Tuesday, February 05, 2008

Two PDS Watches


MESOSCALE DISCUSSION 0161
NWS STORM PREDICTION CENTER NORMAN OK
0336 PM CST TUE FEB 05 2008

AREAS AFFECTED...NRN LA AND AR

CONCERNING...TORNADO WATCH 36...

VALID 052136Z - 052300Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 36 CONTINUES.

...INCREASING RISK FOR LONG-LIVED SUPERCELLS WITH VERY LARGE
HAIL...DMGG WINDS AND STRONG TORNADOES THROUGH THE EVENING OVER A
LARGE PART OF AR AND NRN LA AND POINTS EWD...

21Z JACKSON SOUNDING SUGGESTS THAT THE CAP HAS ERODED. INCREASING
ASCENT SPREADING ACROSS THE UNSTABLE WARM SECTOR WAS RESULTING IN
NUMEROUS CONVECTIVE ELEMENTS SPROUTING INTO TSTMS. STRONG WIND
PROFILES AND MAGNITUDE OF LOW-LVL SHEAR IN PLACE /LZK VWP SRH 330+
M2/S2/ ARE FAVORABLE FOR SUPERCELLS WITH ATTENDANT RISKS FOR STRONG
TORNADOES...DMGG WINDS AND VERY LARGE HAIL. THE UNSTABLE WARM
SECTOR COVERS A LARGE REGION OVER THE MID-SOUTH AND ANY STORM THAT
BECOMES ESTABLISHED COULD BE LONG-LIVED.

LATER THIS EVENING...A COLD FRONT WILL BEGIN TO ENTER WRN PORTIONS
OF THE WW WITH ADDITIONAL RISKS FOR SVR TSTMS WITH ALL FACETS OF SVR
WEATHER PSBL.




   URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 37
NWS STORM PREDICTION CENTER NORMAN OK
310 PM CST TUE FEB 5 2008

THE NWS STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF

EASTERN ARKANSAS
SOUTHERN ILLINOIS
SOUTHWEST INDIANA
WESTERN KENTUCKY
SOUTHEAST MISSOURI
CENTRAL AND NORTHERN MISSISSIPPI
WESTERN TENNESSEE

EFFECTIVE THIS TUESDAY AFTERNOON FROM 310 PM UNTIL MIDNIGHT CST.

...THIS IS A PARTICULARLY DANGEROUS SITUATION...

DESTRUCTIVE TORNADOES...LARGE HAIL TO 2 INCHES IN DIAMETER...
THUNDERSTORM WIND GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE
POSSIBLE IN THESE AREAS.

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 85 STATUTE
MILES EAST AND WEST OF A LINE FROM 40 MILES NORTH OF CAPE
GIRARDEAU MISSOURI TO 25 MILES EAST OF JACKSON MISSISSIPPI. FOR
A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH
OUTLINE UPDATE (WOUS64 KWNS WOU7).

REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR
TORNADOES AND SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
AND POSSIBLE WARNINGS.

OTHER WATCH INFORMATION...CONTINUE...WW 34...WW 35...WW 36...

DISCUSSION...COMPLEX SITUATION EVOLVING THIS AFTERNOON WITH
SCATTERED THUNDERSTORMS DEVELOPING IN THE OPEN WARM SECTOR FROM MS
NWD INTO WRN TN/KY. ADDITIONAL SEVERE STORMS WILL MOVE INTO NW MS
FROM AR/LA...AND INTO TN/KY/IL/INDIANA FROM THE W BY EARLY TONIGHT
IN ASSOCIATION WITH THE PRIMARY SYNOPTIC SYSTEM NOW LOCATED FARTHER
TO THE W. MODERATE INSTABILITY AND BOUNDARY LAYER DEWPOINTS IN THE
60S COVER A WIDE AREA...WHILE LOCAL VWP/S AND FORECAST SOUNDINGS
SHOW STRONG VERTICAL SHEAR OVER THE MAJORITY OF THE WARM SECTOR.
THE NET RESULT WILL BE A THREAT FOR SCATTERED TORNADIC SUPERCELLS
THROUGH THE AFTERNOON...FOLLOWED BY SUPERCELLS/BOW ECHOES WITH THE
LATER CONVECTION TONIGHT. A FEW STRONG TORNADOES AND LARGE HAIL
WILL BE THE MAIN SEVERE THREATS THIS AFTERNOON...WHILE THE DAMAGING
WIND THREAT WILL INCREASE AS WELL INTO TONIGHT AS THE MORE
WIDESPREAD CONVECTION MOVES E OF THE MS RIVER.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 2 INCHES. EXTREME TURBULENCE AND SURFACE
WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
450. MEAN STORM MOTION VECTOR 23050.

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