929
FXUS63 KJKL 200800
AFDJKL
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
400 AM EDT THU AUG 20 2026
KEY MESSAGES
- A COLD FRONT BRINGS SCATTERED TO WIDESPREAD THUNDERSTORMS TODAY
AND FRIDAY. A FEW STRONG WIND GUSTS AS WELL AS LOCALIZED
EXCESSIVE RAINFALL ARE POSSIBLE WITH STORMS, MAINLY TODAY INTO
TONIGHT.
- NOTICEABLY COOLER AND LESS HUMID AIR ARRIVES THIS WEEKEND AND
CONTINUES INTO EARLY NEXT WEEK.
SHORT TERM
(TODAY THROUGH FRIDAY)
ISSUED AT 400 AM EDT THU AUG 20 2026
ALL IS QUIET ACROSS EASTERN KENTUCKY EARLY THIS MORNING. FOG HAS
DEVELOPED THROUGH MANY OF THE MAINSTEM RIVER VALLEYS, THOUGH NOT AS
DENSE OR EXTENSIVE AS YESTERDAY. TEMPERATURES ARE ALSO SEVERAL
DEGREES WARMER THAN THIS TIME YESTERDAY, RANGING FROM THE MID 60S
IN THE COOLER NORTHEASTERN VALLEYS TO THE LOW TO MID 70S NEAR LAKE
CUMBERLAND. IT IS MUCH MORE UNSETTLED LOOKING UPSTREAM--THERE IS
AN MCS OVER WESTERN KENTUCKY AND NORTHWEST TENNESSEE WHILE A
SECOND MCS IS PASSING OVER CENTRAL AND SOUTHERN INDIANA.
INSTABILITY, HOWEVER, IS VERY MEDIOCRE ACROSS EASTERN KENTUCKY,
GENERALLY RANGING FROM 100 TO 250 J/KG OF MUCAPE. INTERESTINGLY
THOUGH, THIS UPSTREAM CONVECTION HAS BEEN ABLE TO MAINTAIN FAIRLY
WELL, THOUGH ON ONLY ABOUT 500 J/KG OF MUCAPE (BASED ON SPC
MESOANALYSIS) FEEDING INTO THE COMPLEXES ON A ~30 KT LOW-LEVEL
SOUTHWESTERLY JET. SO THE CONVECTIVE COMPLEXES, ESPECIALLY THE
SOUTHERN ONE WHICH IS ANCHORED ALONG A POOL OF 2.0+ INCH PWATS,
MAY BE ABLE TO HOLD TOGETHER BETTER THAN WHAT ONE WOULD TYPICALLY
EXPECT WITH SUCH WEAK CAPE AS BOTH SYSTEMS TRACK IN A GENERALLY
EASTERLY DIRECTION. THIS COMPLEXES ARE ALMOST CERTAINLY BEING
SUPPORTED BY UPPER-LEVEL FORCING INHERENT WITH BEING LOCATED JUST
EAST OF A POSITIVELY-TILTED 500 HPA TROUGH AXIS AND A MODERATELY
STRONG (FOR THIS TIME OF YEAR) UPPER-LEVEL VORT MAX. THERE IS
FURTHER UPPER-LEVEL SUPPORT IN THE FORM OF DIVERGENCE FROM THE
RIGHT ENTRANCE REGION OF THE 250 HPA JET DIPPING ACROSS THE OHIO
VALLEY. THE STRONGER FLOW IS THUS ALSO SUPPORTING SUFFICIENT
SHEAR (EBWD +/- 35 KTS) FOR CONTINUED CONVECTIVE ORGANIZATION.
FARTHER UPSTREAM, A SLUGGISH COLD FRONT EXTENDS FROM SOUTHERN
QUEBEC SOUTHWARD ACROSS THE EASTERN GREAT LAKES AND THEN
SOUTHWESTWARD TO KANSAS.
EASTERN KENTUCKY WILL SPEND THE ENTIRE SHORT-TERM PERIOD AFFLICTED BY
PERIODICALLY UNSETTLED WEATHER CAUSED BY PERTURBATIONS MOVING THROUGH
THE UPPER-LEVEL TROUGH AND THE SLOW-MOVING INCOMING COLD FRONT. THAT
FIRST PERTURBATION AND THE ATTENDANT MCSS WILL TRANSIT EASTWARD,
LIKELY IMPACTING EASTERN KENTUCKY BETWEEN 6 AM AND NOON. THIS ACTIVITY
WILL STILL LIKELY WEAKEN WITH TIME, THOUGH, AS ITS LOW-LEVEL
MOISTURE AND INSTABILITY INFLOW WEAKENS WITH EASTWARD EXTENT.
STRONG WINDS ARE STILL POSSIBLE ALONG THE LEADING EDGE OF THE
CONVECTION, BUT LOW-LEVEL CIN FROM NIGHTTIME RADIATIONAL COOLING
IS LIKELY TO LIMIT THE OVERALL MIXDOWN OF WINDS TO THE SURFACE.
