800
FXUS65 KPSR 111113
AFDPSR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
413 AM MST THU JUN 11 2026
UPDATE...UPDATED 12Z AVIATION DISCUSSION
KEY MESSAGES
- FAIRLY STABLE TEMPERATURES AROUND 4 TO 8 DEGREES ABOVE DAILY
NORMALS WILL RESULT IN WIDESPREAD MODERATE HEAT RISK, WITH
ISOLATED POCKETS OF MAJOR HEAT RISK AT TIMES, THROUGH THE MIDDLE
OF NEXT WEEK.
- AN INCREASE IN MOISTURE BY THE END OF THE WEEK INTO THE WEEKEND
WILL LEAD TO SLIGHT CHANCES FOR SHOWERS AND STORMS, WITH BETTER
CHANCES CURRENTLY FOCUSED DURING MORNING AND OVERNIGHT PERIODS.
- OVERNIGHT LOW TEMPERATURES WILL BE NOTICEABLY WARMER AS A RESULT
OF INCREASED HUMIDITY, WITH THE TYPICALLY WARMER LOWER DESERT
LOCALES STRUGGLING TO COOL BELOW 80 DEGREES BY THE WEEKEND.
SHORT TERM /TODAY THROUGH SATURDAY/
EARLY MORNING MIDLEVEL WATER VAPOR IMAGERY AND 500 MB RAP
ANALYSIS REVEALS A COUPLE STRIKING DEFORMATION AXES DRAPED ACROSS
THE REGION AND INTERSECTING OVER THE FORECAST AREA. THESE AREAS OF
DEFORMATION HAVE COME ABOUT IN BETWEEN TO TWO SEPARATE
GEOPOTENTIAL HIGH/LOW COUPLETS: ONE NORTHERN COUPLET LARGER IN
SCALE AND FORMED VIA CURVATURE IN THE POLAR JET STREAM, WITH AN
UPPER LEVEL RIDGE OFF THE WEST COAST AND DOWNSTREAM MEAN TROUGHING
OVER THE INTERMOUNTAIN WEST AND NORTH-CENTRAL CONUS, AND A
SECOND, SOUTHERN COUPLET IS COMPRISED OF A CUTOFF UPPER LOW OFF
THE BAJA COAST AND A SUBTROPICAL ANTICYCLONE CENTERED
APPROXIMATELY OVER FAR NORTHERN MEXICO/WESTERN TEXAS. THE SOUTHERN
COUPLET WILL PLAY A MORE PROMINENT ROLE IN OUR LOCAL WEATHER, AS
ENSEMBLES REMAIN IN GOOD AGREEMENT THAT THE BAJA LOW WILL MEANDER
NORTHWARD OVER THE NEXT 24-36 HOURS AND THE SUBTROPICAL HIGH WILL
EDGE EAST NORTHEASTWARD AS THE NORTHERN STREAM/MEAN TROUGHING
RETREATS SLIGHTLY NORTHWARD. THIS EVOLUTION WILL ALLOW A PERIOD OF
MOIST SOUTHERLY FLOW TO ESTABLISH OVER THE FORECAST AREA,
IMPORTING ANOMALOUSLY HIGH PWATS (UP TO AROUND 200- 250% OF
NORMAL, 1.1-1.5") AND LEADING TO SLIGHT CHANCES FOR SHOWERS AND
THUNDERSTORMS AS EARLY AS FRIDAY MORNING.
