129
FXUS65 KTWC 290924
AFDTWC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
213 AM MST THU MAY 29 2025
SYNOPSIS
TEMPERATURES WILL BE SLIGHTLY ABOVE NORMAL THROUGH
FRIDAY WITH GENERALLY DRY CONDITIONS PREVAILING. A WEATHER SYSTEM
THIS WEEKEND WILL BRING A SUBSTANTIAL MOISTURE INCREASE INTO THE
REGION, INITIALLY WITH A SLIGHT CHANCE OF MAINLY DRY THUNDERSTORMS
EAST OF TUCSON FRIDAY, THEN SLIGHT CHANCES OF SHOWERS AND ISOLATED
THUNDERSTORMS SATURDAY. WIDESPREAD SHOWERS AND ISOLATED
THUNDERSTORMS WILL OCCUR SUNDAY AFTERNOON INTO EARLY MONDAY WITH DRY
CONDITIONS RETURNING THEREAFTER. BELOW NORMAL TEMPERATURES RETURN
SUNDAY INTO EARLY NEXT WEEK.
DISCUSSION
PARTLY CLOUDY SKIES THIS MORNING ACROSS SOUTHEAST
ARIZONA AS THE REGION IS GETTING SOME CLOUDS OUT AHEAD OF THE UPPER
LOW OFF THE NORTHERN COAST OF BAJA. THE UPPER LOW WILL CONTINUE TO
MOVE EAST TODAY AND APPROACH THE COAST OF NORTH CENTRAL BAJA BEFORE
IT STOPS ITS EASTWARD PROGRESSION. WHILE THE UPPER LOW WILL GET A
BIT CLOSER TO US TODAY, WE'RE NOT GOING TO SEE ANY SENSIBLE WEATHER
FROM IT YET OTHER THAN SOME OF THE INCREASED CLOUDS. HIGHS TODAY
WILL CONTINUE TO BE SLIGHTLY ABOVE NORMAL WITH A FEW AFTERNOON
BREEZES.
THIS UPPER LOW WILL BECOME COMPLETELY CUT OFF FROM THE MAIN FLOW AND
RETROGRADE WEST FRIDAY INTO SATURDAY BEFORE EVENTUALLY GETTING
EJECTED EASTWARD ACROSS ARIZONA LATER SUNDAY INTO MONDAY. WE'VE BEEN
ADVERTISING OVER THE PAST FEW DAYS A CONSIDERABLE MOISTURE INCREASE
AS THE SOUTH TO SOUTHEAST FLOW TO THE EAST OF THE UPPER LOW WILL
DRAW MOISTURE NORTHWARD. THE MOISTURE SOURCE TO OUR SOUTH WILL HAVE
SOME ADDITIONAL AID FROM TD ONE-E NOW NEAR 13N/105W AND PROGGED TO
GRADUALLY MOVE NORTHWARD CLOSER TO THE SOUTHERN TIP OF BAJA OVER THE
NEXT FEW DAYS. PWAT VALUES ARE EXPECTED TO PEAK ON SUNDAY THROUGH
SUNDAY NIGHT AT 200-300 PERCENT OF NORMAL, TRANSLATING TO 1"-1.25"
(OR EVEN SLIGHTLY HIGHER) AT ITS PEAK.
IN THE NEARER TERM, THE ATMOSPHERE WILL STILL REMAIN DRY WITH PWAT
VALUES STILL MAINLY LESS THAN 0.5" FRIDAY. A LITTLE BIT OF MID LEVEL
MOISTURE WILL TRANSLATE INTO EASTERN GRAHAM, EASTERN COCHISE AND
GREENLEE COUNTIES FRIDAY AFTERNOON INTO EVENING WHERE A FEW CLOUD
BUILD-UPS WILL RESULT IN A SLIGHT CHANCE OF DRY THUNDERSTORMS.
OTHERWISE, FRIDAY WILL CONTINUE TO SEE SLIGHTLY ABOVE NORMAL
TEMPERATURES WITH VARYING AMOUNTS OF SUN THROUGH WIDESPREAD HIGH
LEVEL CLOUDS.
