956
FXUS64 KHUN 201436
AFDHUN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HUNTSVILLE AL
936 AM CDT MON JUL 20 2026
..NEW NEAR TERM, SHORT TERM
KEY MESSAGES
UPDATED AT 936 AM CDT MON JUL 20 2026
- A HEAT ADVISORY WILL BE IN EFFECT FOR MOST OF THE TENNESSEE
VALLEY FROM 10 AM TODAY THROUGH TUESDAY AT 7 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 INTO EARLY THIS WEEK.
A FEW STORMS COULD BECOME STRONG TO MARGINALLY SEVERE TUESDAY
EVENING/NIGHT. GUSTY TO DAMAGING WINDS, FREQUENT LIGHTNING, AND
LOCALLY HEAVY RAINFALL WILL BE THE MAIN THREATS.
NEAR TERM
(TODAY AND TONIGHT)
ISSUED AT 936 AM CDT MON JUL 20 2026
CURRENT SATELLITE IMAGERY SHOWS A FEW AREAS OF PATCHY FOG IN
LOCATIONS THAT RECEIVED RAINFALL YESTERDAY ACROSS NORTHEAST
ALABAMA. FOG WILL DISSIPATE OVER THE NEXT HOUR OR TWO AS DAYTIME
HEATING COMMENCES, WITH A MOSTLY CLEAR SKY THROUGH THE MORNING
INTO THE EARLY AFTERNOON ALLOWING TEMPERATURES TO CLIMB INTO THE
LOW TO MID 90S LATE TODAY. THE COMBINATION OF THESE VERY WARM
TEMPERATURES AND DEWPOINTS IN THE 70S WILL CREATE DANGEROUSLY HIGH
HEAT INDEX VALUES BETWEEN 100-109 DEGREES THIS AFTERNOON (WITH
MANY LOCATIONS, SUCH AS THE MSL/DCU/HSV METROS EXCEEDING 105
DEGREES). A HEAT ADVISORY IS IN EFFECT BEGINNING AT 10 AM TODAY
THROUGH 8 PM TUESDAY.
AN OUTFLOW BOUNDARY WAS STRETCHING FROM NEAR MERIDIAN, MS NNE
THROUGH THE BANKHEAD NATIONAL FORECAST AND ACROSS OUR SOUTHERN
MIDDLE TENNESSEE COUNTIES. A COUPLE SMALL CLUSTERS OF SHOWERS
CONTINUE TO HUG THIS BOUNDARY THIS MORNING AND THIS FEATURE WILL
LIKELY SERVE AS A FOCUS ADDITIONAL THUNDERSTORMS (30-40% CHANCE)
THIS AFTERNOON. THERMODYNAMICALLY, THE STORM ENVIRONMENT SHOULD
NOT BE QUITE AS FAVORABLE AS YESTERDAY, WITH SLIGHTLY LOWER LOW-
LEVEL LAPSE RATES (7-8 C/KM AND MLCAPE ~ 1500-2000 J/KG). STILL,
THESE VALUES WILL BE MORE THAN SUFFICIENT FOR PULSE, OUTFLOW
DRIVEN THUNDERSTORMS, ESPECIALLY DURING THE PEAK HEATING OF THE
DAY. INVERTED-V SOUNDING PROFILES WILL AGAIN FAVOR A LOCALIZED
DOWNBURST THREAT WITH ANY STRONGER STORMS THAT CAN INITIATE.
HOWEVER, WITH PWATS EXCEEDING 2", OUR MAIN CONCERN CONTINUES TO BE
TORRENTIAL DOWNPOURS RESULTING IN LOCALIZED FLASH FLOODING.
CONVECTION WILL WANE OVERNIGHT, WITH PATCHY FOG LIKELY TO DEVELOP
IN LOCATIONS THAT DO RECEIVE RAINFALL. WITH OVERNIGHT REMAINING
AROUND OR JUST ABOVE 75 DEGREES, AT LEAST MODERATE HEAT IMPACTS
WILL CONTINUE OVERNIGHT AND THE HEAT ADVISORY WILL REMAIN IN
EFFECT.
SHORT TERM
(TUESDAY THROUGH WEDNESDAY)
ISSUED AT 936 AM CDT MON JUL 20 2026
MAJOR (LEVEL 3/4) HEAT IMPACTS WILL DEVELOP ACROSS MUCH OF THE
TENNESSEE VALLEY ON TUESDAY AS HIGH PRESSURE (AND THE SUBSEQUENT
HEAT DOME) BUILDS EAST INTO THE TENNESSEE VALLEY. THIS WILL
PROMOTE MOSTLY SUNNY AND VERY WARM CONDITIONS ACROSS THE REGION ON
TUESDAY, WITH SOUTHERLY FLOW HELPING TO PUSH HIGH TEMPERATURES
INTO THE MID 90S IN MOST LOCATIONS. COMBINED WITH DEWPOINTS IN THE
MID TO UPPER 70S, THIS WILL CREATE HEAT INDEX VALUES BETWEEN
105-110 DEGREES ACROSS MUCH OF THE REGION AND A HEAT ADVISORY
REMAINS IN EFFECT THROUGH 8 PM TUESDAY.
