TO THE SYNOPTIC AND MESOSCALE SETUP BEING SUPPORTIVE
OF SCATTERED TO WIDESPREAD SHOWERS AND STORMS CAPABLE OF PRODUCING
1-HR RAIN RATES UP AROUND 1-2" AND HIGHER OVER SHORTER TIME
FRAMES. HI-RES MODELING CONTINUES TO SHOW QPF UPWARDS OF 1-3" OVER
A LARGE PORTION OF SOUTH-CENTRAL AZ, AND THERE ARE EVEN HIGH END
AMOUNTS UP TO AROUND 4" (10% CHANCE). RAINFALL AMOUNTS ARE STILL
LIKELY TO VARY WIDELY, WITH SOME AREAS POTENTIALLY MISSING OUT AND
RECEIVING LITTLE TO NONE. THE FLOOD WATCH HAS BEEN EXPANDED TO
INCLUDE PORTIONS OF LA PAZ AND YUMA COUNTIES STARTING AT 11AM AND
ALSO GOING THROUGH 11 PM. SEVERAL OF THE LATEST HI-RES MODELS HAVE
SUPPORTED TRAINING STORMS IN THIS AREA. THIS AREA IS ALSO
FORECAST TO HAVE HIGHER INSTABILITY AND RECEIVE BETTER DAYTIME
HEATING WITH MORE SUNSHINE HEADING INTO THE AFTERNOON. ANY STORMS
THAT DEVELOP IN THIS AREA MAY ACTUALLY HAVE THE HIGHEST RAIN RATES
BUT BE MORE ISOLATED IN COVERAGE. WPC'S UPDATED DAY 1 ERO
EXPANDED THE COVERAGE OF BOTH SLIGHT AND MODERATE RISK AREAS. THE
MODERATE NOW INCLUDES ALL OF GILA AND PINAL COUNTIES AND MOST OF
MARICOPA COUNTY. THE LAST TIME A MODERATE RISK COVERED THIS AREA
WAS BACK IN 2022.
THE HEAVY RAIN THREAT LOOKS LIKE IT WILL COME TO AN END ACROSS
SOUTH-CENTRAL AZ LATER THIS EVENING AND TONIGHT, ONCE THE LOW
CIRCULATION MOVES NORTH OF THE AREA, THE ENVIRONMENT BECOMES
OVERWORKED, AND SUBSIDENCE INCREASES ON THE BACK SIDE OF THE LOW.
STILL, A NARROW AXIS OF SHOWERS AND STORMS MAY LINGER INTO THE
OVERNIGHT HOURS, MOST LIKELY TOWARD EASTERN AZ. DRIER AIR WILL
BEGIN MOVING IN ALOFT THROUGH THE DAY THURSDAY WITH INCREASED
WEST-SOUTHWEST FLOW, WHICH WILL LIMIT SHOWERS AND STORMS MOSTLY
TO NORTHERN AZ HIGH TERRAIN. FURTHER DRYING OF THE ENTIRE COLUMN IS
EXPECTED THROUGH FRIDAY, WITH MIXING RATIOS DROPPING TO OR BELOW 8
G/KG AND PWATS FALLING BELOW 1.00" BY THE END OF THE DAY WHICH
WILL HURT ANY CHANCE AT RAIN EVEN IN THE HIGH TERRAIN.
TEMPERATURES THIS AFTERNOON MAY STRUGGLE TO REACH 90 DEGREES
ACROSS SOUTH-CENTRAL AZ, WITH AMPLE CLOUD COVER AND RAIN AROUND,
WHILE AREAS FURTHER WEST, WITH MORE SUN, STILL WARM INTO THE
MIDDLE 90S TO AROUND 100 DEGREES. TEMPERATURES WILL WARM BACK UP
BY THE END OF THE WEEK, BUT ONLY BACK TO AROUND SEASONAL LEVELS,
WITH HIGHS AROUND 100 DEGREES ACROSS THE LOWER DESERTS, AS BROAD
TROUGHING REMAIN IN PLACE ACROSS MUCH OF THE WEST.
