SPC AC 201624

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1124 AM CDT Tue Jun 20 2017

   Valid 201630Z - 211200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF
   WESTERN AND CENTRAL KS...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF
   SOUTHERN LA/MS...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE CENTRAL
   PLAINS STATES INTO THE DESERT SOUTHWEST...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PARTS OF
   IL/IN...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF
   THE NORTHERN GREAT BASIN INTO THE NORTHERN PLAINS...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PARTS OF
   THE CENTRAL GULF COAST REGION...

   ...SUMMARY...
   Severe thunderstorms are expected this afternoon and evening over
   parts of the central High Plains.  A few tornadoes may occur this
   afternoon through tonight over the central Gulf Coast.  Isolated
   severe storms also are possible over parts of Illinois and the mid
   Mississippi Valley, as well as from the northern Rockies and High
   Plains into South Dakota.

   ...KS...
   Southwesterly low-level winds are helping to transport rich low
   level moisture back into KS today, with dewpoints rising through the
   60s.  By mid/late afternoon, strong CAPE values are forecast to
   develop, leading to the development of scattered thunderstorms. 
   Favorably strong northwesterly flow aloft will promote supercell
   structures capable of large hail and damaging wind gusts.  The
   primary severe risk should remain well-focused in west-central and
   western KS as the low-level jet strengthens this evening.

   ...LA/MS Coast...
   PTC #3 continues to slowly organize in the central Gulf of Mexico. 
   as the circulation drifts northwestward, and low-level winds
   strengthen in the northeast quadrant of the circulation, the
   potential for a few rotating cells and isolated tornadoes will
   increase.  Current indications are the best chance of tornadoes will
   be this evening across parts of southern LA and the immediate MS
   coast.

   ...IL/IN...
   Water vapor loop shows a fast-moving upper trough tracking
   southeastward across MN/WI.  This feature will promote scattered
   thunderstorm development this afternoon over parts of northern and
   central IL.  Storms will also eventually spread into parts of IN. 
   Vertical shear profiles are quite favorable for severe storms. 
   However, forecast soundings show that unstable layer will be
   relatively shallow due to a large mid/upper level inversion across
   the region.  The stronger cells may produce gusty/damaging winds and
   hail, but the complex thermodynamic structure limits confidence in a
   greater severe threat.

   ...MT/WY/SD...
   A few thunderstorms are expected to develop over the mountains of
   southwest and southern MT today, and spread east-southeastward into
   parts of northern WY and eventually into western SD.  The strongest
   of these storms may produce hail and gusty winds.

   ...Eastern ID/Western WY into Northern UT...
   Widely scattered high-based thunderstorms are expected to develop
   over parts of eastern ID and northwest UT this afternoon, spreading
   eastward across the MRGL risk area.  Forecast soundings suggest the
   potential for strong downdrafts in the more robust cells.

   ..Hart/Gleason.. 06/20/2017

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