848
FXUS65 KPSR 232355
AFDPSR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
455 PM MST SAT MAY 23 2026
UPDATE
UPDATED AVIATION DISCUSSION.
KEY MESSAGES
- TEMPERATURES NEAR TO SLIGHTLY ABOVE NORMAL THROUGH EARLY NEXT
WEEK WILL COOL INTO A BELOW NORMAL CATEGORY DURING THE LATTER
HALF OF THE WEEK, ESPECIALLY FOR THE WESTERN DESERTS.
- TYPICAL AFTERNOON BREEZINESS WILL PREVAIL THROUGH THE BEGINNING
OF THE UPCOMING WORK WEEK FOLLOWED BY INCREASING WINDS ACROSS
THE REGION DURING THE MIDDLE OF THE WEEK.
- A SLIGHT CHANCE OF THUNDERSTORMS WILL EXIST OVER THE EASTERN
ARIZONA HIGH TERRAIN MONDAY, ALBEIT WITH LIMITED RAINFALL
POTENTIAL.
SHORT TERM /TODAY THROUGH MONDAY/
SENSIBLE WEATHER CONDITIONS AND/OR CHANGES THROUGH THE NEXT 48-60
HOURS CAN BE TIED TO AN INTENSIFYING SUBTROPICAL JET STREAK AND
ATTENDANT UPPER LOW DEVELOPING OVER THE EASTERN PACIFIC, FAR OFF
THE BAJA PENINSULA EARLY THIS AFTERNOON. IN THE NEAR TERM, THIS
DEVELOPING SYSTEM OVER THE EASTERN PACIFIC WILL HELP PUMP HEIGHTS
ALOFT DOWNSTREAM, FORMING A TRANSIENT SHORTWAVE RIDGE OVER THE
SOUTHWEST US THAT WILL SLIDE TO OUR EAST BY SUNDAY BUT NONETHELESS
BRING POSITIVE HEIGHT ANOMALIES OVERHEAD. RAP ANALYSIS ALREADY
SHOWS H5 HEIGHTS NEAR OR JUST ABOVE 580 DAM OVER SOUTHERN AZ AT
THIS HOUR, AN INCREASE OF 2-4 DAM FROM EARLY THIS MORNING.
ENSEMBLES CONTINUE TO ADVERTISE H5 HEIGHTS PEAKING AROUND 581-584
DAM ON SUNDAY, REPRESENTING A RANGE BETWEEN THE 60TH-80TH
PERCENTILE OF CLIMATOLOGY FOR THIS TIME OF YEAR. DESPITE THE
NOTABLE POSITIVE HEIGHT ANOMALIES, THEY WILL BE SHORT-LIVED, AND
SO LOWER LEVEL THERMAL PROFILES WILL HAVE LITTLE TIME TO RESPOND.
AS A RESULT, LOWER DESERT HIGHS WILL LIKELY REMAIN IN THE MIDDLE
TO UPPER 90S DAILY THROUGH MONDAY, WITH SOME OF THE WARMEST SPOTS
TOUCHING 100F ON SUNDAY.
DEEP SOUTHERLY FLOW WILL BE IMPARTED OVER MUCH OF THE STATE AS
THE SHORTWAVE RIDGE SLIDES EAST OF THE FORECAST AREA SUNDAY,
IMPORTING A MODEST AMOUNT OF MOISTURE IN THE MID-UPPER LEVELS.
MEANWHILE, GLOBAL GUIDANCE REMAINS IN EXCELLENT AGREEMENT THAT THE
SUBTROPICAL JET STREAK AND ATTENDANT UPPER LOW (WHICH IS SHOWN
KEEPING IN PACE WITH THE "LEFT EXIT" REGION OF THE JET) WILL PUSH
ONSHORE ALONG SOCAL/NORTHERN BAJA CALIFORNIA SUNDAY NIGHT INTO
MONDAY. GIVEN THIS PROGRESSION, EXPECT SYNOPTIC ASCENT MECHANISMS
TO BE MAXIMIZED OVER THE STATE SUNDAY NIGHT INTO MONDAY MORNING.
