942
FXUS65 KTWC 161529
AFDTWC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
829 AM MST TUE SEP 16 2025
SYNOPSIS
MOISTURE HAS MOVED INTO THE REGION WHICH WILL LEAD TO
SCATTERED SHOWERS AND THUNDERSTORMS TODAY THROUGH THE END OF THE
WORK WEEK. TEMPERATURES WILL BE SLIGHTLY ABOVE NORMAL TODAY, THEN
AROUND NORMAL TO JUST BELOW NORMAL INTO THE WEEKEND.
UPDATE
PARTLY TO MOSTLY CLOUDY SKIES THIS MORNING ACROSS
SOUTHEAST ARIZONA. MOISTURE LEVELS ARE ABOVE NORMAL FOR THIS OF YEAR
WITH PWAT VALUES IN THE 1 TO 1.3 INCH RANGE TODAY WHICH IS ABOUT 120
TO 140 PERCENT OF NORMAL AND ENOUGH TO SUSTAIN CONVECTION. MOISTURE
IMPORT WILL CONTINUE OVER THE NEXT FEW DAYS WITH HELP FROM TS MARIO
AND EVENTUAL REMNANTS. MARIO IS CURRENTLY LOCATED ABOUT 465 MILES
WEST OF THE SOUTHERN TIP OF BAJA CALIFORNIA AND CONTINUES TO MOVE
NW. CLOSER TO HOME, A WEAK NW-SE ORIENTED RIDGE IS OVER THE AREA AT
500 MB WITH 700MB TROUGH NEAR THE INTERNATIONAL BORDER AND ADJACENT
NORTHERN SONORA. THIS TROUGHING WILL HELP AID CONVECTIVE DEVELOPMENT
MAINLY FROM THE TUCSON AREA SOUTH AND EASTWARD THIS AFTERNOON, WITH
INDIVIDUAL STORMS TENDING TO DRIFT TOWARDS THE NORTH TO WEST. MAIN
CONCERNS TODAY WILL BE LOCALLY HEAVY RAIN WITH ISOLATED FLASH
FLOODING THREAT AND GUSTY OUTFLOW WINDS. NOTE THAT DCAPE VALUES ARE
IN THE 1000 TO 1200 J/KG RANGE FROM TUCSON AND POINTS NORTH AND WEST
SO THERE IS A BLOWING DUST THREAT AS WELL FOR ANY STORMS IN THIS
REGION. CURRENT FORECAST LOOKS LIKE IT'S IN GOOD SHAPE THIS MORNING
SO NO UPDATES.
DISCUSSION
SKIES ARE MOSTLY CLOUDY ACROSS SOUTHEAST ARIZONA
WITH A FEW WEAK SHOWERS SOUTH OF TUCSON. ALOFT HIGH PRESSURE IS
CENTERED OVER NORTHERN MEXICO AND A WEAK SHORTWAVE SITS OFF THE
COAST OF NORTHERN BAJA. THERE IS ALSO TROPICAL STORM MARIO ABOUT 300
MILES WEST OF CABO. MARIO WILL FEED SIGNIFICANT MOISTURE INTO
SOUTHERN CALIFORNIA AND ARIZONA LATER THIS WEEK. SOME OF THIS
MOISTURE IS ALREADY BEGINNING TO MOVE IN. BY THIS AFTERNOON PWATS
WILL BE 100-150 PERCENT OF NORMAL WITH THE BEST MOISTURE SOUTH OF
TUCSON. THIS WILL RESULT IN AN UPTICK IN THUNDERSTORM ACTIVITY
COMPARED TO YESTERDAY. HI-RES GUIDANCE SHOWS SCATTERED CONVECTION
BEGINNING THIS AFTERNOON OVER MOST OF SOUTHEAST ARIZONA. INITIALLY
STORMS WILL FORM FROM TUCSON SOUTH AND EASTWARD THEN EXPAND WEST
INTO THE TOHONO O'ODHAM NATION. LATE IN THE AFTERNOON AND EARLY
EVENING OUTFLOWS FROM STORMS COULD LEAD TO SOME BLOWING DUST IN
PINAL COUNTY AND PARTS OF PIMA COUNTY. STORMS WILL BE CAPABLE OF
STRONG WIND GUSTS AND HEAVY RAINFALL, WHICH COULD LEAD TO LOCALIZED
FLASH FLOODING.
