270
FXUS65 KPSR 211740
AFDPSR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
1040 AM MST MON SEP 21 2026
UPDATE
UPDATED AVIATION DISCUSSION.
KEY MESSAGES
- DRY AND TRANQUIL CONDITIONS, ALONG WITH NEAR TO SLIGHTLY ABOVE
NORMAL TEMPERATURES, WILL CONTINUE FOR MOST OF THE REGION
THROUGH AT LEAST THE MIDDLE PORTION OF THE WEEK.
- LOW PRESSURE AND ASSOCIATED MOISTURE WILL REINTRODUCE RAIN
CHANCES FOR PORTIONS OF ARIZONA OVER THE NEXT FEW DAYS, BUT ANY
RAINFALL ACTIVITY FOR OUR FORECAST AREA WILL BE FOCUSED
PRIMARILY OVER FOOTHILL AND HIGH TERRAIN AREAS THROUGH
WEDNESDAY.
- ISOLATED LOWER DESERT RAINFALL CHANCES GET INTRODUCED TO THE
FORECAST DURING THE LATTER PORTION OF THE WEEK.
SHORT TERM /TODAY THROUGH WEDNESDAY/
CURRENT OBJECTIVE ANALYSIS REVEALS SHORTWAVE TROUGHING OVER THE
NORTHERN PLAINS, WHILE A MORE POTENT UPPER-LEVEL LOW SPINS OVER
CALIFORNIA. THE LATTER OF THESE SYSTEMS WILL BE THE MAIN WEATHER
REGIME OVER THE DESERT SOUTHWEST DURING THE FRONT HALF OF THIS WEEK
AS IT PUSHED INTERMEDIATE LOW-AMPLITUDE RIDGING FURTHER EASTWARD.
HOWEVER, THE EXPECTATION IS THAT THE PACIFIC WAVE WILL WEAKEN AS IT
MOVES FURTHER INLAND, SO NO SIGNIFICANT DAY-TO-DAY CONDITIONS
CHANGES ARE IN THE FORECAST AS DRY AND TRANQUIL CONDITIONS WILL
CONTINUE FOR THE VAST MAJORITY OF THE REGION. EVEN WITH MODEST
HEIGHT FALLS, TEMPERATURES WILL CONTINUE TO RUN NEAR TO SLIGHTLY
ABOVE NORMAL FOR THIS TIME OF YEAR, WHICH TRANSLATES TO LOWER
ELEVATION HIGHS HOVERING BETWEEN 93-102 DEGREES.
THE ONE EXCEPTION TO THE DRY AND TRANQUIL STATEMENT ABOVE DURING THE
FRONT HALF OF THE WEEK WILL BE PORTIONS OF NORTHERN AND EASTERN
ARIZONA THANKS TO INCREASED MOISTURE ADVECTION FROM THE PREVIOUSLY-
MENTIONED PACIFIC LOW. NOT ONLY WILL DECENT MOISTURE BE IN PLACE
OVER THESE AREAS WITH PWATS APPROACHING 150-200% OF NORMAL, UPPER-
LEVEL ASCENT FROM ANTI-CYCLONIC FLOW AND AN UPPER-LEVEL JET STREAK
WILL PROVIDE AND ADDED LAYER OF SUPPORT FOR THE DEVELOPMENT OF
SHOWER AND THUNDERSTORM ACTIVITY. WITH THAT BEING SAID, COVERAGE
OVER OUR FORECAST AREA WILL BE MINIMAL AT BEST AS ATMOSPHERIC
THERMODYNAMIC PROFILES WILL NOT BE QUITE ENOUGH TO PROVIDE LOWER
DESERT RAINFALL. RATHER, MOST, IF NOT ALL, POTENTIAL RAINFALL WITHIN
OUR FORECAST BOUNDARIES WILL BE CONFINED TO HIGHER TERRAIN AREAS.
LONG TERM /THURSDAY THROUGH SUNDAY/
BY THE LATTER HALF OF THE WORK WEEK, THE INFLUENCE OF THE WEAKENING
SOUTHWESTERN LOW WILL ALL BUT DISAPPEAR. THE FOCUS WILL THEN SHIFT
TOWARD THE INTERPLAY BETWEEN LARGE SCALE TROUGHING OVER THE EASTERN
PACIFIC/WEST COAST, AND THE SUB-TROPICAL HIGH OVER THE SOUTHERN
PLAINS AND NORTHERN MEXICO. GLOBAL ENSEMBLES FAVOR THE RETROGRADING
BACK TOWARD THE DESERT SOUTHWEST AS WE APPROACH THE WEEKEND, LIKELY
STAVING OFF ANY ADVANCE, AT LEAST TEMPORARILY, OF MORE ANTI-CYCLONIC
WAVES. THIS PROGRESSION WOULD NOT COMPLETELY SCOUR RESIDUAL MOISTURE
IMMEDIATELY, SO RAIN CHANCES WILL LIKELY LINGER INTO THURSDAY.
CURRENT POPS SHOW 30-50% CHANCES FOR FOOTHILL AND MOUNTAIN AREAS AND
10-30% PROBABILITIES FOR THE SOUTH-CENTRAL ARIZONA DESERTS. BEYOND
THAT, PERSISTENT SOUTHWESTERLY FLOW WOULD EVENTUALLY DRY US OUT
ENOUGH TO LIMIT RAIN CHANCES HEADING INTO THE WEEKEND. ANOTHER
INFLUX OF MOISTURE BY THE END OF THE SEVEN DAY PERIOD MAY BRING
RAIN CHANCES BACK ONCE AGAIN, BUT MAX CHANCES AT THIS TIME ONLY
RANGE BETWEEN 20-30%.