UPPER LEVEL DIVERGENCE AND SOME MODEST PVA FROM THE BAJA LOW WILL
PROVIDE FOR GOOD ASCENT FRIDAY, HOWEVER, THE MAIN LIMITATION WILL
BE MOISTURE AS THE ATMOSPHERE MOISTENS THROUGHOUT THE DAY. BY
SATURDAY, ASCENT MECHANISMS ARE LESS WELL-DEFINED OR WILL HAVE
SHIFTED AWAY FROM THE FORECAST AREA, BUT DECENT MOISTURE (NEAR-
SURFACE MIXING RATIOS AS MUCH AS 9-10 G/KG, PWATS PEAKING AROUND
1.5") AND INSTABILITY (GFS BUFR SOUNDINGS INDICATE MUCAPE UP TO
500-750 J/KG) WILL BE PRESENT. AS A RESULT, ONLY SLIGHT (15-20%)
CHANCES FOR SHOWERS AND STORMS ENTER THE PICTURE BOTH DAYS, AND
THE COVERAGE AND EXACTLY WHERE THEY WILL FORM REMAINS FAIRLY
UNCERTAIN. CURRENT CAMS THAT EXTEND OUT 60-84 HOURS SEEM TO
SUPPORT AN AREA OF ISOLATED TO SCATTERED SHOWERS DEVELOPING OVER
SOUTHEAST CA AND/OR SOUTHWEST AZ FRIDAY MORNING AND DRIFTING
NORTH/NORTHEAST HEADING INTO THE AFTERNOON. CAMS CURRENTLY SHOW
VERY LITTLE IN THE WAY OF LOWER DESERT SHOWER/STORM DEVELOPMENT
SATURDAY BUT MORE ACTIVITY FOCUSED OVER THE AZ HIGH TERRAIN AND
FAR SOUTHEAST AZ/EASTERN SONORA DURING THE AFTERNOON. HOWEVER,
THINGS SUCH AS SUBTLE VORTICITY LOBES OR GRAVITY WAVES FROM
DISTANT CONVECTION THE PREVIOUS DAY COULD BE SUFFICIENT TO TRIGGER
ELEVATED CONVECTION SATURDAY MORNING OVER THE LOWER DESERTS. THIS
FORECAST WILL BEAR CLOSE WATCHING, AS CUTOFF LOWS ARE FAMOUSLY
TRICKY FOR MODELS TO HANDLE, AND SUBTLE DIFFERENCES IN THE
EVOLUTION DESCRIBED HERE COULD LEAD TO SIGNIFICANT CHANGES IN THE
COVERAGE/LOCATION OF SHOWERS AND STORMS.
HEIGHTS ALOFT WILL INCREASE VERY SLIGHTLY TODAY AND GENERALLY
STABILIZE FRIDAY ONWARD, WITH ENSEMBLE MEAN H5 HEIGHTS
FLUCTUATING BETWEEN 588-592 DAM (65TH-90TH PERCENTILE OF
CLIMATOLOGY) OVER THE FORECAST AREA. THIS WILL TRANSLATE TO
AFTERNOON HIGHS COMMONLY 103F-110F ACROSS THE LOWER DESERTS
THROUGH SATURDAY, AROUND 5F ABOVE DAILY NORMALS. ONE NOTABLE
DIFFERENCE WILL BE WARMER OVERNIGHT LOWS, THANKS IN LARGE PART TO
THE INCREASE IN MOISTURE AND SOME INFLUENCE FROM CLOUD COVER
FRIDAY-SATURDAY. DEWPOINT TEMPERATURES ARE FORECAST TO INCREASE
RELATIVELY QUICKLY FROM THEIR CURRENT OBSERVED VALUES BETWEEN
25F-35F INTO A 50F-60F RANGE ACROSS MUCH OF THE AREA OVER THE NEXT
24-48 HOURS. AS A RESULT, OVERNIGHT LOWS RANGING FROM THE MIDDLE
70S TO MIDDLE 80S WILL BECOME COMMON AS EARLY AS FRIDAY MORNING.
