027
FXUS65 KTWC 111707
AFDTWC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
1007 AM MST FRI SEP 11 2026
SYNOPSIS
A MORE ACTIVE DAY IS FORECAST ACROSS SOUTHEAST ARIZONA
TODAY WITH ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS. MAIN
THREAT FROM STORMS TODAY WILL BE HEAVY RAIN AND LOCALIZED FLASH
FLOODING, ESPECIALLY ACROSS SANTA CRUZ COUNTY AND SOUTHWEST COCHISE
COUNTY. A MORE TYPICAL ISOLATED TO SCATTERED COVERAGE OF STORMS IS
FORECAST THIS WEEKEND INTO NEXT WEEK. DAILY HIGH TEMPERATURES WILL
FLUCTUATE BETWEEN NEAR NORMAL AND A FEW DEGREES BELOW NORMAL.
KEY MESSAGES
-ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS THIS AFTERNOON
MAINLY SOUTH AND EAST OF TUCSON CAPABLE OF PRODUCING POTENTIALLY
HEAVY RAINFALL.
-SLIGHT RISK (LEVEL 2 OF 4) TODAY FOR EXCESSIVE RAINFALL THAT MAY
LEAD TO LOCALIZED INSTANCES OF FLASH FLOODING IN FLOOD PRONE AREAS.
SENSITIVE LOW WATER CROSSINGS MAY BECOME IMPASSIBLE.
-ABOVE NORMAL MOISTURE FOR MID SEPTEMBER CONTINUES OVER THE WEEKEND
INTO EARLY NEXT WEEK RESULTING IN CONTINUED CHANCES FOR SHOWERS AND
STORMS AND A MARGINAL RISK (LEVEL 1 OF 4) FOR EXCESSIVE RAINFALL.
UPDATE
FORECAST FOR TODAY REMAINS ON TRACK WITH ISOLATED TO
SCATTERED STORMS EXPECTED THIS AFTERNOON MAINLY TO THE SOUTH AND
EAST OF TUCSON. THE MAIN CONCERN WITH STORMS THIS AFTERNOON WILL BE
THE POTENTIAL FOR HEAVY RAINFALL RATES OF 1.0 TO 2.5 INCHES PER HOUR
SUPPORTED BY PLENTY OF MOISTURE AVAILABLE IN THE ATMOSPHERIC COLUMN
ACROSS SOUTHEAST ARIZONA. THE WEATHER PREDICTION CENTER'S EXCESSIVE
RAINFALL OUTLOOK HAS PORTIONS OF SANTA CRUZ, COCHISE, AND PIMA
COUNTIES UNDER SLIGHT RISK, AT LEAST 15% CHANCE, FOR EXCESSIVE RAIN
LEADING TO FLASH FLOODING. ALSO, PARTS OF EASTERN SANTA CRUZ COUNTY
AND SW COCHISE COUNTY HAS SEEN HEAVY RAIN OVER THE PAST 72 HOURS, SO
THE SOILS ARE WET, AND THE SAN PEDRO HAS HAD SOME INCREASED FLOW
SEVERAL DAYS AGO.
THE LATEST SPC MESOSCALE ANALYSIS DEPICTS BETWEEN 1 INCH OF
PRECIPITABLE WATER FROM NEAR SAFFORD AND ALONG THE AZ/NM BORDER TO
NEARLY 2 INCHES OF PRECIPITABLE WATER CONTENT ACROSS FAR WESTERN
PIMA COUNTY. A AREA OF DEFORMATION ALOFT STRETCHING ACROSS SOUTHERN
COCHISE COUNTY AND SANTA CRUZ COUNTY WILL SUPPORT ENHANCED LIFT
RESULTING IN ISOLATED TO SCATTERED THUNDERSTORMS THIS AFTERNOON AND
EVENING.
BOTH THE REFS AND THE HREF ARE HIGHLIGHTING THE POTENTIAL FOR HEAVY
RAINFALL WHICH INCREASES MY CONFIDENCE AND CONCERN FOR FLASH
FLOODING, BUT THE REFS IS A BIT MORE BULLISH ALBEIT VERY PRECISE IN
WHERE IT IS PLACING THE HEAVIEST RAINFALL ACROSS PORTIONS OF SANTA
CRUZ AND COCHISE COUNTIES WITH RESPECT TO PREVIOUS MODEL RUNS. THE
HREF, ON THE OTHER HAND, SEEMS A BIT MORE REASONABLE WITH THE QPF,
BUT FROM MY ANALYSIS I BELIEVE THIS TO BE DUE TO LESS AGREEMENT
AMONGST THE INDIVIDUAL MEMBERS IN TERMS OF MAGNITUDE AND INDIVIDUAL
PLACEMENT OF THE STORMS THAT FORM WHICH MAY BE WASHING OUT THE MEAN
QPF. LOOKING PROBABILISTICALLY, THE HREF DEPICTS A SWATH OF 30 TO 60
PERCENT CHANCE OF EXCEEDING 2 INCHES IN A 3 HOUR PERIOD OVER SANTA
CRUZ COUNTY AND FAR SOUTHWEST COCHISE COUNTY AND EVEN A SLIGHT
CHANCE (10-20%) FOR EXCEEDING 3 INCHES OF RAIN IN A 3 HOUR PERIOD.
