Severe Thunderstorm Warning 114, NWS Jackson, KY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
323 PM EDT SUN AUG 26 2001

FEATURES TO CONTEND WITH ARE FAIRLY WEAK. MAIN PROBLEM WILL BE WHAT
LEVEL OF POP TO USE TONIGHT AND WHEN TO INCLUDE A POP AFTER TONIGHT.

WE ARE CERTAINLY UNSTABLE TO START. A FEW SCATTERED SHOWERS AND
STORMS HAVE POPPED SO FAR THIS AFTERNOON...BUT COVERAGE HAS BEEN
VERY LOW THUS FAR. THERE HAS BEEN VERY LITTLE IMPETUS FOR
CONVECTION. GUIDANCE POPS ARE ONLY 20 TO 40 PERCENT IN THE FIRST
PERIOD. ALL MODELS GENERATE LIGHT PRECIP OVER THE AREA. IN REALITY
IT SHOULD BE SCATTERED. WE ARE IN A RIGHT REAR QUAD OF UPPER JET AND
A WEAK 500 MB VORTICITY/TROUGH AXIS WILL BE SWINGING THROUGH FROM
THE NORTHWEST TONIGHT WHICH WOULD FAVOR PRECIP. CONVECTION HAS JUST
RECENTLY IGNITED TO OUR WEST ALONG TROUGH LEFT FROM DECAYING FRONTAL
BOUNDARY NEAR THE OHIO RIVER. WILL PLAN TO GO WITH A 40 TO 50
PERCENT POP IN ZFP IN ALL AREAS TONIGHT. WILL PROBABLY SCALE THIS
BACK WITHIN THE CHANCE CATEGORY IN THE CCF...SINCE PART OF THIS
CHANCE IS BEFORE 00Z...AND IT DOES NOT LOOK WORTHWHILE TO SPLIT OFF
AN EARLY EVENING PERIOD IN THE ZONES SINCE EVEN THEN WE ARE ONLY
DEALING WITH CHANCE POPS. WILL ALSO MENTION VALLEY FOG (DENSEST IN
ANY AREAS WHICH GET RAIN).

ON MONDAY THE MODELS SHOW A MID LEVEL INVERSION...MOST EVIDENT IN
THE HIGHER RESOLUTION MESO ETA AND LEAST EVIDENT IN THE LOWER
RESOLUTION AVN. ALL MODELS ALSO BRING MEAGER DRYING TO THE LOWER
LEVELS IN THE NORTH. MEANWHILE...THE SURFACE TROUGH DISSOLVES
FURTHER AND THE 500 MB TROUGH AXIS SHOULD BE PAST US. THIS
CONSIDERED...WILL USE A 20 PERCENT POP NORTH AND FOREGO MENTION OF
PRECIP. IN THE SOUTH LOW LEVEL MOISTURE WILL LINGER AND INSTABILITY
WILL CONTINUE...BUT WITH LITTLE OTHER SUPPORT FOR PRECIP WILL USE
JUST A 30 PERCENT POP...WHICH WILL AGAIN STILL BE ABOVE NGM MOS.

WITH LOSS OF HEATING ANY CONVECTION SHOULD DIE OFF MONDAY NIGHT AND
CU SHOULD DRY UP. WITH NIGHTS GETTING LONGER...FOG IS MORE AND MORE
PROMINENT. WITH LIGHT WINDS AND LACK OF STRONG DRYING...WILL PUT
VALLEY FOG IN THE FORECAST FOR MONDAY NIGHT.

ON TUESDAY ANOTHER SHORTWAVE SWINGS ACROSS THE GREAT LAKES AND
BRINGS A LITTLE STRENGTHENING TO THE MID/UPPER TROUGH CENTERED OVER
THAT AREA. AN ASSOCIATED SURFACE COLD FRONT IS SHOWN TO MOVE INTO KY
LATE TUESDAY OR TUESDAY NIGHT. THE TREND ON THIS FRONT IS SLOWER ON
BOTH THE ETA AND AVN SINCE THE 00Z RUN...AND WILL LEAN TO THE SLOWER
OF THE TWO MODELS WHICH IS THE ETA. THIS BEING THE CASE...WILL NOT
INTRODUCE PRECIP DURING THE DAY TUESDAY...BUT WILL INCLUDE A SMALL
CHANCE TUESDAY NIGHT.

ASSUMING THIS FRONT BRINGS IN A DECENT DRY PUSH...WILL STICK
WITH A DRY FORECAST FOR WEDNESDAY AND THURSDAY. UNCERTAINTIES BEYOND
THIS AS TO AMPLITUDE OF MID/UPPER FEATURES AND ASSOCIATED
STRENGTH/POSITION OF SURFACE FEATURES. BEST ESTIMATE IS THAT ANOTHER
FRONT WILL APPROACH TOWARD THE WEEKEND. WILL USE JUST A LOW CHANCE
EACH PERIOD WHICH IS AT LEAST SUPPORTED BY CLIMATOLOGY.

.JKL...NONE.

HAL