316
FXUS65 KTWC 240417
AFDTWC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
917 PM MST THU JUL 23 2026
UPDATE
IOSLATED THUNDERSTORMS HAVE BEEN OCCURING MOST OF THIS
EVENING MAIN E-NE OF TUCSON. A FEW STORMS HAVE PRODUCED BRIEF
HEAVY RAIN. RAN OUT A QUICK SINCE NBM HAD NO STORMS IN THE 8 TO
11 PM TIME FRAME. ADDED ISOLATED STORMS FROM SE PINAL COUNTY NE
TO CENTRAL GREELEE COUNTY.
SYNOPSIS
JUST ISOLATED THUNDERSTORM ACTIVITY TONIGHT AND FRIDAY AS THE
COMBINATION OF DRIER AIR AND A RIDGE OF HIGH PRESSURE ALOFT MOVE
INTO THE REGION FROM THE EAST. HIGH TEMPERATURES WILL INCREASE
TO 5 TO 10 DEGREES ABOVE NORMAL WITH THE ARRIVAL OF THIS HIGH
PRESSURE RIDGE. AN EXTREME HEAT WARNING IS IN EFFECT FRIDAY AND
SATURDAY. THE UPPER LEVEL PATTERN WILL THEN BECOME MORE
FAVORABLE FOR THUNDERSTORM ACTIVITY SATURDAY INTO NEXT WEEK.
DISCUSSION
IN THE UPPER LEVELS, A RIDGE IS CENTERED OVER TEXAS AND THE
SOUTHERN PLAINS TODAY WHILE TROPICAL STORM BERTHA BEGINS TO
CROSS THE TEXAS GULF COAST AND HURRICANE FAUSTO APPROACHES
HAWAII IN THE PACIFIC. THOUGH MEAN SOUTHEASTERLY FLOW CONTINUES
INTO SOUTHERN ARIZONA VIA THE RIDGE TO THE EAST, THE PLACEMENT
OF THIS RIDGE HAS WARMED TEMPERATURES ALOFT, SUPPRESSING
THUNDERSTORM CHANCES TODAY TO JUST ISOLATED COVERAGE (10-15
PERCENT) ACROSS SOUTHEASTERN ARIZONA. SATELLITE DERIVED
PRECIPITABLE WATER VALUES THIS AFTERNOON RANGE FROM AROUND 1
INCH IN THE FAR SOUTHEAST TO OVER 1.5 INCHES IN SOUTHWEST
ARIZONA, ADEQUATE FOR AT LEAST A FEW THUNDERSTORMS TO FORM WITH
BRIEF HEAVY RAINFALL AND A 30-40 MPH WIND GUST THREAT. AS THE
RIDGE CENTER NUDGES WEST ON FRIDAY SO WILL THE THUNDERSTORM
CHANCES WITH JUST SLIGHT CHANCES (10-20 PERCENT) EXPANDING WEST
INTO CENTRAL- WESTERN PIMA.
THE DISCUSSED WESTWARD SHIFT OF THE UPPER RIDGE WILL ALSO BRING
A HEATING TREND TO SOUTHEASTERN ARIZONA. HIGH TEMPERATURES WILL
BECOME 5-10 DEGREES ABOVE NORMAL FRIDAY AND SATURDAY, RANGING
FROM 105-112 IN THE TUCSON METRO, WESTERN DESERTS, AND UPPER
GILA RIVER VALLEY. IN LOWER ELEVATION AREAS OF SANTA CRUZ AND
COCHISE COUNTIES HIGHS RANGE FROM 100-105. CAN'T RULE OUT HIGHS
COMING IN A BIT HOTTER THAN CURRENTLY FORECAST WITH THE STRENGTH
OF THE RIDGE MOVING OVERHEAD. NBM PROBABILITIES GIVE A 33%
CHANCE FOR THE TUCSON AIRPORT TO HIT 110 DEGREES ON SATURDAY.
ADDITIONALLY NOTABLE WILL BE THE OVERNIGHT LOWS WITH FORECAST
LOWS FROM TUCSON WEST RANGING FROM 82 TO 88 DEGREES SATURDAY
MORNING. THE LACK OF RELIEF FROM THE HEAT PLUS THE AFTERNOON
HIGHS COMBINE TO PRODUCE MAJOR HEATRISK WITH THE EXTREME HEAT
WARNING IN EFFECT FRIDAY AND SATURDAY.
