617
FXUS65 KPSR 101940
AFDPSR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
1240 PM MST SAT OCT 10 2026
KEY MESSAGES
- AN UNSETTLED WEATHER PATTERN WILL PREVAIL THROUGHOUT THE
WEEKEND AS THE REMNANTS OF TROPICAL CYCLONE RACHEL MOVE INTO THE
SOUTHWEST UNITED STATES, RESULTING IN HEIGHTENED CHANCES FOR
SHOWERS AND THUNDERSTORMS, WIDESPREAD GUSTY WINDS ON SUNDAY, AND
MUCH COOLER TEMPERATURES.
- RAIN CHANCES WILL CONTINUE FOR PORTIONS OF THE REGION,
ESPECIALLY ACROSS SOUTH CENTRAL ARIZONA, EARLY NEXT WEEK ALONG
WITH WELL-BELOW NORMAL TEMPERATURES.
- A DRIER AND QUIETER WEATHER PATTERN IS EXPECTED BY THE MIDDLE
AND LATTER PORTION OF NEXT WEEK ALONG WITH GRADUALLY WARMING
TEMPERATURES.
SHORT TERM /TODAY THROUGH SUNDAY/
AN EXPANSIVE AREA OF ABUNDANT MIDLEVEL MOISTURE HAS SPREAD INTO THE
SOUTHWESTERN US AHEAD OF TROPICAL STORM RACHEL, WHICH CAN BE SEEN IN
MIDLEVEL WATER VAPOR IMAGERY QUICKLY EJECTING NORTHEASTWARD TOWARDS
NORTHERN BAJA. A SUBTROPICAL CUTOFF LOW INTENSIFYING TO ITS WEST,
WELL OFFSHORE, IS ALSO APPARENT AND LEADING TO AN INTENIFYING JET
STREAK DOWNSTREAM. THE COMBINATION OF ABUNDANT MIDLEVEL MOISTURE AND
UPPER LEVEL DIFFLUENCE HES LED TO FAIRLY WIDESPREAD ELEVATED SHOWERS
AND SCATTERED THUNDERSTORMS ACROSS SOUTHWEST AZ AND SOUTHEAST CA SO
FAR. LOCALLY STRONG WIND GUSTS AND TRANSIENT LINEAR ORGANIZATION
HAVE BEEN OBSERVED WITH SOME OF THESE STORMS, DESPITE THE WEAK
INSTABILITY (RAP ANALYZED MLCAPE NO MORE THAN 500 J/KG). INVERTED-V
GFS BUFR SOUNDINGS AND DCAPE UPWARDS OF 1000 J/KG ACROSS MUCH OF THE
FORECAST AREA WILL MEAN THAT EVEN WEAK STORMS ARE CAPABLE OF WIND
GUSTS UPWARDS OF 35-50 MPH AND KICKING UP AT LEAST LOCALIZED BLOWING
DUST, AS WAS OBSERVED IN GILA BEND LATE THIS MORNING. THIS ACTIVITY
WILL CONTINUE TO PUSH NORTH AND EAST WITH TIME, REACHING PORTIONS OF
THE GREATER PHOENIX AREA OVER THE NEXT HOUR OR SO.
A WINDOW OF TIME WITH AN ENVIRONMENT SUPPORTIVE OF MORE ROBUST AND
POTENTIALLY ORGANIZED CONVECTION IS STILL EXPECTED TO ARRIVE LATE
TONIGHT INTO SUNDAY MORNING, AS BETTER LOW-LEVEL MOISTURE WITH THE
ARRIVAL OF RACHEL WILL SUPPORT BRIEFLY HIGHER INSTABILITY UPWARDS OF
500-1000 J/KG OF MUCAPE. THE HIGHER INSTABILITY COMBINED WITH
VERTICAL WIND SHEAR IN EXCESS OF 40 KTS WILL SUPPORT A SEVERE
THREAT, WITH SPC HIGHLIGHTING MUCH OF THE AREA UNDER A MARGINAL
RISK. DAMAGING WIND GUSTS WILL BE THE MAIN THREAT, HOWEVER, WITH LOW-
LEVEL SHEAR INCREASING ABOVE 20 KTS ALONG WITH 0-3 KM STORM RELATIVE
HELICITY OVER 100-200 M2/S2, THERE WILL BE A NON-ZERO THREAT FOR A
BRIEF TORNADO OR TWO.
