624
FXUS65 KPSR 182037
AFDPSR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
135 PM MST SUN OCT 18 2026
KEY MESSAGES
- CHANCES FOR LIGHT RAIN WILL PERSIST OVER ARIZONA HIGHER TERRAIN
LOCATIONS EAST OF PHOENIX THE NEXT COUPLE DAYS WITH MINIMAL
ACCUMULATION.
- TEMPERATURES WILL GRADUALLY WARM CLOSER TO THE SEASONAL NORMAL
THROUGH THE MIDDLE OF THE WEEK BEFORE ABRUPTLY COOLING LATER THIS
WEEK.
- A PACIFIC LOW PRESSURE SYSTEM MOVING INTO THE SOUTHWEST LATER
THIS WEEK WILL RESULT IN MUCH BETTER RAINFALL CHANCES WITH THE
POSSIBILITY OF A FEW EMBEDDED THUNDERSTORMS.
SHORT TERM /TODAY THROUGH TUESDAY/
EARLY AFTERNOON WV IMAGERY AND OBJECTIVE ANALYSIS DEPICTS AN UPPER
LEVEL TROUGH BECOMING ELONGATED ACROSS THE SW CONUS WITH ONE
VORTICITY CENTER EJECTING THROUGH THE FOUR CORNERS, WHILE A
SECONDARY CIRCULATION SLOWLY MOVES INTO SW ARIZONA. A PLUME OF
HIGHER, ANOMALOUS PWATS AROUND 1" CONTINUES TO HOVER OVER SOUTHERN
ARIZONA WITHIN THE SOUTHWEST FLOW ON THE LEADING EDGE OF THE TROUGH
AXIS, THOUGH THE MAJORITY OF THIS MOISTURE WAS RELEGATED TO THE H7
LAYER AND ABOVE. ASCENT WILL CONTINUE TO BE MAXIMIZED AHEAD OF THE
SW ARIZONA VORTICITY CENTER THROUGH THIS EVENING, WITH SOME MEASURE
OF SUBSIDENCE AND DRIER MIDTROPOSPHERIC AIR MOVING INTO THE CWA IN
ITS WAKE. HOWEVER, ENOUGH MOISTURE WILL REMAIN IN THE MIDLEVELS
COINCIDENT WITH FAVORABLE CYCLONIC FLOW, SHEARED VORTICITY, AND
ANOTHER SUBTROPICAL JET STREAK TO SUPPORT BANDS OF LIGHT SHOWERS
THROUGH MONDAY AFTERNOON. OROGRAPHIC AREAS WILL BE PRIMARILY FAVORED
FOR ACCUMULATING LIGHT RAIN, BUT EVEN A FEW ISOLATED SHOWERS COULD
AFFECT LOWER DESERT LOCATIONS IN SOUTH-CENTRAL ARIZONA. WITH THE
TROUGH FINALLY ABSORBED INTO THE MEAN FLOW BY TUESDAY, PRECIPITATION
CHANCES DWINDLE WHILE MODEST HEIGHT/THERMAL INCREASES BRIEFLY SPREAD
INTO THE FORECAST AREA. AS A RESULT, FORECAST CONFIDENCEIS EXCELLENT
THAT TEMPERATURES WILL REBOUND NEAR, OR EVEN A COUPLE DEGREES ABOVE
THE DAILY NORMALS.
LONG TERM /WEDNESDAY THROUGH SATURDAY/
BY WEDNESDAY, DEEP TROUGHING AND STRONG NEGATIVE HEIGHT ANOMALIES
WILL BE ESTABLISHED OFF THE CENTRAL/SOUTHERN CALIFORNIA COAST, AND
POISED TO MOVE INLAND THE REMAINDER OF THE WEEK. ENSEMBLE AND
DETERMINSTIC MODELING HAVE COME INTO MUCH BETTER AGREEMENT OVER THE
PAST 24 HOURS WITH EPS MEMBERS LARGELY ABANDONING THE IDEA OF A
DEEPER, SLOWER TROUGHING DRIVING EASTWARD THROUGH THE CWA. INSTEAD,
THE PREPONDERANCE OF ENSEMBLE OUTPUT NOW SUPPORT PREVIOUS GEFS
SOLUTIONS SHOWING SHORTWAVE ENERGY AND THE MAIN COLD CORE LIFTING
FROM SOUTHERN CALIFORNIA INTO SOUTHERN UTAH IN REPSONSE TO
ANOMALOUS HIGH AMPLITUDE, STRONG RIDGING STATIONED OVER THE
CENTRAL/SOUTHERN PLAINS. HOWEVER, ECMWF FORECASTS CONTINUE TO
HIGHLIGHT MORE ROBUST MOISTURE ADVECTION VIA DEEP, MERIDIONAL FLOW
AHEAD OF THE TROUGH PASSAGE INTO ARIZONA, THOUGH DIFFERENCES AMONG
ENSEMBLE MEMBERS ARE NOW BECOMING MUCH SMALLER.
