989
FXUS64 KHUN 211108
AFDHUN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HUNTSVILLE AL
608 AM CDT TUE JUL 21 2026
..NEW AVIATION
KEY MESSAGES
UPDATED AT 402 AM CDT TUE JUL 21 2026
- A HEAT ADVISORY IS IN EFFECT FOR MOST OF THE TENNESSEE VALLEY
THROUGH 8 PM.
- MODERATE (LEVEL 2/4) TO MAJOR (LEVEL 3/4) HEAT RISK WILL BUILD
INTO THE TENNESSEE VALLEY THROUGH THE MIDDLE OF THE WEEK, WITH
PEAK HEAT INDEX VALUES BETWEEN 100 TO 109 DEGREES LIKELY IN
MOST LOCATIONS TODAY AND TUESDAY.
- DAILY THUNDERSTORM CHANCES WILL CONTINUE BEFORE ENDING LATER IN
THE DAY ON WEDNESDAY. A FEW STORMS COULD BECOME STRONG TO
MARGINALLY SEVERE THIS EVENING INTO EARLY WEDNESDAY MORNING.
GUSTY TO DAMAGING WINDS, FREQUENT LIGHTNING, AND LOCALLY HEAVY
RAINFALL WILL BE THE MAIN THREATS.
NEAR TERM
(TODAY)
ISSUED AT 402 AM CDT TUE JUL 21 2026
CLEAR SKIES CONTINUE TO BE IN PLACE ACROSS NORTHERN ALABAMA AND
SOUTHERN MIDDLE TENNESSEE. EXPECT THAT TO CONTINUE THROUGH
DAYBREAK. GIVEN CURRENT DEW POINT DEPRESSIONS, PATCHY FOG WILL
CONTINUE TO BE POSSIBLE THROUGH THE DAYBREAK HOURS. ADVECTION OF
LOWER DEWPOINTS FROM THE NE SHOULD HELP TO KEEP DENSE FOG FROM
FORMING THOUGH GIVEN UPSTREAM WEAK FLOW SEEN AT 1000 MB FROM THE
EAST OR SOUTHEAST.
EXPECT MORE SCATTERED CLOUDS TO FORM OVER THE AREA AFTER DAYBREAK.
THESE CLOUDS SHOULD NOT HAVE MUCH IMPACT ON AREA TEMPERATURES.
EXPECTING A WARMER DAY TODAY THAN YESTERDAY AS A RESULT WITH HIGH
TEMPERATURES CLIMBING INTO THE 92 TO 95 DEGREE RANGE IN MANY
LOCATIONS. WITH A FRONT PUSHING SOUTH TOWARDS THE AREA THIS
EVENING, HIGHER DEWPOINTS SHOULD BE FOCUSED OVER OUR AREA AGAIN
TODAY IN THE MID TO LATE AFTERNOON HOURS INTO THE EVENING HOURS.
THIS WILL DRIVE HEAT INDEX VALUES INTO THE 105 TO 109 DEGREE RANGE
IN MANY LOCATIONS AS WELL. THE EXCEPTION TO THIS LOOKS TO BE
DEKALB COUNTY AND PORTIONS OF JACKSON COUNTY. MODELS CONTINUE TO
KEEP THE AREA DRY THROUGH THE AFTERNOON HOURS. A HEAT ADVISORY
REMAINS IN EFFECT THROUGH 8 PM THIS EVENING.
SHORT TERM
(TUESDAY NIGHT THROUGH THURSDAY)
ISSUED AT 610 AM CDT TUE JUL 21 2026
AT SUNSET, STORMS WILL LIKELY BE ON THE HORIZON TO OUR NORTH
ALONG AN APPROACHING COLD FRONT. MODELS MAINTAIN A LATER ARRIVAL
OF STORMS, BETWEEN 9 PM - 12 AM. FORTUNATELY, THE LATER ARRIVAL
WILL ALLOW TIME FOR INSTABILITY TO ERODE, LEAVING ONLY A FEW
HUNDRED J/KG OF CAPE BY THE TIME STORMS GET HERE. MODELS DIVERGE
ON COVERAGE OF SHOWERS AND STORMS. SOME DISSIPATE STORMS AS THEY
ARRIVE AND OTHERS DRAG A BROKEN LINE OF STORMS THROUGH, DISSIPATING
AS THEY GO. WHAT IS CONSISTENT IS THE LACK OF SHEAR, MEANING
REGARDLESS OF THE ACTUAL COVERAGE OF STORMS, ANY STORMS THAT DO
MAKE IT THROUGH WILL OBTAIN ONLY A LOW SEVERE THREAT WITH THE
PRIMARY HAZARD BEING DAMAGING WINDS.
THE ACTUAL FRONT LOOKS TO PUSH THROUGH MOST OF THE AREA WEDNESDAY
MORNING. HOWEVER, SOME MODELS DO SHOW THE FRONT LINGERING OVER OR
JUST SOUTHEAST OF CULLMAN/MARSHALL/DEKALB COUNTIES INTO WEDNESDAY
AFTERNOON. AT THIS POINT, STORMS DO NOT LOOK SEVERE. THEN MOST
GUIDANCE PUSHES IT FURTHER SOUTHEAST OF THE AREA, BUT STALLS THE
BOUNDARY JUST TO THE SOUTHEAST OF CULLMAN/MARSHALL/DEKALB COUNTIES.
