Damaging Wind in Tennessee, June 2, 2001

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NASHVILLE TN
255 PM CDT SAT JUN 2 2001

FORECAST QUANDARIES...CONVECTION AMOUNT AND STRENGTH ASSOCIATED
WITH THIS EVENING/S FRONTAL PASSAGE...AND SUNDAY NIGHT INTO
MONDAY...TEMPS.

CURRENT ASOS/AWOS OBSERVATIONS AND REGIONAL SATELLITE/RADAR IMAGERY
DEPICTING BREAKS IN LOW LEVEL CLOUD COVER ACROSS CNTRL AND W
PORTIONS OF THE MID STATE...WITH SHRA ACTIVITY EXITING THE PLATEAU.
MSAS/HAND SFC ANALYSES SHOWING POSITION OF COLD FRONT...STRETCHING
FROM LOW IN E MI...SWD TO NEAR ERIN IN HOUSTON CO...AND JUST N OF
MEM. TEMPS SPANNING A WIDE RANGE...FROM MID 60S ACROSS THE PLATEAU
TO MID 70S S. GUSTY SW WINDS TO AROUND 20 MPH...WITH SOME DRYING OF
NOTE AS DEWPOINT DEPRESSIONS IN THE 10 TO 15 DEGREE RANGE...WITH
DEWPOINTS THEMSELVES UPPER 50S TO LOWER 60S. STRONG DEWPOINT GRADIENT
ACROSS THE CNTRL U.S...WITH DEWPOINTS LOWERING INTO THE 40 W
MISSOURI AND N OHIO RIVER VALLEY. DEWPOINT...INSTABILITY
PARAMETERS...AND THETA-E RIDGING JUST AHEAD OF THE FRONT.
RADAR MOSIAC IMAGERY SHOWING CONVECTION DEVELOPING ACROSS CNTRL KY.
RUC SHOWING UPPER AIR PATTERN STILL DOMINATED BY BROAD UPPER LEVEL
TROUGH ACROSS THE OHIO AND TN VALLEY/S...WITH A VORT MAX OVER EXTREME
W KY.

12Z SAT REGIONAL MODEL EVOLUTIONS THROUGH 12Z TUE IN GOOD GENERAL
AGREEMENT...ESPECIALLY IN THE UPPER LEVELS. ALL MODELS INITIALIZE
WELL WITH CURRENT UPPER LEVEL PATTERN AND ASSOCIATED LOW PRESSURE
POSITION. SIMILAR IN SFC FEATURES ALSO. HOWEVER...ETA BEST
INITIALIZED WITH STRENGTH OF SFC LOW IN E MI...AND CURRENT DEPICTION
OF FRONTAL POSITION AND STRENGTH. LATEST MODEL DIAGNOSTIC
DISCUSSION POINTING OUT THE VERY GOOD RUN TO RUN CONSISTENCY OF
THE ETA. WITH THESE REASONS IN MIND...WILL LEAN TOWARD AN ETA
SOLUTION.

FRONT MOVING SLOWER THAN PREVIOUSLY THOUGHT...AND NOW EXPECTED TO
PASS NEAR BNA BY 00Z SUN. WILL HAVE TO MONITOR THIS SITUATION
THROUGH PRESS TIME...WITH ABOVE MENTIONED INSTABILITY PARAMETERS
JUST AHEAD OF FRONT AND BREAKAGE OF LOW LEVEL CLOUD COVER THIS
AFTERNOON...POSSIBLE INGREDIENTS FOR LATE AFTERNOON OR EARLY EVENING
CONVECTION. RADAR MOSIAC SHOWING WIDELY SCT SHRA ACROSS THE N MID
STATE AT THIS TIME...AND WILL LEAN TOWARD ADDRESSING POPS DURING THIS
TIME PERIOD IN A WIDELY SCT FORMAT ALSO.