LONG TERM /SATURDAY THROUGH TUESDAY/
THE MONSOON PATTERN MAY BE DONE AFTER TODAY, SHIFTING INTO THE
TRANSITIONAL SEASON WITH MORE FREQUENT TROUGHS. DRY AIR WILL
CONTINUE TO SPREAD ACROSS THE REGION THROUGH THIS WEEKEND WITH
PWATS FORECAST TO DROP BELOW NORMAL, AS LOW AS 0.4-0.7" ACROSS THE
LOWER DESERTS. THE WILL INHIBIT ANY CHANCE AT RAIN. THE BROAD
TROUGH MOVING THROUGH THE WEST, HELPING DRIVE THE WESTERLY FLOW
AND DRY AIR, IS EXPECTED TO SHIFT EAST INTO THE PLAINS BY THE
START OF NEXT WEEK. GLOBAL ENSEMBLE GUIDANCE THEN SHOWS AN UPPER
LOW MOVING OUT OF THE PACIFIC TOWARD THE SOCAL COAST BY THE END OF
THE DAY MONDAY. THERE IS STILL PLENTY OF UNCERTAINTY REGARDING
THIS LOW THIS FAR OUT, BUT IT MAY BE WHAT HELPS EVENTUALLY DRIVE
MOISTURE BACK UP IN THE DESERTS AND DRIVE THE NEXT CHANCE AT RAIN.
AVERAGE TO SLIGHTLY ABOVE AVERAGE TEMPERATURES ARE FORECAST THIS
WEEKEND THROUGH THE FIRST HALF OF NEXT WEEK WITH THIS FORECAST,
WITH AFTERNOON HIGHS AROUND TO SLIGHTLY ABOVE 100 DEGREES. WITH
THE DRIER AIR COMING IN, THE MORNING LOWS WILL FINALLY BE MORE
PLEASANT, CONSISTENTLY DROPPING INTO THE 70S FOR MOST LOWER
DESERT LOCATIONS.
AVIATION
UPDATED AT 0515Z.
SOUTH CENTRAL ARIZONA INCLUDING KPHX, KIWA, KSDL, AND KDVT:
A LOW CONFIDENCE FORECAST CONTINUES THROUGH WEDNESDAY NIGHT WITH THE
THREAT OF A LONGER DURATION, HIGH IMPACT TS EVENT AT SOME POINT
WEDNESDAY. BEFORE THAT, CONFIDENCE IN WIND TRENDS OVERNIGHT IS ONLY
MODERATE WITH A BRIEF PERIODS OF LIGHT SW OVER PARTS OF THE AIRSPACE
BEFORE SWITCHING BACK TO EASTERLY. TRENDS IN MODELS SUGGESTS CHANCES
FOR SHRA/TSRA PUSHED BACK LATER INTO THE DAY WEDNESDAY WITH LOWER
CHANCES OF MORNING IMPACTS, AND BETTER CHANCES DURING THE MID/LATE
AFTERNOON.
IN ADDITION TO DIRECT TSRA IMPACTS AT TERMINALS WITHIN THE PHX
AIRSPACE, INSTANCES OF MVFR (AND POSSIBLE BRIEF IFR) FLIGHT
CATEGORIES ARE POSSIBLE IN THE FORM OF LOWERED VSBY AND CIGS. A
PERIOD OF STRONG OUTFLOW WIND GUSTS AND BLDU ARE ALSO POSSIBLE WITH
THE INITIAL SURGE OF TS, THOUGH PRECISE DETAILS ON TIMING AND
LOCATION PRECLUDE ANY MENTION IN THIS TAF PACKAGE. SHRA MAY LINGER
WELL INTO THE EARLY EVENING DEPENDING ON EVOLUTION OF THE TS
COMPLEX, WITH A LOWER CHANCE OF ADDITIONAL TSRA. THE MOST LIKELY
OUTCOME IS FOR TS TO EXIT THE PHX AREA LATE AFTERNOON LEAVING AN
OVERTURNED ATMOSPHERE WITH EXPANSIVE MIDLEVEL CIGS AND LACK OF
INSTABILITY FOR FURTHER SHRA/TSRA DEVELOPMENT. HAVE MAINTAINED A
PROB30 MENTION WEDNESDAY EVENING WITH LOW CONFIDENCE.
