Severe Thunderstorm Warning 75, NWS Jackson, KY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
300 PM EDT TUE JUN 20 2000

A WET OUTLOOK. WARM FRONT CURRENTLY MOVING NORTHEAST THROUGH THE
FORECAST AREA BRINGING IN A VERY MOIST AIRMASS. AT 12Z PRECIPITABLE
WATER FROM CENTRAL IL TO CENTRAL MS WAS RUNNING ABOVE 2 INCHES.
SHOWERS AND THUNDERSTORMS DEVELOPED OVER THE SOUTHWEST PART OF THE
AREA AND ARE DEVELOPING NORTHEASTWARD AS OUR ATMOSPHERE MOISTENS AND
A MID/UPPER LEVEL WAVE MOVES OVER FROM WEST TO EAST LATE TODAY.

SOME OF THE CONVECTION MAY LINGER PAST 00Z TONIGHT...BUT SHOULD THEN
SETTLE DOWN FOR A WHILE. LATE TONIGHT/TOWARD MORNING THE CHANCE OF
RAIN INCREASES AGAIN AS LOW LEVEL JET SINKS SOUTH BRINGING AN
UPGLIDE FEED OF WARM MOIST AIR. BEST CHANCE TOWARD MORNING WILL BE
IN THE NORTH AND WEST. THE ETA IS MOST IMPRESSIVE WITH THIS FEATURE
FOR EAST KY...BUT EVEN THE AVN AND NGM SHOW SOME PRECIP. WILL GO
WITH LIKELY POP NORTH AND WEST TONIGHT...THINKING THAT COMBINING THE
EVENING AND PREDAWN PERIODS WILL YIELD A POP THAT HIGH.
HOWEVER...EITHER EPISODE ALONE WOULD ONLY BE WORTHY OF A CHANCE POP.
WILL GO WITH ONLY A CHANCE POP SOUTHEAST...WHERE PREDAWN PROSPECT OF
RAIN IS LESS.

ON WEDNESDAY...RIGHT REAR QUADRANT OF UPPER JET WILL PROVIDE LIFT.
WITH LITTLE CAP ANTICIPATED WE SHOULD SEE MORE CONVECTION.  AS WARM
AS THE AIR MASS IS...HAIL WILL PROBABLY NOT BE A BIG CONCERN.
HOWEVER...WITH MID LEVEL SPEED MAX OF 40 TO 45 KNOTS MOVING
OVER...WOULD NOT RULE OUT SOME MARGINALLY SEVERE GUSTS.

DIFFERENCES SHOW UP AMONG MODELS ON WEDNESDAY NIGHT. THE NGM IS
MUCH MUCH FASTER WITH THE COLD FRONT THAN THE ETA OR AVN. THE NGM
HAS IT MIDWAY THROUGH EAST KY AT 00Z AND INTO VA BY 06Z. MODELS
TRENDS ARE SLOWER...AND WILL DISCOUNT THE NGM. THE ETA AND AVN DO
NOT HAVE FRONTAL PASSAGE UNTIL THE DAY THURSDAY. WILL GO WELL ABOVE
NGM MOS POPS FOR BOTH WEDNESDAY NIGHT AND THURSDAY.

ALTHOUGH RIVERS ARE NOT RUNNING HIGH...RECENT RAINS HAVE MOISTENED
THE SURFACE SOIL CONSIDERABLY. SMALL STREAM FLOOD ADVISORIES ARE
ALREADY BEING ISSUED THIS AFTERNOON.  WITH SUCH A MOIST AIR MASS AND
A SLOW FRONTAL PASSAGE...SMALL STREAM FLOODING COULD BE AN EVEN
LARGER CONCERN IN THE SECOND OR THIRD PERIOD.  WILL NOT ISSUE A
WATCH AT THIS TIME...BUT LATER SHIFTS WILL NEED TO MONITOR THIS.

THINK THAT NGM SURFACE DEW POINTS ARE A LITTLE TOO LOW ON WEDNESDAY.
AS A RESULT...CONVECTIVE TEMPERATURES WOULD BE LOWER THAN SUGGESTED
BY THE NGM. THIS TRANSLATES INTO NGM MOS TEMPS WHICH ARE PROBABLY
TOO HIGH. WILL UNDERCUT BY SEVERAL DEGREES. WITH FRONTAL PASSAGE
EXPECTED TO BE SLOWER THAN THE NGM SUGGESTS...NGM MOS LOW TEMPS ARE
PROBABLY A FEW DEGREES TOO COOL ON WEDNESDAY NIGHT. CONVERSELY...NGM
MOS LOOKS TOO WARM ON THURSDAY.

.JKL...NONE.

HAL