648
FXUS64 KHUN 170855
AFDHUN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HUNTSVILLE AL
355 AM CDT MON AUG 17 2026
..NEW NEAR TERM
KEY MESSAGES
UPDATED AT 355 AM CDT SUN AUG 16 2026
- DANGEROUS HEAT WILL IMPACT THE TENNESSEE VALLEY TODAY, WITH
MAJOR (LEVEL 3/4) TO EXTREME (LEVEL 4/4) HEAT IMPACTS FORECAST.
SOME RELIEF IS EXPECTED TUESDAY, BUT THE HEAT RETURNS
WEDNESDAY AND THURSDAY.
- A HEAT ADVISORY IS IN EFFECT FOR ALL OF NORTHERN ALABAMA AND
SOUTHERN MIDDLE TENNESSEE THROUGH 7 PM THIS EVENING, WITH
EXTENSIONS ON THE TABLE IN FUTURE UPDATES INTO THE MID- WEEK.
- A SLIGHT (2 OUT OF 5) RISK FOR SEVERE THUNDERSTORMS IS FORECAST
TODAY ACROSS EASTERN FRANKLIN COUNTY TENNESSEE AND PORTIONS OF
FAR NORTHEAST ALABAMA, WITH A MARGINAL (1 OUT OF 5) RISK FOR
MOST OF THE AREA.
NEAR TERM
(TODAY)
ISSUED AT 355 AM CDT MON AUG 17 2026
AS HAS BEEN THE CASE THE LAST FEW DAYS, STRONG UPPER RIDGING
ACROSS THE SOUTHERN CONUS HAS BEEN THE MAIN FEATURE CONTROLLING
OUR SENSIBLE WEATHER. THIS RIDGING HOWEVER WAS SHOWING SIGNS OF
SLIGHT WEAKENING, WITH IT SHIFTING MORE TO THE SOUTH AND WEST OF
THE REGION. ALSO, AN UPPER LOW OVER CENTRAL CANADA SHOULD MOVE TO
THE SE ACROSS NORTHERN ONTARIO TO THE SOUTHERN HUDSON BAY IN THE
MID WEEK. THIS WILL INDUCE SYNOPTIC SCALE TROUGHING ACROSS THE
EASTERN CONUS FROM THE MIDWEEK ONWARD, AND BRING MORE SEASONABLE
CONDITIONS TO THE REGION.
BEFORE THEN, WE HAVE AT LEAST ONE MORE DAY OF VERY WARM TO HOT
CONDITIONS. HIGH TEMPERATURES LATER TODAY ONCE AGAIN SHOULD SOAR
INTO MID/UPPER 90S, WITH CORRESPONDING HEAT INDEXES FROM THE
UPPER 90S TO 110 DEGREES. WE DO HAVE SOME HIGHER HEAT INDEXES
(HI), BUT COVERAGE OF THEM IS TOO LOW TO WARRANT GOING TO AN
EXTREME HEAT WARNING AT THIS TIME. ANOTHER FACTOR OF MORE MIXING
THAT COULD LOWER DEWPOINTS AND THE HI. A THIRD ITEM, MORE CLOUDS
ACCOMPANYING A COLD FRONT APPROACHING FROM THE NW.
THIS FRONT WAS POSITIONED FROM THE SOUTHERN GREAT LAKES TO THE
OK/TX RED RIVER VALLEY. THIS BOUNDARY SHOULD HEAD TO THE SE
DURING THE COURSE OF THE DAY, REACHING THE TENNESSEE VALLEY THIS
AFTERNOON INTO THE EVENING. SCATTERED TO NUMEROUS SHOWERS AND
THUNDERSTORMS WERE ALREADY IN PROGRESS FROM PARTS OF SE MISSOURI
TO SOUTHERN OHIO, PRECEDING THE FRONT. STRONG DAYTIME HEATING
AHEAD OF THIS FRONT OF A VERY MOIST ENVIRONMENT WILL PRODUCE
SURFACE BASED CAPES OVER 2000 J/KG, WITH A NOTICEABLE INVERTED-V
FORECAST IN SOUNDINGS THIS AFTERNOON. THAT AND A LINEAR 20-30 KT
ENVIRONMENTAL SHEAR WILL ALLOW STRONG TO SEVERE THUNDERSTORM
DEVELOPMENT. THE MAIN THREAT WILL BE DAMAGING DOWNBURST-TYPE WIND
GUSTS OVER 60 MPH. PRECIPITABLE WATER AMOUNTS FROM 1.8" TO 2.1"
SUPPORTS TORRENTIAL DOWNPOURS IN THE HEAVIER SHOWERS AND/OR
STRONGER STORMS.
