Severe Thunderstorm Warning 17, NWS Jackson, KY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
330 PM EDT THU APR 20 2000

MOST SIGNIFICANT FACTOR IN THE FORECAST IS THE THREAT OF SEVERE
WEATHER IN THE FIRST PERIOD...ESPECIALLY IN THE WESTERN PORTION OF
THE FORECAST AREA. THE FORECAST PROCESS SHOULD BE EASED BY THE FACT
THAT THERE IS GOOD AGREEMENT AMONG MODELS ON THE EVOLUTION OF
SYSTEMS OVER THE NEXT COUPLE OF DAYS...WITH SOME TYPICAL DIFFERENCES
SHOWING UP.

ONE OF THESE DIFFERENCES IS THE SURFACE DEW POINTS ON THE ETA AND
NGM...WITH THE NGM BEING DRIER THAN THE ETA. AS A RESULT...THE NGM
IS WEAKER ON THE INSTABILITY. THERE IS GOOD AGREEMENT ON THE FORECAST
TEMPERATURE/MOISTURE PROFILE ALOFT. AT EARLY AFTERNOON...UPSTREAM
SURFACE DEW POINTS ARE FALLING IN BETWEEN THE FORECAST VALUES OF THE
ETA AND NGM. USING COMPROMISE VALUES GENERATES AN LI OF -3 TO -4 FOR THE
WESTERN EDGE OF THE AREA THIS EVENING...WITH A CAPE NEAR 1000.
ALTHOUGH THIS IS NOT PARTICULARLY STRONG INSTABILITY...WIND FIELDS
ARE IMPRESSIVE AND ARE DEFINITELY SUPPORTIVE OF SEVERE
WEATHER...EVEN WITHOUT STRONG INSTABILITY. THE ETA FORECASTS
HELICITY ON THE ORDER OF 150 TO 300...AND BOTH THE ETA AND NGM CARRY
WINDS OF 50 KTS PLUS FROM 850 MB ON UP. A LIMITING FACTOR FOR THE
EASTERN PART OF THE AREA MAY BE THE INABILITY FOR DEW POINTS TO
CLIMB. WE CURRENTLY HAVE LOW LEVEL WINDS WITH SOME DOWNSLOPE
COMPONENT AND JKL DEW POINT HAS BEEN HOVERING ONLY FROM 48 TO 50 DEG
F. SUSPECT THAT STORMS WILL BE WEAKENING AS THEY PROGRESS ACROSS THE
FORECAST AREA.

COLD FRONT SHOULD BE THROUGH THE AREA BY SHORTLY PAST MIDNIGHT. WILL
EXPECT A DECREASE IN PRECIP OVERNIGHT. BUT...ON FRIDAY WRAP AROUND
MOISTURE WILL MOVE BACK IN FROM THE NORTHWEST WITH MORE SHOWERS
LIKELY. THIS PERSISTS INTO FRIDAY NIGHT AND POSSIBLY SATURDAY...AND
WILL GO ABOVE NGM MOS POPS.

WILL NOT STRAY FAR FROM NGM MOS TEMPS. READINGS WILL BE STEADY OR
SLOWLY\ FALLING ON FRIDAY.

.JKL...NONE.

HAL

KYZ044-050>052-058>060-068-069-079-080-083>088-104-106>120-202200-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE JACKSON KY
221 PM EDT THU APR 20 2000

...SEVERE THUNDERSTORMS POSSIBLE TONIGHT...

THE STORM PREDICTION CENTER IN NORMAN OKLAHOMA INDICATES THAT THERE
IS A MODERATE RISK OF SEVERE THUNDERSTORMS THIS EVENING FOR A
PORTION OF EASTERN KENTUCKY. THE GREATEST RISK IS IN AN AREA
EXTENDING FROM MCCREARY AND WAYNE COUNTIES NORTHEAST TO FLEMING
COUNTY. THIS INCLUDES LARGER COMMUNITIES SUCH AS SOMERSET...
LONDON...MONTICELLO...IRVINE...STANTON...MOUNT STERLING...AND
FLEMINGSBURG. EAST OF THIS AREA THERE IS STILL A SLIGHT RISK OF
SEVERE THUNDERSTORMS OVER THE REMAINDER OF EASTERN KENTUCKY TONIGHT.

A STRONG LOW PRESSURE SYSTEM TRACKING EAST ACROSS THE SOUTHERN GREAT
LAKES WILL PUSH A COLD FRONT THROUGH EASTERN KENTUCKY TONIGHT.
THUNDERSTORMS WILL DEVELOP ALONG AND AHEAD OF THE FRONT.

THE BEST CHANCE FOR SEVERE THUNDERSTORMS IN THE MODERATE RISK AREA
WILL BE BETWEEN ABOUT 6 AND 10 PM EDT. AS THE COLD FRONT MOVES
THROUGH...THE GREATEST RISK OF SEVERE WEATHER WILL SHIFT EASTWARD
TOWARD THE EASTERN EDGE OF KENTUCKY BY MIDNIGHT. THE GREATEST THREAT
WILL BE FROM DAMAGING WINDS. HOWEVER...LARGE HAIL OR ISOLATED
TORNADOES CAN NOT BE RULED OUT...ESPECIALLY IN THE MODERATE RISK
AREA.

EMERGENCY MANAGERS AND SPOTTERS SHOULD REMAIN ALERT AND BE PREPARED
FOR ACTIVATION THIS EVZENING.

EVERYONE SHOULD REMAIN TUNED TO NOAA WEATHER RADIO (OR LOCAL MEDIA
SOURCES) FOR THE LATEST INFORMATION ON THIS DEVELOPING SITUATION.

HAL