CURIOUS TO SEE HOW THIS ALL PLAYS OUT, BUT RIGHT NOW THE MOST LIKELY
OUTCOME APPEARS TO BE A COMBINATION OF BOTH PATTERN RECOGNITION OVER
THE PAST FEW DAYS AND ADJUSTING FOR THE DYNAMICAL CONSIDERATIONS
THAT COME INTO PLAY SUPPORTIVE OF THESE AFOREMENTIONED HEAVY
RAINFALL RATES.
PREV DISCUSSION
/ISSUED 330 AM MST FRI SEP 11 2026/
BROAD HIGH PRESSURE OVER THE DESERT SOUTHWEST WITH MID-LEVEL FLOW
TURNING TO THE SOUTHEAST THIS AFTERNOON AND TO THE SOUTH TONIGHT AS
THE UPPER HIGH MOVES INTO SW NM. HIGHER UP AROUND 300-200 MB, THE
FLOW WILL BE WESTERLY THAT BECOMES DIVERGENT ALONG THE INTL BORDER
THIS AFTERNOON AND EVENING. PWATS RANGE FROM 1.25" NEAR AZ/NM BORDER
TO 1.70" ACROSS WESTERN PIMA COUNTY. SE AZ WILL SEE MUCH MORE
THUNDERSTORM ACTIVITY TODAY VERSUS YESTERDAY WITH THE MOST RECENT
RUNS FROM THE HRRR, RRFS AND HREF ALL HIGHLIGHTING SW COCHISE COUNTY
AND MOST OF SANTA CRUZ COUNTY AS THE AREA FOR CONCERN TODAY FROM
SCATTERED TO NUMEROUS THUNDERSTORMS. THE MAIN THREAT IN THIS AREA
WILL BE VERY HEAVY RAIN WITH SOME OF THE STRONGEST CORES PRODUCING
RAINFALL RATES OF 1"-2.5"/HR. HREF HAS THIS AREA PAINTED WITH 10+%
CHANCE FOR 3-HOUR RAINFALL TOTALS EXCEEDING 3+". WPCS ERO HAS THIS
AREA UNDER SLIGHT RISK, AT LEAST 15% CHANCE, FOR EXCESSIVE RAIN
LEADING TO FLASH FLOODING. ALSO, PARTS OF EASTERN SANTA CRUZ COUNTY
AND SW COCHISE COUNTY HAS SEEN HEAVY RAIN OVER THE PAST 72 HOURS, SO
THE SOILS ARE WET, AND THE SAN PEDRO HAS HAD SOME INCREASED FLOW
SEVERAL DAYS AGO. WITH THAT SAID I CONTEMPLATED HOISTING A SMALL
FLASH FLOOD WATCH AREA BETWEEN I-19 IN SANTA CRUZ COUNTY EAST TO
SIERRA VISTA AREA. WILL LET DAY SHIFT LOOK AT NEW MODEL DATA IN CASE
ONE NEEDS TO BE ISSUED.
SATURDAY: MIGHT BE A DOWN DAY DEPENDING HOW TODAY EVOLVES.
SUNDAY THROUGH THURSDAY: SOUTHERLY FLOW ALOFT WILL KEEP SLIGHTLY
ABOVE NORMAL MOISTURE ACROSS THE AREA FOR MID-SEPTEMBER RESULTING IN
A CHANCE OF SHOWERS AND THUNDERSTORMS WITH DAY-TO- DAY VARIABILITY
IN AREAL COVERAGE OF STORMS, MAINLY ACROSS THE EASTERN HALF OF THE
FORECAST AREA.
HIGH TEMPERATURES THROUGH MONDAY WILL BE AT OR SLIGHTLY ABOVE NORMAL
THEN BE AT OR SLIGHTLY BELOW NORMAL TUESDAY THROUGH THURSDAY.
AVIATION
VALID THRU 12/12Z.
SCT DEBRIS CLOUDS MOSTLY ABOVE 10K FT AGL THRU 11/16Z. AFT 11/19Z
SCT-BKN 7K-10K FT AGL WITH LAYERS ABV. ISOLD TO SCT SHRA/TSRA MAINLY
S AND E OF KTUS. ISOLD VSBY 1-3 MILES NR TS. LCLZD TS OUTFLOW WINDS
OF 30-40 KTS. OTRW, SFC WINDS TERRAIN DRIVEN LESS THAN 10 KTS UNTIL
11/18Z AND THEN AGAIN AFT 12/04Z. AT OTHER TIMES, WLY/NWLY 6-10 KTS.
AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.
FIRE WEATHER
SCATTERED SHOWERS AND THUNDERSTORMS TODAY. A
MORE TYPICAL ISOLATED TO SCATTERED COVERAGE OF STORMS IS FORECAST
THIS WEEKEND INTO NEXT WEEK. HIGH TEMPERATURES WILL 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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