SPEAKING OF THUNDERSTORM CHANCES, ONE OF THE REASONS THAT WE'RE SO
CONFIDENT IN THE HEAT RISK ON TUESDAY IS THAT WE SHOULD BE LARGELY
DEVOID OF STORMS AND CLOUD COVER DURING THE DAY. THE MAIN FOCUS
FOR THESE STORMS WILL BE A COLD FRONT IN THE OHIO VALLEY AND
STORMS AREN'T EXPECTED TO INITIATE ON IT UNTIL THE VERY LATE
AFTERNOON AND EVENING. LATEST GUIDANCE, ESPECIALLY THE HI-RES KEEP
POPS VERY LOW DURING THE AFTERNOON AND MUCH OF THE EVENING
(10-20%), WITH THE LINE OF STORMS NOT MAKING IT IN UNTIL AROUND
MIDNIGHT. AT THIS POINT, THE THREAT SHOULD BE CONSIDERABLY LOWER
GIVEN THE LIMITED INSTABILITY. STILL, SPC HAS NORTHERN PORTIONS
OF THE REGION CLIPPED BY A MARGINAL RISK (LEVEL 1/5) TO HIGHLIGHT
THE LOW-END THREAT FOR A COUPLE STRONG TO MARGINALLY SEVERE WIND
GUSTS IN THE LATE EVENING AND OVERNIGHT TIMEFRAME. THESE STORMS
WILL CONTINUE TO WEAKEN AS THEY MOVE THROUGH THE AREA LATE
TUESDAY, WITH GUSTY WINDS/HEAVY DOWNPOURS THE MAIN THREAT.
FOR WEDNESDAY, THE ACTUAL COLD FRONT SHOULD BE PUSHING THROUGH THE
REGION FROM THE LATE MORNING THROUGH THE AFTERNOON. THE STORM
ENVIRONMENT SHOULD BE FAIRLY WORKED OVER THANKS TO THE OVERNIGHT
CONVECTION, BUT A LOW-MEDIUM (30-60) CHANCE FOR SHOWERS AND A FEW
STORMS WILL EXIST THROUGH THE AFTERNOON. THE CLOUDS/RAIN CHANCES
SHOULD LOWER HIGHS A TOUCH INTO THE UPPER 80S TO LOWER 90S, BUT
HEAT INDEX VALUES COULD STILL REACH OR JUST EXCEED TO THE 100
DEGREE MARK ACROSS MUCH OF THE AREA.
LONG TERM
(WEDNESDAY NIGHT THROUGH SUNDAY)
ISSUED AT 1014 PM CDT SUN JUL 19 2026
THE PASSAGE OF A COLD FRONT ON WEDNESDAY WILL MARK THE START OF
THE LONG TERM FORECAST WITH SLIGHTLY LOWER TEMPS AND DEW POINTS.
HIGHS THROUGH THE LONG TERM PERIOD WILL BE RELEGATED TO THE LOW
90S WITH DEW POINTS DROPPING BACK TO THE HIGH 60S TO LOW 70S. THE
PASSAGE OF THE COLD FRONT WILL MARK A PATTERN CHANGE WITH A
TROUGHING EAST/RIDGING WEST REGIME SETTING UP THROUGH THE LONG
TERM FORECAST. AS SUCH, WE WILL FIND OURSELVES SOLIDLY IN NW FLOW
AS WE HEAD INTO THE WEEKEND AND INTO EARLY NEXT WEEK. THIS WILL
KEEP MEDIUM RAIN CHANCES IN THE FORECAST AS SEVERAL SHORTWAVES
RIPPLE ALONG THE BASE OF THE TROUGH. THIS SET UP DOES FAVOR MCSS
DROPPING SOUTH ALONG THE BASE OF THE TROUGH, POTENTIALLY INTO OUR
AREA. AS THE SET UP DRAWS NEARER, WE WILL CONTINUE TO EVALUATE MCS
POTENTIAL AND ANY INCREASED THREATS FOR SEVERE WEATHER OR
FLOODING.
AVIATION
(12Z TAFS)
ISSUED AT 558 AM CDT MON JUL 20 2026
AN AREA OF SHOWERS HAS DEVELOPED EAST OF THE KMSL TERMINAL.
DESPITE THAT, VFR CONDITIONS ARE CURRENTLY IN PLACE AT THIS
TERMINAL, AS WELL AS THE KHSV TERMINAL. NEWER GUIDANCE DOES
SUGGEST THIS ACTIVITY COULD SPREAD EAST TO NEAR THE KHSV TERMINAL
THROUGH 15Z BEFORE DISSIPATING. HOWEVER, CONFIDENCE IN COVERAGE IS
LOW AT THE TERMINALS, SO ONLY INCLUDED A PROB30 GROUP FOR -SHRA
FOR NOW WITH MVFR VSBYS AT TIMES. MOST GUIDANCE SHOWS THIS
ACTIVITY POSSIBLY WEAKENING, BUT THEN INCREASING IN COVERAGE AGAIN
EARLY THIS AFTERNOON. FOR NOW, KEPT CLOSE TO THE CURRENT FORECAST
WITH VCSH IN AT KMSL AFTER 18Z AND AT KHSV AFTER 19Z. A TEMPO
GROUP BETWEEN 18Z AND 22Z AT KMSL/19Z AND 23Z AT KHSV WAS
INCLUDED TO ADDRESS A HIGHER CHANCE OF -TSRA ACTIVITY. MVFR CIGS
WERE INCLUDED, BUT MAY NEED TO BE AMENDED IF IFR OR LOWER
VSBYS/CIGS DEVELOP. EXPECT ACTIVITY TO DISSIPATE AFTER 21/01Z. MAY
HAVE TO WATCH FOR FOG DEVELOPMENT TOWARDS THE END OF THE TAF
PERIOD, BUT LEFT IT OUT FOR NOW.
HUN WATCHES/WARNINGS/ADVISORIES
AL...HEAT ADVISORY UNTIL 8 PM CDT TUESDAY FOR ALZ001>009-016.
TN...HEAT ADVISORY UNTIL 8 PM CDT TUESDAY FOR TNZ076-096-097.
NEAR TERM...AMP.24
SHORT TERM....AMP.24
LONG TERM....RAD
AVIATION...KTW
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