579
FXUS65 KPSR 272300
AFDPSR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
400 PM MST WED AUG 27 2025
UPDATE
UPDATED AVIATION...
KEY MESSAGES
- ISOLATED SHOWERS AND THUNDERSTORMS WILL CONTINUE THROUGH THIS
AFTERNOON INTO THE EVENING AREAWIDE WITH LIGHT SHOWER ACTIVITY THEN
AFFECTING SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA TONIGHT THROUGH
THURSDAY AFTERNOON.
- TEMPERATURES THURSDAY WILL RANGE FROM NEAR NORMAL ACROSS SOUTH-
CENTRAL ARIZONA TO BELOW NORMAL ACROSS SOUTHEAST CALIFORNIA AND
SOUTHWEST ARIZONA. WIDESPREAD MODERATE HEAT RISK IS EXPECTED FOR
THIS WEEKEND.
- OVERALL DRY CONDITIONS WILL PREVAIL LATER THIS WEEK AND LIKELY
THROUGH THE WEEKEND BEFORE RAIN CHANCES GRADUALLY INCREASE DURING
THE FIRST HALF OF NEXT WEEK.
SHORT TERM /TODAY THROUGH THURSDAY/
EARLY AFTERNOON RAP ANALYSIS SHOWED A WEAK PACIFIC TROUGH OFF THE
CALIFORNIA COAST, WHICH HAS PROMOTED DRIER SOUTHWESTERLY FLOW ALOFT
OVER MUCH OF OUR REGION. TODAY'S 18Z YUMA SOUNDING AND 12Z PHOENIX
SOUNDING SHOWED CONSIDERABLE DRY AIR ABOVE 500 MB WITH PWATS NOW
AROUND 1.2-1.5". MEANWHILE LOOKING FURTHER TO THE SOUTH, VISIBLE
SATELLITE AND WV IMAGERY SHOW TROPICAL STORM JULIETTE ADVANCING
NORTHWARD, WHICH WILL HELP TO BRING IN BETTER MOISTURE ALOFT.
LATEST RADAR EARLY THIS AFTERNOON SHOWED ISOLATED SHOWERS AND
THUNDERSTORMS DEVELOPING ACROSS PARTS OF THE FORECAST AREA,
INCLUDING AREAS SUCH AS DESERT CENTER IN SOUTHEAST CALIFORNIA OVER
TO AREAS IN SOUTHERN GILA COUNTY. THIS ACTIVITY WILL CONTINUE TO
REMAIN ISOLATED THROUGH THE AFTERNOON WITH SOME GUSTY OUTFLOW WINDS
POSSIBLE. AS MENTIONED BEFORE, TROPICAL STORM JULIETTE WILL CONTINUE
TO ADVANCE NORTHWARD WHILE WEAKENING AND WILL BRING US INCREASING
MID AND UPPER LEVEL MOISTURE THIS EVENING INTO THURSDAY,
PARTICULARLY FOR THE WESTERN PART OF OUR AREA. WITH THIS INCREASE IN
MOISTURE ALOFT, GUIDANCE SHOW PWATS RISING TO UPWARDS OF AROUND 1.5-
1.8" ACROSS SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA WITH LOWER
VALUES ANTICIPATED TO THE EAST ACROSS SOUTH- CENTRAL ARIZONA. GIVEN
THIS INCREASE IN MOISTURE ALONG WITH SOME EXPECTED UPPER FORCING, HI-
RES GUIDANCE SHOW A LIGHT BAND OF SHOWER ACTIVITY DEVELOPING
TONIGHT AND PERSISTING INTO TOMORROW OVER SOUTHEAST CALIFORNIA AND
SOUTHWEST ARIZONA. THIS SHOWER ACTIVITY IS EXPECTED TO PERSIST
THROUGH THE MORNING AND INTO THE AFTERNOON TOMORROW AS THE
AFOREMENTIONED WEAK PACIFIC TROUGH PULLS THE REMNANTS OF JULIETTE
NORTHEASTWARD INTO THE DESERT SOUTHWEST. THIS SHOWER ACTIVITY IS
LARGELY EXPECTED TO REMAIN WEST OF THE PHOENIX AREA WITH AREAS
ACROSS SOUTH-CENTRAL ARIZONA PRIMARILY SEEING THICKER MID AND HIGH
LEVEL CLOUD COVER. RAINFALL AMOUNTS WITH THE SHOWER ACTIVITY TO THE
WEST WILL MOSTLY REMAIN ON THE LIGHT SIDE BEFORE SHOWERS PUSH OUT OF
THE AREA BY THURSDAY EVENING.
CURRENT NBM TEMPERATURES SHOW HIGHS FOR THURSDAY TOPPING OUT AROUND
100-103 DEGREES ACROSS THE VALLEY, WHILE AREAS OUT WEST ARE FORECAST
TO ONLY SEE HIGHS IN THE LOWER TO MID 90S. DEPENDING ON HOW MUCH
SHOWER ACTIVITY THESE AREAS SEE, THESE TEMPERATURES COULD END UP
BEING A BIT LOWER.
