649
FXUS65 KPSR 101920
AFDPSR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
1220 PM MST SAT OCT 10 2026
UPDATE
UPDATED AVIATION DISCUSSION.
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 AZ, 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/
AFTER A FAIRLY BENIGN WEATHER PATTERN ACROSS THE SOUTHWESTERN
UNITED STATES DURING THE LAST WEEK, BIG CHANGES ARE COMING FOR
THIS UPCOMING WEEKEND. CURRENT WATER VAPOR SATELLITE IMAGERY AS
WELL AS OBJECTIVE ANALYSIS SHOW A LARGE NORTHERN STREAM TROUGH
DIVING INTO THE PACIFIC NORTHWEST WHILE TROPICAL STORM RACHEL,
BEING STEERED NORTHEASTWARD BY ANOTHER CUTOFF LOW IS LOCATED
SEVERAL HUNDRED MILES TO THE SOUTH- SOUTHWEST OF SAN DIEGO. RACHEL
WILL CONTINUE TO MIGRATE NORTH- NORTHEASTWARD THROUGHOUT THE DAY,
MAKING LANDFALL ALONG THE FAR NORTHERN BAJA PENINSULA BY LATE
TONIGHT BEFORE ACCELERATING NORTH-NORTHEASTWARD THROUGH SAN DIEGO
AND WESTERN RIVERSIDE COUNTIES AND TOWARDS THE MOHAVE DESERT
DURING THE DAY SUNDAY.
SOUTH SOUTHWESTERLY FLOW WILL TRANSPORT ABUNDANT MOISTURE INTO
THE REGION THROUGHOUT THE DAY TODAY, WITH THE ENSEMBLES SHOWING
MEAN PWATS EXCEEDING OVER 200-250% OF NORMAL BY EARLY THIS
EVENING. THE INCREASING MOISTURE COMBINED WITH THE INCREASING JET
DYNAMICS FROM THE WEST COAST TROUGH WILL SUPPORT SCATTERED SHOWERS
AND STORMS TO BREAK OUT. LATEST HI-RES GUIDANCE SHOWS ACTIVITY,
MOSTLY IN THE FORM OF ELEVATED SHOWERS, DEVELOPING OVER SOUTHWEST
AZ STARTING LATE MORNING WITH SCATTERED SHOWERS AND STORMS
DEVELOPING ACROSS PORTIONS OF SOUTH-CENTRAL AZ THROUGH SOUTHEAST
CA DURING THE AFTERNOON/EARLY EVENING HOURS. SOME GUSTY WINDS AND
BRIEF HEAVY RAINFALL WILL BE THE MAIN THREATS WITH ANY STORMS THAT
MATERIALIZE AS INSTABILITY WILL BE QUITE MARGINAL WITH MUCAPE
VALUES AT LESS THAN 500 J/KG. THE CHANCES FOR MORE ROBUST
CONVECTION WILL LIKELY COME LATE TONIGHT INTO SUNDAY MORNING AS
BETTER LOW-LEVEL MOISTURE WITH THE ARRIVAL OF RACHEL WILL SUPPORT
A WINDOW OF 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.
AS THE REMNANTS OF RACHEL APPROACH SOUTHERN CA COMBINED WITH HEIGHT
FALLS FROM THE LARGE SCALE TROUGH TO THE WEST, LOW-LEVEL WINDS WILL
BE INCREASING WITH A BELT OF 850 MB UPWARDS OF 50 KTS. THIS WILL
SUPPORT NON-THUNDERSTORM WIND GUSTS EXCEEDING 40 MPH STARTING AFTER
MIDNIGHT ACROSS SOUTHEAST CA INTO SOUTHWEST AZ BEFORE THE STRONGER
WINDS SPREAD FURTHER EAST INTO SOUTH-CENTRAL AZ BY THE EARLY TO MID-
MORNING HOURS SUNDAY. 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, 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.
AFTER THE COUPLE OF DAYS OF WIDESPREAD HIGHS IN THE TRIPLE DIGITS,
TEMPERATURES THIS WEEKEND WILL STEADILY COOL. LOWER DESERT HIGHS
THIS AFTERNOON WILL BE ABOUT 10 DEGREES COOLER COMPARED TO FRIDAY
WITH 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 WILL DEVELOP OVER THE WEEKEND
AS INCREASING MOISTURE ASSOCIATED WITH THE REMNANTS OF TROPICAL
STORM RACHEL BRINGS INCREASING RAIN CHANCES. THE CHANCES FOR
SHOWERS AND STORMS INCREASE STARTING THIS AFTERNOON/EVENING AND
CONTINUES INTO SUNDAY 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 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...LOJERO
LONG TERM...LOJERO
AVIATION...BENEDICT
FIRE WEATHER...LOJERO
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