962
FXUS65 KTWC 280929
AFDTWC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
229 AM MST WED MAY 28 2025
SYNOPSIS
TEMPERATURES WILL BE SEVERAL DEGREES ABOVE NORMAL
THROUGH FRIDAY WITH GENERALLY DRY CONDITIONS PREVAILING. A WEATHER
SYSTEM THIS WEEKEND WILL BRING SOME MOISTURE INTO THE REGION,
INITIALLY WITH A SLIGHT CHANCE OF MAINLY DRY THUNDERSTORMS EAST OF
TUCSON FRIDAY, THEN CONTINUED SLIGHT CHANCES OF SHOWERS AND
THUNDERSTORMS SATURDAY AREA-WIDE. THE BEST CHANCES FOR SHOWERS AND
THUNDERSTORMS WILL OCCUR SUNDAY INTO EARLY MONDAY WITH DRY
CONDITIONS RETURNING THEREAFTER. BELOW NORMAL TEMPERATURES RETURN
SUNDAY INTO EARLY NEXT WEEK.
DISCUSSION
BENIGN WEATHER IN THE NEAR TERM BEFORE A MUCH MORE
ACTIVE WEATHER REGIME FOR LATE MAY AND EARLY JUNE THIS WEEKEND. FOR
TODAY, THE AREA WILL BE UNDER DRY WEST TO SOUTHWEST FLOW ALOFT WITH
WEAK RIDGING NEAR THE AZ/NM BORDER. A LITTLE BIT OF MID LEVEL
MOISTURE WILL SNEAK ACROSS FROM NM INTO THE WHITE MOUNTAINS, PERHAPS
JUST ENOUGH FOR A FEW CLOUD BUILD-UPS THAT WAY THIS AFTERNOON BUT NO
LIGHTNING EXPECTED. OTHERWISE, SOME HIGH LEVEL CLOUDS WILL BE ON THE
INCREASE LATER THIS AFTERNOON WITH TYPICAL AFTERNOON BREEZES. HIGHS
WILL BE A FEW DEGREES ABOVE NORMAL TOPPING OUT RIGHT AROUND 100 IN
TUCSON.
THE PATTERN EVOLUTION OVER THE NEXT FEW DAYS INTO THE WEEKEND WILL
BE DOMINATED BY A TROUGH APPROACHING THE SOUTHERN CALIFORNIA COAST
THAT WILL TRANSITION INTO A NEARLY STATIONARY CLOSED LOW OFF NORTH
CENTRAL BAJA THURSDAY THROUGH SATURDAY. THE ENSEMBLES ARE IN REALLY
GOOD AGREEMENT THROUGH SATURDAY ON THE PLACEMENT OF THIS SYSTEM.
BEYOND THE UPPER LOW, WE'VE GOT OUR EYE ON THE TROPICS WHERE A
DISTURBANCE NEAR 15N/105W HAS A NEAR 100 PERCENT CHANCE OF FORMATION
INTO A TROPICAL CYCLONE OVER THE NEXT 48 HOURS PER NHC. THE
COMBINATION OF THE UPPER LOW WHICH WILL PROVIDE A LONG DURATION
SOUTH TO SOUTHEASTERLY FLOW ON ITS EAST FLANK, AND ADDITIONAL
MOISTURE INPUT COURTESY OF THE TROPICAL CYCLONE WILL EVENTUALLY HELP
PUSH OUR PWAT LEVELS THIS WEEKEND TO AROUND 200-300 PERCENT OF
NORMAL.
FOR THURSDAY, STILL PLENTY OF DRY AIR OVER OUR FORECAST AREA WITH
SIMILAR TEMPERATURES TO TODAY.
FRIDAY WILL BE THE START OF THE TRANSITION AS MOISTURE (ALREADY IN
PLACE) OVER NEW MEXICO WILL NUDGE WESTWARD. THIS INITIAL MOISTURE
PUSH IS MAINLY IN THE MID LEVELS WITH THE MAIN CONCERN BEING SOME
BUILD-UPS PRODUCING A SLIGHT CHANCE OF DRY THUNDERSTORMS EAST OF
TUCSON. GIVEN THE DRY SUB-CLOUD LAYER, GUSTY WINDS WOULD OCCUR NEAR
ANY DRY THUNDERSTORMS. TEMPERATURES REMAIN A FEW DEGREES ABOVE
NORMAL FRIDAY.
SATURDAY WILL START TO TRANSITION TO HIGHER MOISTURE LEVELS COMING
UP FROM THE SOUTH WITH ENSEMBLES INCREASING PWAT'S TO 0.75" TO 1
INCH WHICH IS OVER 200 PERCENT OF NORMAL. WHILE THE MOISTURE IS ON
THE UPSWING, THESE PWAT VALUES SATURDAY ARE STILL LOW IN THE CONTEXT
OF OUR TYPICAL MONSOON LEVELS. ADDITIONALLY, THERE JUST ISN'T MUCH
IN THE WAY OF DYNAMICS FOR US YET AS THE UPPER LOW IS STILL FAR
ENOUGH TO OUR WEST. WITH THAT SAID, WE'LL JUST BROAD BRUSH POPS IN
THE 10 TO 20 PERCENT RANGE SATURDAY WITH DRY THUNDERSTORMS AND GUSTY
WINDS ONCE AGAIN A POSSIBILITY WITH THE CLOUD BUILD-UPS.
