Severe Thunderstorm Warning 225, NWS Morristown, TN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MORRISTOWN TN
950 AM EDT SAT AUG 24 2002

THE FOLLOWING ARE ALL THE FORECAST DISCUSSIONS FROM THE PAST 24
HOURS...WITH THE MOST RECENT ON TOP. THIS PROVIDES A HISTORY OF THE
DEVELOPMENT OF THE CURRENT FORECAST.

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LATE MORNING FORECAST DISCUSSION (UPDATE)
950 AM EDT SAT AUG 24 2002

NO UPDATES PLANNED THIS MORNING.  SHOWERS HAVE DISSIPATED ACROSS THE
CWA...BUT STILL EXPECTING SCATTERED SHOWERS AND THUNDERSTORMS TO
REDEVELOP THIS AFTERNOON WITH AN UNSTABLE ATMOSPHERE AND A FEW
SHORTWAVES MOVING THROUGH.  COLD FRONT NOT EXPECTED UNTIL THIS
EVENING.  POPS AND TEMPERATURES LOOK GOOD.

GH

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EARLY MORNING FORECAST DISCUSSION
315 AM EDT SAT AUG 24 2002

MODELS CONTINUE TO ADVERTISE A SIGNIFICANT LONG WAVE PATTERN CHANGE
OVER THE NEXT FEW DAYS AS THE PERSISTENT UPPER RIDGE OVER THE
SOUTHEASTERN CONUS GIVES WAY TO A TROUGH. THIS TRANSITION WILL CAUSE
AN INCREASE IN POPS OVER OUR FORECAST AREA AS A COLD FRONT APPROACHES
LATE SATURDAY. HAVE CONTINUED WITH THE ONGOING CHANCE POPS IN THE
FIRST PERIOD. AN UPPER LEVEL CLOSED LOW IS PROJECTED TO DEVELOP OVER
THE SOUTHERN APPALACHIAN REGION BE EARLY MONDAY. LOWERING HEIGHTS
ASSOCIATED WITH THIS TRANSITION SUGGESTS THAT THE SIGNIFICANTLY ABOVE
CLIMATOLOGY TEMPS WILL COME TO AN END ALSO...AT LEAST TEMPORARILY.

MODEL TIME HEIGHTS SHOW MID AND UPPER LEVELS DRYING OUT CONSIDERABLY
BY LATE SATURDAY. THEREFORE...EXPECT PRECIP TO GENERALLY END BY THE
SECOND PERIOD. THUS...TEND TO FAVOR LOWER NGM MOS POPS THROUGH THE
REMAINDER OF THE NEAR TERM.

ONCE AGAIN...GUIDANCE TEMPS ARE GENERALLY CLOSE AND APPEAR
REASONABLE. HAVE NOT STRAYED VERY FAR FROM THOSE NUMBERS.

PRELIMINARY TEMPS AND POPS FOLLOW FOR COORDINATION:

CHA   92  72  91  70 /  40  20  10  10
TYS   89  69  88  68 /  50  20  10  10
TRI   85  65  84  62 /  50  20  10  10
OQT   89  69  87  67 /  50  20  10  10

.MRX...
NC...NONE.
TN...NONE.
VA...NONE.

LCM

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EVENING FORECAST DISCUSSION (UPDATE)
910 PM EDT FRI AUG 23 2002

LARGE AREA OF SHOWERS AND THUNDERSTORMS IN MIDDLE TN SEEM TO BE
HOLDING TOGETHER.  WILL UPDATE FORECAST TO INCREASE POPS EVERYWHERE
TO 30 PERCENT FOR THE REST OF TONIGHT.  TEMPERATURES STILL LOOK GOOD.

GH

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AFTERNOON FORECAST DISCUSSION
255 PM EDT FRI AUG 23 2002

CURRENT RADAR IMAGES SHOW SCATTERED TSTORMS ACROSS NORTHEAST TN AND
SOUTHWEST VA...WITH VIRTUALLY NO ECHOES OVER THE SOUTHERN AND CENTRAL
PORTIONS OF EAST TN. WITH A VERY MOIST AND MODERATELY UNSTABLE
AIRMASS IN PLACE...WILL CONTINUE WITH A MENTION EVERYWHERE OF
ISOLATED TSTORMS THIS EVENING. BY TOMORROW...A WEAK COLD FRONT WILL
PROVIDE A BETTER FOCUSING MECHANISM FOR CONVECTIVE DEVELOPMENT
ACROSS THE ENTIRE AREA. WILL CONTINUE WITH 50 POPS EVERYWHERE...WITH
SCATTERED CONVECTION EXPECTED TOMORROW. ALL MODELS INDICATE THAT THIS
FRONT WILL MOVE THROUGH THE FORECAST AREA BY 12Z SUNDAY. THUS...WILL
CONTINUE WITH A DRY FORECAST ON SUNDAY.

IN THE EXTENDED...AVN MODEL CONTINUES TO SHOW INCONSISTENCIES FROM
RUN TO RUN WITH THE HANDLING OF THE POSITION OF AN UPPER-LEVEL LOW
EARLY NEXT WEEK. HOWEVER...THE MORE CONSISTENT ECMWF MODEL CONTINUES
TO SHOW A STRONG UPPER-LEVEL LOW OVER THE TN VALLEY MONDAY THRU
WEDNESDAY. THUS...WILL CONTINUE WITH A MENTION OF SHOWERS AND TSTORMS
THESE THREE DAYS. MORE ISOLATED AND DIURNALLY DRIVEN CONVECTION IS
EXPECTED ON THURSDAY AND FRIDAY...AS THIS UPPER LOW MOVES NORTHEAST
OF THE AREA AND WEAKENS ACROSS THE MID-ATLANTIC STATES.

AS FOR TEMPS...WILL TREND TOWARD THE COOLER AVN NUMBERS TOMORROW
WITH THE EXPECTED INCREASE IN CLOUDS AND CONVECTION. OTHERWISE...
GUIDANCE NUMBERS ARE IN GOOD AGREEMENT THROUGH THE FORECAST PERIOD
AND LOOK REASONABLE.

THE FOLLOWING NUMBERS ARE PRELIMINARY AND FOR COORDINATION ONLY:

CHA   73  90  70  90 /  20  50  30  10
TYS   73  88  70  88 /  20  50  30  10
TRI   68  86  65  86 /  30  50  30  10
OQT   73  88  70  88 /  20  50  30  10

DMG