HOWEVER, FORECAST SOUNDINGS SUGGEST SHALLOW, TRANSIENT SATURATED
LAYERS ABOVE 700 MB, WITH A DEEP, DRY NEAR-SURFACE LAYER
EXHIBITING LARGE T/TD SPREAD. AS A RESULT, AND CONSISTENT WITH
LATEST CAMS, SCATTERED LIGHT SHOWERS/VIRGA MAY DEVELOP OVER
SOUTHEASTERN AZ LATE SUNDAY AFTERNOON AND PUSH NORTHWARD SUNDAY
EVENING/NIGHT, RESULTING IN SPOTTY (IF ANY) MEASURABLE
PRECIPITATION PRIMARILY EAST/SOUTHEAST OF THE GREATER PHOENIX
AREA. AS THE CORE OF THE UPPER LOW DRAWS OVERHEAD MONDAY, LAPSE
RATES WILL STEEPEN MORE NOTICEABLY, AND INSTABILITY IS EXPECTED
TO DEVELOP PRIMARILY OVER THE HIGH TERRAIN OF SOUTHERN GILA
COUNTY, WHICH COULD LEAD TO A FEW THUNDERSTORMS. THE VERY DRY SUB-
CLOUD LAYER WILL MEAN THE PRIMARY THREAT FROM ANY STORMS WILL BE
DRY LIGHTNING AND GUSTY OUTFLOW WINDS, AND THE THREAT WILL BE
SHORT- LIVED FOR OUR FORECAST AREA AS DRY AIR SHOULD QUICKLY
ARRIVE FROM THE SOUTHWEST MONDAY AFTERNOON.
LONG TERM /TUESDAY THROUGH FRIDAY/
AN OVERWHELMING PREPONDERANCE OF ENSEMBLE MEMBERS ARE NOW
ADVERTISING A WESTERN CONUS PATTERN PREVIOUSLY PREFERRED BY HUMAN
FORECASTERS WITH DEVELOPING BLOCKING, AND DEEPENING SLOW MOVING
FEATURES AFFECTING THE WESTERN CONUS. AS A RESULT, CONFIDENCE HAS
IMPROVED THAT PRONOUNCED NEGATIVE HEIGHT ANOMALIES ENTERING THE
PACIFIC NW WILL DESCEND INTO THE GREAT BASIN, THEN STALL IN THE
FORM OF A LARGE CUTOFF LOW, PERHAPS AS FAR SOUTH AS SOUTHERN
UT/NORTHERN AZ. GIVEN THIS EVOLUTION, TEMPERATURES WILL RETREAT
INTO A BELOW NORMAL CATEGORY DURING THE MIDDLE OF THE WEEK, AND
POSSIBLY PERSISTING THROUGH THE REMAINDER OF THE WEEK. AUTOMATED
NBM/WPC OUTPUT HAS STARTED REFLECTING THIS TREND, THOUGH IT WOULD
NOT BE UNEXPECTED THAT FUTURE FORECASTS TRIM A COUPLE MORE DEGREES
CLOSER TO THE LOWER QUARTILE OF THE NUMERICAL DISTRIBUTION DURING
THE LATTER HALF OF THE WEEK.
OTHERWISE, THE GREATEST IMPACT WITH THIS SYSTEM SHOULD BE INCREASED
WIND SPEEDS WITH A SEASONALLY STRONG JET AND AGGRESSIVE HEIGHT FALLS
ENTERING THE REGION. THE INITIAL SURGE WILL ENTER SE CALIFORNIA LATE
TUESDAY, THEN SWEEP ACROSS THE ENTIRE CWA ON WEDNESDAY. DEEP
MECHANICAL MIXING SHOULD TAP HIGHER MOMENTUM 20-30KT WINDS THROUGH
THE BOUNDARY LAYER WITH THE MOST INTENSE SPEEDS IN DOWNSLOPING
REGIONS OF SE CALIFORNIA AND AROUND TERRAIN FEATURES OF THE EASTERN
CWA. RECENT MANDATED NBM FORECASTS HAVE STARTED CATCHING UP ON THIS
INCREASED WIND SPEED PARADIGM, HOWEVER SOME OF THE DEFICIENCIES IN
THE ENSEMBLING PROCESS ARE LIKELY STILL RESTRICTING THE FULL EXTENT
OF WIND SPEEDS. REGARDLESS, ADVISORIES IN THE MOST WIND PRONE AREAS
OF SE CALIFORNIA ARE LOOKING MORE LIKELY, WHILE LOW RELATIVE
HUMIDITY AND DRY FUELS MAY FOSTER AN ENHANCED FIRE DANGER ACROSS
MUCH OF THE REGION. DEPENDING ON THE POSITIONING AND PROGRESSION OF
THE ATTENDANT CLOSED LOW, THESE IMPACTS MAY PERSIST INTO THURSDAY
BEFORE RELAXING LATE IN THE WEEK.
