Severe Thunderstorm Warning 18, NWS Nashville, TN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NASHVILLE TN
952 PM CST THU FEB 26 2009

.UPDATED DISCUSSION AT 952 PM...
WILL UPDATE THE ZONES AND THROW IN SOME GUSTS TO ACCOMPANY THE
SUSTAINED 10-25 MPH SPEEDS ACROSS THE CWA. OTW...STARTING TO SEE A
FEW SHOWERS OFF TO THE NW OF MIDDLE TN. SVR TSTM WATCH HAS BEEN
EXTENDED EASTWARD AND NOW INCLUDES 6 COUNTIES IN FAR WEST TN.

.UPDATED DISCUSSION AT 758 PM...
NOT MUCH GOING ON PRESENTLY ACROSS MIDDLE TN. GRADIENT SLOWLY
BEGINNING TO TIGHTEN AS THE FRONTAL BOUNDARY IS PUSHING ACROSS
CENTRAL MO AND INTO WESTERN AR. LINE OF SHOWERS AND STORMS IS
LOCATED JUST TO THE EAST OF THE ADVANCING BOUNDARY.

FOR THE FORECAST TONIGHT...LOOKS AS THOUGH THE SHOWER AND TSTMS
ACTIVITY WILL HOLD OFF UNTIL AFTER MIDNIGHT. LATEST TIME
EXTRAPOLATION HAS THE LINE REACHING WESTERN AREAS OF THE MID STATE
AROUND 08-10Z OR SO. THUS...LIKELY CATS WEST AND CHANCE CATS EAST
STILL LOOK TO BE FINE. BUT...FOR THE UPDATE WILL NEED TO HIT THE
AFTER MIDNIGHT WORDING A LITTLE HARDER.

SVR TSTM WATCH BOX IS INDICATED ACROSS AR IN ADVANCE OF THE LINE.
WILL THEREFORE CONTINUE TO MENTION THE POSSIBILITY OF SVR STORMS FOR
OUR WESTERN ZONES LATE.

OTW...WIND SPEEDS IN THE 15 TO 25 MPH RANGE STILL LOOK OK. 850 MB
JET WILL REACH THE 50KT LEVEL AS WE GO THROUGH THE OVERNIGHT SO THE
AFOREMENTIONED WIND SPEEDS SHOULD BE SUSTAINABLE.

AS FOR TEMPS...CURRENT FCST OK AS MINS IN THE 50S IS EXPECTED.

&&
.UPDATE...FOR 00Z AVIATION DISCUSSION
&&

.PREV DISCUSSION... /ISSUED 313 PM CST THU FEB 26 2009/

.SHORT TERM...AT 200 PM THIS AFTERNOON, IT WAS 67 DEGREES AT THE
NASHVILLE AIRPORT, WITH SOUTHERLY WINDS GUSTING AS HIGH AS 30 MPH.
SIMILAR TEMPERATURES AND WINDS WERE REPORTED ELSEWHERE AROUND THE
MID STATE, EXCEPT ALONG THE CUMBERLAND PLATEAU WHERE TEMPERATURES
HELD IN THE 50S.

WITH HIGHS IN THE 60S TODAY, ITS ALMOST HARD TO BELIEVE WE COULD BE
LOOKING AT SOME SNOW ON THE GROUND BY SATURDAY NIGHT AND SUNDAY
MORNING. HOWEVER, THATS THE WAY THINGS SEEM TO BE SHAPING UP.

MODEL RUNS HAVE BEEN VERY CONSISTENT WITH THE UNFOLDING WEATHER
EVENTS OVER THE NEXT SEVERAL DAYS, AND HERES THE SCOOP...

