521
FXUS64 KHUN 200712
AFDHUN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HUNTSVILLE AL
212 AM CDT SUN SEP 20 2026
..NEW NEAR TERM
KEY MESSAGES
UPDATED AT 804 PM CDT SAT SEP 19 2026
- CONDITIONS WILL BE FAVORABLE FOR STRONG-SEVERE THUNDERSTORMS
EACH AFTERNOON INTO TUESDAY, WITH THE GREATEST SPATIAL COVERAGE
OF STORMS EXPECTED MONDAY AND TUESDAY. LOCALLY DAMAGING
DOWNBURST WINDS, FREQUENT LIGHTNING AND HEAVY RAINFALL WILL
BE THE MAIN STORM IMPACTS.
- HOT TEMPERATURES WILL CONTINUE INTO TUESDAY, WITH HIGHS IN THE
90S EACH DAY ACCOMPANIED BY HEAT INDICES UP TO AROUND 100-104
DEGREES.
- A SLIGHTLY COOLER AND DRIER AIRMASS WILL ARRIVE LATE IN THE
FORECAST PERIOD, WITH HIGHS DROPPING BACK INTO THE 80S MID WEEK.
NEAR TERM
(TODAY)
ISSUED AT 212 AM CDT SUN SEP 20 2026
HEAT WILL PERSIST AGAIN TODAY. YESTERDAY, WE HIT 100 DEGREES AT
HSV AND MSL! THAT TIED A RECORD AT MSL AND MISSED THE RECORD BY
ONE DEGREE AT HSV. DAYTIME HIGHS TODAY WILL RANGE FROM THE LOWER
90S IN HIGHER ELEVATIONS TO THE MID/UPPER 90S ELSEWHERE. THE
HEATRISK IS MODERATE (LEVEL 2/4) FOR MOST OF US WITH A FEW
LOCATIONS SEEING MAJOR (LEVEL 3/4). HEAT INDEX VALUES WILL REMAIN
BELOW ADVISORY LEVEL OF 105 DEGREES TODAY, THUS THE HEAT ADVISORY
WAS NOT EXTENDED INTO TODAY.
THIS MORNING, SOME OF US COULD SEE PATCHY FOG, ESPECIALLY FOR
THOSE THAT RECEIVED RAINFALL YESTERDAY. THE NIGHTTIME MICROPHYSICS
RGB SHOWS FOG STARTING TO FUNNEL INTO THE VALLEYS, AND EXPECT
THAT TO CONTINUE OVER THE NEXT FEW HOURS. TODAY WE WILL BE ON
THE EASTERN EDGE OF AN UPPER LEVEL RIDGE WITH A CONVERGENCE AXIS
BETWEEN IT AND A MEANDERING UPPER LEVEL LOW OVER FL LOCATED OFF TO
OUR EAST. THERE IS WHERE YOU WILL FIND GREATER COVERAGE OF
SHOWERS AND THUNDERSTORMS WITH JUST A LOW CHANCE (20%) FOR THE TN
VALLEY THIS AFTERNOON INTO EARLY THIS EVENING. WITH PWATS ~1.7",
DCAPE ~1,100 J/KG, AND MLCAPE ~1,500 J/KG, LOCALLY DAMAGING WIND
GUSTS FROM DOWNBURSTS ARE POSSIBLE WITHIN STRONGER STORMS. THE
STEERING FLOW IS ALSO VERY WEAK SO STORMS WILL BE MOVING SLOWLY SO
HEAVY RAINFALL IS ALSO A CONCERN. WITH COVERAGE EXPECTED TO BE
LOW, SPC HAS KEPT US OUT OF THE MARGINAL RISK (LEVEL 1/5) AT THIS
TIME. REGARDLESS, IT WILL BE HOT AND REMAIN WEATHER AWARE
THROUGHOUT THE DAY. BE HEAT SMART: SLOW DOWN, COOL DOWN, STAY
HYDRATED AND NEVER LEAVE PEOPLE OR PETS IN VEHICLES.
