Severe Thunderstorm Warning 227, NWS Morristown, TN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MORRISTOWN TN
300 PM 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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EVENING FORECAST DISCUSSION (UPDATE)
915 PM EDT SAT AUG 24 2002

MOST OF THE SHOWERS HAVE DIMINISHED OVER THE FORECAST AREA SO HAVE
UPDATED FORECAST TO REFLECT THIS CHANGE.  AVN MODEL SHOWS CURRENT
PRECIP OVER MIDDLE AND WEST TENNESSEE MAY IMPACT THE SOUTHERN VALLEY
LATER TONIGHT...SO HAVE LEFT CHANCE PRECIPITATION IN SOUTHEAST
TENNESSEE AND SOUTHWEST NORTH CAROLINA COUNTIES.

NO OTHER CHANGES.

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AFTERNOON FORECAST DISCUSSION
300 PM EDT SAT AUG 24 2002

CURRENT SURFACE ANALYSIS SHOWS A WEAK COLD FRONT ALONG THE OHIO AND
MID MISSISSIPPI VALLEYS...WITH AREA RADARS SHOWING SCATTERED TSTORMS
ACROSS THE FORECAST AREA. SOUNDINGS INDICATE THAT THE LOCAL AIRMASS
IS VERY MOIST (PRECIPITABLE WATER VALUES NEAR 2 INCHES) AND
MODERATELY UNSTABLE (LIFTED INDICES NEAR -6 AND CAPES AROUND 3500
J/KG). THUS...WILL PLAN TO CONTINUE A MENTION OF SCATTERED TSTORMS
OVERNIGHT AS THIS FRONT SLOWLY MOVES INTO THE AREA. MODELS ARE NOW
INDICATING THAT THIS FRONT WILL NOT MAKE IT THROUGH THE FORECAST AREA
UNTIL TOMORROW NIGHT...WHERE IT WILL LIKELY BECOME STATIONARY ALONG
THE SPINE OF THE APPALACHIANS. THUS...WILL INTRODUCE A MENTION OF
TSTORMS EVERYWHERE TOMORROW. AN UPPER-LEVEL LOW IS EXPECTED TO THEN
DEVELOP SUNDAY NIGHT ACROSS THE TN VALLEY...WHICH WILL HELP DEVELOP A
SURFACE LOW ALONG THIS STATIONARY FRONT ON MONDAY.

IN THE EXTENDED...MODELS INDICATE THAT THE UPPER-LEVEL AND SURFACE
LOWS WILL LINGER ACROSS THE TN VALLEY THROUGH THE REST OF THE WEEK.
THUS...WILL INCLUDE A MENTION OF SHOWERS AND TSTORMS EVERY DAY FROM
TUESDAY THROUGH SATURDAY. EXPECT MAINLY AFTERNOON AND EVENING
ACTIVITY...BUT WILL NOT MENTION THIS IN THE ZONES SINCE CONVECTION
COULD FORM ANY TIME DURING THE DAY OR NIGHT.

AS FOR TEMPS...WILL TREND TOWARD THE WARMER NGM AND ETA NUMBERS
THROUGH THE FORECAST PERIOD...SINCE BREAKS IN CLOUD COVER EXPECTED
WITH ONLY SCATTERED CONVECTION. TEMPS LOOK TO RETURN TO MORE SEASONAL
LEVELS FOR NEXT WEEK.

THE FOLLOWING NUMBERS ARE PRELIMINARY AND FOR COORDINATION ONLY:

CHA   72  88  68  86 /  30  40  30  40
TYS   70  87  66  84 /  30  30  30  40
TRI   66  85  63  82 /  30  20  30  40
OQT   70  87  66  84 /  30  30  30  40

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

DMG

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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

LCM

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