National Weather Service United States Department of Commerce

Very Heavy Rain, Severe Thunderstorms, and High Flash Flood Risk moves into the Mississippi Valley and Midwest

Thunderstorms, some severe, with very heavy rain have moved into the Mid South and Tennessee Valley today. Flash flooding and severe thunderstorms will be possible from the central Gulf Coast to the Upper Great Lakes. The greatest threat of excessive rains will be in portions of the Lower and Middle Mississippi Valleys. This storm system has a history of producing life threatening flash floods. Read More >

Mesoscale Discussion #0440 issued at 0054 UTC 11 April 2009
MESOSCALE DISCUSSION 0440
NWS STORM PREDICTION CENTER NORMAN OK
0754 PM CDT FRI APR 10 2009
   
AREAS AFFECTED...CNTRL SC...FAR SRN NC
   
CONCERNING...TORNADO WATCH 135...
   
VALID 110054Z - 110200Z
   
THE SEVERE WEATHER THREAT FOR TORNADO WATCH 135 CONTINUES.
   
SUPERCELLS EMBEDDED WITHIN QLCS ACROSS UPSTATE SC/NERN GA SHOULD
PROGRESS EWD WITH ATTENDANT THREATS FOR DAMAGING WINDS...ISOLATED
TORNADOES AND HAIL. HOWEVER...THE ERN EXTENT OF THE SEVERE THREAT
APPEARS UNCERTAIN GIVEN WEAKER INSTABILITY. AREA DOWNSTREAM OF WW
135 IS BEING MONITORED FOR EITHER A NEW WW OR POSSIBLE WFO AREAL
EXTENSION.
   
AS 0045Z...RADAR IMAGERY DEPICTED A QLCS STRETCHING FROM CHEROKEE
COUNTY SC TO CLARKE COUNTY GA WITH SEVERAL EMBEDDED MESOCYCLONES AND
BOWING SEGMENTS. THE OVERALL TREND FOR A LINEAR CONVECTIVE MODE
SUGGESTS THAT DAMAGING WINDS SHOULD BECOME THE PRIMARY SEVERE
THREAT...ALTHOUGH 0-1 KM SRH AOA 300 M2/S2 WILL SUPPORT POTENTIAL
FOR ISOLATED TORNADOES. CURRENT QLCS TRACK SHOULD APPROACH THE ERN
EXTENT OF WW 135 AROUND 02Z. HOWEVER...THE SEVERE THREAT SHOULD WANE
FARTHER E AS THE ACTIVITY PROGRESSES E OF ANSON COUNTY NC TO
ALLENDALE SC OWING TO AN APPARENT MARINE LAYER BOUNDARY NOTED
EARLIER ON VIS/RADAR IMAGERY. INSTABILITY SHOULD BE QUITE LACKING E
OF THIS LINE /AS DEPICTED IN 00Z CHS RAOB/. THUS...THERE IS
UNCERTAINTY WHETHER A NEW WW WILL NEED TO BE ISSUED OR WHETHER A
WFO-AREAL EXTENSION OF A FEW COUNTIES IN CNTRL SC WILL BE NEEDED.
   
..GRAMS.. 04/11/2009
   
   
ATTN...WFO...RAH...ILM...CHS...CAE...GSP...FFC...
   
LAT...LON   35098152 35168040 34977945 34427927 33138027 32608115
            32688203 33328254 34098255 34108244 35098152