855
FXUS65 KPSR 222010
AFDPSR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
110 PM MST TUE SEP 22 2026
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 1733Z.
SOUTH CENTRAL ARIZONA INCLUDING KPHX, KIWA, KSDL, AND KDVT:
PRIMARY AVIATION IMPACT WILL BE THE POTENTIAL FOR VCSH/VCTS THIS
AFTERNOON/EVENING, AND GUSTY OUTFLOWS. A WESTERLY SHIFT THIS
AFTERNOON LOOKS UNLIKELY WITH A BRIEF PERIOD OF S-SSW CROSS WINDS
BEFORE SHIFTING BACK OUT OUT THE SE FOR THE REMAINDER OF THE TAF
PERIOD. UNDER 10% CHANCES REMAINS FOR SHRA/TSRA ACTIVITY TO DEVELOP
IN THE METRO, WITH ACTIVITY EXPECTED TO REMAIN THE THE SOUTH AND
EAST OF THE TERMINALS. THE THE MAIN SE'RELY OUTFLOW FROM THE
PREVIOUS PACKAGE HAS BEEN SHIFTED BACK A FEW HOURS NOW EXPECTED JUST
PAST MIDNIGHT TONIGHT, HOWEVER A FEW GUSTY PERIODS MAY STILL DEVELOP
THIS EVENING AHEAD OF THE MAIN OUTFLOW. GUSTS WILL LIKELY BE NEAR
20KTS WITH LOW CONFIDENCE OF BLDU OR REDUCED VIS. FEW-SCT CLOUDS
WILL BE COMMON THROUGH THE AFTERNOON WITH LOWEST BASES AROUND 8-10
KFT AGL. THERE WILL ALSO BE INCREASING HIGH CLOUDS (AROUND 25 KFT)
THROUGH THE PERIOD AND SHOULD BECOME BKN BY THIS EVENING.
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:
NO MAJOR AVIATION IMPACTS ARE ANTICIPATED THROUGH THE NEXT 24 HOURS
WITH MOSTLY CLEAR SKIES. WINDS WILL FAVOR W/NW AT BOTH KIPL AND
KBLH, 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...RYAN
FIRE WEATHER...RW
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