SPC AC 031728

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1228 PM CDT Sat Jun 03 2017

   Valid 041200Z - 051200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
   THE LOWER GREAT LAKES...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
   THE NORTHERN ROCKIES...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM NORTHEAST
   MO INTO WESTERN NY...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM SOUTHEAST
   OR INTO NORTH-CENTRAL MT...

   ...SUMMARY...
   Scattered strong to severe thunderstorms are expected across parts
   of the lower Great Lakes and Ohio Valley regions on Sunday. Strong
   winds and hail will be the main threats with these storms.
   Additional strong to severe thunderstorms are also expected across
   the northern Rockies.

   ...Lower Great Lakes and Mid-MS/OH Valley Vicinity...

   A compact upper trough located over the upper Midwest early Sunday
   will progress southeastward into the lower Great Lakes and Ohio
   Valley vicinity by the end of the period. A surface low will develop
   from the upper Great Lakes to western NY and an attendant cold front
   will push east/southeast across the Great Lakes region. Showers and
   thunderstorms may be ongoing across parts of NY/PA early Sunday.
   This activity could pose a marginal wind/hail threat initially. As
   shear and forcing for ascent increase during the afternoon,
   additional thunderstorm development is expected along the
   pre-frontal confluence zone from northeast MO into western NY. Shear
   profiles in the vicinity of lakes Ontario and Erie suggest line
   segments will be favored with an attendant threat of strong wind
   gusts. Some hail also will be possible. Further west toward the
   mid-MS Valley, steeper lapse rates will be present. Marginally
   severe hail in addition to gusty winds will be possible from
   northeast MO into northern IL.

   ...Northern Rockies...

   An upper trough will shift east into the Pacific Northwest by late
   afternoon and deep layer shear will increase from eastern OR into
   western MT. A cold front will reside from northern ID into eastern
   OR early Sunday, and slowly shift east into central MT after
   06z/Mon. Pockets of stronger heating ahead of the front will result
   in modest destabilization by afternoon and scattered thunderstorms
   are expected to develop over higher terrain of southeast OR into
   central ID and western MT. Steep midlevel lapse rates and strong
   shear will support storms capable of hail. Additionally, a
   deeply-mixed/dry sub-cloud layer and fast storm motion could result
   in some strong wind gusts. The greatest threat for large hail and
   damaging wind gusts appears to exist from the central ID mountains
   into parts of western MT where steep midlevel lapse rates, strong
   shear and around 1000 J/kg MUCAPE will align, and a slight risk has
   been introduced for this area.

   ..Leitman.. 06/03/2017

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