SATURDAY WILL START TO TRANSITION MORE MOISTURE INTO THE REGION FROM
THE SOUTH, WITH PWATS UP TO AROUND 0.8 INCHES TO 1 INCH. HOWEVER,
WITH THE UPPER LOW STILL FAR TO THE WEST, WE'LL BE RELIANT ON WEAK
DISTURBANCES TO HELP WITH LIFT ON THE FAR NORTHEAST FLANK OF THE
UPPER LOW. WITH THAT SAID, THE GENERAL THEME OF SLIGHT CHANCES FOR
LIGHT SHOWERS AND ISOLATED (MAINLY DRY) THUNDERSTORMS LOOKS GOOD
WITH THE BEST CHANCE FOR THUNDER SOUTH AND EAST OF TUCSON. IF YOU'VE
GOT OUTDOOR ACTIVITIES THIS WEEKEND, SATURDAY IS LOOKING LIKE THE
BETTER OF THE TWO DAYS.
THE MOST IMPACTFUL PART OF THIS WEATHER SYSTEM WILL BE SUNDAY
THROUGH SUNDAY NIGHT, PERHAPS LINGERING INTO MONDAY MORNING
ESPECIALLY TO THE NORTH AND EAST OF TUCSON. THIS IS WHEN THE UPPER
LOW WILL EJECT THROUGH ARIZONA AND COMBINE WITH PEAK MOISTURE AND
DYNAMICS FOR WIDESPREAD SHOWERS AND EMBEDDED THUNDERSTORMS.
ENSEMBLES MEANS HAVE TRENDED UP ON QPF, AVERAGING 0.25" TO 0.50" IN
VALLEYS WITH HIGHER AMOUNTS IN THE MOUNTAINS BUT WE SHOULD NOTE
THERE IS MORE SPREAD IN THE ENSEMBLE DISTRIBUTION THAN NORMAL SO
CONFIDENCE IS STILL A BIT LOW ON QPF AMOUNTS. BASED ON THE CURRENT
TIMING, BEST PRECIPITATION CHANCES (60-80 PERCENT) WILL OCCUR SUNDAY
AFTERNOON THROUGH SUNDAY NIGHT. TEMPERATURES ON SUNDAY WILL DROP TO
BELOW SEASONAL NORMALS WITH HIGHS ABOUT 5 DEGREES BELOW NORMAL.
ONCE THIS SYSTEM PASSES BY AND ANY RESIDUAL SHOWERS END ON MONDAY,
THERE WILL BE A BRIEF PERIOD OF SHORTWAVE RIDGING BEFORE ANOTHER
TROUGH AND POTENTIAL UPPER LOW ACROSS CALIFORNIA ON TUESDAY SHIFT
EASTWARD AROUND THE MIDDLE OF NEXT WEEK. THIS PATTERN WILL KEEP
TEMPERATURES BELOW NORMAL WITH AN UPTICK IN BREEZES.
AVIATION
VALID THROUGH 30/12Z.
SCT TO FEW CLOUDS MAINLY AOA 15K FT MSL THRU THE VALID PERIOD.
GENERALLY LIGHT AND TERRAIN DRIVEN WINDS LESS THAN 12 KTS THROUGH
THE FORECAST PERIOD WITH WLY/SWLY AFTERNOON GUSTS AROUND 15 KTS.
AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.
FIRE WEATHER
DRY CONDITIONS CONTINUE TODAY WEEK WITH SINGLE DIGIT
MIN RH VALUES AT ALL ELEVATION. EXPECT SEASONALLY TYPICAL AFTERNOON
BREEZES/GUSTS DUE TO STRONG DAYTIME HEATING.
A MORE CHANGEABLE WEATHER PATTERN DEVELOPS STARTING FRIDAY AND INTO
EARLY NEXT WEEK AS A WEATHER SYSTEM TO OUR SOUTHWEST WILL DRAW
MOISTURE INTO THE AREA. THE MOISTURE INCREASE WILL INITIALLY 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 ESPECIALLY SOUTH AND EAST OF TUCSON, THEN
SUNDAY INTO MONDAY SHOULD FEATURE ADEQUATE MOISTURE FOR A HIGH
LIKELIHOOD OF 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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