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000
FXUS64 KMRX 181911
AFDMRX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MORRISTOWN TN
310 PM EDT SAT MAY 18 2013

.SHORT TERM (TONIGHT THROUGH MONDAY NIGHT)...
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CURRENT SURFACE
ANALYSIS SHOWS A WEAK AREA OF LOW PRESSURE OVER THE WESTERN TN RIVER
VALLEY...WITH A WARM AND VERY HUMID AIR MASS OVER THE FORECAST AREA.
AREA RADARS REVEAL SCATTERED CONVECTION DEVELOPING OVER THE FORECAST
AREA THIS AFTERNOON...WHICH SHOULD CONTINUE TO INCREASE IN AREAL
COVERAGE AND INTENSITY AS DAYTIME HEATING COMBINES WITH AN UPPER-
LEVEL TROUGH TO PRODUCE A POTENTIALLY MODERATELY UNSTABLE AIR MASS
OVER THE FORECAST AREA. THE NAM MODEL ONLY REVEALS SOME MARGINAL
INSTABILITY OVER THE FORECAST AREA FOR LATER TODAY AND AGAIN ON
SUNDAY AFTERNOON...BUT THE GFS MODEL INDICATES MODERATE INSTABILITY
DEVELOPING (DUE TO ITS WARMER SURFACE TEMPS) WITH THE POTENTIAL FOR
A HIGHLY UNSTABLE AIR MASS AROUND THE CUMBERLAND PLATEAU ON SUNDAY
AFTERNOON AND AREAWIDE ON MONDAY AFTERNOON. IF THE GFS MODEL
VERIFIES...THINK THAT SOME ISOLATED SEVERE STORMS WILL BE POSSIBLE
ON SUNDAY AFTERNOON AND MONDAY AFTERNOON...WITH THE POSSIBILITY OF
DAMAGING WINDS...LARGE HAIL...AND LOCALLY HEAVY RAINFALL (DUE TO
SLOW-MOVING CONVECTION IN AN ENVIRONMENT WITH PRECIPITABLE WATER
VALUES RANGING BETWEEN 1.5 AND 1.75 INCHES). THIS SLOW-MOVING UPPER-
LEVEL TROUGH WILL FINALLY DRIFT EAST OF THE FORECAST AREA BY
MONDAY...BUT COOLER NORTHWEST FLOW ALOFT BEHIND THE TROUGH WILL HELP
TO DESTABILIZE THE LOCAL AIR MASS ALLOWING FOR ADDITIONAL SCATTERED
CONVECTION TO DEVELOP. AS FOR TEMPS...GFS AND NAM GUIDANCE NUMBERS
ARE IN GENERAL AGREEMENT THROUGH MONDAY NIGHT...BUT WILL COMPROMISE
BETWEEN THE TWO WHERE SOME SLIGHT DIFFERENCES ARE NOTED.

.LONG TERM (TUESDAY THROUGH SATURDAY)...A WARM...MOIST AIRMASS IN
PLACE EARLY IN THE EXTENDED WITH SOUTHWEST FLOW ALOFT. THE RESULT
WILL BE DIURNAL CONVECTION TUESDAY AND WEDNESDAY. BROAD...WEAK
FRONTAL BOUNDARY SLIDES THROUGH AROUND THURSDAY...AND WILL PROVIDE
OUR BEST CHANCE OF CONVECTION. TROUGH AXIS WILL MOVE THOUGH THURSDAY
NIGHT INTO FRIDAY...KEEPING UNSETTLED WEATHER OVER THE AREA.
SATURDAY CURRENTLY LOOKS TO BE OUR BEST SHOT AT A DRY DAY...AS THE
FRONTAL BOUNDARY PULLS AWAY FROM THE REGION.
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&&

.PRELIMINARY POINT TEMPS/POPS...
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CHATTANOOGA AIRPORT, TN   65  83  65  88  67 /  60  60  30  20  10
KNOXVILLE AIRPORT, TN     64  82  64  87  66 /  60  60  40  20  10
OAK RIDGE, TN             65  82  65  87  67 /  60  60  30  20  10
TRI CITIES AIRPORT, TN    59  80  59  85  61 /  70  70  40  30  10
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&&

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

$$

DMG/MJB