751
FXUS65 KPSR 230606
AFDPSR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
1106 PM MST TUE SEP 22 2026
UPDATE
UPDATED 06Z AVIATION DISCUSSION.
KEY MESSAGES
- RAIN CHANCES RETURN TO PORTIONS OF EASTERN ARIZONA WITH MOST
ACTIVITY FOCUSED OVER FOOTHILL AND HIGH TERRAIN AREAS.
- BEST CHANCES FOR LOWER DESERT RAINFALL WILL OCCUR WEDNESDAY AND
THURSDAY, THOUGH MOST ACTIVITY SHOULD REMAIN TO THE NORTH AND
EAST OF THE PHOENIX METRO.
- NEAR TO SLIGHTLY ABOVE NORMAL TEMPERATURES WILL PERSIST OVER
THE NEXT SEVERAL DAYS.
SHORT TERM /TODAY THROUGH THURSDAY/
AS ONE VORTICITY CENTER LIFTS NORTHEAST THROUGH THE GREAT BASIN,
A LINGERING, ELONGATED TROUGH REMAINS ACROSS THE SW CONUS
EXTENDING SOUTH OF THE BAJA PENINSULA. PER WV IMAGERY, SEVERAL
VORTICITY CENTERS ARE EMBEDDED IN THIS WEAK SOUTHERLY FLOW AND
WILL STREAM NORTH OVER THE NEXT 72 HOURS PERIODICALLY ENHANCING
ASCENT STRUCTURE AS WELL AS IMPORTING MARGINALLY BETTER MOISTURE
POLEWARD. THE FIRST SUCH FEATURE CURRENTLY OVER SONORA WILL
PROGRESS THROUGH EASTERN ARIZONA LATER TODAY WHILE A MORE DEFINED
CIRCULATION CENTER OVER THE SOUTHERN BAJA EJECTS THROUGH CENTRAL
NEW MEXICO WEDNESDAY. A FINAL PIECE OF ENERGY INCORPORATING THE
ENTIRE TROUGH BASE AND FULL EXTENT OF CYCLONIC INFLUENCE WILL
SURGE THROUGH CENTRAL ARIZONA THURSDAY AFTERNOON/EVENING
POTENTIALLY BRINGING THE GREATEST SHORT TERM IMPACTS TO THE LOCAL
FORECAST AREA.
OBJECTIVE ANALYSIS INDICATES A POOL OF 10 G/KG MIXING RATIOS
ACROSS SE ARIZONA EARLY THIS AFTERNOON WITH A MARKED GRADIENT
TOWARDS UNDER 6 G/KG ACROSS THE PHOENIX METRO. THIS HAS CONFINED
THE AREA OF INSTABILITY LARGELY OUTSIDE THE CWA THOUGH AN
INCREASING SYNOPTIC PRESSURE GRADIENT AMPLIFIED BY COOL OUTFLOW
WILL CONTINUE TO ENHANCE EASTERLY BOUNDARY LAYER FLOW SUCH THAT
INCREASING SHALLOW MOISTURE SHOULD SLOSH WESTWARD OVER THE NEXT 24
HOURS. FORECAST CONFIDENCE IS MODERATE REGARDING SCATTERED
SHOWERS AND A COUPLE EMBEDDED STORMS MOVING INTO SOUTHERN GILA
COUNTY THIS EVENING, ALBEIT WITH LOW INSTABILITY LIMITING THE
AREAL AND TEMPORAL EXTENT. EASTERLY WINDS SHOULD BE INVIGORATED BY
THIS ACTIVITY WHICH COULD CONCEIVABLY RESULT IN SOME LOFTED DUST
INTO LOWER ELEVATIONS, HOWEVER EVEN AMONG THE MOST AGGRESSIVE HIGH
RESOLUTION MODELS, A SUDDEN SURGE AND/OR PROLONGED INSTANCE OF
GUSTY WINDS APPEARS UNLIKELY REDUCING THE THREAT FOR DENSE DUST.
