178
FXUS64 KHUN 170441
AFDHUN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HUNTSVILLE AL
1141 PM CDT WED SEP 16 2026
..NEW AVIATION
KEY MESSAGES
UPDATED AT 1020 PM CDT WED SEP 16 2026
- A HEAT ADVISORY IS IN EFFECT THROUGH 8 PM SATURDAY ACROSS ALL
OF SOUTHERN MIDDLE TENNESSEE AND NORTHERN ALABAMA.
- NWS HEAT RISK HIGHLIGHTS MODERATE (LEVEL 2/4) TO MAJOR (LEVEL
3/4) HEAT IMPACTS THROUGH THE WEEKEND ACROSS THE TENNESSEE
VALLEY. LOCALIZED EXTREME (LEVEL 4/4) IMPACTS MAY OCCUR IN
URBANIZED AREAS.
NEAR TERM
(THIS EVENING THROUGH THURSDAY)
ISSUED AT 1020 PM CDT WED SEP 16 2026
A STRONG MID-LEVEL HIGH (INITIALLY POSITIONED ACROSS EAST TN)
WILL CONTINUE TO MIGRATE WEST-SOUTHWESTWARD OVER THE COURSE OF THE
NEAR TERM PERIOD, BECOMING CENTERED ACROSS SOUTHWESTERN AR BY 0Z
FRIDAY. AS THIS OCCURS, N-NE FLOW WILL BECOME ESTABLISHED ACROSS
THE TN VALLEY TONIGHT AND SHOULD INCREASE INTO THE 10-20 KNOT
RANGE TOMORROW AS A DEVELOPING UPPER LOW RETROGRADES ACROSS THE
SOUTHWESTERN NORTH ATLANTIC AND APPROACHES THE FL PENINSULA LATE
IN THE PERIOD. IN THE LOW-LEVELS, OUR FORECAST AREA WILL CONTINUE
TO BE INFLUENCED BY A WEAKENING SURFACE HIGH AS IT SHIFTS EASTWARD
INTO THE NORTHWESTERN ATLANTIC, WITH A LIGHT SSE-CALM WIND
ANTICIPATED OVERNIGHT, FOLLOWED BY LIGHT/VARIABLE FLOW (WITHIN A
RELAXING PRESSURE GRADIENT) TOMORROW. DUE TO A MORE FAVORABLE
ENVIRONMENT FOR RADIATIONAL COOLING, DEVELOPMENT OF PATCHY, EARLY-
MORNING MIST AND FOG APPEARS A BIT MORE LIKELY TONIGHT AS
TEMPERATURES DROP INTO THE U60S-L70S.
IN SIMILAR FASHION TO THE PAST SEVERAL DAYS, TEMPERATURES WILL
BEGIN TO INCREASE QUICKLY AFTER SUNRISE, AND WITH CONTINUING
INFLUENCE FROM THE DEPARTING MID-LEVEL RIDGE, ONLY A SCATTERED
CUMULUS FIELD IS EXPECTED. THUS, HIGHS WILL ONCE AGAIN RANGE FROM
THE U80S-L90S IN ELEVATED TERRAIN TO THE M-U 90S IN THE VALLEY,
WITH DEWPOINTS MIXING DOWN INTO THE M60S KEEPING HEAT INDICES IN
THE 98-102F RANGE FOR MOST OF THE REGION. HOWEVER, WITH HEAT RISK
LARGELY IN THE LEVEL 2/3 RANGE AND HIGH TEMPS RUNNING 5-10F ABOVE
NORMAL (LOW TEMPS RUNNING 10-15F ABOVE NORMAL), WE WILL RETAIN THE
PREEXISTING HEAT ADVISORY TO HIGHLIGHT IMPACTS FROM THIS RECENT
STRETCH OF HOT WEATHER. ALTHOUGH A FEW, SMALL AND LOW-TOPPED
SHOWERS MAY EVOLVE DURING THE CREST OF THE DIURNAL WARMING CYCLE
TOMORROW AFTERNOON, THE COVERAGE OF SHOWERS AND THUNDERSTORMS
SHOULD BE HIGHER TO OUR NORTH/EAST AS AN MCV TRAVELING AROUND THE
NORTHEASTERN PERIPHERY OF THE RIDGE ALOFT ENHANCES LIFT ACROSS THE
CENTRAL/SOUTHERN APPALACHIANS. THUS, RAIN CHANCES FOR OUR REGION
WILL REMAIN IN THE 5-10% RANGE (SLIGHTLY HIGHER IN THE ELEVATED
TERRAIN OF NORTHEAST AL/SOUTHERN MIDDLE TN).