PERHAPS THE MOST WIDESPREAD IMPACT FROM THE ARRIVAL OF THE REMNANTS
OF RACHEL WILL BE GUSTY WINDS. GUIDANCE IS STILL IN EXCELLENT
AGREEMENT THAT THE INTENSIFYING JET DOWNSTREAM FROM THE CUTOFF LOW
AND REMNANT LOW/CIRCULATION OF RACHEL WILL SUPPORT 850 MB SOUTHERLY
FLOW UPWARDS OF 40 KTS NEAR/JUST EAST OF THE LOWER COLORADO RIVER
SUNDAY MORNING. THIS IS IN EXCESS OF CLIMATOLOGICAL MAXIMUM WIND
SPEEDS AT 850 MB FOR THIS TIME OF YEAR. ADDITIONALLY, A DRY SLOT
BEHIND THE REMNANT RACHEL CIRCULATION MAY ADD TO THE WIND THREAT, AS
THERE WILL BE ADDITIONAL MIXING THROUGH THE BL DURING THE DAY ON
SUNDAY, HELPING TAP THE HIGHER MOMENTUM AIR ALOFT. AS A RESULT,
EXPECT FAIRLY WINDESPREAD GUSTS UPWARDS OF 35-45 MPH ACROSS THE
FORECAST AREA SUNDAY, WITH LOCALLY HIGHER SPEEDS UPWARDS OF 50-60
MPH (ESPECIALLY OVER HIGHER TERRAIN). WIND GUSTS THIS HIGH COULD
CERTAINTY RESULT IN AREAS OF BLOWING DUST IN THE DUST PRONE AREAS.
AS THE REMNANTS OF RACHEL MOVE NORTHWARD INTO SOUTHERN NEVADA BY
LATE SUNDAY AFTERNOON/EARLY EVENING, WINDS WILL WEAKEN AS THE
GRADIENT WEAKENS.
IN TERMS OF RAINFALL AMOUNTS, GIVEN THAT MUCH OF THE ACTIVITY WILL
BE MOSTLY SCATTERED IN NATURE, EVENT-TOTAL RAINFALL AMOUNTS ACROSS
MUCH OF THE AREA WILL BE UNDER 0.75" WITH THE POTENTIAL THAT SOME
AREAS SEE NEXT TO NOTHING. HOWEVER, THERE CAN BE SOME LOCALLY HIGHER
AMOUNTS IN EXCESS OF 1" IN AREAS THAT SEE A TRAINING OF CONVECTION.
THE MORE FAVORABLE AREA FOR MORE WIDESPREAD ACTIVITY WILL BE MAINLY
ACROSS JOSHUA TREE NATIONAL PARK, CLOSE TO WHERE RACHEL WILL TRACK,
AND THUS THE POTENTIAL WILL EXIST FOR MORE WIDESPREAD AMOUNTS IN
EXCESS OF 1" WITH A FLOOD WATCH IN EFFECT FROM THIS EVENING THROUGH
SUNDAY AFTERNOON.
TEMPERTURES ACROSS THE AREA WILL DECREASE OVER THE WEEKEND, WITH
LOWER DESERT HIGHS THIS AFTERNOON ABOUT 10 DEGREES COOLER COMPARED
TO FRIDAY AND READINGS IN THE LOW TO MID 90S. THE MORE ABUNDANT
CLOUD COVER AS WELL AS RAINFALL ACTIVITY WILL CAUSE TEMPERATURES TO
COOL ANOTHER 7-10 DEGREES ON SUNDAY AS AFTERNOON HIGHS ONLY REACH
THE LOW TO MIDDLE 80S.
