437
FXUS65 KTWC 161002
AFDTWC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
302 AM MST WED SEP 16 2026
SYNOPSIS
A WEATHER SYSTEM MOVING IN FROM NORTHERN MEXICO
TODAY WILL BRING WIDESPREAD SHOWERS AND THUNDERSTORMS INTO THURSDAY
MORNING WHICH WILL BE CAPABLE OF PRODUCING HEAVY RAINFALL. DRIER
CONDITIONS MOVE IN FRIDAY LIMITING THE DAILY CHANCE THROUGH THIS
WEEKEND INTO EARLY NEXT WEEK. HIGH TEMPERATURES WILL BE BELOW
NORMAL TODAY AND THURSDAY, THEN BE AROUND NORMAL FRIDAY INTO
EARLY NEXT WEEK.
DISCUSSION
A VERY MOIST ATMOSPHERE FOR MID-SEPTEMBER IS IN
PLACE AWAITING THE DYNAMICS FROM A SMALL UPPER LOW THAT WAS
SOUTH OF HERMOSILLO, MX THIS MORNING. THIS FEATURE WILL SWING
NORTH ACROSS THE AREA TODAY BRINGING MODERATE TO HEAVY RAINFALL
TO PORTIONS OF SOUTHEAST ARIZONA AND THE INCREASED CHANCES FOR
FLASH FLOODING DUE TO MOIST ANTECEDENT CONDITIONS. A FLASH FLOOD
WATCH IS IN EFFECT UNTIL 11 PM TONIGHT.
SATELLITE IMAGERY SHOWED SOUTHERLY FLOW ACROSS THE AREA WHICH
CONTINUES TO SLOWLY INCREASE PWAT VALUES INTO THE 1.3" TO 1.8"
RANGE WHICH IS 175%-200% OF NORMAL. RADAR SHOWING INITIAL AREA
OF SHOWERS/STORMS MOVING INTO SOUTHERN COCHISE COUNTY. EXPECT
AREAL COVERAGE OF SHOWERS/STORMS TO SLOWLY INCREASE OVER THE
NEXT 2-5 HOURS BEFORE MORE RAPID DEVELOPMENT OCCURS LATER THIS
MORNING AS THE UPPER LOW EDGES CLOSER TO THE INTL BORDER. HOURLY
RAINFALL RATES OF 1"-2.5" WITH SOME OF THE HEAVY SHOWERS WITH
SOME STORMS OVER 3".
THURSDAY: PRECIPITABLE WATER REMAINS ELEVATED FOR THIS TIME OF
YEAR WITH A SLIGHT RISK FOR EXCESSIVE RAINFALL CONTINUING EAST
AND SOUTH OF TUCSON. SHOWERS AND STORMS THAT DEVELOP WILL STILL
HAVE THE POTENTIAL FOR LOCALLY HEAVY RAINFALL, BUT WITHOUT THE
DISTURBANCE NEARBY THERE WILL BE A LACK OF FORCING TO HELP AID
IN HIGHER RAINFALL RATES LIKE WEDNESDAY.
FRIDAY THROUGH TUESDAY: DRIER AIR FINALLY BEGINS TO FILTER INTO
SOUTHEAST ARIZONA AS FLOW ALOFT SHIFTS MORE
WESTERLY/SOUTHWESTERLY. THIS COULD HELP LIMIT THUNDERSTORM
ACTIVITY SOMEWHAT AND KEEP ACTIVITY MAINLY EAST AND SOUTH OF
TUCSON. HIGH TEMPERATURES RETURN TO AT OR SLIGHTLY ABOVE NORMAL.
8 TO 14 DAY OUTLOOKS (WED SEP 23 TO TUE SEP 29)
TEMPERATURE: LEANING ABOVE NORMAL, 39-42% CHANCE
PRECIPITATION: LEANING ABOVE NORMAL, 39-42% CHANCE
AVIATION
VALID THRU 17/12Z.
SCT-BKN CLOUDS 7K-10K FT AGL WITH ISOLD -SHRA/-TSRA BCMG THRU
MUCH OF THE VALID PD. AFTER 16/17Z, SCT-NUM SHRA/TSRA THRU END
OF VALID PD. VSBYS NR 1 SM AT TIMES WITH SHRA+/TS. GUSTY AND
ERRATIC OUTFLOW WINDS TO AROUND 35-45 KTS NR STRONGEST TS.
OUTSIDE OF TS, SFC WINDS SLY/SWLY AT 7-12 KTS. AVIATION
DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.
FIRE WEATHER
A WEATHER SYSTEM MOVING IN FROM NORTHERN MEXICO
TODAY WILL BRING WIDESPREAD SHOWERS AND THUNDERSTORMS INTO THURSDAY
MORNING WHICH WILL BE CAPABLE OF PRODUCING HEAVY RAINFALL. DRIER
CONDITIONS MOVE IN FRIDAY LIMITING THE DAILY CHANCE THROUGH THIS
WEEKEND INTO EARLY NEXT WEEK. HIGH TEMPERATURES WILL BE BELOW
NORMAL TODAY AND THURSDAY, THEN BE AROUND NORMAL FRIDAY INTO
EARLY NEXT WEEK. MIN RH VALUES MAINLY 20 TO 45 PERCENT IN THE
VALLEYS AND 35 TO 65 PERCENT IN THE MOUNTAINS OVER THE NEXT
WEEK. RH RECOVERIES WILL CONTINUE TO BE EXCELLENT OVERNIGHT.
WINDS WILL GENERALLY REMAIN LESS THAN 15 MPH AND TERRAIN DRIVEN.
GUSTY AND ERRATIC WINDS WILL ACCOMPANY THUNDERSTORMS.
TWC WATCHES/WARNINGS/ADVISORIES
FLOOD WATCH THROUGH THIS EVENING FOR AZZ501>515.
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