SHORT TERM
(SUNDAY NIGHT THROUGH TUESDAY)
ISSUED AT 804 PM CDT SAT SEP 19 2026
THE PRIMARY TALKING POINT IN THE SHORT TERM PERIOD IS A LOW CHANCE
OF STRONG TO SEVERE STORMS ON MONDAY DURING THE AFTERNOON INTO THE
EVENING HOURS DUE TO ANOTHER THREAT OF DOWNBURST WINDS AHEAD OF AN
APPROACHING COLD FRONT. THE TENNESSEE VALLEY IS CURRENTLY
OUTLOOKED IN A MARGINAL RISK (LEVEL 1 OF 5) FOR SEVERE WEATHER
FROM SPC, WHOSE DISCUSSION SPECIFICALLY MENTIONS MLCAPE OF 1500+
J/KG AND PWATS OF AROUND 1.75" (NEAR 90TH PERCENTILE SOUNDING
CLIMATOLOGY PER BMX) BRINGING A THREAT OF WET MICROBURSTS. BE SURE
TO KEEP AN EYE ON THE LATEST FORECAST AND HAVE MULTIPLE WAYS TO
GET WARNINGS LEADING INTO MONDAY AFTERNOON.
OTHERWISE, HEAT CONTINUES TO BE A CONCERN THROUGH THE SHORT TERM
AS AN UPPER LEVEL RIDGE CONTINUES TO IMPACT THE TENNESSEE VALLEY
FROM THE WEST- BRINGING ABOVE NORMAL TEMPERATURES. ON THE BRIGHT
SIDE, DUE TO ATMOSPHERIC MIXING, HEAT INDICES WILL BE SLIGHTLY
COOLER THAN THE PAST SEVERAL DAYS (REACHING 100-104 DEGREES). IN
TURN, WE HAVE ALLOWED OUR HEAT ADVISORY TO EXPIRE THIS EVENING
RATHER THAN EXTEND IT IN TIME. WHILE THERE IS A LOW CHANCE OF
ISOLATED AREAS REACHING 105 DEGREE HEAT INDEX TEMPERATURES
(ESPECIALLY URBAN AREAS), IT WILL NOT BE WIDESPREAD ENOUGH TO
WARRANT THE CONTINUATION OF THE ADVISORY. WE CONTINUE TO URGE
EVERYONE TO STAY HYDRATED AND SEEK SHADE WHEN OUTDOORS DURING THE
HOTTEST PART OF THE DAY.
LONG TERM
(TUESDAY NIGHT THROUGH SATURDAY)
ISSUED AT 804 PM CDT SAT SEP 19 2026
THE LONG TERM FORECAST PERIOD WILL BE CHARACTERIZED BY A WELCOMED
PATTERN CHANGE. AN UPPER LEVEL TROUGH DIGS DOWN ACROSS THE MIDWEST
TOWARDS THE SOUTHEAST DURING THE MIDDLE OF THE WEEK. THIS WILL PUSH
A COLD FRONT THROUGH THE AREA TUESDAY NIGHT THROUGH WEDNESDAY AND AS
A RESULT, LOW TO MEDIUM CHANCES (30-60%) FOR SHOWERS AND STORMS ARE
EXPECTED. AS THE UPPER LEVEL TROUGH AXIS SHIFTS TO OUR EAST,
NORTHWEST FLOW BEGINS TO ADVECT IN A NOTICEABLY COOLER AND DRIER
AIRMASS BRINGING SOME MUCH NEEDED RELIEF FROM THE HEAT. WE BEGIN TO
REALLY FEEL THE DRIER AIR LATE WEDNESDAY NIGHT INTO THURSDAY AS
DEWPOINTS FALL INTO THE LOWER 60S. AFTERNOON HIGHS THURSDAY THROUGH
SATURDAY ARE FORECAST TO ONLY RISE INTO THE LOW TO MID 80S WITH
OVERNIGHT LOWS IN THE UPPER 50S TO LOWER 60S.
AVIATION
(06Z TAFS)
ISSUED AT 1219 AM CDT SUN SEP 20 2026
VFR CONDITIONS WILL PREVAIL THROUGH THE TAF PERIOD AT KHSV AND
KMSL. THERE IS A LOW CHANCE THAT PATCHY FOG COULD AFFECT THE
TERMINALS BEFORE DAYBREAK, BUT CONFIDENCE IS TOO LOW TO INCLUDE
IT AT THIS TIME. THERE IS ALSO A LOW CHANCE FOR SHOWERS AND
THUNDERSTORMS THIS AFTERNOON BUT COVERAGE IS TOO LOW TO INCLUDE
IT AS WELL. WILL MONITOR FOR ANY NEEDED ADJUSTMENTS, HOWEVER FOR
THE MOMENT, AMENDMENTS ARE NOT SCHEDULED DUE TO A NATIONAL ISSUE
WITH RECEIVING METAR DATA.
HUN WATCHES/WARNINGS/ADVISORIES
AL...NONE.
TN...NONE.
NEAR TERM...JMS
SHORT TERM....HC
LONG TERM....GH
AVIATION...JMS
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