LONG TERM /MONDAY THROUGH FRIDAY/
UNSETTLED WEATHER WILL CONTINUE THROUGH EARLY NEXT WEEK AS THE LARGE-
SCALE TROUGH THAT WILL SETTLE ACROSS THE WEST COAST OVER THE WEEKEND
WILL GRADUALLY MIGRATE EASTWARD. THE ASSOCIATED LARGE-SCALE FORCING
FOR ASCENT COMBINED WITH AMPLE LOW-LEVEL MOISTURE WILL SUPPORT
SCATTERED SHOWERS AND EMBEDDED THUNDERSTORMS DURING THE DAY, MAINLY
ACROSS THE FOOTHILLS AND HIGHER TERRAIN AREAS NORTH AND EAST OF
PHOENIX IN UPSLOPE FLOW. THEREAFTER, AS THE MAIN COLD FRONT
ASSOCIATED WITH THE TROUGH MOVES THROUGH LATE MONDAY NIGHT INTO
TUESDAY MORNING, THERE WILL LIKELY BE A BAND OF SHOWERS WITH
EMBEDDED THUNDERSTORMS THAT MOVES THROUGH, PARTICULARLY ACROSS SOUTH-
CENTRAL AZ, BEFORE RAIN CHANCES END BY TUESDAY AFTERNOON/EVENING AS
DRIER AIR FILTERS IN. AT THIS POINT ANY OF THE RAIN THAT FALLS EARLY
NEXT WEEK WILL GENERALLY BE OF THE NUISANCE TYPE. QUIETER WEATHER
WITH NEAR ZERO RAIN CHANCES CAN BE EXPECTED STARTING WEDNESDAY
AND WILL PERSIST THROUGH THE END OF THE WEEK.
WITH THE PRESENCE OF THE TROUGH AS WELL AS MORE ABUNDANT CLOUD
COVER, WELL-BELOW NORMAL TEMPERATURES ARE EXPECTED DURING THE FIRST
HALF OF THE WEEK WITH MANY OF THE LOWER DESERT LOCATIONS LIKELY
STAYING IN THE 70S FOR AFTERNOON HIGHS. EARLY MORNING LOWS WILL ALSO
BE BELOW NORMAL WITH THE COOLEST MORNING EXPECTED ON WEDNESDAY WHEN
MANY AREAS ARE EXPECTED TO DROP INTO THE 50S WITH EVEN SOME 40S
ACROSS THE HIGHER TERRAIN AREAS. TEMPERATURES WILL THEN GRADUALLY
REBOUND INTO THE 80S BY THE LATTER PORTION OF THE WEEK.
AVIATION
UPDATED AT 1920Z.
SOUTH CENTRAL ARIZONA INCLUDING KPHX, KIWA, KSDL, AND KDVT:
SCATTERED SHOWERS AND STORMS, STRONG WINDS, AND POTENTIAL
SLANTWISE VISIBILITY REDUCTIONS ARE ALL IN THE FORECAST THROUGH
THE NEXT 24 HOURS. CONFIDENCE IN TIMING OF EVERYTHING IN THE
LATEST TAF PACKAGE IS LOW TO MODERATE. SHOWERS AND STORMS WILL BE
POSSIBLE AT JUST ABOUT ANY TIME, BUT WITH ODDS SLIGHTLY BETTER
THIS AFTERNOON THROUGH TONIGHT AND SUNDAY MORNING. SE WINDS ARE
EXPECTED TO VEER SW THIS AFTERNOON AND THEN EVENTUALLY BACK SE-E
THIS EVENING, BUT WIND DIRECTIONS MAY BECOME VARIABLE THIS EVENING
BASED ON SHOWER AND STORM ACTIVITY. STORMS WILL BE CAPABLE OF
GENERATING STRONG WIND GUSTS AND BLOWING DUST. THE MOST IMPACTFUL
TIME PERIOD WILL LIKELY BE SUNDAY MORNING BETWEEN 14-19Z WHEN A
BAND OF SHOWERS AND STORMS ARE FORECAST TO MOVE THROUGH WITH LOWER
CIGS DOWN TO 4-5K FT AGL AND SOUTHERLY WIND GUSTS UP TO 30KT.