SHORT TERM
(TONIGHT THROUGH WEDNESDAY)
ISSUED AT 956 PM CDT SUN AUG 16 2026
CONVECTION WILL WANE IN THE EVENING HOURS AS THE BOUNDARY DROPS
SOUTH OF THE REGION. SOME PATCHY FOG MAY DEVELOP IN LOCATIONS THAT
RECEIVE RAINFALL LATE MONDAY, BUT OTHERWISE IT SHOULD BE A FAIRLY
TRANQUIL NIGHT. AN EVER SO SUBTLE CHANGE TO THE AIR MASS MAY TAKE
PLACE TUESDAY AS DEWPOINTS WILL RUN A LITTLE LOWER AND
SUBSEQUENTLY HEAT INDEX VALUES IN THE 100-105 DEGREE RANGE WILL BE
MORE COMMON. STILL, MODERATE (LEVEL 2/3) TO MAJOR (LEVEL 3/4)
HEAT IMPACTS ARE FORECAST AND EVERYONE SHOULD STILL OBSERVE COMMON
SENSE HEAT SAFETY. HEAT IMPACTS WILL TEMPORARILY CREEP BACK INTO
THE REGION ON WEDNESDAY AS HIGHS RETURN TO THE MID TO UPPER 90S
AND DEWPOINTS IN THE 70S PUSH PEAK HEAT INDEX VALUES ABOVE 105
DEGREES OVER MUCH OF THE AREA.
LONG TERM
(WEDNESDAY NIGHT THROUGH SUNDAY)
ISSUED AT 956 PM CDT SUN AUG 16 2026
AFTER WEDNESDAY, THE UPPER-RIDGE WILL BEGIN TO FLATTEN AND SHIFT
BACK TO THE WEST OVER THE SOUTHERN ROCKIES AND GREAT BASIN. THIS
WILL PLACE THE TENNESSEE VALLEY INTO NORTHWEST FLOW ALOFT, OPENING
US UP TO A COUPLE OF SHORTWAVES THAT WILL PUSH THROUGH THE AREA
THURSDAY AND FRIDAY, RESULTING IN MEDIUM (30-60%) CHANCES FOR
SHOWERS AND THUNDERSTORMS BOTH AFTERNOONS. A FRONT WILL SAG SOUTH
OF THE AREA BY THE WEEKEND, KEEPING THE BETTER CHANCES FOR SHOWERS
AND STORMS DISPLACED TO SOUTH OF US ACROSS CENTRAL AND SOUTH
ALABAMA. THIS WILL ALSO GIVE US A RELATIVE BREAK FROM THE HEAT AS
HIGHS WILL DROP TO THE UPPER 80S TO LOWER 90S, WITH OVERNIGHT LOWS
IN THE 60S BY THE WEEKEND.
AVIATION
(06Z TAFS)
ISSUED AT 1254 AM CDT MON AUG 17 2026
FOR THE MOST PART, VFR FLIGHT CONDITIONS SHOULD CONTINUE FOR THE
GREATER TN VALLEY. BUT A FEW REPORTS OF PATCHY FOG HAVE BEEN NOTED
AROUND THE REGION THANKS TO MOISTURE LOADED ENVIRONMENT. WE CANNOT
RULE OUT AN INSTANCE OF FOG IMPACTING A TERMINAL BEFORE DAYBREAK,
WITH CHANCES OF IT TOO LOW TO MENTION IN THE TAF. MORE NOTABLE IS
A COLD FRONT MOVING TO THE REGION THIS AFTERNOON AND EVENING. WITH
STRONG DAYTIME HEATING AND HIGH INSTABILITY, CONVECTION SHOULD
FORM THIS AFTERNOON. SOME OF THE STORMS COULD PRODUCE STRONG TO
SEVERE OUTFLOW WIND GUSTS, AS WELL AS HEAVY DOWNPOURS FROM LOWERED
CIG/VSBY. SHOWER ACTIVITY SHOULD FADE AFTER SUNSET WITH VFR
CONDITIONS EXPECTED THEREAFTER.
HUN WATCHES/WARNINGS/ADVISORIES
AL...HEAT ADVISORY UNTIL 7 PM CDT THIS EVENING FOR ALZ001>010-016.
TN...HEAT ADVISORY UNTIL 7 PM CDT THIS EVENING FOR TNZ076-096-097.
NEAR TERM...RSB
SHORT TERM....AMP.24
LONG TERM....AMP.24
AVIATION...RSB
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