THE WEAKEST CIN SHOULD BE NEAR LAKE CUMBERLAND AND THE KY/TN
BORDER, SO THAT WILL BE THE PRIMARY AREA TO WATCH FOR THE GUSTIEST
WINDS. MOST AREAS SHOULD JUST SEE A BLUSTERY BREEZE AS THE
SHOWERS AND STORMS ARRIVE, AND THEN SHOULD EXPERIENCE A PERIOD OF
RAIN WITH OCCASIONAL THUNDER. SOME MINOR POOR-DRAINAGE FLOODING
CANNOT BE RULED OUT WITH THIS INITIAL ROUND, BUT THE OVERALL
PROGRESSIVE NATURE OF THESE SYSTEMS AND A COUPLE DAYS OF DRYING
SHOULD MITIGATE ANY MORE SIGNIFICANT HYDRO CONCERNS.
ONCE THE REMNANTS OF THAT CONVECTION AND THE ATTENDANT UPPER-LEVEL
SUPPORT MOVE EAST, IT APPEARS THE COLD FRONT WILL SLOWLY SAG TO NEAR
THE LOWER OHIO RIVER BY MIDDAY, BUT WITH LITTLE FANFARE AS
INSTABILITY REMAINS WEAK AND NEGATIVE DIFFERENTIAL VORTICITY ADVECTION
INITIALLY SUPPRESSES LIFT. ANOTHER PERTURBATION DOES PASS THROUGH THE
APPROACHING 500HPA TROUGH AXIS THIS EVENING AND IS QUITE LIKELY
TO KICK OFF CONVECTION OVER TENNESSEE WHERE THERE IS BETTER
OPPORTUNITY FOR AFTERNOON DESTABILIZATION; CONFIDENCE IN
SUFFICIENT DESTABILIZATION FOR RENEWED CONVECTIVE DEVELOPMENT IS
LESS CERTAIN OVER EASTERN KENTUCKY, HOWEVER, THOUGH SOME OF THE
CAMS DO SUGGEST AT LEAST SCATTERED CONVECTION REDEVELOPING, MOSTLY
SOUTH OF THE MOUNTAIN PARKWAY. SHOULD CONVECTION DEVELOP AND BE
PERSISTENT, THE PARAMETER SPACE IS SUPPORTIVE OF TORRENTIAL
RAINFALL RATES WITH STORMS LATE TODAY INTO TONIGHT NEAR AND SOUTH
OF THE HAL ROGERS PARKWAY/KY-80 CORRIDOR. THE 500 HPA VORT MAX
PERTURBATION (EMBEDDED IN THE TROUGH AXIS) THEN SPINS ITS WAY
ACROSS KENTUCKY AND TENNESSEE DURING THE MORNING AND AFTERNOON ON
FRIDAY. CAMS VARY ON OVERALL CONVECTIVE COVERAGE BY MIDDAY OR
EARLY AFTERNOON, BUT OVERALL CONVECTIVE INTENSITY APPEARS ANEMIC.
AT THE SURFACE, A WEAK WAVE OF LOW PRESSURE WILL RIDE ALONG THE
COLD FRONT AS IT INCHES SOUTHEAST ACROSS THE JKL CWA. MODEL
SOUNDINGS REVEAL A RELATIVELY SKINNY CAPE PROFILE AND A LOT OF DRY
AIR IN THE MID AND UPPER LEVELS--SO IT SEEMS THAT CAMS ARE
INDICATING THAT CONVECTION WILL STRUGGLE TO DEVELOP AND MAINTAIN
DUE TO SIGNIFICANT DRY AIR ENTRAINMENT. THAT FRONT (OR WHATEVER
IS LEFT OF IT) WASHES OUT OR DRIFTS SOUTH OF THE AREA BY EVENING,
WITH ENOUGH DRY AIR SEEPING IN FOR GRADUAL CLEARING.
IN SENSIBLE WEATHER TERMS, LOOK FOR A ROUND OF SHOWERS WITH SOME
THUNDER MOVING FROM WEST TO EAST BETWEEN 6 AM AND 12 PM TODAY. A
FEW PLACES COULD EXPERIENCE A PERIOD OF STRONG WINDS AS THE
ACTIVITY ARRIVES. A PERIOD OF CLOUDS AND THEN SOME PARTIAL SUN
FOLLOWS THE SHOWERS AND STORMS HEADING INTO THE AFTERNOON BEFORE
ADDITIONAL HIT-AND-MISS SHOWERS AND STORMS DEVELOP LATE IN THE DAY
AND EVENING, WITH THE GREATEST CHANCES CLOSER TO THE TN AND VA
BORDERS. IT WILL BE SEASONABLY WARM WITH HIGHS IN THE LOWER TO MID
80S WHILE TONIGHT'S LOW TEMPERATURES RANGE IN THE MID TO UPPER
60S. FOR FRIDAY, LOOK FOR A MIX OF CLOUDS, SUN, AND PERHAPS A FEW
POP-UP SHOWERS OR PERHAPS A THUNDERSTORM WITH HIGHS RANGING
THROUGH THE MID 80S.
