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Jack’s

Saturday Evening Update: Severe Weather Moving Closer

Posted on: 5:37 pm, December 21, 2013, by , updated on: 07:11pm, December 21, 2013

Update: The Storm Prediction Center has issued a new tornado watch for much of Western and Southern Middle Tennessee until midnight. For more information click here.

Several reports of wind damage along with a couple of tornadoes have been produced by the line of severe thunderstorms moving into Western Tennessee, Northwestern Mississippi, and Louisiana this afternoon. The Storm Prediction Center has issued an update on the ongoing tornado watch affecting these areas.

mcd2104

For our weather savvy readers, the full text from the SPC can be found at the end of the post, but the basic gist is that widespread wind damage is likely  for portions of Mississippi and Louisiana as the line progresses slowly east, along with occasional tornadoes.

In the meantime here in the Tennessee Valley, we’re seeing a windy evening with scattered showers. The severe threat is currently limited with the ongoing showers  in North Alabama/Southern Tennessee, but the threat for wind damage as well as a possibility for isolated tornadoes will be increasing as the main line of storms moves into the area later tonight.

Radar

For additional information on how we expect things to unfold in the Tennessee Valley tonight and how you should prepare, see this post from earlier today.

-Brandon

Full text of mesoscale discussion from the SPC:

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 580...582...CONTINUES.

   SUMMARY...THE SEVERE THREAT WILL CONTINUE AS A LINEAR MCS MOVES INTO
   MIDDLE TN...WRN MS AND SE LA BY EARLY THIS EVENING. WIND DAMAGE WILL
   BE LIKELY AND TORNADOES WILL BE POSSIBLE WITH THE STRONGER LINES
   SEGMENTS AND ROTATING CELL ELEMENTS. WW ISSUANCE WILL BECOME LIKELY
   ACROSS PARTS OF THE MCD AREA AS THE LINE MOVES TOWARD THE ERN EDGE
   OF WW 580 AND WW 582.

   DISCUSSION...A WELL-DEVELOPED LINEAR MCS WILL CONTINUE MOVE QUICKLY
   EWD INTO THE TN VALLEY AND LOWER MS VALLEY FROM LATE THIS AFTERNOON
   INTO THE EARLY EVENING. SFC ANALYSIS SHOWS A SFC LOW NEAR THE MS
   RIVER SOUTH OF MEMPHIS WITH A COLD FRONT EXTENDING SWD FROM THE LOW
   JUST BEHIND THE SQUALL-LINE. ENHANCED LOW-LEVEL CONVERGENCE ALONG
   THE FRONT COMBINED WITH STRONG LARGE-SCALE ASCENT ASSOCIATED WITH A
   NEGATIVELY-TILTED SRN PLAINS UPPER-LEVEL TROUGH WILL HELP THE LINE
   TO REMAIN ORGANIZED THROUGH THIS EVENING. AHEAD OF THE
   SQUALL-LINE...AN AXIS OF INSTABILITY IS ANALYZED FROM SE LA NNEWD
   ACROSS WCNTRL MS INTO MIDDLE TN WITH MLCAPE ESTIMATED IN THE 600 TO
   1200 J/KG RANGE. IN ADDITION TO THESE FACTORS...THE WIND SHEAR
   ENVIRONMENT IS VERY FAVORABLE FOR SEVERE STORMS. THE WSR-88D VWP AT
   JACKSON MS SHOWS STRONG SPEED SHEAR FROM THE SFC TO 1 KM WITH A
   GRADUALLY VEERING PROFILE ABOVE THAT. THIS SHOULD BE FAVORABLE FOR
   TORNADOES WITH ROTATING CELLS EMBEDDED IN OR JUST AHEAD OF THE LINE.
   WIDESPREAD WIND DAMAGE WILL BE LIKELY WITH THE LINE DUE TO A FAST
   FORWARD NELY MOTION AROUND 50 KT.