005
FXUS65 KPSR 082320
AFDPSR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
420 PM MST THU OCT 8 2026
UPDATE
UPDATED AVIATION
KEY MESSAGES
- DRY CONDITIONS ALONG WITH TEMPERATURES AROUND 10 DEGREES ABOVE
NORMAL WILL PERSIST THROUGH FRIDAY.
- AN EXTREME HEAT WARNING REMAINS IN EFFECT FOR PORTIONS OF
SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA THROUGH FRIDAY AS
TEMPERATURES WARM TO NEAR RECORD LEVELS RESULTING IN AREAS OF MAJOR
HEATRISK.
- AN UNSETTLED WEATHER PATTERN WILL ARRIVE THIS WEEKEND AS A SERIES
OF WEATHER SYSTEMS AFFECT THE REGION RESULTING IN COOLER
TEMPERATURES, STRONG WINDS, AND HEIGHTENED RAIN CHANCES.
SHORT TERM /TODAY THROUGH FRIDAY/
BROAD RIDGING REMAINS IN PLACE OVER THE DESERT SW, WHILE A SMALL
SHORT WAVE CONTINUES TO PUSH THROUGH THE FOUR CORNERS REGION THIS
AFTERNOON. WITH ENOUGH MOISTURE THIS SHORT WAVE MAY PROVIDE ENOUGH
EXTRA LIFT TO PRODUCE LIGHT ISOLATED SHOWERS OVER THE WHITE
MOUNTAINS, AND CAN ALREADY BE SEEN ON SATELLITE BEGINNING TO FORM.
OTHERWISE, THE REST OF THE REGION CAN EXPECT TO BE UNDER THE
EFFECTS OF THE HIGH PRESSURE OVERHEAD, WITH DRY CONDITIONS LASTING
THROUGH AT LEAST FRIDAY.
THE AFOREMENTIONED HIGH PRESSURE OVER THE DESERT SW TODAY HAS H5
HEIGHTS RANGING BETWEEN 587-589 DAM RESULTING IN HIGHS THIS
AFTERNOON BETWEEN 101F-103F IN SOUTH-CENTRAL AZ. MEANWHILE, HIGHS IN
SE CA, AND ALONG THE CO. RIVER VALLEY WILL BE BETWEEN 104F-108F. BY
FRIDAY A TROUGHING FEATURE WILL BEGIN TO DIVE DOWN THE PACIFIC NW
STATES. THIS WILL HELP DAMPEN HEIGHTS ALOFT OVER THE LOWER DESERTS,
WITH FORECASTED H5 HEIGHTS BETWEEN 582-858 DAM. AFTERNOON HIGHS WILL
BE 1-2 DEGREES COOLER FRIDAY, HOWEVER MODERATE TO MAJOR HEATRISK
WILL PERSIST IN THE WESTERN LOWER DESERTS. THAT SAID, AN EXTREME
HEAT WARNING REMAINS IN EFFECT FOR IMPERIAL, LOWER COLORADO RIVER,
AND GILA RIVER VALLEYS AS WELL AS FOR YUMA TODAY, THEN RESTRICTED TO
IMPERIAL VALLEY AND YUMA AREA THROUGH FRIDAY.
LONG TERM /SATURDAY THROUGH WEDNESDAY/
A MAJOR PATTERN SHIFT IS STILL ON SCHEDULE FOR THE WEEKEND THROUGH
EARLY NEXT WEEK AS A TROUGHING PATTERN WILL SET UP ACROSS MUCH OF
THE WESTERN THIRD OF THE CONUS. A LARGE NORTHERN STREAM TROUGH IS
EXPECTED TO DIVE INTO THE PACIFIC NORTHWEST ON SATURDAY BEFORE
DIVING INTO CA BY SUNDAY. IN THE MEANTIME, A SHORTWAVE TROUGH
SWEEPING ACROSS THE EASTERN PACIFIC WILL PICK UP TROPICAL STORM
RACHEL WITH BOTH SYSTEMS TO BE STEERED NORTHEASTWARD OUT AHEAD OF
THE LARGE WEST COAST TROUGH. THE LATEST TRACK FORECAST FROM THE
NATIONAL HURRICANE CENTER CONTINUES TO SHOW RACHEL TRACKING INTO THE
FAR NORTHERN PART OF THE BAJA PENINSULA LATE SATURDAY NIGHT BEFORE
ACCELERATING NORTH-NORTHEASTWARD THROUGH THE COLORADO RIVER VALLEY
DURING THE DAY SUNDAY AS A POST- TROPICAL STORM. SOUTH TO SOUTHWEST
FLOW ALOFT OUT AHEAD OF THE PACIFIC TROUGH AND TROPICAL STORM RACHEL
WILL ADVECT SIGNIFICANT MOISTURE INTO THE DESERT SOUTHWEST DURING
THE DAY ON SATURDAY WITH BOTH THE EPS AND GEFS SHOWING PWATS
EXCEEDING 200-250% OF NORMAL BY SATURDAY EVENING. THE INCREASING
MOISTURE COMBINED WITH AN UPPER- LEVEL JET STREAK MOVING THROUGH THE
GREAT BASIN, INCREASING THE UPPER-LEVEL FORCING FOR ASCENT, WILL
CAUSE AREAS OF SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS TO BREAK
OUT, MAINLY OVER CENTRAL AND SOUTHERN AZ SATURDAY AFTERNOON/EVENING.