GLOBAL AND HREF MEMBERS AGREE THAT A WELL DEFINED CIRCULATION
CENTER WILL PROPAGATE FROM THE NORTHERN MEXICO THROUGH
WESTERN/CENTRAL NEW MEXICO WEDNESDAY. THIS WILL PLACE THE EASTERN
PORTIONS OF THE CWA WITHIN A DEFORMATION ZONE WEST OF THE
CIRCULATION CENTER WITH THE EXPECTATION OF THICKER MID/HIGH CLOUDS
AND PERSISTENT SHOWERS HAMPERING INSOLATION. HOWEVER, WITH BETTER
BOUNDARY LAYER MOISTURE IN PLACE (~10 G/KG MIXING RATIOS),
CLEARING OVER MOUNTAINS WEST OF THE DEFORMATION BAND SHOULD HELP
REALIZE MLCAPE 1000-1500 J/KG. NORTHEAST STEERING FLOW SHOULD
DIRECT STORMS AND OUTFLOW ALONG THE MOGOLLON RIM TOWARDS THE
PHOENIX METRO, HOWEVER CINH AROUND 50 J/KG WILL NEED TO BE
BREACHED. MULTIPLE COLLIDING OUTFLOW BOUNDARIES NECESSARY TO
ACHIEVE LOWER ELEVATION STORMS ARE CERTAINLY POSSIBLE, HOWEVER
THERE IS ONLY MARGINAL SUPPORT FOR THIS OUTCOME AMONG THE FULL
MODEL SUITE AND HAVE MAINTAINED RELATIVELY LOW POPS.
THE MAIN BASAL SHORTWAVE WILL PASS DIRECTLY INTO SOUTH-CENTRAL
ARIZONA THURSDAY WITH THE FULL CYCLONIC CURVATURE REGION AND STRONG
ASCENT SIGNAL JUXTAPOSED WITH MODEST INSTABILITY. SIMILAR TO
WEDNESDAY, LOWER ELEVATION MOISTURE LEVELS MAY BE TOO LOW TO SUPPORT
MORE THAN ISOLATED THUNDERSTORM FORMATION, HOWEVER ASCENT STRUCTURE
WILL BE FAR MORE CONDUCIVE THAN WEDNESDAY. GIVEN THIS STRONG LIFT
AND DCAPE IN EXCESS OF 1500 J/KG, MODELS HAVE BEEN CONSISTENT IN
ADVERTISING AT LEAST 1 STRONG OUTFLOW BOUNDARY SURGING THROUGH THE
ARIZONA LOWER DESERTS. COLLIDING BOUNDARIES MAY BE SUFFICIENT
TOWARDS ADDITIONAL DEVELOPMENT IN LOWER DESERTS, AND PATTERN
RECOGNITION AND MODEL EVIDENCE INDICATES THIS POTENTIAL MAY SKIP
OVER THE PHOENIX METRO TOWARDS WESTERN ARIZONA, THOUGH HAVE
INCREASED POPS MARGINALLY OVER THE INITIALIZED NBM. REGARDLESS,
SIGNALS CONTINUE TO SHOW THE POSSIBILITY OF AN ORGANIZED EXPANSIVE
AND LONG DURATION BLOWING DUST EVENT.
LONG TERM /FRIDAY THROUGH TUESDAY/
LATE IN THE WEEK, SHORTWAVE ENERGY WILL HAVE EJECTED NORTHEAST AND
BECOME ABSORBED INTO THE STRONGER WESTERLY FLOW OVER THE PLAINS. IN
ITS WAKE, DEEP QUASI-ZONAL WESTERLY FLOW WILL GRADUALLY SCOUR AWAY
MOISTURE SUCH THAT PWATS FALL BELOW 1" AND BOUNDARY LAYER MIXING
RATIOS UNDER 9 G/KG BY FRIDAY AFTERNOON. A PERIOD OF SHORTWAVE
RIDGING THROUGH THE FIRST HALF OF THE WEEKEND WILL ALSO IMPOSE
EXPANSIVE SYNOPTIC SCALE SUBSIDENCE SUCH THAT ONLY THE MOST
SUSCEPTIBLE HIGH TERRAIN LOCATIONS WOULD SUPPORT BRIEF AFTERNOON
DEEP CONVECTION. IN FACT, INSTABILITY AND ASCENT PARAMETERS ARE SO
POOR SATURDAY THAT NBM POPS ARE ESSENTIALLY UNDER 5% ACROSS THE
ENTIRE REGION.