LONG TERM /FRIDAY THROUGH TUESDAY/
BY FRIDAY, THE REMNANT MOISTURE FROM TC JULIETTE IS EXPECTED TO
SHIFT OUT OF THE REGION WITH DRIER WESTERLY FLOW TAKING OVER AS THE
SUBTROPICAL RIDGE CENTERED NEAR EL PASO BECOMES THE MAIN DRIVER OF
OUR WEATHER. WE SHOULD RETURN TO FULL SUNSHINE ON FRIDAY WITH
BOUNDARY LAYER MOISTURE GRADUALLY GETTING MIXED OUT, LOWERING
SURFACE DEW POINTS DOWN INTO THE LOW 50S AND THEN INTO THE MID TO
UPPER 40S ON SATURDAY. THE RIDGE WILL BRING SOME INCREASING HEIGHTS
OVER THE REGION FRIDAY INTO THE WEEKEND AND HELPING TO BRING HOTTER
CONDITIONS AS HIGHS WARM TO JUST ABOVE NORMAL STARTING SATURDAY. WE
ARE EXPECTING TO SEE WIDESPREAD MODERATE HEATRISK DEVELOP BY
SATURDAY AND POSSIBLY SOME VERY LOCALIZED MAJOR HEATRISK ON SUNDAY
AS SOME OF THE LOWER DESERTS COULD TOP OUT NEAR 110 DEGREES.
EVENTUALLY ENSEMBLE GUIDANCE SHOWS THE RIDGE CENTER SHIFTING
NORTHWARD TO OVER OR NEAR NORTHERN ARIZONA EARLY NEXT WEEK ALLOWING
SOME WEAK SOUTHEASTERLY MOIST FLOW BACK INTO AT LEAST SOUTHERN
ARIZONA. THERE IS STILL A GOOD DEAL OF UNCERTAINTY WITH THE TIMING
OF THE MOISTURE RETURN AND THE NBM TRIES TO EVEN INTRODUCE SLIGHT
CHANCE POPS ALREADY ON SUNDAY, BUT THAT SEEMS TOO EARLY. OUR
THINKING IS WE MAY SEE SOME HIGH TERRAIN CONVECTION RETURN BY MONDAY
AND THEN POTENTIALLY INTO THE LOWER DESERTS AROUND NEXT TUESDAY OR
WEDNESDAY. TEMPERATURES EARLY NEXT WEEK ARE LIKELY TO START TO TREND
DOWNWARD WITH THE INCREASE IN MOISTURE, BUT MORE THAN LIKELY WILL
REMAIN AT LEAST A COUPLE DEGREES ABOVE NORMAL INTO THE MIDDLE PART
OF NEXT WEEK.
AVIATION
UPDATED AT 2300Z.
SOUTH CENTRAL ARIZONA INCLUDING KPHX, KIWA, KSDL, AND KDVT:
NO MAJOR WEATHER ISSUES SHOULD EXIST THROUGH THURSDAY EVENING UNDER
THICKENING MIDLEVEL CIGS. CONFIDENCE IS GOOD THAT W/SW WINDS WILL
PREVAIL SOMEWHAT LONGER INTO THE OVERNIGHT AT KPHX THAN USUAL, AS
15K FT CIGS SPREAD INTO THE REGION. ANY REGIONAL TSRA SHOULD REMAIN
OUTSIDE THE TERMINAL FOOTPRINT THIS EVENING BEFORE DISSIPATING AFTER
SUNSET. THICK CIGS WILL PERSIST THURSDAY WITH SOME OCCASIONAL VIRGA
POSSIBLE, HOWEVER NO SHRA/TSRA ACTIVITY IS EXPECTED. LIGHT EAST (OR
VARIABLE) WINDS IN THE MORNING SHOULD SWITCH BACK TO W/SW BY NOON.
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:
GUSTY W/NW WINDS THURSDAY WITH WIDESPREAD VIRGA/SHRA WILL BE THE
GREATEST ISSUE UNDER THICKENING CIGS LOWERING TO AROUND 10K FT AGL.
CONFIDENCE IS VERY GOOD THAT CIGS WILL LOWER TO 15K FT THIS EVENING
WITH THE ONSET OF SCATTERED LIGHT SHRA THURSDAY MORNING. GUSTS
AROUND 25KT WILL BE PREVALENT WITH THE ONSET OF VIRGA/SHRA, AND KIPL
WOULD STAND THE BEST CHANCE FOR PROLONGED LIGHT RAIN, GUSTY WINDS,
AND LOWEST CIGS. ACTIVITY SHOULD BEGIN CLEARING THE AREA LATE
THURSDAY AFTERNOON.
FIRE WEATHER
CHANCES FOR SHOWERS AND THUNDERSTORMS WILL OVERALL REMAIN LOW (20%
OR LESS) ACROSS SOUTH-CENTRAL ARIZONA OVER THE NEXT COUPLE OF DAYS,
WHILE THE BEST CHANCES ARE EXPECTED ACROSS THE WESTERN DISTRICTS
THROUGH TOMORROW AFTERNOON. PRIMARY THREAT WITH ANY THUNDERSTORMS
THIS AFTERNOON WILL BE GUSTY, ERRATIC OUTFLOW WINDS. RAIN CHANCES
DROP BELOW 10% BY FRIDAY WITH DRIER CONDITIONS PREVAILING. MINRHS
OVER THE NEXT COUPLE OF DAYS WILL MOSTLY RANGE BETWEEN 20-30% BEFORE
GRADUALLY DECREASING INTO THE TEENS BY THE WEEKEND. TEMPERATURES
WILL REMAIN NEAR TO SLIGHTLY BELOW NORMAL THROUGH THURSDAY BEFORE
RISING TO SLIGHTLY ABOVE NORMAL BY SATURDAY. CHANCES FOR MONSOONAL
ACTIVITY INCREASE AGAIN GOING INTO NEXT WEEK.
PSR WATCHES/WARNINGS/ADVISORIES
AZ...NONE.
CA...NONE.
SHORT TERM...SMITH
LONG TERM...KUHLMAN
AVIATION...18
FIRE WEATHER...SMITH/KUHLMAN
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