THE RIDGE CENTER IS EXPECTED TO LIFT NORTH AFTER SHIFTING WEST
AND BECOME CENTERED CLOSER TO THE FOUR CORNERS REGION ON
SATURDAY, PUTTING SOUTHEASTERN ARIZONA UNDER A MORE FAVORABLE
PATTERN FOR THUNDERSTORM ACTIVITY. AFTER A PERIOD OF MODEST
DRYING THROUGH FRIDAY, MOISTURE RETURN SHOULD ARRIVE IN EARNEST
THROUGH SATURDAY, PARTIALLY DRIVEN BY POTENTIAL NORTHERLY DRIVEN
OUTFLOWS FROM NORTHERN MEXICO THUNDERSTORM ACTIVITY AND THE
CROSSING REMNANTS OF TROPICAL STORM BERTHA. THE COMBINATION OF
THIS INCOMING MOISTURE WITH SATURDAY'S HOT TEMPERATURES AND SOME
MODEST MID-LEVEL FLOW WILL PROVIDE AN ENVIRONMENT FOR STRONG TO
SEVERE THUNDERSTORMS CAPABLE OF SEVERE WIND GUSTS, BLOWING DUST,
AND HEAVY RAINFALL RATES. IN COLLABORATION WITH SPC, A DAY 3
MARGINAL RISK FOR SEVERE THUNDERSTORMS HAS BEEN INTRODUCED ON
SATURDAY FOR MUCH OF SOUTHEASTERN ARIZONA.
THE UPPER RIDGE WILL REMAIN IN A SIMILAR SPOT FOR THE COMING
DAYS INTO NEXT WEEK, BRINGING DAILY CHANCES FOR THUNDERSTORMS
ACROSS THE REGION WITH DAY TO DAY VARIABILITY. THIS WILL ALSO
BRING TEMPERATURES DOWN CLOSER TO NORMAL BY MONDAY. LOOKING DOWN
THE LINE, ENSEMBLES BRING THE UPPER RIDGE CENTER INTO ARIZONA
AND AMPLIFY THE RIDGE BY THE END OF NEXT WEEK, WHICH WOULD
INCREASE TEMPERATURES AND REDUCE THUNDERSTORM CHANCES, DEPENDING
ON WHERE THIS RIDGE CENTER SETS UP.
AVIATION /04Z FRIDAY THROUGH 04Z SATURDAY/
VALID THROUGH 24/00Z.
ISOLATED THUNDERSTORMS THROUGH 24/03Z WITH FEW-SCT CEILINGS
8K-11K FT. SURFACE WINDS LIGHT AND UNDER 10 KTS THOUGH ANY
THUNDERSTORM MAY PRODUCE A WIND GUST UP TO 35 KTS. LIGHT AND
TERRAIN DRIVEN WINDS THROUGH FRIDAY WITH ADDITIONAL SLIGHT
CHANCES FOR THUNDERSTORMS FRIDAY AFTERNOON AND EVENING. AVIATION
DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.
FIRE WEATHER
A RIDGE OF HIGH PRESSURE BUILDING ALOFT WILL RAISE TEMPERATURES
THROUGH SATURDAY WITH HIGH TEMPERATURES BECOMING 5 TO 10 DEGREES
ABOVE NORMAL FRIDAY AND SATURDAY. THIS TREND WILL ALSO REDUCE
THUNDERSTORM CHANCES ON FRIDAY TO JUST ISOLATED COVERAGE IN THE
AFTERNOON AND EVENING. MINIMUM RELATIVE HUMIDITY VALUES FRIDAY
AND SATURDAY FALL TO 15-20 PERCENT IN DESERT LOCATIONS WHILE
WINDS OVERALL WILL BE LIGHT AND UNDER 12 MPH. DEEPER MOISTURE IS
EXPECTED TO RETURN THROUGH THE WEEKEND WITH INCREASING
THUNDERSTORM CHANCES LATE SATURDAY AFTERNOON THROUGH THE
EVENING. ANY THUNDERSTORM MAY COME WITH THE THREAT OF STRONG
GUSTY WINDS AND HEAVY RAIN. DAILY CHANCES FOR THUNDERSTORMS
RETURN IN THE FOLLOWING DAYS INTO NEXT WEEK. MINIMUM RELATIVE
HUMIDITY VALUES SHOULD RISE AS WELL SUNDAY THROUGH THE FIRST
HALF OF NEXT WEEK.
TWC WATCHES/WARNINGS/ADVISORIES
AIR QUALITY ALERT FROM 9 AM TO 9 PM MST FRIDAY FOR AZZ504.
EXTREME HEAT WARNING FROM 10 AM FRIDAY TO 8 PM MST SATURDAY
FOR AZZ501>509.
UPDATE...
SYNOPSIS...
DISCUSSION...
AVIATION...
FIRE WEATHER...
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