927
FXUS64 KHUN 301944
AFDHUN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HUNTSVILLE AL
244 PM CDT WED JUL 30 2025
..NEW NEAR TERM
NEAR TERM
(TONIGHT)
ISSUED AT 244 PM CDT WED JUL 30 2025
SEVERAL AREAS OF SHOWERS AND THUNDERSTORMS HAVE DEVELOPED ACROSS
THE TN VALLEY THIS AFTERNOON. ONE FORCING MECHANISM IS A
CONVERGENCE BOUNDARY DRAPED FROM NORTHEAST TN DOWN THROUGH
NORTHWEST AL. NEAR-STATIONARY STORM MOTIONS AND THE LACK OF SHEAR
HAVE LED TO NUMEROUS STORMS GENERATED BY NEARLY PERFECTLY-ROUND
OUTFLOW BOUNDARY COLLISIONS. THIS ACTIVITY HAS BEGUN TO DRIFT INTO
OUR SOUTHERN MIDDLE TN COUNTIES. THE SECOND FORCING FOR ASCENT
NEAR OUR AREA IS A LOCALIZED CYCLONIC ROTATION OVER I-65, EVIDENT
IN SATELLITE-DERIVED PRECIPITABLE WATER IMAGERY. PW VALUES OVER
2" EAST OF I-65 ARE BEING PULLED NORTHWARD BY SOUTHERLY WINDS,
WHEREAS WEST OF I-65 LOWER PWS NEAR 1.5" ARE BEING PULLED
SOUTHWARD BY NORTH/NORTHWESTERLY WINDS. I-65 IS ALMOST PERFECTLY
IN THE MIDDLE OF THIS, AND THE CONVERGENT ROTATION (ON A
RELATIVELY LARGE SCALE) IS PROVIDING LOCALIZED FORCING FOR ASCENT
IN THIS VICINITY.
ALSO SPLIT IN THE WEST VS. EAST BIFURCATION IS THE RESPONSIBLE
FACTOR FOR THE GUSTY WIND POTENTIAL. IN THE DRIER WEST, DCAPE
VALUES EXCEED 1400 J/KG DUE TO STEEPER LOW- AND MID-LEVEL LAPSE
RATES. IN THE MORE MOIST EAST, PW VALUES OVER 2" WILL ALLOW FOR
HYDROMETEOR LOADING AND STRONG DOWNDRAFTS. FOR BOTH, THE POTENTIAL
FOR SLOW, NEARLY STATIONARY STORMS AND STRONG DOWNDRAFTS OF 40-50
MPH WILL BE THE PRIMARY THREAT THIS AFTERNOON AND EVENING. LOSS OF
DAYTIME HEATING SHOULD RESULT IN LOSS OF CONVECTIVE COVERAGE AFTER
7-8 PM, UNLESS FUELED BY LOCALIZED OUTFLOW BOUNDARY INTERACTIONS.
NOT TO BE OUTDONE, HEAT INDEX VALUES HAVE REACHED OVER 105 FOR
MOST OF THE AREA. AT LEAST ALL THREE ASOS SITES IN HSV, MSL, AND
DCU HAVE REACHED OR EXCEEDED 105, WITH SEVERAL AWOS SITES ALSO
CRESTING INTO HEAT ADVISORY CRITERIA. AFTERNOON DEW POINT MIXING
HAS DECREASED THE COVERAGE OF SITES CURRENTLY AT 105. TEMPERATURES
WILL FALL OVERNIGHT INTO THE LOW TO MID 70S.
SHORT TERM
(THURSDAY THROUGH SATURDAY)
ISSUED AT 1102 AM CDT WED JUL 30 2025
AS MUCH AS WE HAVE HOPED FOR A PATTERN SHIFT LATER THIS WEEK, IT
LOOKS AS THOUGH THE RIDGE ALOFT IS TAKING ITS SWEET TIME
TRANSLATING WESTWARD. AS A RESULT, THE HEAT ADVISORY HAS BEEN
EXTENDED AN ADDITIONAL 24 HOURS UNTIL 9 PM ON THURSDAY FOR HEAT
INDEX VALUES OF 105-109 F. DIURNAL SHOWER AND STORM DEVELOPMENT IS
ANTICIPATED ONCE AGAIN, WITH NOT AS HIGH OF A CEILING FOR STRONG
STORMS AS TODAY. HOWEVER, THE ADDITIONAL CLOUD COVER AND
CONVECTION SHOULD BE DELAYED UNTIL LATER IN THE AFTERNOON, SIMILAR
TIMING TO TODAY, WHICH WOULD ALLOW MOST OF THE AREA TO HEAT UP
INTO THE HEAT ADVISORY CRITERIA.
