598
FXUS65 KTWC 221621
AFDTWC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
921 AM MST WED JUL 22 2026
SYNOPSIS
EXPECT A DOWNTURN IN THUNDERSTORM ACTIVITY ACROSS
SOUTHEAST ARIZONA TODAY WITH WIDELY SCATTERED SHOWERS AND
THUNDERSTORMS MAINLY EAST OF TUCSON TODAY. ALTHOUGH WE WILL
MAINTAIN A LOW-GRADE THUNDERSTORM PATTERN THE NEXT FEW DAYS, WE
WILL ALSO SEE AFTERNOON HIGH TEMPERATURES RAPIDLY INCREASE LATE
THIS WEEK INTO THIS WEEKEND. THE UPPER PATTERN EVENTUALLY MOVES
INTO A MORE FAVORABLE LOCATION FOR AN INCREASED POTENTIAL FOR
STRONG AND ORGANIZED THUNDERSTORMS SATURDAY AND SUNDAY.
UPDATE
FORECAST IS ON TRACK FOR A DOWNWARD TREND IN THUNDERSTORM
ACTIVITY THIS AFTERNOON AND EVENING. LINGERING MOISTURE WILL
ALLOW FOR THUNDERSTORMS AND CLOUD BUILD-UPS IN THE MOUNTAINS
THANKS TO OROGRAPHIC LIFT, BUT WILL STRUGGLE TO MAINTAIN
STRUCTURE AND/OR COME OFF THE TERRAIN INTO THE VALLEYS. BEST
CHANCES FOR STORM DEVELOPMENT IS IN THE WHITE MOUNTAINS AT
30-60% CHANCE THEN THE REST OF THE SKY ISLANDS AT 30-50% CHANCE.
WITH THESE STORMS, THERE CAN BE LOCALLY HEAVY RAINFALL AND GUSTY
OUTFLOWS.
PREV DISCUSSION
THE THEME OF TODAY'S FORECAST IS BEST SUMMED UP
BY THE GREEK PHILOSOPHER HERACLITUS WHO WAS ATTRIBUTED AS
SAYING, "NOTHING ENDURES BUT CHANGE." I THINK THIS FITS BECAUSE
WE WILL SEE SEVERAL CHANGES OVER THE NEXT SEVERAL DAYS ACROSS
SOUTHEAST ARIZONA.
FIRST, WE ARE FINALLY SHIFTING AWAY FROM THE WET PERIOD WE HAVE
BEEN IN THE PAST SEVERAL DAYS WHERE WIDESPREAD SHOWERS AND
THUNDERSTORMS PRODUCED SIGNIFICANT RAINFALL TO THE EAST AND
SOUTH OF TUCSON. EXPECT A SIGNIFICANT DOWNTURN IN THUNDERSTORM
ACTIVITY TODAY AS WE ARE FINALLY IN THE SUBSIDENT WAKE OF THE
UPPER DISTURBANCE WHICH IS CURRENTLY OBSERVED ON GOES WATER
VAPOR IMAGERY MOVING NORTH THROUGH NE ARIZONA. IN ADDITION, THE
GOES PRECIPITABLE WATER IMAGERY INDICATED A DRIER AIRMASS
(BETWEEN 1.10 AND 1.25 INCHES OF PWAT) IN CENTRAL CHIHUAHUA
MEXICO THAT WILL MOVE NNW INTO THE EASTERN PORTIONS OF THE CWA
BOTH TODAY AND TOMORROW...ERODING THE DEEP MOISTURE THAT HAS
BEEN IN PLACE. THE 22/00Z CAMS ARE ALL OVER THE PLACE WITH BOTH
THE TIMING AND TRACK OF AN MCV THAT IS SEEN OVER EXTREME NW
CHIHUAHUA EARLY THIS MORNING. MY HUNCH TELLS ME WE WILL SEE THIS
FEATURE HOVER ALONG THE AZ/NM BORDER AS IT MOVES NORTH THROUGH
THE MID-MORNING MORNING HOURS AND THIS TOO WILL RESULT IN A
SUBSIDENT WAKE AS WELL. WHAT DOES THIS ALL MEAN, I WOULD EXPECT
A LOW-GRADE MONSOON DAY WITH WIDELY SCATTERED SHOWERS AND
THUNDERSTORMS EAST OF TUCSON WORKING OFF OF THE RESIDUAL
MOISTURE.