WEDNESDAY INTO THURSDAY MARIO WILL WEAKEN BUT TRAVEL NORTHWARD WHICH
WILL FURTHER INCREASE MOISTURE VALUES IN SOUTHEAST ARIZONA,
ESPECIALLY FROM TUCSON WESTWARD. WEDNESDAY EXPECT ANOTHER ROUND OF
SCATTERED SHOWERS AND THUNDERSTORMS WITH THE MOST ACTIVITY EXPECTED
IN CENTRAL PIMA COUNTY AND THE SKY ISLANDS. PWAT VALUES WILL BE 1.5"-
1.8" FROM TUCSON TO FAR WESTERN PIMA COUNTY. STORMS WILL BE CAPABLE
OF HEAVY RAINFALL AND STRONG WINDS.
PERSISTENT SOUTHERLY TO SOUTHWESTERLY FLOW WILL CONTINUE TO ADVECT
TROPICAL MOISTURE FROM THE REMNANTS OF MARIO THROUGH FRIDAY. MARIO'S
UPPER LEVEL CIRCULATION WILL MOVE INTO SOUTHERN CALIFORNIA DURING
THIS TIME. SOUTHEAST ARIZONA WILL BE ON THE THE EASTERN PERIPHERY OF
ITS SYNOPTIC SCALE FORCING, BUT THERE SHOULD BE ENOUGH TO HELP
FACILITATE DAILY SCATTERED THUNDERSTORMS CAPABLE OF HEAVY RAINFALL
BOTH DAYS. IT'S POSSIBLE ONE OF THESE DAYS COULD BE LESS ACTIVE
BECAUSE OF THE PREVIOUS DAY'S CONVECTION OR BECAUSE OF THICK MID-
LEVEL CLOUDS THAT HINDER INSOLATION. THE ADDED MOISTURE WILL BRING
TEMPERATURES DOWN TO AROUND NORMAL OR JUST BELOW NORMAL WEDNESDAY
INTO THE WEEKEND.
THIS WEEKEND STORM CHANCES DECREASE AS THE BETTER MOISTURE MOVES TO
THE NORTH AND UPPER LEVEL FORCING WEAKENS. HOWEVER ANOTHER TROPICAL
WAVE, CURRENTLY SOUTH OF MARIO, IS GIVEN AN 80 PERCENT CHANCE TO
FORM INTO A TROPICAL CYCLONE OVER THE NEXT 7 DAYS. THE TRACK OF THIS
NEXT SYSTEM WILL HAVE AN IMPACT ON THIS WEEKEND'S AND EARLY NEXT
WEEK'S FORECAST. HOWEVER LOTS OF UNCERTAINTY THIS FAR OUT WITH HOW
IT WILL TRACK.
AVIATION
VALID THROUGH 17/12Z.
SCT-OVC CLOUDS 6K-10K FT AGL THROUGH THE PERIOD WITH A BKN LAYER
AOA 20K FT AGL MOVING IN FROM THE SOUTH AFTER 16/15Z. SCATTERED
TSRA WILL BE POSSIBLE FROM KTUS SOUTH AND EASTWARD AFTER 16/20Z
THROUGH 17/04Z. WITH STORMS AND SHOWERS EXPECT LOCALLY HEAVY
RAINFALL AND ERRATIC WINDS UP TO 45 KTS. OTHER THAN THUNDERSTORM
DRIVEN WINDS, SFC WINDS WILL BE FROM THE EAST SOUTHEAST 5-10 KTS.
AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.
FIRE WEATHER
MOISTURE WILL BE ON THE INCREASE THIS WEEK LEADING
TO MIN RH 20-40 PERCENT THROUGH THE WEEKEND. THANKS TO THE
MOISTURE EXPECT DAILY THUNDERSTORM CHANCES THROUGH FRIDAY. TODAY
STORMS START FROM TUCSON SOUTH AND EASTWARD THEN SPREAD TO
CENTRAL PIMA COUNTY EARLY THIS EVENING. THEREAFTER CHANCES WILL
BE AREA WIDE GENERALLY 30-60 PERCENT. THIS WEEKEND STORMS CHANCES
DECREASE, BUT STILL LINGER AROUND 15-20 PERCENT. 20-FOOT WINDS
WILL BE 8-12 MPH WITH SOME AFTERNOON/EARLY EVENING GUSTS TO AROUND
20 MPH OVER THE NEXT WEEK. WIND DIRECTION WILL BE EASTERLY TODAY
THEN RETURN TO NORMAL DIURNAL PATTERNS THROUGH THE WEEKEND.
TWC WATCHES/WARNINGS/ADVISORIES
NONE.
UPDATE...GL
DISCUSSION/AVIATION/FIRE WEATHER...HARDIN
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