FORECAST CONFIDENCE DETERIORATES SIGNIFICANTLY NEXT WEEK DUE
UNCERTAINTIES IN A PROGRESSIVE WESTERLY WAVE AND POTENTIAL
INTERACTION WITH TROPICAL MOISTURE. ENSEMBLE MEMBERS ARE IN GOOD
AGREEMENT THAT A SHORTWAVE WILL DEEPEN NEAR THE CALIFORNIA COAST
EARLY NEXT WEEK, THEN RAPIDLY PROPAGATE THROUGH THE INTERMOUNTAIN
WEST DURING THE FIRST HALF OF THE WEEK. HOWEVER, THERE IS
SUBSTANTIAL DIFFERENCES IN DEPTH AND TIMING OF THIS FEATURE, WHICH
WILL BE CRUCIAL IN DETERMINING THE ABILITY TO TAP DEEP, TROPICAL
MOISTURE AND RESULTING IMPACTS ACROSS THE SW CONUS. IN GENERAL,
OPERATIONAL MEMBERS ARE DEEPER AND FASTER WITH THIS WAVE THAN THE
PREPONDERANCE OF NAEFS MEMBERSHIP; AND BASED ON HISTORICAL
PRECEDENT, WOULD FAVOR A SOMEWHAT SLOWER PROGRESSION OF THE CENTRAL
COLD CORE AND TROUGH AXIS THOUGH INTENSITY TOWARDS THE DEEPER
SOLUTIONS IS PREFERRED. WHILE CONCEPTUALLY A SLOWER, DEEPER OUTCOME
WOULD FAVOR DRAWING THE FULL BRUNT OF REMNANT TROPICAL CIRCULATION
AND ASSOCIATED MOISTURE INTO THE SOUTHWEST (AKIN TO THE LATEST 12Z
GFS), THE WIDE UNCERTAINTY IN THE ACTUAL LOCATION OF THE TROPICAL
SYSTEM COMBINED WITH DISPARITY IN THE LOCATION AND TIMING OF THE
TROUGH PASSAGE YIELDS A LARGE VARIATION OF POSSIBLE OUTCOMES.
NEVERTHELESS AT THE VERY LEAST, ENSEMBLES HINT AT JET ENERGY AND
SHEARED SHORTWAVE DRAWING MIDLEVEL MOISTURE INLAND SUNDAY/MONDAY
YIELDING SCATTERED SHOWERS AND STORMS. THEREAFTER BECAUSE OF THE
VAST ENSEMBLE SPREAD, MANDATED NBM POPS ARE ESSENTIALLY MODEST
VALUES SPREAD OVER A PROLONGED PERIOD AND OFFER MINIMAL ACTIONABLE
DETAILS AT THIS TIME.