FIRST, WE WILL WATCH A LOW PRESSURE SYSTEM CRANK UP OVER THE MIDDLE
MISSISSIPPI VALLEY TONIGHT AND SWING RAPIDLY NORTHEAST TO THE
EASTERN GREAT LAKES BY SUNRISE FRIDAY. THIS WILL DRAG A COLD FRONT
THROUGH MIDDLE TENNESSEE ON FRIDAY, WHICH SHOULD REACH NORTHERN
ALABAMA BY 00Z SATURDAY. THERE WILL BE A POSSIBILITY FOR ISOLATED
SEVERE STORMS WITH THIS COLD FRONT, STARTING IN OUR NORTHWESTERN
AREAS TONIGHT AND SPREADING INTO OTHER AREAS DURING THE DAY ON
FRIDAY. PRE-FRONTAL CONDITIONS ARE VERY SIMILAR TO WHAT WEVE SEEN
WITH MOST COLD FRONTS AS OF LATE: LOW CAPE, HIGH HELICITY
ENVIRONMENT, WITH DEW POINTS RISING INTO THE 50S JUST BEFORE THE
FRONT PASSES. WET-BULB ZERO VALUES ARE ALSO IN A GOOD RANGE FOR
THE POTENTIAL FOR LARGE HAIL (BETWEEN 9K AND 10K FT.) SPC HAS
PLACED MUCH OF OUR AREA IN A SLIGHT RISK AREA FOR FRIDAY.

EXPECT ISENTROPIC OVERRUNNING TO DEVELOP FRIDAY NIGHT AS A COLD
CORE, CLOSED UPPER LOW DROPS SOUTHEASTWARD OUT OF THE NORTHERN
PLAINS. RAIN WILL SPREAD BACK TO THE NORTH ACROSS OUR AREA AND
CONTINUE DURING THE DAY ON SATURDAY. SINCE SURFACE WINDS WILL
REMAIN OUT OF THE NORTH ON SATURDAY, DONT EXPECT A WARM-UP.
INDEED, AS SURFACE LOW PULLS INTO THE CAROLINAS LATE IN THE DAY,
AND UPPER LOW DROPS TO NEAR MEMPHIS, EXPECT SOME RAPID LATE-DAY
COOLING, WITH A TRANSITION TO ALL SNOW ACROSS OUR NORTHWESTERN
COUNTIES BY LATE AFTERNOON. EXPECT A CHANGE-OVER TO SNOW OVER
OTHER PARTS OF THE MID STATE SATURDAY EVENING, WITH SNOW TAPERING
OFF FROM WEST TO EAST SUNDAY MORNING. RIGHT NOW, IT LOOKS LIKE
MOST AREAS COULD SEE AT LEAST A BRIEF 3 TO 4 HOUR WINDOW WHEN THE
SNOW COULD COME DOWN PRETTY GOOD. WITH TEMPERATURES DROPPING INTO
THE UPPER 20S, WE WILL PROBABLY BE LOOKING AT A FLUFFY WET SNOW
THAT COULD EVEN SLUSH UP SOME ROADS IF IT COMES DOWN HARD ENOUGH.

HAVE UNDERCUT MOS MAX TEMPERATURES ON SUNDAY, WITH THE EXPECTATION
FOR SOME SNOW COVER.

.LONG TERM...AFTER THE POSSIBLE QUICKIE SNOW EVENT SATURDAY NIGHT
AND EARLY SUNDAY, EXPECT A TREND TOWARD DRY AND TRANQUIL
CONDITIONS FOR THE REST OF NEXT WEEK, WITH TEMPERATURES MODERATING
BACK TO CLIMATOLOGICAL LEVELS RATHER QUICKLY.
&&

.AVIATION...
STILL REMAINS SOME UNCERTAINTY ON EXACT TIMING OF PRE-FRONTAL
THUNDERSTORM DEVELOPMENT AND DEVELOPMENT OF THUNDERSTORMS ALONG
FAST MOVING COLD FRONT ITSELF. KEEPING EVERYTHING IN MIND...
BELIEVE MAIN AREA OF CONCERN WILL BE BETWEEN 10Z TO 12Z BNA AND
12Z TO 14Z CSV...WITH MVFR CEILINGS AND VISIBILITIES EXPECTED AT
BOTH LOCATIONS. WILL CONTINUE WITH MVFR CEILINGS THROUGH AT LEAST
14Z...WITH VFR CEILINGS AND VISIBILITIES THROUGH 00Z SAT.
&&

