TN Valley Upgraded To Moderate Risk

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Moderate Risk For All of Tennessee Valley

   NWS Storm Prediction Center Norman OK
   0952 AM CDT Mon Mar 19 2018

   Areas affected...north-central and northern AL...northwest GA...far
   southern middle TN

   Concerning...Outlook upgrade 

   Valid 191452Z - 191615Z

   SUMMARY...An upgrade to a Moderate Risk categorical outlook (driven
   by a 15% significant tornado risk) is planned for the 1630Z outlook (10:30am CT).

   DISCUSSION...It appears increasingly probable the risk for several
   tornadic supercells will traverse across northern portions of AL
   late this afternoon and through the early evening.  Thunderstorm
   activity will be largely void across a large part of this area
   (north-central AL) prior to peak heating and a moderately unstable
   airmass is expected to develop by mid afternoon.  The arrival of a
   speed max in the mid-levels will correspondingly lead to a marked
   strengthening in low-level flow and increasing hodograph size, which
   will be more favorable for supercells and low-level mesocyclones. 
   Given these factors, confidence has increased such that a 15%
   significant tornado risk and the potential for longer lived
   supercells and damaging tornadoes will focus across north-central
   and northern AL, far southern middle TN beginning during the late
   afternoon/early evening, then moving east into northeast AL and far
   northwest GA later this evening.