IN TERM OF TEMPERATURES, MUCH LIKE DURING THE SHORT TERM, NOT MUCH
FLUCTUATION IN DAY-TO-DAY READINGS IS EXPECTED TO OCCUR. DAILY
VALUES WILL HOVER RIGHT AROUND TO JUST ABOVE NORMAL, WHICH
TRANSLATES TO LOWER DESERT READINGS RANGING BETWEEN 94-105 DEGREES
THROUGH THE WEEKEND. OVERNIGHT LOWS WILL BE SLIGHTLY MORE ELEVATED
COMPARED TO WHERE THEY TYPICALLY ARE FOR LATE SEPTEMBER, LIKELY AN
EFFECT OF LINGERING MOISTURE AND CLOUD COVER (AT LEAST FOR SOME
SPOTS), WITH READINGS BETWEEN 70-82 DEGREES. MEANWHILE HIGHER
ELEVATION CONDITIONS WILL BE QUITE COMFORTABLE AS MOST LOCATIONS
SHOULD BE IN THE 80S, WITH PERHAPS A FEW SPOTS TOUCHING THE LOWER
90S. LOWS FOR THESE SPOTS IN THE UPPER 50S TO LOWER 70S WILL BE
COMMON.
AVIATION
UPDATED AT 0606Z.
SOUTH CENTRAL ARIZONA INCLUDING KPHX, KIWA, KSDL, AND KDVT:
POTENTIAL RA/TS IMPACTS AND GUSTY OUTFLOW WINDS WILL BE THE
PRIMARY FORECAST CHALLENGE AND POTENTIAL IMPACT THROUGH WEDNESDAY
EVENING. LIGHT E WINDS WILL PERSIST THROUGH MIDNIGHT BEFORE A MORE
PRONOUNCED E/SE WIND DEVELOPS BY 07-09Z AND CONTINUES THROUGH
WEDNESDAY MORNING WITH SPEEDS UP TO 8-12 KTS AND OCCASIONAL GUSTS
INTO THE MID-TEENS. AN ISOLATED SHOWER CANNOT BE RULED OUT MID
WEDNESDAY MORNING AND THEN THERE WILL BE A SLIGHT CHANCE (20%)
FOR VCSH/VCTS AT TERMINALS IN THE LATE AFTERNOON AND EVENING.
STORMS ARE MOST LIKELY TO THE N AND NE WEDNESDAY AFTERNOON AND
WILL BE CAPABLE OF SENDING OUTFLOW WINDS DOWN INTO THE METRO WHICH
MAY LEAD TO ADDITIONAL ACTIVITY. TIMING CURRENTLY LOOKS TO BE
AROUND 01-02Z FOR THE ARRIVAL OF OUTFLOW WINDS. FEW TO SCT CLOUDS
BASES DOWN TO 8-10K FT AGL WILL BE COMMON THROUGH THE TAF PERIOD
WITH SCT TO BKN MID AND HIGH CLOUDS.
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:
NO AVIATION WEATHER IMPACTS ARE ANTICIPATED THROUGH THE NEXT 24
HOURS WITH MOSTLY CLEAR SKIES. WINDS WILL FAVOR W/NW AT BOTH KIPL
AND KBLH THROUGH WEDNESDAY MORNING AND THEN A SHIFT TOWARD E/SE BY
THE AFTERNOON, WITH WIND SPEEDS MOSTLY STAYING BELOW 10 KTS AND
PERIODS OF LIGHT AND VARIABLE WINDS.
FIRE WEATHER
NEAR TO SLIGHTLY ABOVE NORMAL TEMPERATURES WILL PREVAIL OVER THE
NEXT SEVERAL DAYS, WITH MINIMAL DAY-TO-DAY FLUCTUATIONS. DAILY RAIN
CHANCES RETURN FOR THE HIGH TERRAIN THROUGH THE END OF THE WORKWEEK
WITH LOWER DESERT CHANCES FOCUSED ON WEDNESDAY. MINRHS BETWEEN 15-
30% WILL BE COMMON ACROSS THE REGION THROUGH THE START OF THE
WEEKEND, 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. DRIER AIR BY THE WEEKEND WILL LOWER RHS SLIGHTLY,
BUT THEY SHOULD REMAIN ABOVE CRITICAL FIRE WEATHER THRESHOLDS.
OUTSIDE OF ANY THUNDERSTORM RELATED OUTFLOWS, 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...18
LONG TERM...18/RW
AVIATION...BENEDICT
FIRE WEATHER...RW
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