Severe Thunderstorm Warning 396, NWS Morristown, TN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KNOXVILLE/TRI-CITIES TN
310 PM EDT WED JUN 24 1998

SHORT-TERM...ISOLD TO WIDELY SCTRD RW/TSTMS CONT TO DVLP IN AREA
WHERE ADAP SHOWS CAP HAS ERODED.  THIS COINCIDES WITH WEAK MOISTURE
DISCONTINUITY AXIS EXTENDING FROM WESTERN WEST VIRGININA INTO
NORTHWESTERN NORTH CAROLINA.  WE FEEL THE CONVECTION IS PARTIALLY
TERRAIN INDUCED OVER SE KY...SWRN VA AND HIGHER TERRAIN OF NE TIP OF
TN.  HIGH CAPE AND UNIDIRECTIONAL (BUT WEAK) WIND PROFILE INDCS MAIN
THREAT WOULD BE ISOLD DAMAGING DOWNBURST WINDS (WINDEX PROGS 70+ KTS).
OF COURSE...THIS ALL MEANS THAT WE MAY NEED TO CONSIDER POPS FOR REST
OF THE AFTN INTO EARLY EVNG.  BY THE WAY...CRWS UPDATE TO 30% POPS IS
LOOKING LIKE AN EXCELLENT MOVE  TSTM MOVG INTO WISE COUNTY HAS PULSED
UP TO 61 VIL AND JUST ISSUED A SVR TSTM WARNING...WATCH NOW IN EFFECT
TIL 25/00Z.  FOR SURROUNDING NWS SITES...MID 50S VIL RECENTLY PRODUCED
DIME TO NICKEL SIZED HAIL IN SULLIVAN COUNTY TN...ALTHOUGH CELL DID
BRIEFLY INCRS TO AT LEAST LWR 60S VIL.

REST OF TNGT AND LATER PERIODS...RIDGE AT ALL LEVELS (SURFACE-500MB)
CONTINUES TO AMPLIFY FORCING SHORTWAVE ENERGY OVER THE TOP OF THE
RIDGE AND INTO SOUTHERN CANADA.  WITH NO SYNOPTIC SCALE BOUNDARIES
TO FOCUS CONVERGENCE...CONVECTION SHOULD BE EVEN LESS SCATTERED THAN
IT IS TODAY.  THE PREFERRED OROGRAPHIC CONVERGENCE ZONES...SUCH AS THE
CUMBERLAND PLATEAU AND SPINE OF THE APPALACHAIN MOUNTAINS WILL...
ONCE AGAIN...SERVE AS THE ONLY FOCUSING MECHANISMS. FURTHERMORE...
ATMOSPHERE SHOULD BE SLIGHTLY MORE STABLE THAN IT IS TODAY DUE TO
WARMING TEMPERATURES AT 850 AND 700 MBS...HENCE...LESS CAPE AND LESS
CHANCE OF SEVERE CONVECTION.

IN THE LONG RUN...ENERGY FROM STRONG SHORTWAVE DIGGING INTO THE
PACIFIC NORTHWEST ON FRIDAY WILL SERVE TO FLATTEN THE UNSEASONABLY
STRONG RIDGE FIRMLY IN PLACE OVER THE EASTERN HALF OF THE UNITED
STATES.  THIS MAY HELP TO INCREASE THE CHANCES OF SHOWERS AND
THUNDERSTORMS ON SATURDAY...BUT WILL NEED TO WATCH CLOSELY FOR NOW.

FOR TONIGHT AND TOMORROW...WOULD SUGGEST ADJUSTING HIGH TEMPERATURES
ON THURSDAY TO NEAR 90 IN THE SMOKY MOUNTAINS AND UPPER 90S FOR
CHATTANOOGA.  WOULD ALSO SUGGEST NEAR 90 FOR THE SOUTHWEST VIRGINIA
COUNTIES IN OUR CWA.  PARTLY SUNNY WORDING IS GOOD FOR TOMORROW
AFTERNOON...GIVEN AMOUNT OF BOUNDARY LAYER MOISTURE.  MAY NEED TO
MONITOR FOG POTENTIAL OVERNIGHT FOR ANY LOCATIONS IN NORTHEAST
TENNESSEE AND SOUTHWEST VIRGINIA THAT RECEIVE RAINFALL THIS EVENING.

TG/DD