479
FXUS64 KHUN 201058
AFDHUN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HUNTSVILLE AL
558 AM CDT MON JUL 20 2026
..NEW AVIATION
KEY MESSAGES
UPDATED AT 1014 PM CDT SUN JUL 19 2026
- A HEAT ADVISORY WILL BE IN EFFECT FOR MOST OF THE TENNESSEE
VALLEY FOR THE 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
SOME LOCATIONS MONDAY AND TUESDAY.
- DAILY THUNDERSTORM CHANCES WILL CONTINUE INTO EARLY NEXT WEEK.
A FEW STORMS COULD BECOME STRONG TO MARGINALLY SEVERE TUESDAY.
GUSTY TO DAMAGING WINDS, FREQUENT LIGHTNING, AND LOCALLY HEAVY
RAINFALL WILL BE THE MAIN THREATS.
NEAR TERM
(TODAY)
ISSUED AT 350 AM CDT MON JUL 20 2026
A FEW SHOWERS HAVE DEVELOPED OVER THE PAST TWO HOURS OVER PORTIONS
OF NW ALABAMA. MESOSCALE GUIDANCE IS HINTING THIS MAY CONTINUE ON
AND OFF FOR A FEW MORE HOURS. ELSEWHERE, AREAS OF FOG HAVE BEEN
DEVELOPING OVER THE LAST FEW HOURS, AS HIGHS CLOUDS DISSIPATED.
THERE ARE SOME LOW CLOUDS IN PLACE BELOW THEM, BUT NOT ENOUGH TO
KEEP MORE AREAS OF FOG DEVELOPING OVER THE NEXT FEW HOURS.
MESOSCALE GUIDANCE SEEMS TO WANT TO INCREASE THIS LOW LEVEL CLOUD
COVER (AROUND 850 MB) INTO THE DAYBREAK HOURS, ESPECIALLY OVER
SOUTHERN MIDDLE TENNESSEE AND AREAS NEAR WEST OF THE I-65
CORRIDOR. HOWEVER, NOT SEEING THAT OCCUR AS MUCH AS MODELS WERE
PREDICTING SO FAR. GIVEN LIGHT WINDS ALREADY IN PLACE AND A FAIR
AMOUNT OF FOG DEVELOPMENT SEEN IN 2.30-10.35 RGB IMAGERY SATELLITE
IMAGERY, A DENSE FOG ADVISORY FOR OUR SOUTHERN MIDDLE TENNESSEE
AND PORTIONS OF NE ALABAMA (MADISON, JACKSON, AND DEKALB COUNTIES)
MAY BE NEED WITHIN THE NEXT HOUR TO GO THROUGH 7 AM. THIS FOG
SHOULD BURN OFF RATHER QUICKLY AFTER SUNRISE. TEMPERATURES WILL
REMAIN WARM WHEN YOU WAKE UP THIS MORNING, ONLY DROPPING INTO THE
70 TO 75 DEGREE RANGE. A HEAT ADVISORY REMAINS IN EFFECT FOR
TODAY WITH EXPECTED HEAT INDEX VALUES REACHING THE 105 TO 107
DEGREE RANGE.
SEVERAL MODELS SHOW A MEDIUM CHANCE OF SHOWER AND THUNDERSTORM
DEVELOPMENT THIS AFTERNOON. GIVEN HIGH PWAT VALUES AND EXPECTED
INSTABILITY, HEAVY RAINFALL AND FREQUENT LIGHTNING COULD OCCUR
WITH STRONGER THUNDERSTORMS. LOCALIZED FLASH FLOODING MAY OCCUR AS
WELL.
SHORT TERM
(MONDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 1014 PM CDT SUN JUL 19 2026
AS HAS BEEN THE CASE THE PAST FEW NIGHTS, SHOWERS THAT FORM SHOULD
FADE AS WE GO INTO MON NIGHT. WE CANNOT RULE OUT PATCHY LATER
NIGHT FOG IN AREAS THAT RECEIVE WETTING RAINFALL, AS WELL AS FOG
FAVORED SPOTS. ANOTHER MUGGY AND HUMID NIGHT WITH LOWS IN THE
LOW/MID 70S. THE MILDER LOWS IN THE MID 70S WOULD HELP SET THE
STAGE FOR MORE HEAT ISSUES TUE. INLAND DEEP MOISTURE TRANSPORT
FROM THE GULF OF AMERICA SHOULD BE LIMITED BY THE TROPICAL ENTITY,
THUS WITH LOWER RAIN CHANCES, HOT CONDITIONS WILL AGAIN RULE.
HIGH TEMPERATURES SHOULD WARM INTO THE LOW/MID 90S, WITH HEAT
INDEX VALUES FROM THE UPPER 90S TO 109 DEGREES. WILL HAVE THE HEAT
ADVISORY CONTINUING INTO EARLY TUE EVENING.
SULTRY CONDITIONS ARE EXPECTED TUE NIGHT, AS LOW TEMPERATURES
COOL ONLY INTO THE MID 70, WITH SOME UPPER 70S IN THE MORE
URBANIZED HEAT ISLANDS. DEPENDING UPON HOW MUCH OF THE AREA WILL
BE IMPACTED BY CLOUDS AND SHOWERS IN LATER FORECASTS, THE HEAT
ADVISORY MAY BE NEEDED FOR SOME OF THE AREA WED. VERY WARM UPPER
RIDGING THAT WAS POSITIONED OVER THE CENTRAL HIGH PLAINS EARLIER
IN THE WEEK, SHOULD WEAKEN SOMEWHAT AND BUILD MORE TOWARDS THE SW.
WHILE THIS OCCURS, A SYSTEM MOVING IN THE MAIN WESTERLIES OVER
CANADA WILL INDUCE MORE TROUGHING FROM THE GREAT LAKES TO THE MID
ATLANTIC IN THE MID WEEK. THIS WILL HELP BRING A SURFACE COLD
FRONT TOWARDS THE FORECAST AREA ON WED. LIFT PROVIDED BY THE
FRONT, ALONG WITH MEDIUM TO HIGH SHOWER AND THUNDERSTORM CHANCES
(GREATER RAIN CHANCES EAST) WILL HELP PROVIDE RELIEF FROM THE
HEAT. HIGHS SHOULD BE A TAD COOLER, FROM THE MID/UPPER 80S EAST TO
LOW/MID 90S WEST, WITH HEAT INDEX VALUES FROM THE MID 90S TO 105
IN A FEW SPOTS. CONDITIONS SHOULD COOL DOWN A LITTLE MORE WED
NIGHT WITH LOWS FALLING INTO THE UPPER 60S TO AROUND 70.
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 FROM 10 AM THIS MORNING TO 8 PM CDT TUESDAY FOR
ALZ001>009-016.
TN...HEAT ADVISORY FROM 10 AM THIS MORNING TO 8 PM CDT TUESDAY FOR
TNZ076-096-097.
NEAR TERM...KTW
SHORT TERM....RSB
LONG TERM....RAD
AVIATION...KTW
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