THE BIG CHANGE WITH THE FORECAST WILL OCCUR THE NEXT FEW DAYS AS
THE STRONG UPPER-HIGH CENTER OVER OKLAHOMA MOVES WSW INTO SRN
NEW MEXICO BY 24/00Z THURSDAY AFTERNOON THEN INTO ERN ARIZONA
BY 25/00Z FRIDAY AFTERNOON. WE WILL SEE AFTERNOON TEMPERATURES
JUMP RAPIDLY FROM A FEW DEGREES BELOW NORMAL TODAY TO 6-10
DEGREES ABOVE NORMAL BOTH FRIDAY AND SATURDAY. THE 22/00Z NBM
TEMPERATURES FOR THE TUCSON INTERNATIONAL AIRPORT (KTUS) SEEM A
LITTLE TOO LOW WITH THE MAXT OF 106 DEGREES. THE NBM
PROBABILITY OF 110+ DEGREES FOR KTUS IS CURRENTLY AT 2-5% FOR
BOTH FRIDAY AND SATURDAY. THIS CONTRASTS WITH THE DETERMINISTIC
22/00Z GFS AND ECMWF 850-700MB THICKNESSES THAT BOTH SUGGEST A
THICKNESS BETWEEN 1700-1710 M WHICH TRANSLATES VIA REGRESSION
EQUATION TO TO A MAXT OF 110-114. EVEN THE OLD-SCHOOL MEX MOS
GUIDANCE EVEN HAS 111/112 FRI/SAT. I DO THINK THAT GIVEN THE
SATURATED SOIL MOISTURE ACROSS SOUTHEAST ARIZONA RIGHT NOW, THAT
WE CAN SHAVE OFF A FEW DEGREES FROM THIS...BUT IT MAY STILL BE
HOT ENOUGH TO ELEVATE THE HEATRISK ACROSS SOUTHEAST ARIZONA.
GIVEN THE UNCERTAINTY AT THIS TIME, I WILL PUNT THE DECISION ON
ANY EXTREME HEAT PRODUCTS TO THE DAYSHIFT.
OTHERWISE, THE HEAT IS NOT THE ONLY CHANGE. THE UPPER-HIGH MOVES
INTO A MORE FAVORABLE LOCATION NEAR THE FOUR CORNERS SATURDAY
THEN NW ARIZONA SUNDAY. THIS OPENS OUR NECK OF THE WOODS UP TO
A RIM-SHOT PATTERN. THE COMBINATION OF STRONG SURFACE HEATING,
DRIER AIR ALOFT AND MODEST MID-LEVEL FLOW WILL INCREASE THE
POTENTIAL FOR STRONGER, MORE ORGANIZED CLUSTERING OF SHOWERS AND
THUNDERSTORMS NEXT WEEKEND...ESPECIALLY SATURDAY. WITH THE
CHANGE, THE MONSOON ROLLS-ON.
AVIATION
VALID THROUGH 23/18Z.
SCT-BKN 12-15K FT AGL THROUGH 22/20Z THIS AFTERNOON, THEN SCT-
BKN 6-8K FT AGL AND BKN 12-14K FT AGL WITH WIDELY SCATTERED
-SHRA/-TSRA GENERALLY TO THE EAST OF KTUS. VFR, WITH THE
EXCEPTION OF BRIEF MVFR DUE TO STRONGER SHOWERS AND
THUNDERSTORMS...ESPECIALLY NEAR KDUG. SURFACE WINDS GENERALLY
LESS THAN 12 KTS, EXCEPT FOR AROUND STORMS WHERE VRB GUSTS TO 35
KTS WILL BE POSSIBLE. AVIATION DISCUSSION NOT UPDATED FOR TAF
AMENDMENTS.
FIRE WEATHER
EXPECT A DOWNTURN IN THUNDERSTORM ACTIVITY ACROSS
SOUTHEAST ARIZONA TODAY WITH WIDELY SCATTERED SHOWERS AND
THUNDERSTORMS MAINLY EAST OF TUCSON TODAY. ALTHOUGH WE WILL
MAINTAIN A LOW-GRADE THUNDERSTORM PATTERN THE NEXT FEW DAYS, WE
WILL ALSO SEE AFTERNOON HIGH TEMPERATURES RAPIDLY INCREASE LATE
THIS WEEK INTO THIS WEEKEND. THE UPPER PATTERN EVENTUALLY MOVES
INTO A MORE FAVORABLE LOCATION FOR AN INCREASED POTENTIAL FOR
STRONG AND ORGANIZED THUNDERSTORMS SATURDAY AND SUNDAY. MIN RHS
25-30% IN THE LOWER DESERT LOCATIONS AND ABOVE 40% IN THE
MOUNTAINS TODAY. BY THURSDAY INTO THE WEEKEND, RHS COULD DIP
INTO THE 17-22% RANGE FOR THE LOWER DESERTS WEST OF TUCSON AND
THE UPPER GILA RIVER VALLEY AS TEMPERATURES WARM TO ABOVE
AVERAGE. WINDS THIS WEEK WILL REMAIN MAINLY LIGHT AND UNDER 15
MPH, THOUGH STRONG AND ERRATIC WINDS WILL BE POSSIBLE WITH ANY
THUNDERSTORM.
TWC WATCHES/WARNINGS/ADVISORIES
NONE.
UPDATE...JT
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