FRONT EXPECTED TO SAG E AND S OF CWA BY 06Z SUN...PUSHING INTO
CNTRL MS/AL BY 12Z SUN. UPPER LEVEL LOW FINALLY MOVING INTO
THE E GREAT LAKES BY 12Z SUN ALSO. FRONT WILL BECOME STATIONARY
DURING THE AFTERNOON HOURS AND DEVELOP WARM FRONTAL CHARACTERISTICS
BY 00Z MON. DURING THIS TIME PERIOD...LOOK FOR SFC HIGH PRESSURE TO
BUILD IN FROM THE MIDWEST...AS UPPER LEVEL FLOW ORIENTATES
ITSELF FROM A NWLY TO ZONAL FLOW PATTERN. ETA RH PROGS SHOWING THAT
ENOUGH LOW AND MID LEVEL MOISTURE WILL BE PRESENT...ALONG WITH
ADVECTION OF UPPER LEVEL MOISTURE FROM NWLY FLOW...THAT WILL
DIURNAL AFFECTS...VARIABLE SKY CONDITIONS COULD OCCUR ON SUN.
WILL CONTINUE WITH PARTLY CLOUDY W/CNTL...AND BECOMING PARTLY
CLOUDY E WORDING IN ZONES TONIGHT...WITH ALL AREAS EXPERIENCING
VARIABLE SKY CONDITIONS ON SUN. WARM FRONT TO OUR S AND W COULD
ACT AS A FOCUSING MECHANISM FOR AFTERNOON CONVECTION. WILL ADDRESS
SCT POPS SW ZONES TO WIDELY SCT N AND SE DUE TO THIS POSSIBLITY.

NEXT BEST CHANCE FOR RAINFALL WILL OCCUR AFTER 00Z MON...AS WARM
FRONT MOVES N AND INTO THE MID STATE BY 12Z MON. NCEP 6HR QFP
SHOWING PCPN A WIDE-SWATH OF PCPN OVER REGION THROUGH 12Z MON...
WITH HIGHER AMOUNTS TO OUR NORTH THROUGH 00Z TUE. DAY TWO
CONVECTIVE OUTLOOK PLACES W PORTIONS OF REGION IN SLIGHT RISK
...AND REST IN GENERAL CRITERIA THROUGH 12Z MON. SLIGHT RISK CRITERIA
WELL REFLECT BY ETA BNA/CSV SOUNDING PROFILES WITH HIGH
SWEAT/HELICITY/CAPE AND LI VALUES BY 12Z MON. FLY IN THE OINTMENT
AGAIN IS POSSIBLE MCS THAT MIGHT DEVELOP ACROSS KS/MS DURING THE
LATE AFTERNOON AND MOVE ESEWD. THIS PATH OR ANY DEVIATION TO ITS
RIGHT COULD CAUSE ADDITIONAL INSTABILTIY. INSTABILITY SHOULD CONTINUE
THROUGH 12Z TUE. WITH THIS IN MIND...WILL UP THE POPS TO
LIKELY W...SCT MIDDLE AND E. WILL CONTINUE WITH SCT POPS ALL AREAS
THROUGH 12Z TUE.

EXTENDED...SFC LOW IN CNTRL IL AND TRAILING COLD FRONT INTO W TX
...EXPECTED TO MOVE NEWD...DRAGGING FRONT TO NEAR BNA BY 12Z WED.
UPPER LEVEL PATTERN WILL PRESENT AN LOW OVER THE N GREAT LAKES...
WITH BROAD TROUGHING INFLUENCING THE AREAS WEATHER PATTERN BY
12Z WED ALSO. LOOK FOR FRONT AND UPPER LEVEL TROUGH TO MOVE E BY 00Z
THU. THIS ABOVE PATTERN WILL BRINGING SCATTERED SHRA AND TS TO
THE MID STATE THROUGH 00Z THU.

STRONG RIDGE IN UPPER LEVEL PATTERN WILL RESULT ACROSS THE SW U.S.
...WITH A DEEP TROUGH RESULTING TO OUR E. SFC HIGH PRESSURE
WILL BUILD IN FROM THE UPPER MIDWEST THROUGH 00Z SUN. THIS WILL
PROVIDE PARTLY CLOUDY THROUGH 00Z SUN.

TEMPS...GUIDANCE WAS TOO WARM ON LOWS LAST NIGHT...AND SEEM TO
CONTINUE THAT TREND TONIGHT. WILL UNDERCUT LOWS BY A FEW DEGREES
TONIGHT...AND MORE IN LINE WITH AVN MOS VALUES. WILL GO WITH
COMPROMISE SOLUTION BETWEEN MOS...FAN...AND ETA IN HOUSE BOUNDARY
TEMPERATURE SCHEME VALUES THROUGH THE PERIOD.

PRELIMINARY NUMBERS FOR COORDINATION PURPOSES ONLY...

BNA 054/076/063/083 2255
CSV 049/070/057/077 2145

.BNA...NONE.
14
JBW