.OHX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

21

HAZARDOUS WEATHER OUTLOOK...CORRECTED TYPO
NATIONAL WEATHER SERVICE NASHVILLE TN
549 AM CST THU FEB 26 2009

TNZ005>011-022>034-056>066-075-077>080-093>095-271200-
STEWART-MONTGOMERY-ROBERTSON-SUMNER-MACON-CLAY-PICKETT-BENTON-
HOUSTON-HUMPHREYS-DICKSON-CHEATHAM-DAVIDSON-WILSON-TROUSDALE-
SMITH-JACKSON-PUTNAM-OVERTON-FENTRESS-PERRY-HICKMAN-LEWIS-
WILLIAMSON-MAURY-MARSHALL-RUTHERFORD-CANNON-DEKALB-WHITE-
CUMBERLAND-BEDFORD-COFFEE-WARREN-GRUNDY-VAN BUREN-WAYNE-LAWRENCE-
GILES-
549 AM CST THU FEB 26 2009

THIS HAZARDOUS WEATHER OUTLOOK IS FOR MIDDLE TENNESSEE.

.DAY ONE...TODAY AND TONIGHT

A COLD FRONT WILL MOVE TOWARD THE MIDSTATE LATE TONIGHT WITH SCATTERED
TO NUMEROUS SHOWERS AND THUNDERSTORMS...MAINLY AFTER MIDNIGHT.
SOME THUNDERSTORMS MAY BE SEVERE WITH DAMAGING WINDS AND HAIL...
MAINLY OVER THE NORTHWEST COUNTIES.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

THE COLD FRONT WILL MOVE THROUGH THE MIDSTATE ON FRIDAY AND BECOME STATIONARY
OVER ALABAMA AND GEORGIA FRIDAY NIGHT. SCATTERED TO NUMEROUS
SHOWERS AND THUNDERSTORMS ARE EXPECTED FRIDAY...MAINLY OVER THE
NORTH HALF IN THE MORNING AND THE SOUTH HALF IN THE AFTERNOON. SOME
THUNDERSTORMS MAY BE SEVERE WITH DAMAGING WINDS AND HAIL.

AS COLD AIR DIVES INTO THE MIDSTATE ON SATURDAY AFTERNOON AND
SATURDAY NIGHT...THE POTENTIAL FOR SNOWFALL WILL DEVELOP. SOME SNOW
ACCUMULATION IS POSSIBLE SATURDAY NIGHT.

.SPOTTER INFORMATION STATEMENT...

DUE TO THE BRIEF AND ISOLATED NATURE OF POSSIBLE SEVERE WEATHER...
SPOTTER ACTIVATION IS NOT ANTICIPATED. ALL SPOTTERS SHOULD KEEP
ABREAST OF THE WEATHER FORECAST IN THE EVENT OF CHANGES.

JLM

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NASHVILLE TN
314 AM CST FRI FEB 27 2009

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0305 AM     HAIL             DOVER                   36.48N 87.84W
02/27/2009  M1.00 INCH       STEWART            TN   EMERGENCY MNGR

&&

MGIRODO

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE NASHVILLE TN
329 AM CST FRI FEB 27 2009

TNZ006>008-022>027-056>061-271130-
MONTGOMERY-ROBERTSON-SUMNER-BENTON-HOUSTON-HUMPHREYS-DICKSON-
CHEATHAM-DAVIDSON-PERRY-HICKMAN-LEWIS-WILLIAMSON-MAURY-MARSHALL-
INCLUDING THE CITIES OF...CLARKSVILLE...SPRINGFIELD...GALLATIN...
CAMDEN...ERIN...WAVERLY...DICKSON...ASHLAND CITY...
KINGSTON SPRINGS...NASHVILLE...LINDEN...LOBELVILLE...
CENTERVILLE...HOHENWALD...FRANKLIN...BRENTWOOD...COLUMBIA...
LEWISBURG
329 AM CST FRI FEB 27 2009

A LINE OF STRONG THUNDERSTORMS IS PUSHING EAST ACROSS NORTHWEST
PORTIONS OF THE MID STATE. SOME WIND GUSTS NEAR 50 MPH HAVE BEEN
REPORTED...AND HAIL UP TO QUARTER SIZE. THIS LINE WILL AFFECT
AREAS INCLUDING DICKSON...WAVERLY AND ASHLAND CITY BY AROUND 4
AM....AND POSSIBLY REACH NASHVILLE BY 430 AM.

GIRODO