261
FXUS63 KJKL 200805
AFDJKL
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
405 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 REDEVELOPMENT/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 NIGHT THROUGH WEDNESDAY)
ISSUED AT 405 AM EDT THU AUG 20 2026
AT THE ONSET OF THE LONG TERM PERIOD, A HIGH AMPLITUDE UPPER
LEVEL PATTERN WILL BE IN PLACE, WITH DEEP TROUGHING OVER THE
EASTERN CONUS AND STRONG RIDGING OVER THE WESTERN CONUS. AT THE
SURFACE, A WEAK HIGH WILL SIT TO THE NORTHWEST OF THE FORECAST
AREA; MEANWHILE, AN AREA OF LOW PRESSURE WILL BE LOCATED NEAR LAKE
MICHIGAN, WITH A COLD FRONT DRAPED TO ITS SOUTHWEST. BY FRIDAY
NIGHT, SHOWERS AND STORMS WILL BE EXITING THE FORECAST AREA AS
PREVIOUS SHORTWAVE FORCING DEPARTS. OVERNIGHT, SKIES WILL CLEAR
SOMEWHAT, ALLOWING FOR TEMPERATURES TO COOL INTO THE LOW TO MID
60S, WITH WIDESPREAD FOG DEVELOPING.
BY SATURDAY AFTERNOON, ANOTHER SHORTWAVE WILL MOVE THROUGH THE
EASTERN CONUS TROUGH, WHICH WILL PUSH THE AFOREMENTIONED COLD
FRONT SOUTHEAST INTO THE FORECAST AREA. IN THEORY, THIS COULD
BRING ANOTHER ROUND OF SHOWERS AND STORMS, ALTHOUGH MODEL SPREAD
REMAINS QUITE HIGH AT THIS TIME. WITH EASTERN KENTUCKY SITTING IN
CLOSE PROXIMITY TO THE UPPER LEVEL TROUGH AXIS ON SATURDAY, ANY
DIFFERING SPEED IN THE MOTION OF THIS TROUGH COULD HAVE
IMPLICATIONS FOR POPS. ACCORDINGLY, NBM OUTPUT KEEPS RAIN CHANCES
ISOLATED FOR MUCH OF THE FORECAST AREA TO ACCOUNT FOR THIS
UNCERTAINTY. FOLLOWING THE PASSAGE OF THIS FRONT, HEIGHT RISES ARE
ANTICIPATED AS THE WESTERN RIDGE CONTINUES TO PROGRESS EASTWARD
AND THE TROUGH BECOMES LESS AMPLIFIED.
FROM SUNDAY THROUGH EARLY NEXT WEEK, RIDGING WILL DOMINATE THE
FORECAST. BEHIND SATURDAY'S COLD FRONT, A MUCH DRIER AIR MASS
WILL BE IN PLACE. NORTHERLY TO NORTHEASTERLY WINDS WILL MAINTAIN
DEWPOINTS IN THE LOW 60S TO EVEN UPPER 50S, WITH RAIN CHANCES NEAR
ZERO. HIGH TEMPERATURES WILL RANGE FROM THE LOW TO MID 80S ACROSS
THE FORECAST AREA. OVERNIGHT, LOWS WILL FALL INTO THE UPPER 50S
IN MANY VALLEY LOCATIONS AND THE LOW 60S ELSEWHERE, WITH TYPICAL
FOG FORMATION EXPECTED. THIS TRANQUIL WEATHER WILL CONTINUE UNTIL
MIDWEEK, WHEN AN ADDITIONAL DISTURBANCE LOOKS TO APPROACH THE
AREA.
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...FAGAN
AVIATION...GEERTSON/HAL/GREIF
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