THE CLOSED LOW WILL FINALLY EJECT EASTWARD SUNDAY INTO MONDAY BUT
WE'RE SEEING SOME TIMING DIFFERENCES WITH THE EPS THE SLOWEST, THE
GEFS IN THE MIDDLE AND THE GEPS QUICKEST WITH TIMING. THAT WILL
DETERMINE WHETHER THE BEST CHANCES FOR SHOWERS AND THUNDERSTORMS
WILL OCCUR SUNDAY AFTERNOON OR HOLD OFF UNTIL SUNDAY NIGHT INTO
MONDAY. THE CURRENT FORECAST TAKES A MIDDLE OF THE ROAD APPROACH BUT
WOULDN'T BE SURPRISED IF IT SLOWS DOWN A BIT MORE. THE GREATEST
MOISTURE LEVELS WITH PWAT VALUES 1-1.25 INCHES WILL OCCUR OUT AHEAD
OF THIS TROUGH WHICH COMBINED WITH THE DYNAMICS AND LIFT WILL RESULT
IN MORE WIDESPREAD COVERAGE OF SHOWERS AND THUNDERSTORMS. ENSEMBLE
MEAN QPF VALUES ARE GENERALLY AROUND 0.25" BUT THERE ARE A FEW
OUTLIER MEMBERS ON THE HIGH SIDE WITH LOCALLY UP TO AROUND AN INCH.
KEEP IN MIND WE'RE STILL IN A VERY DRY TIME OF YEAR CLIMATOLOGICALLY
SO ANY PRECIPITATION IS NOTABLE AND WOULD BE HELPFUL GIVEN OUR
DROUGHT. ONCE THE SYSTEM PASSES, ANY RESIDUAL PRECIPITATION CHANCES
WILL RAPIDLY DIMINISH ON MONDAY FROM WEST TO EAST WITH DRY
CONDITIONS RETURNING.
THESE DRY CONDITIONS WILL THEN PREVAIL THROUGH THE MIDDLE OF NEXT
WEEK WITH A RETURN TO SOUTHWESTERLY FLOW ALOFT WITH WINDS THE NEXT
CONCERN AS TROUGHING BECOMES ESTABLISHED OVER THE GREAT BASIN.
TEMPERATURES WILL BE 3 TO 7 DEGREES BELOW NORMAL EARLY NEXT WEEK.
AVIATION
VALID THROUGH 29/12Z.
GENERALLY LIGHT AND TERRAIN DRIVEN WINDS LESS THAN 12 KTS THROUGH
THE FORECAST PERIOD WITH A WLY/SWLY AFTERNOON GUSTS AROUND 15 KTS.
SKC THRU 29/18Z THEN SCT-BKN CLOUDS AOA 20K FT AGL THRU THE VALID
PERIOD. AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.
FIRE WEATHER
DRY CONDITIONS CONTINUE THROUGH THURSDAY
WEEK WITH SINGLE DIGIT MIN RH VALUES AT ALL ELEVATIONS, WITH POOR
OVERNIGHT RECOVERIES. EXPECT SEASONALLY TYPICAL AFTERNOON
BREEZES/GUSTS DUE TO STRONG DAYTIME HEATING.
A MORE VARIABLE WEATHER PATTERN DEVELOPS LATE IN THE WEEK AND INTO
EARLY NEXT WEEK AS A WEATHER SYSTEM TO OUR WEST AND SOUTHWEST WILL
DRAW MOISTURE INTO THE AREA. THE MOISTURE INCREASE WILL INITIALLY
MAINLY OCCUR IN THE MID LEVELS EAST OF TUCSON BY FRIDAY, WHERE BUILD-
UPS MAY RESULT IN DRY LIGHTNING. ADDITIONAL MOISTURE PUSHING INTO
THE AREA IS LIKELY THROUGH THE WEEKEND. SATURDAY MAY SEE ANOTHER DAY
OF BUILD-UPS FOR DRY LIGHTNING, THEN SUNDAY INTO MONDAY SHOULD
FEATURE ADEQUATE MOISTURE FOR MORE WIDESPREAD WETTING RAIN
OPPORTUNITIES. GUSTY AND ERRATIC WINDS WOULD OCCUR WITH ANY
THUNDERSTORM ACTIVITY. DRY WEATHER RETURNS BY NEXT TUESDAY.
TWC WATCHES/WARNINGS/ADVISORIES
NONE.
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