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:
NO MAJOR WEATHER ISSUES WILL EXIST THROUGH WEDNESDAY NIGHT UNDER
MOSTLY CLEAR SKIES. CONFIDENCE IS GOOD THAT KIPL WINDS WILL LARGELY
MAINTAIN A SE DIRECTION, HOWEVER PERIODS OF VARIABILITY WILL BE
LIKELY DURING THE MORNING HOURS. WINDS AT KBLH WILL CONTINUE WITH A
SOUTHERLY COMPONENT WITH AFTERNOON GUSTS 20-25 KTS. CONFIDENCE IS
GROWING THAT A STRONG OUTFLOW BOUNDARY WITH GUSTY EAST WINDS WILL
SURGE WESTWARDS ACROSS THE COLORADO RIVER LATE AFTERNOON. THE
CURRENT ODDS SUGGEST SHRA/TSRA REMAINING WELL EAST OF THE TERMINAL
LOCATION, HOWEVER BLDU COULD MOVE INTO THE AREA WITH THE GUSTY EAST
WINDS.
FIRE WEATHER
PERIODS OF SCATTERED TO WIDESPREAD SHOWERS AND THUNDERSTORMS ARE
EXPECTED TODAY, FOCUSING MOSTLY ACROSS THE EASTERN DISTRICTS THIS
AFTERNOON THROUGH THIS EVENING. THERE WILL BE A HEAVY RAINFALL
AND FLOOD THREAT WITH THE ACTIVITY. MOISTURE LEVELS WILL BE
ELEVATED MOST AREAS, HIGHEST ACROSS EASTERN DISTRICTS, WHERE
MINIMUM RH THIS AFTERNOON WILL BE AROUND 50-60%. MINIMUM RHS WILL
BE LOWEST ACROSS SOUTHEAST CA, WITH VALUES AROUND 20-30%. A DRYING
TREND WILL BEGIN THURSDAY WITH CONDITIONS BECOMING VERY DRY BY
THIS WEEKEND. MINIMUM RHS BY SATURDAY DIP TO 10-25% ACROSS THE
LOWER DESERTS (LOWEST ACROSS WESTERN DISTRICTS). OVERNIGHT
RECOVERIES WILL STILL BE GOOD ACROSS EASTERN DISTRICTS THIS
WEEKEND AT 40-60%, WHILE WESTERN DISTRICTS HOVER AROUND 25-45%.
THE DRIER AIR MOVING IN WILL ELIMINATE RAIN CHANCES BY FRIDAY,
WITH LOW CHANCES IN GILA COUNTY THURSDAY AFTERNOON. WINDS WILL
FAVOR THE SOUTH TO SOUTHEAST OVER MUCH OF THE AREA THROUGH
WEDNESDAY WITH GUSTS OF 20-30 MPH AT TIMES ACROSS SOUTHWEST AZ AND
SOUTHEAST CA. IN THE FOLLOWING DAYS WINDS WILL RETURN TO A MORE
TYPICAL DIURNAL WITH MODEST AFTERNOON UPSLOPE GUSTINESS.
PSR WATCHES/WARNINGS/ADVISORIES
AZ...FLOOD WATCH FROM 11 AM MST THIS MORNING THROUGH THIS EVENING FOR
AZZ531-533-536.
FLOOD WATCH THROUGH THIS EVENING FOR AZZ534-537>563.
CA...NONE.
SHORT TERM...BENEDICT
LONG TERM...BENEDICT
AVIATION...18
FIRE WEATHER...BENEDICT
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