Area Forecast Discussion
Issued by NWS Knoxville/Tri Cities, TN

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FXUS64 KMRX 020715
AFDMRX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MORRISTOWN TN
315 AM EDT TUE SEP 2 2014

.SHORT TERM (TODAY AND TONIGHT)...CURRENT SURFACE ANALYSIS SHOWS A
WARM AND VERY MOIST AIR MASS OVER THE FORECAST AREA...WITH A WEAK
COLD FRONT OVER THE MID MS RIVER VALLEY WHERE A LARGE MCS WAS
OCCURRING AHEAD OF IT. THIS COLD FRONT IS PROGGED TO SLOWLY
APPROACH THE TN RIVER VALLEY LATE THIS AFTERNOON...WITH A
MODERATELY TO POSSIBLY VERY UNSTABLE AIR MASS DEVELOPING AHEAD OF
IT OVER THE FORECAST AREA. MODEL SOUNDINGS FOR THIS AFTERNOON
REVEAL A FAIRLY STEEP LAPSE RATE UP TO AROUND 700 MB...WITH NOT
MUCH CONVECTIVE INHIBITION ABOVE THAT. THUS...THE POTENTIAL FOR
SEVERE STORMS APPEARS TO BE BETTER TODAY WITH CAPE VALUES IN THE
2000 TO 2500 J/KG RANGE...A DECENT MID LEVEL WIND FLOW AROUND 25
KT...AND AN INVERTED-V PROFILE BELOW 850 MB WHERE DRY AIR MAY HELP
TO ENCOURAGE STRONG DOWNDRAFTS. THE COLD FRONT SHOULD THEN SLOWLY
DRIFT ACROSS THE FORECAST AREA TONIGHT...WITH CONVECTION GRADUALLY
WEAKENING AFTER MIDNIGHT. AS FOR TEMPS...GFS AND NAM GUIDANCE
NUMBERS ARE IN GOOD AGREEMENT FOR TODAY AND TONIGHT...AND ARE
ESSENTIALLY A PERSISTENCE FORECAST.

.LONG TERM (WEDNESDAY THROUGH MONDAY)...A FAIRLY ZONAL UPPER FLOW
ACROSS THE UNITED STATES...EXCEPT FOR A SHORT-WAVE TROUGH MOVING
THROUGH SOUTHERN CANADA/NORTHERN GREAT LAKES FRIDAY AND SATURDAY.
THIS FAST MOVING TROUGH WILL PULL A FRONT INTO THE AREA FOR SATURDAY.

FOR WEDNESDAY...A STATIONARY FRONT WILL BE LOCATED NEAR THE
TENNESSEE/GEORGIA STATE-LINE WITH UPSLOPE FLOW INTO THE MOUNTAINS.
BEST CHANCES OF CONVECTION WILL BE ACROSS THE SOUTHEAST AND FAR
EASTERN TENNESSEE MOUNTAINS. THIS BOUNDARY LIFTS NORTH OVER THE AREA
THURSDAY PULLING MOISTURE/INSTABILITY BACK INTO THE REGION. MAIN
FORCING FOR STORMS THURSDAY AND FRIDAY WILL MAINLY BE THE LOCAL
TERRAIN.

FOR SATURDAY...COLD FRONT MOVES INTO THE AREA BEFORE STALLING AS
BOUNDARY BECOMES PARALLEL WITH THE UPPER FLOW. THIS BOUNDARY REMAINS
OVER THE AREA FOR SUNDAY AND MONDAY. HIGH CHANCE/LIKELY POPS
EXPECTED SATURDAY THROUGH MONDAY...ESPECIALLY OVER THE HIGH TERRAIN.

MAIN CONCERN THROUGH THE PERIOD WILL BE LOCALLY HEAVY RAINS...BUT
ISOLATED TO STRONG TO SEVERE THUNDERSTORMS POSSIBLE...ESPECIALLY FOR
SATURDAY.
&&

.PRELIMINARY POINT TEMPS/POPS...
CHATTANOOGA AIRPORT, TN             92  71  92  70 /  50  40  30  20
KNOXVILLE MCGHEE TYSON AIRPORT, TN  89  69  90  68 /  60  40  30  10
OAK RIDGE, TN                       89  69  91  67 /  60  40  30  10
TRI CITIES AIRPORT, TN              88  67  88  61 /  60  50  20  20
&&

.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...NONE.
VA...NONE.
&&

$$

DMG/DH


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