SHORT TERM
(THURSDAY NIGHT THROUGH SATURDAY NIGHT)
ISSUED AT 1020 PM CDT WED SEP 16 2026
THROUGHOUT THE SHORT TERM PERIOD, A WEAKENING SUBTROPICAL HIGH IN
THE MID-LEVELS WILL REMAIN CENTERED OVER THE ARKLATEX AS A
DEVELOPING UPPER LOW TRAVELS WEST-SOUTHWESTWARD ACROSS THE FL
PENINSULA AND INTO THE EASTERN GULF. THIS CONFIGURATION WILL
SUSTAIN N-NE FLOW ALOFT OF 10-20 KNOTS, ALTHOUGH GRADUAL
MOISTENING OF THE LOWER TROPOSPHERIC COLUMN WILL SUPPORT A MINOR
INCREASE IN PWAT AS WE PROGRESS THROUGH THE PERIOD (WITH VALUES
RISING BACK TO 1.6-1.7" EARLY THIS WEEKEND).
LATEST GUIDANCE STILL SUGGESTS THAT A CANADIAN SURFACE HIGH WILL
TRANSLATE SOUTHEASTWARD ACROSS OT AND INTO SOUTHERN QC FROM
THURSDAY NIGHT-FRIDAY NIGHT, WITH A COLD FRONT EDGING SLOWLY
SOUTHWESTWARD BETWEEN THE LOWER GREAT LAKES AND OH VALLEY. IT
STILL APPEARS AS IF A PREFRONTAL WIND SHIFT AXIS WILL INITIATE
AFTERNOON CONVECTION FROM THE OH VALLEY INTO THE SOUTHERN MID-
ATLANTIC STATES ON FRIDAY, WITH A GREATER COVERAGE OF TERRAIN-
INDUCED THUNDERSTORMS ACROSS THE SOUTHERN APPALACHIANS, AS WELL.
STORM COVERAGE WILL LIKELY BE A BIT HIGHER ACROSS OUR CWFA
(PARTICULARLY THE EASTERN HALF) DURING THE AFTERNOON AND EVENING
HOURS DUE TO THE DIMINISHING INFLUENCE OF THE SUBTROPICAL RIDGE.
HOWEVER, THIS WILL BE CONTINGENT ON A SOURCE OF LOW-LEVEL ASCENT
(LIKELY A COMBINATION OF CONVECTIVE OUTFLOW AND TOPOGRAPHY).
SHOULD STRONGER UPDRAFTS MANAGE TO DEVELOP IN OUR REGION, THE
THERMODYNAMIC ENVIRONMENT FRIDAY AFTERNOON WILL SUPPORT LOCALLY
DAMAGING DOWNBURST WINDS, ALONG WITH FREQUENT LIGHTNING.