AS BOTH THE PACIFIC SHORTWAVE AND THE REMNANTS OF RACHEL MOVE
THROUGH LATE SATURDAY NIGHT THROUGH SUNDAY, EVEN DEEPER MOISTURE
WILL BE PULLED INTO THE REGION AND THIS WILL LIKELY BE THE TIMEFRAME
FOR THE BEST RAIN CHANCES ACROSS THE REGION WITH NBM POPS AT GREATER
THAN 50-60% AREA WIDE. THERE CONTINUES TO BE QUITE A BIT UNCERTAINTY
WITH THE RAINFALL AMOUNTS AS IT WILL BE DEPENDENT ON THE EVENTUAL
TRACK OF THE REMNANTS OF RACHEL AND WILL LIKELY HAVE TO WAIT FOR THE
HI-RES GUIDANCE DATA TO HAVE BETTER CONFIDENCE ON AMOUNTS. IN
ADDITION TO THE RAINFALL ACTIVITY, WINDS WILL LIKELY BE ANOTHER
HAZARD TO DEAL WITH, ESPECIALLY FOR AREAS EAST OF THE TRACK OF
RACHEL AS THE GUIDANCE IS DEPICTING 850 MB WINDS TO EXCEED 40-50
KTS, WHICH WILL LIKELY TRANSLATE TO SURFACE WIND GUSTS IN EXCESS OF
40 MPH. AS BOTH THE PACIFIC SHORTWAVE AND THE REMNANTS OF RACHEL
LIFT TO THE NORTH LATE SUNDAY THROUGH MONDAY, SUBSIDENCE LEFT BEHIND
WILL RESULT IN DECREASING RAIN CHANCES DURING THIS PERIOD BEFORE
CHANCES INCREASE ONCE AGAIN, MAINLY FOR SOUTH-CENTRAL AND EASTERN
AZ, ON TUESDAY AS THE LARGER WEST COAST TROUGH PROGRESSES EASTWARD.
WITH THE TROUGHING PATTERN EXPECTED TO TAKE PLACE THIS WEEKEND
THROUGH EARLY NEXT WEEK ALONG WITH THE INCREASING CLOUD COVER AND
MOISTURE, TEMPERATURES ARE EXPECTED TO TAKE A NOSE DIVE. AFTERNOON
HIGHS ACROSS THE LOWER DESERTS WILL GO FROM THE LOW TO MID 90S ON
SATURDAY TO LOW 80S ON MONDAY, WITH MANY AREAS TUESDAY AND WEDNESDAY
LIKELY TOPPING OUT IN THE 70S.
AVIATION
UPDATED AT 2320Z.
SOUTH CENTRAL ARIZONA INCLUDING KPHX, KIWA, KSDL, AND KDVT:
NO MAJOR WEATHER ISSUES WILL EXIST THROUGH FRIDAY EVENING UNDER
GRADUALLY INCREASING MIDLEVEL CLOUD DECKS. HIGHLY VARIABLE WIND
DIRECTIONS WILL BE COMMON THROUGH MID/LATE EVENING BEFORE REVERTING
TO AN E/SE COMPONENT. A FEW LATE MORNING GUST 15-20KT WILL BE
POSSIBLE, BUT SHOULD BE SPATIALLY AND TEMPORALLY LIMITED. VERY LOW
CONFIDENCE EXISTS REGARDING WIND DIRECTIONS FRIDAY AFTERNOON WHERE
SOME AERODROMES MAY BECOME VARIABLE, AND OTHERS OBTAIN A LIGHT
SOUTHERLY CROSS RUNWAY COMPONENT. REGARDLESS, DIRECTIONS SHOULD
QUICKLY SWITCH BACK TO E/SE FRIDAY EARLY/MID EVENING.
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:
NO WEATHER ISSUES WILL EXIST THROUGH FRIDAY EVENING UNDER CLEAR
SKIES. EXTENDED PERIODS OF LIGHT AND VARIABLE WINDS WILL PERSIST
WITH DIRECTIONS GENERALLY VARYING BETWEEN NORTHERLY AND WESTERLY.
FIRE WEATHER
DRY CONDITIONS ALONG WELL-ABOVE NORMAL TEMPERATURES WILL CONTINUE
THROUGH FRIDAY AS LOWER DESERT HIGHS REACH INTO THE TRIPLE DIGITS.
WINDS TODAY GENERALLY BE LIGHT AND DIURNALLY DRIVEN BEFORE
INCREASING FRIDAY AND ESPECIALLY BY LATE THIS WEEKEND. AFTERNOON
MINRHS THROUGH FRIDAY WILL RANGE BETWEEN 15-25% WITH FAIR TO GOOD
OVERNIGHT RECOVERIES (35-60%). BY THIS WEEKEND MINRH'S WILL RAPIDLY
IMPROVE AS A MUCH MORE UNSETTLED WEATHER PATTERN IS EXPECTED THROUGH
EARLY NEXT WEEK. DURING THAT TIME A SERIES OF WEATHER SYSTEMS ARE
EXPECTED TO AFFECT THE AREA WITH MUCH COOLER TEMPERATURES ALONG WITH
INCREASING MOISTURE AND CHANCES FOR WETTING RAINFALL.
CLIMATE
RECORD HIGHS:
DATE YUMA EL CENTRO
---- ---- ---------
OCT 8 107 IN 1996 106 IN 1996
OCT 9 106 IN 2024104 IN 1996
PSR WATCHES/WARNINGS/ADVISORIES
AZ...EXTREME HEAT WARNING UNTIL 8 PM MST FRIDAY FOR AZZ532.
EXTREME HEAT WARNING UNTIL 8 PM MST THIS EVENING FOR AZZ530-536.
CA...EXTREME HEAT WARNING UNTIL 8 PM PDT FRIDAY FOR CAZ566-567.
EXTREME HEAT WARNING UNTIL 8 PM PDT THIS EVENING FOR CAZ569-570.
SHORT TERM...RYAN
LONG TERM...LOJERO
AVIATION...18
FIRE WEATHER...LOJERO/RYAN
CLIMATE...RW
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