521
FXUS65 KTWC 131629
AFDTWC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
929 AM MST SUN SEP 13 2026
SYNOPSIS
AN ACTIVE WEEK AHEAD WITH DAILY CHANCES OF SHOWERS
AND THUNDERSTORMS. DAILY HIGH TEMPERATURES WILL FLUCTUATE
BETWEEN NEAR NORMAL AND A FEW DEGREES BELOW NORMAL.
UPDATE
MOSTLY SUNNY SKIES THIS MORNING ACROSS SOUTHEAST ARIZONA
PER LATEST VISIBLE SATELLITE IMAGERY. PLENTY OF MOISTURE OUT THERE
WITH PWAT VALUES RANGING FROM ABOUT 1.3 INCHES TO THE EAST OF TUCSON
TO 1.5 TO 1.7 INCHES FROM TUCSON WESTWARD. THESE VALUES ARE ABOUT
150 TO 200 PERCENT OF NORMAL FOR THIS TIME OF YEAR. LATEST SPC RAP
MESOANALYSIS ALONG WITH MODEL SOUNDINGS SHOW THERE IS A BIT OF
CONVECTIVE INHIBITION TO WORK THROUGH SO CONVECTIVE DEVELOPMENT WILL
BE A BIT DELAYED COMPARED TO THE EARLY START YESTERDAY. EVEN AS
SUCH, WE SHOULD BREAK THROUGH CAPPING AROUND MIDDAY OR EARLY
AFTERNOON WITH ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS THIS
AFTERNOON. CAMS/HREF ARE PRETTY CONSISTENT TODAY WITH ISOLATED TO
SCATTERED SHOWERS AND THUNDERSTORMS MAINLY FROM TUCSON EASTWARD,
THOUGH A STORM OR TWO IS POSSIBLE AS FAR WEST AS SELLS. NO OBVIOUS
UPPER LEVEL SUPPORT TODAY TO HELP THINGS ALONG THOUGH IN THIS
SOUTHERLY FLOW, THOUGH MORE ILL-DEFINED DISTURBANCES CAN SNEAK UP ON
US. MAIN THREAT WILL CONTINUE TO BE LOCALLY HEAVY RAIN WITH AN
ISOLATED FLASH FLOOD THREAT. SEE PREVIOUS DISCUSSION BELOW FOR
ADDITIONAL INFORMATION.
DISCUSSION
MOIST SOUTHERLY FLOW ALOFT FOR MUCH OF THE NEXT
7 DAYS WILL KEEP ANOMALOUSLY HIGH PWAT VALUES FOR SEPTEMBER
ACROSS THE AREA. THIS WILL LEAD TO A DAILY THREAT OF ISOLATED TO
WIDELY SCATTERED FLASH FLOODING WITH SOME OF THE STRONGEST
STORMS PRODUCING RAINFALL RATES OF 1-2"/HR, POSSIBLY HIGHER,
MAINLY DURING THE AFTERNOON AND EVENING HOURS. MODEL GUIDANCES
ARE HINTING THAT MONDAY AND WEDNESDAY WILL SEE THE GREATEST
THREAT OF SCATTERED HEAVY RAIN AND FLASH FLOODING DUE TO THE
POTENTIAL FOR UPPER LEVEL DISTURBANCES MOVING ACROSS THE AREA.
THURSDAY ALSO LOOKS INTERESTING AS MODELS ARE BRINGING THE
REMNANTS OF A TROPICAL UPPER LOW, WHICH IS STILL DEVELOPING OFF
THE MEXICAN COAST THIS MORNING WELL S-SE OF THE TIP OF BAJA,
NORTH ACROSS NW MEXICO ON THE WESTERN FLANK OF THE SUB-TROPICAL
RIDGE WITH THE HIGH CENTERED OVER LOUISIANA. CONFIDENCE LOW ON
TIMING OF THIS FEATURE THIS FAR OUT. WPC IS HIGHLIGHTING THE
EASTERN PORTIONS OF THE FORECAST AREA MONDAY, WEDNESDAY AND
THURSDAY FOR EXCESSIVE RAINFALL. THE POTENTIAL WET WEEK AHEAD
MAY LEAD TO SOME ENHANCED FLOWS IN WASHES, CREEKS, AND RIVERS
ACROSS THE FORECAST AREA THAT ARE ALREADY SATURATED. HIGH
TEMPERATURES THIS WEEK WILL SHOW DAILY VARIATIONS FROM NEAR
NORMAL TO SEVERAL DEGREES BELOW NORMAL.
AVIATION
VALID THRU 14/12Z.
SCT-BKN CLOUDS AOA 20K FT AGL UNTIL 13/17Z, THEN SCT-BKN 8K-10K
FT AGL WITH ISOLD-SCT SHRA/TSRA THRU 14/04Z. SFC WINDS TERRAIN
DRIVEN LESS THAN 10 KTS THRU 13/17Z AND THEN AGAIN AFT 14/05Z.
AT OTHER TIMES, WLY/NWLY 6-10 KTS. AVIATION DISCUSSION NOT
UPDATED FOR TAF AMENDMENTS.
FIRE WEATHER
AN ACTIVE WEEK AHEAD WITH DAILY CHANCES OF
SHOWERS AND THUNDERSTORMS. HIGH TEMPERATURES WILL FLUCTUATE
BETWEEN NEAR NORMAL AND A FEW DEGREES BELOW NORMAL. 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
NONE.
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