EVEN WITH THE COMPETING AIRMASSES, REGIONAL TEMPERATURES WILL ONLY
FLUCTUATE WITHIN A FEW DEGREES THROUGH THE WEEKEND. WHILE THE RIDGE
KEEPS ANOTHER SHORTWAVE FROM PROGRESSING TOWARD THE REGION, AS
MENTIONED PREVIOUSLY, IN RETURN, THE LARGE SCALE TROUGHING TO OUR
WEST WILL KEEP THE HIGH FROM BECOMING TOO AMPLIFIED, THANKFULLY,
PREVENTING ANY FURTHER DISCUSSION OF ABNORMAL HEAT, AT LEAST DURING
THIS FORECAST PERIOD. TEMPERATURES FOR THE LOWER DESERTS THURSDAY
THROUGH SUNDAY WILL RANGE GENERALLY BETWEEN 94-106 DEGREES, WHILE
OVERNIGHT LOWS HOVER NEAR 70-82 DEGREES.
AVIATION
UPDATED AT 1740Z.
SOUTH CENTRAL ARIZONA INCLUDING KPHX, KIWA, KSDL, AND KDVT:
NO MAJOR AVIATION WEATHER CONCERNS WILL EXIST THROUGH TUESDAY
AFTERNOON UNDER PERIODS OF SCT-BKN MID AND HIGH CLOUD DECKS WITH
BASES REMAINING AOA 8K FT AGL. WINDS WILL VEER OUT OF THE SSE/S
AND MAINTAIN THIS DIRECTION THROUGH MUCH OF THE AFTERNOON,
PRESENTING A MINOR CONCERN WITH A SOUTHERLY CROSS-RUNWAY COMPONENT
AT KPHX AND KDVT. HOWEVER, ONLY OCCASIONAL GUSTS TO AROUND 15 KTS
ARE EXPECTED THROUGH THE AFTERNOON WITH SPEEDS REMAINING MOSTLY
AOB 10 KTS. BY THIS EVENING, A MUCH LATER THAN USUAL WESTERLY WIND
SWITCH IS ANTICIPATED. A FAMILIAR PATTERN WILL TAKE SHAPE TONIGHT
AND TUESDAY MORNING, WITH E/SE NOCTURNAL DRAINAGE WINDS
ESTABLISHING FOLLOWED BY WINDS VEERING OUT OF THE SSE TUESDAY
MORNING. CHANCES FOR SHRA/TSRA IN THE PHOENIX AIRSPACE REMAIN
BELOW 10% THROUGH TUESDAY AFTERNOON, WITH MOST ACTIVITY REMAINING
WELL TO THE EAST AND SOUTHEAST, HOWEVER, SOME PERIODS WITH VIRGA
SHOWERS IN THE VICINITY CANNOT BE RULED OUT.
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:
SHRA/TSRA WILL CLEAR KBLH WITHIN THE NEXT HOUR. OUTSIDE OF THIS
ACTIVITY, NO MAJOR IMPACTS ARE ANTICIPATED THROUGH THE NEXT 24
HOURS WITH PERIODS OF SCT MID AND CLOUD DECKS BECOMING CLEAR BY
THIS EVENING. WINDS WILL FAVOR W/NW AT KIPL, WITH A PERIOD OF
GUSTS TO 20-25 KTS EXPECTED THIS EVENING. AT KBLH, WINDS WILL
FAVOR S THROUGH THE DAY WITH AFTERNOON GUSTS BETWEEN 15-20 KTS
LIKELY, FOLLOWED BY SW-W WINDS THIS EVENING INTO THE OVERNIGHT
HOURS.
FIRE WEATHER
NEAR TO SLIGHTLY ABOVE NORMAL TEMPERATURES WILL PREVAIL OVER THE
NEXT SEVERAL DAYS, WITH MINIMAL DAY-TO-DAY FLUCTUATIONS. DRY
CONDITIONS WITH NO CHANCES FOR RAIN CONTINUE THROUGH TODAY AHEAD
RETURNING HIGH TERRAIN RAIN CHANCES FOR FOOTHILL AND HIGH TERRAIN
AREAS STARTING TUESDAY. MINRHS BETWEEN 15-30% WILL BE COMMON ACROSS
THE REGION, WITH EVEN HIGHER READINGS (35-50%) FOR THE FAR EASTERN
DISTRICTS. MAXRHS WILL RANGE FROM FAIR TO GOOD OVER THE WESTERN AND
CENTRAL DISTRICTS, TO GOOD AND EXCELLENT FOR THE EASTERN DISTRICTS
INTO THE WEEKEND. OUTSIDE OF SOME MARGINAL BREEZINESS CAUSED BY
AN APPROACHING WEATHER SYSTEM, WINDS WILL FOLLOW FAMILIAR DIURNAL
TRENDS WITH TYPICAL TERRAIN INDUCED AFTERNOON GUSTS AROUND 15-25
MPH.
PSR WATCHES/WARNINGS/ADVISORIES
AZ...NONE.
CA...NONE.
SHORT TERM...RW
LONG TERM...RW
AVIATION...WHITTOCK
FIRE WEATHER...RW
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