LONG TERM /SUNDAY THROUGH WEDNESDAY/
A FEW CHANGES ARE NOTED IN THE LATEST ENSEMBLES AND GLOBAL MODEL
RUNS: MEASURES OF MOISTURE OVER THE FORECAST AREA (E.G., PWATS,
MIXING RATIOS) ARE PEAKING AT SLIGHTLY LOWER VALUES, HOWEVER,
MOISTURE IS NOT EFFECTIVELY SCOURED OUT AND WILL LIKELY LINGER
INTO EARLY NEXT WEEK, PROVIDING FURTHER CHANCES FOR AFTERNOON AZ
HIGH TERRAIN THUNDERSTORMS. THE LIMITED INSTABILITY WITH LARGE
T/TD SPREADS AND DRY SUB-CLOUD LAYER WILL FAVOR DRY LIGHTNING AND
GUSTY OUTFLOW WINDS VERSUS HEAVY RAINFALL, AS IS TYPICAL WITH
CONVECTIVE ACTIVITY IN JUNE. THESE CHANGES COME AS ENSEMBLES NOW
SHOW THE CYCLONICALLY CURVED POLAR JET, AND ANY ATTENDANT
SHORTWAVE TROUGHS ROTATING THROUGH THE BASE OF THE MEAN TROUGH
OVER THE NORTH-CENTRAL CONUS, REMAINING FURTHER EAST OF THE
REGION. WHILE FLOW ALOFT WILL TURN OUT OF A DRIER WESTERLY OR
NORTHWESTERLY DIRECTION SUNDAY, THE MORE DISTANT INFLUENCE OF
POLAR JET WILL MEAN THAT THE FLOW STAYS FAIRLY WEAK OVER REGION,
MUCH LESS EFFECTIVE AT SCOURING OUT LINGERING MOISTURE. POSITIVE
MIDLEVEL HEIGHT ANOMALIES REMAINING FAIRLY STAGNANT THROUGH THE
MIDDLE OF THE WEEK WILL ALLOW FOR STEADY TEMPERATURES IN A 4 TO 8
DEGREE ABOVE NORMAL RANGE. TEMPERATURES WILL BE SLIGHTLY HIGHER IN
THE WESTERN DESERTS, BUT REGARDLESS, LOWER DESERT HIGHS WILL PEAK
NEAR OR JUST ABOVE 110F FOR THE TYPICALLY HOTTER SPOTS.
AVIATION
UPDATED AT 1110Z.
SOUTH CENTRAL ARIZONA INCLUDING KPHX, KIWA, KSDL, AND KDVT:
NO AVIATION WEATHER CONCERNS UNDER GRADUAL INCREASE IN MID/UPPER
LEVEL CLOUD DECKS CAN BE EXPECTED THROUGHOUT THE TAF PERIOD. THE
OVERALL WIND PATTERN WILL EXHIBIT THE TYPICAL DIURNAL TENDENCIES
WITH SPEEDS GENERALLY AOB 10 KTS. A PERIOD OF GUSTY WESTERLY
WINDS CLOSE TO 20 KTS IS POSSIBLE THIS EVENING.
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:
NO AVIATION WEATHER CONCERNS UNDER A GRADUAL INCREASE IN
MID/UPPER LEVEL CLOUD DECKS CAN BE EXPECTED THROUGHOUT THE TAF
PERIOD. AT KIPL, WINDS THROUGH THIS AFTERNOON WILL BE OUT OF THE
SOUTHEAST BEFORE SHIFTING OUT OF THE WEST FOR A PERIOD EARLY THIS
EVENING. AT KBLH, WINDS WILL FLUCTUATE BETWEEN THE SOUTH TO SOUTH-
SOUTHWEST. OVERALL WIND SPEEDS WILL GENERALLY BE AOB 10 KTS.
FIRE WEATHER
TEMPERATURES 3-6 DEGREES ABOVE NORMAL WILL PREVAIL WITH LOWER
DESERT HIGHS NEAR 110F IN SOME OF THE HOTTER SPOTS, ESPECIALLY BY
THE WEEKEND. DRY CONDITIONS WILL CONTINUE TODAY WITH RELATIVE
HUMIDITY BOTTOMING OUT AROUND 8-15%. LOW LEVEL MOISTURE WILL
IMPROVE BEGINNING FRIDAY AND THROUGH THIS WEEKEND WITH MINIMUM
HUMIDITY LARGELY ABOVE 15% AND OVERNIGHT RECOVERIES GENERALLY
IMPROVING FROM POOR TO FAIR. WITH THE INCREASING MOISTURE WILL
ALSO COME INCREASING CHANCES FOR AT LEAST ISOLATED THUNDERSTORMS
ACROSS THE AZ HIGH TERRAIN OVER THE WEEKEND, WITH GUSTY OUTFLOW
WINDS AND DRY LIGHTNING POTENTIALLY LEADING TO NATURAL FIRE STARTS
BEING THE MAIN HAZARDS. THE OVERALL WIND PATTERN WILL REMAIN
DIURNAL WITH SPEEDS AT OR BELOW 15 MPH AND LIMITED AFTERNOON
UPSLOPE GUSTINESS.
PSR WATCHES/WARNINGS/ADVISORIES
AZ...NONE.
CA...NONE.
SHORT TERM...WHITTOCK
LONG TERM...WHITTOCK
AVIATION...LOJERO
FIRE WEATHER...WHITTOCK/SALERNO
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