REGARDLESS, WEDNESDAY AND THURSDAY CONTINUE TO HAVE THE BEST WINDOW
FOR RAINFALL POTENTIAL WITH THE SYNOPTIC PATTERN STRONGLY FAVORING
PERSISTENT MOIST UPSLOPE AND OROGRAPHICALLY FOCUSED MODERATE
RAINFALL NORTH AND EAST OF PHOENIX. OCCASIONAL BANDS OF SHOWERS WILL
UNDOUBTEDTLY EXTEND INTO LOWER DESERT COMMUNITIES OF SOUTH-CENTRAL
ARIZONA WITH MUCH OF SE CALIFORNIA/SW ARIZONA REMAINING DRY. THE
ADJUSTED NORTHERLY TRACK LIFTING AWAY FROM THE CWA ALSO DECREASES
THE POTENTIAL FOR STRONG THUNDERSTORM DEVELOPMENT, THOUGH A FEW
EMBEDDED STORMS WOULD STILL BE LIKELY BEFORE RAPID DRYING BEHIND A
FRONTAL PASSAGE SWEEPS THROUGH THE REGION FRIDAY. WITH BETTER
ENSEMBLE AGREEMENT, THE FULL SUITE OF THE NBM TEMPERATURE SPREAD HAS
NARROWED SLIGHTLY DURING THIS TIME FRAME WITH THE EXPECTATION OF
ADDITIONAL FORECAST CONFIDENCE IN FUTURE ITERATIONS SHOWING A RAPID
DESCENT TOWARDS READINGS AROUND 10F BELOW NORMAL BY THE END OF THE
WEEK.
AVIATION
UPDATED AT 1815Z.
SOUTH CENTRAL ARIZONA INCLUDING KPHX, KIWA, KSDL, AND KDVT:
NO MAJOR AVIATION WEATHER CONCERNS ARE EXPECTED THROUGHOUT THE TAF
PERIOD. AREAS OF LIGHT SHOWERS AND VIRGA CONTINUE TO MOVE THROUGH
PORTIONS OF THE PHOENIX METRO, WITH MOST OF THE ACTIVITY LOCATED
WEST OF THE METRO. WITH THE SHOWERS CONTINUING VCSH HAS BEEN
EXTENDED IN THE TAFS THROUGH 20-21Z THIS AFTERNOON. OPERATIONAL
IMPACTS WILL REMAIN MINIMAL WITH THIS ACTIVITY. WIND DIRECTIONS
WILL OVERALL EXHIBIT AN EASTERLY COMPONENT THROUGH THE MAJORITY OF
THE TAF PERIOD. A PERIOD OF WESTERLY WINDS IS POSSIBLE THIS
EVENING (23-08Z), BUT WINDS MAY JUST BE LIGHT AND VARIABLE DURING
THIS WINDOW BEFORE THEY REESTABLISH THE EASTERLY COMPONENT
OVERNIGHT. SO, VRB WINDS HAS BEEN ADDED TO THE KPHX AND KIWA TAFS
FOR THIS WINDOW. WINDS AT KSDL AND KDVT WILL BE LIGHT AND VARIABLE
BEGINNING AROUND 00Z THROUGH THE END OF THE TAF PACKAGE. WIND
SPEEDS THROUGH THE EARLY AFTERNOON WILL BE AROUND 10-15 KT BEFORE
DECREASING TO AOB 8 KT THE REST OF THE PERIOD. ABUNDANT MID-LEVEL
CLOUDS WILL REMAIN IN PLACE THROUGH THE EARLY AFTERNOON HOURS
BEFORE SCATTERING OUT HEADING INTO THE EVENING.
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:
NO MAJOR AVIATION CONCERNS ARE EXPECTED THROUGHOUT THE TAF PERIOD
WITH MOSTLY CLEAR SKIES. BOTH TAF SITES WILL HAVE LIGHT AND
VARIABLE WINDS THROUGH THE PERIOD WITH SPEEDS AOB 5 KT. WHILE
WINDS WILL BE LIGHT AND VARIABLE, WINDS AT KIPL WILL TEND TO
EXHIBIT MORE OF A W/NW COMPONENT AND WINDS AT KBLH WILL TEND TO
EXHIBIT MORE OF A NE/NW COMPONENT.
FIRE WEATHER
WIND SPEEDS OVER THE NEXT FEW DAYS WILL BE MUCH WEAKER THAN THIS
PAST WEEKEND WITH MINIMAL GUSTINESS, HOWEVER SPEEDS AND GUST
FREQUENCY WILL INCREASE AGAIN TOWARDS THE MIDDLE OF THE WEEK AHEAD
OF AN INCOMING WEATHER DISTURBANCE. OCCASIONAL LIGHT SHOWERS MAY
CONTINUE TO IMPACT EASTERN DISTRICTS, THOUGH WETTING RAINFALL
POTENTIAL IS UNDER 20%. MUCH BETTER RAINFALL CHANCES WILL ARRIVE
DURING THE MIDDLE OF THE WEEK WITH AMOUNTS GREATER THAN 0.50" LIKELY
EAST OF PHOENIX. MINIMUM HUMIDITY LEVELS IN A 30-50% RANGE WILL BE
COMMON THROUGHOUT THE WEEK WITH EVEN HIGHER READINGS LIKELY ACROSS
EASTERN DISTRICTS. OVERNIGHT RECOVERY SHOULD BE GOOD TO EXCELLENT
RESULTING IN LITTLE TO NO FIRE WEATHER CONCERNS FOR AT LEAST THE
NEXT WEEK.
PSR WATCHES/WARNINGS/ADVISORIES
AZ...NONE.
CA...NONE.
SHORT TERM...18
LONG TERM...18/RYAN
AVIATION...BERISLAVICH
FIRE WEATHER...18
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