ALL INDICATIONS ARE THAT THE PATTERN SHIFT SHOULD TAKE PLACE
ON THURSDAY. A COLD FRONT CURRENTLY STALLED OVER THE MIDWEST WILL
SAG SOUTHWARD. TIMING THIS FRONT IS FAIRLY INCONSISTENT DEPENDING
ON WHICH GUIDANCE SOURCE IS REFERENCED. CLUSTER ANALYSIS OF GLOBAL
ENSEMBLE GUIDANCE IN DESI INDICATES A 60% CHANCE THE FRONT PUSHES
INTO THE TN VALLEY ON THURSDAY EVENING, BRINGING THE HEAVIER
RAINFALL THROUGH AT THAT TIME. THE OTHER 40% SHOWS THE FRONT
SLOWING A BIT AND MOVING THROUGH EARLY FRIDAY MORNING. WHICHEVER
WAY YOU ROLL THE DICE, THURSDAY SHOULD BE WETTER WITH PRE-FRONTAL
CONVECTION (50-70% CHANCE), AND THEN WE COOL DOWN ON FRIDAY WITH
HIGH TEMPS IN THE UPPER 80S TO MAYBE 90.
SHORTWAVE TROUGHS RIPPLING AROUND THE RIDGE WILL PROVIDE
ADDITIONAL FORCING FOR ASCENT ON FRIDAY BEHIND THE FRONT, BRINGING
ANOTHER DAY OF 50-70% POPS. WE COOL OFF MORE ON SATURDAY WITH
HIGHS ONLY IN THE MID 80S AND AFTERNOON RAIN CHANCES PEAKING
BETWEEN 30-50%. THE LOWER END POPS IN THE RANGE WILL BE AREAS WEST
OF I-65, WHERE THE SUPPRESSION OF THE UPPER LEVEL RIDGE WILL
RESULT IN LESS SHOWER COVERAGE.
LONG TERM
(SATURDAY THROUGH TUESDAY)
ISSUED AT 1050 PM CDT TUE JUL 29 2025
AN UPPER LEVEL TROUGH WILL BE SWINGING OVER THE NORTHEASTERN US BY
THE WEEKEND, BUT ANOTHER WILL BE ON ITS HEELS FOR EARLY WEEK.
MEANWHILE, A SERIES OF SHORTWAVES LOOK TO TRAVERSE THE MIDWEST AND
OHIO/TENNESSEE VALLEY REGIONS DURING THIS TIME. AT THE SURFACE, A
COLD FRONT IS EXPECTED TO HAVE PUSHED SOUTH OF THE LOCAL AREA ON
FRIDAY. THIS WILL LIKELY EVENTUALLY STALL NEAR THE GULF COAST THROUGH
TUESDAY. AN INVERTED TROUGH MAY SET UP OVER THE TENNESSEE VALLEY FOR
SUNDAY, BUT HIGH PRESSURE WILL BUILD OVER THE NORTHEAST BY EARLY
NEXT WEEK.
OVERALL, SENSIBLE WEATHER WILL COMPRISE OF DAILY CHANCES OF SHOWERS
AND STORMS, WITH THE HIGHEST CHANCES DURING THE WEEKEND THEN TAPERING
OFF A BIT FOR MONDAY AND TUESDAY. WHILE THERE WILL LIKELY BE AMPLE
INSTABILITY FOR THUNDERSTORM DEVELOPMENT, GUIDANCE SUGGESTS THAT BULK
SHEAR VALUES WILL MOSTLY REMAIN BELOW 30 KNOTS. THUS, SEVERE WEATHER
IS NOT ANTICIPATED AT THIS TIME. THE GOOD NEWS IS THAT TEMPERATURES
ARE FORECAST TO BE MORE MILD THAN WE'VE SEEN RECENTLY, WITH HIGHS
TOPPING OUT IN THE 80S THROUGH MONDAY. ALTHOUGH, BY TUESDAY, AS THE
AFOREMENTIONED HIGH PRESSURE BEGINS TO BUILD SOUTHWEST INTO THE
REGION FROM THE NORTHEAST, TEMPERATURES ARE EXPECTED TO BE A TOUCH
WARMER. SO, HANG IN THERE, SOME RELIEF FROM THE HEAT IS ON ITS
WAY!
AVIATION
(18Z TAFS)
ISSUED AT 1228 PM CDT WED JUL 30 2025
FAIRLY ORDINARY SUMMERTIME DAY FOR AVIATION INTERESTS. AFTERNOON
AND EVENING SHOWER AND STORM DEVELOPMENT MAY RESULT IN SOME AWWS
FOR TERMINALS. OTHERWISE, LIGHT AND VARIABLE WINDS RESUME
OVERNIGHT WITH FOG NOT EXPECTED TO IMPACT TERMINALS.
HUN WATCHES/WARNINGS/ADVISORIES
AL...HEAT ADVISORY UNTIL 9 PM CDT THURSDAY FOR ALZ001>010-016.
TN...HEAT ADVISORY UNTIL 9 PM CDT THURSDAY FOR TNZ076-096-097.
NEAR TERM...30
SHORT TERM....30
LONG TERM....26
AVIATION...30
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page