852
FXUS65 KTWC 170846
AFDTWC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
146 AM MST WED SEP 17 2025
SYNOPSIS
MOISTURE HAS MOVED INTO THE REGION WHICH WILL LEAD TO
SCATTERED SHOWERS AND THUNDERSTORMS THROUGH THE END OF THE WORK WEEK
WITH GRADUALLY DIMINISHING THUNDERSTORM CHANCES OVER THE WEEKEND.
TEMPERATURES NEAR TO JUST BELOW NORMAL INTO THE WEEKEND.
DISCUSSION
CLOUDS COVER MOST OF SOUTHEAST ARIZONA WITH A FEW
ISOLATED SHOWERS AROUND THE HIGHER TERRAIN AND THE AZ/NM BORDER.
PWATS RANGE FROM 1.1"-1.7" ACROSS THE REGION WITH THE KTWC 17/00Z
SOUNDING MEASURING 1.46". PLENTY OF MOISTURE IN PLACE THANKS TO
SOUTHERLY/SOUTHWESTERLY MID-LEVEL FLOW THAT HAS ADVECTED MOISTURE
FROM THE REMNANTS OF MARIO, WHICH HAS BEEN DOWNGRADED TO A POST-
TROPICAL CYCLONE. EXPECT ISOLATED TO SCATTERED SHOWERS AND
THUNDERSTORMS THIS AFTERNOON AND EVENING WITH THE BEST CHANCES
ALONG THE INTERNATIONAL BORDER. CLOUD COVER COULD INHIBIT THE
START TIME AND COVERAGE, BUT MARIO'S UPPER LEVEL CIRCULATION WILL
BE MOVING INTO SOUTHERN CALIFORNIA WHICH WILL LEND SOME SYNOPTIC
SCALE SUPPORT FOR STORMS. THE MAIN THREAT WILL BE HEAVY RAIN WHICH
COULD LEAD TO SOME LOCALIZED FLASH FLOODING. THE HREF SHOWS AREAS
ALONG THE INTERNATIONAL BORDER IN PIMA AND SANTA CRUZ COUNTIES AS
HAVING THE BEST CHANCES FOR HEAVY RAINFALL.
THIS ANOMALOUS MOISTURE WILL BE IN PLACE THROUGH FRIDAY WITH
PWATS 150 PERCENT OF NORMAL ALONG THE ARIZONA BORDER, INCREASING
TO 180 PERCENT OF NORMAL IN WESTERN PIMA COUNTY. THIS WILL LEAD TO
CONTINUED SCATTERED SHOWER AND THUNDERSTORM ACTIVITY BOTH DAYS.
BETTER UPPER LEVEL SUPPORT FOR STORMS WILL BE IN PLACE COMPARED TO
WEDNESDAY THANKS TO A 250 MB JET OVER MOST OF ARIZONA. THE MAIN
SOURCE OF UNCERTAINTY IS HOW MID-LEVEL CLOUD COVER COULD INHIBIT
STORM COVERAGE AND INTENSITY. EVEN WITH THIS UNCERTAINTY THE MAIN
THREAT WILL AGAIN BE HEAVY RAINFALL WHICH COULD LEAD TO LOCALIZED
AREAS OF FLASH FLOODING. EXPECT FLOWING WASHES AND RIVERS
ESPECIALLY FOR AREAS THAT SEE PERSISTENT RAINFALL IN THE SAME AREA
EACH DAY. TEMPERATURES WILL BE AROUND NORMAL TO A FEW DEGREES
BELOW NORMAL.
THIS WEEKEND HIGH PRESSURE BEGINS TO INCH NORTHWARD AND PUTS
SOUTHEAST ARIZONA UNDER WESTERLY AND EVEN NORTHWESTERLY FLOW,
WHICH WILL BEGIN TO DRY THINGS OUT. LINGERING SHOWERS AND
THUNDERSTORMS WILL BE POSSIBLE MAINLY OVER THE HIGHER TERRAIN
EAST OF TUCSON. EARLY NEXT WEEK ENSEMBLES MOVE THE HIGH FURTHER
WEST CENTERING IT OVER BAJA OR JUST WEST OF BAJA. THIS WILL
RESULT IN NORTHERLY FLOW WHICH BRINGS EVEN DRYER AIR INTO THE
REGION. PWATS DROP DOWN TO AROUND 0.5" FOR MOST OF SOUTHEAST
ARIZONA WITH NO PRECIP CHANCES. TEMPERATURES ALSO INCREASE THANKS
TO THE PROXIMITY OF THE HIGH WITH TUCSON POSSIBLE SEEING TRIPLE
DIGITS AGAIN BY MONDAY OR TUESDAY.
AVIATION
VALID THROUGH 18/12Z.
BKN-OVC CLOUDS 6K-10K FT AGL AND BKN-OVC LAYER AOA 20K FT AGL
THRU THE VALID PERIOD. SCATTERED TSRA POSSIBLE AFTER 17/19Z
THROUGH 18/04Z. BEST CHANCES WILL BE AT KDUG AND KOLS TERMINALS.
WITH SHOWERS AND THUNDERSTORMS, EXPECT LOCALLY HEAVY RAINFALL AND
ERRATIC WINDS UP TO 35 KTS. OTHER THAN THUNDERSTORM DRIVEN WINDS,
SFC WINDS WILL BE FROM THE SOUTH SOUTHWEST 5-10 KTS THIS AFTERNOON
AND EVENING AND VARIABLE LESS THAN 7 KTS AT OTHER TIMES. AVIATION
DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.
FIRE WEATHER
ABOVE NORMAL MOISTURE THIS WEEK LEADING TO MIN RH 20-
40 PERCENT THROUGH THE WEEKEND. EXPECT SCATTERED SHOWER AND
THUNDERSTORM CHANCES (30-60 PCT CHANCE) EACH DAY THROUGH FRIDAY,
THEN DIMINISHED THUNDERSTORM CHANCES THIS WEEKEND. DRY CONDITIONS
RETURN NEXT WEEK. 20-FOOT WINDS WILL BE 8-12 MPH WITH SOME
AFTERNOON/EARLY EVENING GUSTS TO AROUND 20 MPH OVER THE NEXT WEEK
WITH NORMAL DIURNAL PATTERNS THROUGH THE WEEKEND.
TWC WATCHES/WARNINGS/ADVISORIES
NONE.
HARDIN
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