HIGH TEMPERATURES ON WEDNESDAY WILL BE RELEGATED BACK TO THE UPPER
80S/LOW 90S DUE TO CLOUD COVER AND LINGERING SCATTERED PRECIPITATION
CHANCES. DEWPOINTS WILL DROP THROUGH THE DAY ON WEDNESDAY INTO THE
65 TO 70 DEGREE RANGE PRIMARILY.
THE STALLING OF THE FRONT JUST TO OUR SOUTHEAST WILL KEEP LOW TO
MEDIUM SHOWER AND THUNDERSTORM CHANCES (30-50%) IN THE FORECAST
THROUGH THURSDAY FOR PORTIONS OF NORTHEASTERN ALABAMA INTO CULLMAN
COUNTY. DRIER AND EVEN COOLER TEMPERATURES (LOW/MID 80S) ARE
EXPECTED FURTHER BEHIND THE FRONT IN SOUTHERN MIDDLE TENNESSEE
INTO NORTHWESTERN ALABAMA WITH MID/UPPER 80S EXPECTED SOUTH OF
THE TENNESSEE RIVER.
LONG TERM
(THURSDAY NIGHT THROUGH MONDAY)
ISSUED AT 905 PM CDT MON JUL 20 2026
THE GENERAL UPPER LEVEL SETUP WILL CONSIST OF A RIDGING WEST AND
TROUGHING EAST PATTERN OVER THE GREATER NORTH AMERICAN DOMAIN. THIS
PATTERN WAS BEING KEPT IN PLACE BY OMEGA-STYLE UPPER BLOCKING OVER
THE NORTHERN PACIFIC BASIN. AT THE BEGINNING OF THE EXTENDED, UPPER
TROUGHING WILL BE IN PLACE OFF OF THE WEST COAST (THE EASTERN ANCHOR
OF THE UPPER BLOCK), WITH STRONG UPPER LEVEL RIDGING SITUATED OVER
THE SOUTHERN GREAT PLAINS. A PASSING UPPER LOW OVER THE CENTRAL
ONTARIO AND QUEBEC REGION WILL DEEPEN, AND HELP AMPLIFY UPPER
TROUGHING FROM THE EASTERN GREAT LAKES TO NORTHERN FLORIDA. THIS WILL
PLACE THE TENNESSEE VALLEY IN A WNW-ESE FLOW FROM THE LATE WEEK INTO
EARLY NEXT WEEK.
A NORTHWESTERLY UPPER LEVEL FLOW ACROSS THIS AREA, ESPECIALLY IF IT
IS DISTURBANCE LADEN, IS KNOWN FOR BRINGING SHOWERS AND THUNDERSTORMS
TO THE VALLEY. CONVECTION IN THESE REGIMES CAN BE ACCOMPANIED BY
STRONG WINDS. FOR THIS AREA, A FEW COMPLICATIONS TO THAT SIMPLISTIC
VIEW. FIRST, A COLD FRONT SHOULD BE SOUTH OF THE AREA BY LATE THU.
MOISTURE FROM TROPICAL STORM BERTHA SHOULD BE STREAMING BACK TO THE
NE, WITH SOME OF IT IMPACTING THE AREA FRI INTO SAT. ALONG WITH LOWER
LEVEL TROPICAL MOISTURE, SOME OF THE EXTENDED GUIDANCE WAS SUGGESTING
THAT UPPER LEVEL SUPPORT MOVING ACROSS THE AREA FROM LATE FRI INTO
SUN COULD BRING MORE THUNDERSTORMS TO THE AREA. IT IS WAY TOO EARLY
TO DISCERN IF THIS CONVECTION COULD BECOME MORE SIGNIFICANT, GIVEN
MUCH MODEL UNCERTAINTY THIS FAR OUT. WITH A MAIN SYNOPTIC FRONT TO
OUR SOUTH AND WITH SOME SHOWER/STORM CHANCES, DAILY HIGH/LOW
TEMPERATURES SHOULD TREND A BIT MILDER, WITH HIGHS FRI/SAT IN THE MID
80S TO AROUND 90. WARMER CONDITIONS LOOK RETURN FOR THE START OF THE
NEW WEEK, WITH HIGHS FROM THE UPPER 80S TO LOWER 90S SUN, AND LOW/MID
90S NEXT MON. LOWS THU NIGHT SHOULD RANGE IN THE MID/UPPER 60S, WITH
MAINLY LOWER 70S FOR THE FRI - SUN NIGHT PERIOD.
AVIATION
(12Z TAFS)
ISSUED AT 610 AM CDT TUE JUL 21 2026
VFR CONDITIONS ARE EXPECCTED AT BOTH TERMINALS THROUGH MUCH OF THE
TAF PERIOD. SOUTHERLY WINDS WILL INCREASE TO BETWEEN 5 AND 10
KNOTS THIS MORNING BEFORE TURNING MORE TO THE SOUTHEAST THIS
EVENING. CONFIDENCE IS LOW THAT ANY -TSRA WILL IMPACT EITHER
THE KHSV OR KMSL TERMINAL THROUGH AT LEAST 3Z (MAYBE AS LATE AS
6Z). HOWEVER, A PROB30 GROUP FOR -TSRA WAS INCLUDED BETWEEN 5Z AND
11Z FOR BOTH TERMINALS THAT LOWERS VSBYS AND CIGS AT TIMES TO MVFR
CRITERIA. THIS MAY NEED TO BE SHIFTED AS WE GET CLOSER TO THAT
TIMEFRAME OR BE MADE MORE PREDOMINANT. FOR NOW, CONFIDENCE IS JUST
TOO LOW TO DO ANYTHING MORE THAN A PROB30 GROUP.
HUN WATCHES/WARNINGS/ADVISORIES
AL...HEAT ADVISORY UNTIL 8 PM CDT THIS EVENING FOR ALZ001>009-016.
TN...HEAT ADVISORY UNTIL 8 PM CDT THIS EVENING FOR TNZ076-096-097.
NEAR TERM...KTW
SHORT TERM....KTW
LONG TERM....RSB
AVIATION...KTW
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