AVIATION
UPDATED AT 2355Z.
SOUTH CENTRAL ARIZONA INCLUDING KPHX, KIWA, KSDL, AND KDVT:
WINDS OVER THE NEXT 24 HOURS WILL FOLLOW A SIMILAR PATTERN TO THE
PREVIOUS 24 HOURS, WITH EXTENDED PERIODS OF 140V220 DURING THE
AFTERNOON HOURS AND RATHER LATE SHIFT - 23-01Z - TO PREDOMINANT
W-SW. THERE IS HIGH CONFIDENCE A GULF SURGE BOUNDARY WILL MOVE
THROUGH THIS EVENING AROUND 05Z AND LEAD TO A BRIEF, 1-2 HR,
UPTICK IN SW WINDS. THERE IS LOW CONFIDENCE OF AN OUTFLOW BOUNDARY
MOVING THROUGH THE TERMINALS FROM THE SE SUNDAY EVENING, AFTER
01Z, WITH A WIND SHIFT AND BRIEF UPTICK IN WINDS. MOSTLY CLEAR
SKIES WILL PREVAIL WITH FEW HIGH-BASED CUMULUS IN THE AFTERNOONS
AND EVENINGS.
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:
NO MAJOR AVIATION WEATHER IMPACTS ARE EXPECTED THROUGH THE NEXT 24
HOURS. GUSTY S-SE WINDS WILL SUBSIDE THROUGH THIS EVENING AT BOTH
TERMINALS. WINDS WILL FAVORSE'RLY COMPONENT AT KIPL AND S'LRY
COMPONENT AT KBLH THROUGH THE TAF PERIOD. AFTERNOON WIND GUSTS UP
TO 20-25 KTS ARE EXPECTED AGAIN AT KBLH SUNDAY AFTERNOON, WITH
LESS GUSTINESS AT KIPL. SKIES WILL BE MOSTLY CLEAR THROUGH SUNDAY.
FIRE WEATHER
TEMPERATURES WILL REMAIN NEAR TO SLIGHTLY ABOVE NORMAL THROUGH
EARLY NEXT WEEK BEFORE MODEST COOLING ARRIVES DURING THE MIDDLE OF
THE WEEK. MINIMUM AFTERNOON HUMIDITY LEVELS WILL FALL INTO A
10-20% RANGE WITH POOR TO FAIR OVERNIGHT RECOVERY OF 25-40%
IMPROVING CLOSER TO A FAIR TO GOOD RANGE NEXT WEEK. A MARGINAL
INCREASE IN MOISTURE WILL RESULT IN A SLIGHT CHANCE FOR AFTERNOON
THUNDERSTORMS AND A FEW LIGHTNING STRIKES OVER HIGH TERRAIN OF
EASTERN DISTRICTS MONDAY. LITTLE TO NO ACCUMULATING RAINFALL
SHOULD BE ANTICIPATED, AND THE THREAT FOR NEW WILDFIRE STARTS DUE
TO LIGHTNING STRIKES WILL BE HEIGHTENED. TYPICAL AFTERNOON UPSLOPE
GUSTINESS OF 15-25 MPH WILL BE COMMON THROUGH EARLY NEXT WEEK
WITH SPEEDS INCREASING MARKEDLY DURING THE MIDDLE OF THE WEEK.
STRONGER GUSTS OVER EASTERN DISTRICT HIGH TERRAIN AND THROUGH THE
LOWER COLORADO RIVER VALLEY WEDNESDAY COMBINED WITH LOW RH AND DRY
FUELS MAY RESULT IN NEAR CRITICAL CONDITIONS.
PSR WATCHES/WARNINGS/ADVISORIES
AZ...NONE.
CA...NONE.
SHORT TERM...WHITTOCK
LONG TERM...18
AVIATION...BENEDICT
FIRE WEATHER...WHITTOCK/18
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