This is basically a pre-watch and means that the SPC is talking about issuing a watch for this area soon. They are saying there is an 80% chance that they will issue a tornado watch for the area shaded in red.
Here is the official statement from the SPC:
MESOSCALE DISCUSSION 0132 NWS STORM PREDICTION CENTER NORMAN OK 0929 PM CST THU FEB 20 2014 AREAS AFFECTED...ERN KY...ERN TN...PARTS OF NRN GA...FAR SWRN VA/NC CONCERNING...SEVERE POTENTIAL...WATCH LIKELY VALID 210329Z - 210430Z PROBABILITY OF WATCH ISSUANCE...80 PERCENT SUMMARY...A NEW WW WILL BE COORDINATED WITH AFFECTED WFO/S FROM ERN KY...ERN TN INTO PARTS OF NRN GA...AND FAR SWRN VA/NC. DISCUSSION...TRENDS IN REGIONAL RADAR IMAGERY THROUGH 0315Z SHOWED A WELL-DEFINED FAST MOVING /ENE AT 50 KT/ QLCS EXTENDING FROM SOUTH CENTRAL KY THROUGH MIDDLE TN /E OF BNA/ TO NWRN AL AND INTO ERN MS. DESPITE A MODESTLY UNSTABLE ENVIRONMENT WITH ERN EXTENT...THE STRENGTH OF THE PARENT MS VALLEY MID-UPPER LEVEL TROUGH BEING FURTHER INTENSIFIED AS A SHORTWAVE TROUGH MOVES INTO THE BASE OF THIS SYSTEM IS EXPECTED TO SUPPORT A CONTINUED SEVERE WEATHER THREAT INTO ERN KY...ERN TN...NRN GA AND ADJACENT PARTS OF NC/VA. THE STRENGTHENING OF THE SYSTEM IS ALSO EVIDENT IN THE STRONG SURFACE PRESSURE RISES EXTENDING FROM THE LOWER OH VALLEY TO E TX...ENHANCING THE EWD MOVEMENT OF THE COLD FRONT TOWARD THE QLCS. IN ADDITION TO A CONTINUED THREAT FOR DAMAGING WINDS...LOW LEVEL AND DEEP LAYER SHEAR WILL FURTHER SUPPORT EMBEDDED MESOVORTICES IN THE QLCS FOR A TORNADO THREAT TO PERSIST. AREA VADS SHOW LOW LEVEL HODOGRAPH CURVATURE AND SFC-1 KM SHEAR OF 35+ KT SUPPORTIVE OF THE TORNADO THREAT. Again this means that the line of storms out west will be getting close enough for a watch pretty soon. We can expect a watch most likely to be issued by around 11:30 or Midnight and last through most likely around 7am.
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On a scale of 1-10 I am going with a 4 on this one for the threat for damaging winds and a very slim chance of a brief spinup.
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