LONG TERM
(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 228 PM EDT WED AUG 19 2026
SOME SHOWERS AND STORMS WILL BE POSSIBLE AT THE START OF THE
EXTENDED PERIOD AHEAD OF A SAGGING COLD FRONT. THE PRIMARY
CORRIDOR FOR PRE-FRONTAL CONVECTION WILL INITIALLY RESIDE ALONG
AND SOUTH OF THE HAL ROGERS PARKWAY/KY-80 CORRIDOR TOWARD THE
TENNESSEE BORDER. ALOFT, THE BROAD PATTERN FEATURES A RIDGE OVER
THE WESTERN CONUS AND A TROUGH OVER THE EASTERN CONUS. WITH BROAD
TROUGHING MODELED OVER THE GREAT LAKES/NORTHEAST AND A DISTINCT
SHORTWAVE AXIS EXTENDING SOUTH- SOUTHWESTWARD THROUGH OH/IN/KY,
MID-LEVEL FORCING WILL LAG BEHIND THE SURFACE BOUNDARY. THIS
LINGERING PVA COMBINED WITH STEEPENING MID-LEVEL LAPSE RATES MAY
SUPPORT ISOLATED TO SCATTERED POST-FRONTAL CONVECTION FRIDAY
AFTERNOON, WITH THE GREATEST CHANCES REMAINING EAST OF THE
POTTSVILLE ESCARPMENT. GIVEN WEAK AMBIENT SHEAR, ANY ACTIVITY THAT
DEVELOPS SHOULD REMAIN PULSE-LIKE. WHILE PWATS REMAIN ELEVATED
BETWEEN 1.3 AND 1.6 INCHES (50TH TO 75TH PERCENTILE) INTO FRIDAY
EVENING, SIGNIFICANT MID-LEVEL DRYING WILL FILTER IN FROM THE
NORTHWEST, AS REFLECTED BY MODELED 700 MB RH DROPPING INTO THE
TEENS. CLEARING SKIES, CALM WINDS, AND STRONG SUBSIDENCE/CAPPING
UNDER HIGH PRESSURE WILL FAVOR AREAS OF FOG OVERNIGHT FRIDAY,
PARTICULARLY WITHIN THE RIVER VALLEYS.
AN EMBEDDED SHORTWAVE WITHIN THE LONGWAVE TROUGH IS MODELED TO
DIG OUT OF NORTHWESTERN CANADA INTO THE GREAT LAKES AND OHIO
VALLEY OVER THE WEEKEND. A REINFORCING COLD FRONT WILL CROSS
KENTUCKY, THOUGH TIMING DISCREPANCIES MAINTAIN UNCERTAINTY IN
POPS. REGARDLESS, PRECIPITATION CHANCES SHOULD REMAIN ISOLATED,
WITH THE HIGHEST POTENTIAL STAYING NORTHEAST OF THE FORECAST AREA.
HIGH PRESSURE BRIEFLY BUILDS ACROSS EASTERN KENTUCKY EARLY NEXT
WEEK, USHERING IN A COOLER AND DRIER AIRMASS. DEW POINTS LOWERING
INTO THE UPPER 50S AND LOWER 60S WILL BE A WELCOME RELIEF FROM
RECENT VALUES IN THE UPPER 60S TO LOWER 70S. DRY WEATHER PERSISTS
THROUGH TUESDAY BEFORE ANOTHER SHORTWAVE PROPAGATES OUT OF THE
UPPER MIDWEST INTO THE REGION MID-WEEK, BRINGING ISOLATED TO
SCATTERED SHOWER AND THUNDERSTORM CHANCES BACK TO THE FORECAST.
AVIATION
(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 150 AM EDT THU AUG 20 2026
VFR CONDITIONS PREVAILED AT THE TAF SITES AT 06Z. VALLEY FOG HAS
ALSO DEVELOPED ALONG MANY OF THE MAINSTEM RIVERS BUT IS NOT
EXPECTED TO REACH THE TERMINALS. INSTEAD, AN MCS PRESENTLY OVER
THE MID-MISSISSIPPI VALLEY IS EXPECTED TO PRESS EASTWARD AND
EVENTUALLY IMPACT ALL TERMINALS FOR A FEW HOURS BETWEEN 10 AND
16Z. THE PRECIPITATION IS LIKELY TO BRING A PERIOD OF SUB-VFR
FLIGHT CATEGORIES. AFTER A LULL, ADDITIONAL - MORE SCATTERED -
STORMS MAY DEVELOP ACROSS THE AREA INTO THE AFTERNOON AND EVENING.
WINDS, AWAY FROM ANY STORM, WILL BE LIGHT AND VARIABLE EARLY THIS
MORNING, BECOMING SOUTHWEST AROUND 5 KTS DURING THE DAYLIGHT
HOURS.
JKL WATCHES/WARNINGS/ADVISORIES
NONE.
SHORT TERM...GEERTSON
LONG TERM...GINNICK
AVIATION...GEERTSON/HAL/GREIF
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