Severe Thunderstorm Warning 188, NWS Jackson, KY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
248 PM EDT THU AUG 17 2000

DYING MCS ASSOCIATED WITH WARM FRONT IS NICKING THE
NORTHERN PART OF THE AREA THIS AFTERNOON...WITH PRECIP EXTENDING
NORTHEAST. ALTHOUGH NOT NAILED BY ANY OF THE MODELS...IT WAS BEST
DEPICTED BY THE ETA/MESOETA. THE NGM AND AVN HAVE NOT HANDLED THIS
AS WELL...WITH THE NGM CONSISTENTLY MISPLACING THE HEAVIEST PRECIP
AND THE AVN HARDLY PICKING UP ON IT. DESPITE THE DISPARITY BETWEEN
THE MODELS EARLY ON...THERE IS DECENT AGREEMENT FOR THE FORECAST
AREA AFTER TODAY. WITH THE BETTER PERFORMANCE OF THE ETA EARLY
ON...WILL RELY MOST HEAVILY ON IT FOR THIS PACKAGE. THE MAIN CONCERN
IS HOW HIGH TO HAVE THE POPS TONIGHT AND FRIDAY...AND THE THREAT OF
SEVERE THUNDERSTORMS.

AS THE ATMOSPHERE DESTABILIZES THIS AFTERNOON...CONVECTION IS EXPECTED TO
FIRE IN THE CONVERGENT FLOW OF THE LOW LEVEL SPEED MAX TO THE
NORTHWEST OF KY.  MCS SHOULD THEN MOVE/PROPAGATE SOUTHEAST.  ALL
MODELS DEPICT SIGNIFICANT PRECIP FOR THE NORTHEASTERN HALF OF THE
AREA TONIGHT...AND WILL GO WITH CATEGORICAL POPS THERE AS SUGGESTED
BY NGM MOS. WILL GO WITH LIKELY WORDING SOUTHWEST.

POTENTIAL FOR HEAVY RAINFALL EXISTS...WITH PRECIPITABLE WATER
FORECAST BY THE ETA TO REACH 2 INCHES. HOWEVER...IT HAS BEEN A WHILE
SINCE SIGNIFICANT RAIN AND FLASH FLOOD GUIDANCE IS RUNNING
HIGH...GENERALLY 1.5 INCHES IN ONE HOUR AND 2.5 INCHES IN 3 HOURS.
THE AREA HAS NOT BEEN PRIMED FOR AN EVENT AND WILL NOT USE A FLASH
FLOOD WATCH AT THIS TIME.

SEVERE POTENTIAL ALSO EXISTS. CAPE IS EXPECTED FROM 2500 TO 3000
J/KG WITH SHEAR PRESENT. DUE TO HIGH WET BULB ZERO HEIGHTS PRIMARY
THREAT WOULD BE WIND.

ON FRIDAY THE COLD FRONT WILL STILL BE NORTHWEST OF THE AREA FOR
MUCH OF THE DAY...SLOWLY PROGRESSING SOUTHEAST ACROSS THE AREA
DURING THE AFTERNOON. IT WILL EVENTUALLY DISSOLVE AND REFORM EAST OF
THE MOUNTAINS ON FRIDAY NIGHT. ETA/MESOETA FORECAST SOUNDINGS DEPICT
AN INVERSION STRENGTHENING AROUND 700 MB DURING THE DAY...MAINLY IN
THE NORTH. WILL GO WITH CHANCE POPS...LOWEST IN THE NORTH AND
HIGHEST IN THE SOUTH ON FRIDAY.

FRIDAY NIGHT THE FRONT WILL COMPLETE ITS DISSOLVING/REFORMING
PROCESS AND DRIER SURFACE AIR WILL MAKE ITS WAY IN. RESULT WILL BE
CLEARING.

ON SATURDAY DRY NORTHWEST FLOW ALOFT AND RELATIVELY COOL AND DRY
SURFACE HIGH PRESSURE TO OUR NORTHEAST WILL BRING US PARTLY SUNNY TO
SUNNY SKIES.

NGM MOS TEMPS APPEAR TO BE A COUPLE DEGREES TOO WARM ON FRIDAY. EVEN
THOUGH THE COLD FRONT WILL NOT BE THROUGH...CLOUDS AND POTENTIAL FOR
CONVECTION WILL PROBABLY LIMIT US TO 80 TO 85 INSTEAD OF MID 80S.
OTHERWISE...NGM MOS TEMPS SEEM REASONABLE OTHER PERIODS.

EXTENDED PERIODS... CANADIAN SURFACE HIGH PRESSURE OVER ONTARIO AT
THE START OF THE PERIOD SPLITS WITH ONE PIECE MOVING TO THE
MIDATLANTIC COAST BY TUESDAY. DRY NORTHWESTERLY UPPER FLOW PRESENT
THROUGHOUT. WILL CONTINUE WITH FORECAST OF DRY AND COMFORTABLE
WEATHER...ALTHOUGH AIR MASS SHOULD START TO MODIFY BY THE END OF THE
PERIOD.

.JKL...NONE.

HAL