AS THE WEAKENING CANADIAN SURFACE HIGH SHIFTS EASTWARD ACROSS NEW
ENGLAND ON SATURDAY/SATURDAY NIGHT, MINOR PRESSURE RISES IN THE
LEE OF THE SOUTHERN APPALACHIANS WILL INDUCE LIGHT SSE FLOW ACROSS
OUR REGION, WITH SCATTERED DIURNAL CONVECTION AND A SIMILAR RISK
FOR LOCALLY DAMAGING DOWNBURST WINDS ON SATURDAY (AND CONTINUING
INTO SATURDAY EVENING) EXPECTED TO BE FOCUSED ALONG THE INTERFACE
OF THIS REGIME. AFTERNOON HIGHS AND OVERNIGHT LOWS WILL EXHIBIT
LITTLE FLUCTUATION THROUGH THE SHORT TERM PERIOD, AND IN ORDER TO
HIGHLIGHT HEAT RISK VALUES IN THE LEVEL 2/3 RANGE, WE WILL
MAINTAIN A HEAT ADVISORY THROUGH 8 PM SATURDAY.
LONG TERM
(SUNDAY THROUGH WEDNESDAY)
ISSUED AT 1020 PM CDT WED SEP 16 2026
EXTENDED RANGE MODEL DATA SUGGESTS THAT LIGHT S-SW FLOW IN THE
LOW-LEVELS WILL EXIST ACROSS THE REGION FROM SUNDAY INTO MONDAY,
AS A WEAK AREA OF LOW PRESSURE TRACKS EAST-NORTHEASTWARD FROM THE
OZARKS INTO NORTHERN PARTS OF THE TN VALLEY. THIS WILL SUSTAIN A
WARM AND INCREASINGLY MOIST AIRMASS, WITH HIGHS REMAINING IN THE
M-U 90S (IN LOWER ELEVATIONS) AND AN ISOLATED-WIDELY SCATTERED
COVERAGE OF MAINLY AFTERNOON/EARLY EVENING SHOWERS AND
THUNDERSTORMS. DURING THE TIMEFRAME FROM MONDAY NIGHT INTO
TUESDAY, THE WEAKENING AREA OF LOW PRESSURE TO OUR NORTH WILL
EVOLVE INTO A FRONTAL WAVE AS IT LIFTS FURTHER NORTHEASTWARD INTO
THE UPPER OH VALLEY, WITH A GENERAL INCREASE IN THE SPATIAL
COVERAGE OF SHOWERS AND THUNDERSTORMS ANTICIPATED BOTH PERIODS AS
THE TRAILING COLD FRONT DRIFTS SOUTHEASTWARD. WHETHER OR NOT THE
FRONT CONTINUES TO ADVANCE SOUTHEASTWARD (AND BRINGS OUR FORECAST
AREA A SLIGHTLY COOLER/DRIER AIRMASS ON TUESDAY NIGHT/WEDNESDAY)
REMAINS UP FOR DEBATE, AND WILL LIKELY BE DEPENDENT ON
AMPLIFICATION OF AN UPPER-LEVEL TROUGH TO OUR NORTH. REGARDLESS,
WE WILL ADVERTISE SLIGHTLY COOLER HIGH TEMPS (U80S-L90S) BY
WEDNESDAY.
AVIATION
(06Z TAFS)
ISSUED AT 1141 PM CDT WED SEP 16 2026
VFR CONDITIONS WILL PREVAIL THROUGH THE PERIOD, WITH LIGHT WINDS
AND A MOSTLY CLEAR SKY. THE ONE EXCEPTION MAY BE BRIEFLY EARLY
THURSDAY MORNING WHEN SOME LIGHT MVFR FOG MAY DEVELOP. HAVE
INCLUDED A TEMPO BETWEEN 10-13Z TO ACCOUNT FOR THIS. ANY FOG THAT
DOES DEVELOP WILL DISSIPATE BY MID MORNING.
HUN WATCHES/WARNINGS/ADVISORIES
AL...HEAT ADVISORY UNTIL 8 PM CDT SATURDAY FOR ALZ001>010-016.
TN...HEAT ADVISORY UNTIL 8 PM CDT SATURDAY FOR TNZ076-096-097.
NEAR TERM...70
SHORT TERM....70
LONG TERM....70
AVIATION...AMP.24
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