BEGINNING WITH AND FOLLOWING THE BAND OF RAIN, S-SW WINDS UP TO
15-20 KTS AND GUSTING UP TO 30-35 KTS IS EXPECTED THROUGH THE
AFTERNOON, WHICH MAY LEAD TO A LOT OF LOFTED DUST AND REDUCE
SLANTWISE VISIBILITY.
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:
PERIODS OF SHRA WITH THE POTENTIAL FOR ISOLATED TSRA ALONG WITH
ERRATIC WIND DIRECTIONS AND STRONG WIND GUSTS WILL BE THE MAIN
WEATHER ISSUES AS THICK MIDLEVEL CIGS DEVELOP OVER THE AREA. WINDS
WILL FAVOR AN E/SE COMPONENT THROUGH TONIGHT AND THEN EVENTUALLY
S/SW BY LATE SUNDAY MORNING. VCSH/VCTS CHANCES WILL EXIST AT BOTH
TERMINALS THROUGH THIS AFTERNOON AND EVENING BEFORE DRYING. VERY
STRONG S/SE WINDS ARE EXPECTED SUNDAY MORNING, ESPECIALLY BETWEEN
10-16Z WITH SUSTAINED SPEEDS AROUND 15-25 KTS AND GUSTS AS HIGH AS
35-45 KTS. THERE IS SOME UNCERTAINTY IF THE STRONGER GUSTS WILL
FULLY MATERIALIZE IN THE MORNING, BUT WINDS WILL BE STRONG ENOUGH
REGARDLESS TO GENERATE BLOWING DUST AND IMPACT SLANTWISE
VISIBILITY.
FIRE WEATHER
A MUCH MORE UNSETTLED WEATHER PATTERN HAS TAKEN SHAPE THIS
WEEKEND AS INCREASING MOISTURE ASSOCIATED WITH THE REMNANTS OF
TROPICAL STORM RACHEL BRINGS INCREASING RAIN CHANCES. CHANCES FOR
WETTING RAIN WILL CONTINUE TO INCREASE THROUGH SUNDAY MORNING
WITH A GREATER THAN 50-70% CHANCE OF WETTING RAINFALL AREA WIDE.
WINDS WILL ALSO INCREASE SIGNIFICANTLY, ESPECIALLY LATE TONIGHT
THROUGH SUNDAY WITH WIDESPREAD GUSTS EXCEEDING 30-40 MPH. WITH THE
INCREASING MOISTURE AND COOLER TEMPERATURES, MINRH VALUES WILL
INCREASE FROM 25-40% TODAY TO 45-70% ON SUNDAY ALONG WITH GOOD TO
EXCELLENT OVERNIGHT RECOVERIES. ANOTHER WEATHER SYSTEM WILL BRING
ADDITIONAL CHANCES FOR WETTING RAINFALL EARLY NEXT WEEK, MAINLY
FOR THE FOOTHILLS AND HIGHER TERRAIN OF THE EASTERN DISTRICTS,
BEFORE QUIETER WEATHER SETTLES IN BY THE MIDDLE OF THE WEEK.
TEMPERATURES WILL STEADILY COOL THIS WEEKEND, WITH WELL-BELOW
NORMAL TEMPERATURES EXPECTED FOR THE FIRST HALF OF THE NEXT WEEK.
PSR WATCHES/WARNINGS/ADVISORIES
AZ...WIND ADVISORY FROM 2 AM TO 5 PM MST SUNDAY FOR AZZ530>533-535-
536.
WIND ADVISORY FROM 8 AM TO 5 PM MST SUNDAY FOR AZZ534-537>563.
CA...WIND ADVISORY FROM 2 AM TO 5 PM PDT SUNDAY FOR CAZ560>570.
FLOOD WATCH FROM 5 PM PDT THIS AFTERNOON THROUGH SUNDAY
AFTERNOON FOR CAZ560-561-568.
SHORT TERM...WHITTOCK/LOJERO
LONG TERM...LOJERO
AVIATION...BENEDICT
FIRE WEATHER...WHITTOCK/LOJERO
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