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

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FXUS64 KMRX 171850
AFDMRX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MORRISTOWN TN
250 PM EDT WED SEP 17 2014

.SHORT TERM (TONIGHT THROUGH FRIDAY NIGHT)...CURRENT SURFACE
ANALYSIS SHOWS A QUASI-STATIONARY FRONTAL BOUNDARY OVER THE DEEP
SOUTH...WITH AN INVERTED TROUGH EXTENDING NORTH OF IT OVER THE
SOUTHERN APPALACHIANS. RADAR AND SATELLITE IMAGERY REVEAL A
MESOSCALE CONVECTIVE SYSTEM OVER THE OZARKS...WHICH WAS MOVING
SOUTHWARD BUT ITS ASSOCIATED HIGH CLOUDS WERE MOVING SOUTHEASTWARD
ACROSS THE TN RIVER VALLEY. ADDITIONAL MOISTURE OVER THE MID MS
RIVER VALLEY WILL MOVE TOWARDS THE FORECAST AREA LATER TONIGHT...SO
THINK THAT ANY FOG DEVELOPMENT LATER TONIGHT SHOULD BE PATCHY AND
MAINLY NEAR AREA WATERWAYS. AN AREA OF HIGH PRESSURE OVER THE MID
WEST THIS AFTERNOON IS PROGGED TO SLOWLY DRIFT EASTWARD INTO THE
NORTHEAST BY FRIDAY...WHICH WILL PRODUCE AN EASTERLY FLOW OVER THE
CAROLINAS. MODELS INDICATE THAT THIS EASTERLY UPSLOPE FLOW WILL
TRIGGER ISOLATED CONVECTION OVER THE SOUTHERN APPALACHIAN MOUNTAINS
ON THURSDAY AND FRIDAY AFTERNOONS...SO WILL INCLUDE A SLIGHT CHANCE
POP IN THESE ZONES. AS FOR TEMPS...GFS AND NAM GUIDANCE NUMBERS ARE
IN GENERAL AGREEMENT THROUGH FRIDAY NIGHT...BUT WILL COMPROMISE
BETWEEN THE TWO WHERE SLIGHT DIFFERENCES ARE NOTED.

.LONG TERM (SATURDAY THROUGH WEDNESDAY)...THE PERIOD STARTS OUT DRY
ON SATURDAY AS THE SOUTHERN APPALACHIAN REGION AWAITS ANOTHER
AMPLIFYING UPPER LEVEL TROUGH AND ASSOCIATED COLD FRONT. MODEL
FORECASTS HAVE SLOWED THIS FEATURE DOWN WITH THE BRUNT OF THE SYSTEM
NOT ARRIVING UNTIL SUNDAY NIGHT INTO MONDAY...SO TWEAKED POPS BACK
A BIT ON THE FRONT END. STILL NOT A GREAT DEAL OF LOW LEVEL
MOISTURE BECOMES ENTRAINED IN THIS SYSTEM...WITH LOW LEVEL RIDGING
REFUSING TO BREAK DOWN TO LARGE DEGREE AHEAD OF THE LOW LEVEL
TROUGH/SURFACE FRONT. SO NOT MUCH MOISTURE AND LIMITED CONVERGENCE
AT THIS TIME ARGUES FOR THE PROBABILITY OF SHOWERS AND THUNDERSTORMS
TO REMAIN IN THE CHANCE CATEGORY. WENT WITH A GO SLOW APPROACH TO
THE DEPARTURE OF THIS SYSTEM ON MONDAY...WITH SOME TRAILING
MOISTURE AN ENERGY BUILDING INTO THE BACK SIDE OF THE DEPARTING
UPPER TROUGH. KEPT TUESDAY AND WEDNESDAY DRY. HOWEVER...MODELS ARE
MOVING IN THE DIRECTION OF THE DEVELOPMENT OF AN INVERTED SURFACE
TROUGH OVER THE MID SOUTH ABOUT TUESDAY INTO WEDNESDAY...WITH
INCREASING ATLANTIC MOISTURE AROUND THE BASE OF THE EASTERN U.S.
RIDGE.
&&

.PRELIMINARY POINT TEMPS/POPS...
CHATTANOOGA AIRPORT, TN             58  83  60  85 /   0   0   0   0
KNOXVILLE MCGHEE TYSON AIRPORT, TN  56  80  58  82 /   0   0   0   0
OAK RIDGE, TN                       56  80  58  82 /   0   0   0   0
TRI CITIES AIRPORT, TN              53  78  54  80 /   0   0   0   0
&&

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

$$

DMG/


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