SPC AC 150535

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1235 AM CDT Fri Jun 15 2018

   Valid 151200Z - 161200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE UPPER MISSISSIPPI VALLEY...

   ...SUMMARY...
   A few severe storms are possible from southern Minnesota into
   western Wisconsin mainly late in the day, with locally damaging wind
   gusts possible. A few severe storms with hail or wind are possible
   during the afternoon from northern Wyoming toward the Black Hills,
   and across coastal South Carolina.

   ...Synopsis...
   An upper high will remain centered over the mid to lower MS Valley,
   with anticyclonic flow aloft from the Plains across the Great Lakes.
   To the west, an upper low will move slowly southward across the
   Pacific Northwest, with a belt of moderately strong southwest flow
   aloft across the northern Rockies. To the east, an upper trough will
   rapidly exit the Northeast, with weak northwesterly flow aloft
   maintained across the Atlantic coast. 

   At the surface, a weak low pressure trough will extend roughly from
   northern MN across NE and into eastern WY, with a warm front lifting
   rapidly north across the upper MS Valley during the day. A broad
   belt of strong southwesterly 850 mb flow will persist over the
   Plains toward the upper Great Lakes, maintaining a flux of
   warm/moist air.

   ...MN and WI...
   Areas of thunderstorms are likely to be ongoing from northern MN
   into WI early in the day, but they will likely continue to lift
   generally northeastward out of the area. Behind this activity, and
   ahead of the weak surface trough, will be a very moist and unstable
   air mass. Depending on early day storm coverage, a potential outflow
   boundary could also reside across the area. By late afternoon, the
   atmosphere will be largely uncapped, but forcing for ascent will be
   quite weak. In addition, winds aloft will be weak under the upper
   ridge. Predictability is low for precisely when and where storms may
   develop, with model solutions ranging from late afternoon through
   late evening. Conditionally, an slow-moving MCS will be possible,
   with wind the primary threat, in addition to heavy rain. Given this
   potential and despite uncertainty, will maintain a Slight Risk.

   ...WY into the central High Plains...
   A weak area of low pressure will develop from the Great Basin into
   southern WY, coincident with strong heating. Meanwhile, east to
   northeasterly surface winds will maintain 40s and 50s F dewpoints
   across the region resulting in substantial instability given very
   steep lapse rates aloft. Hodographs will be relatively long given 60
   kt midlevel flow, and this will all favor cellular activity capable
   of large hail.

   ...Coastal SC into far southern NC...
   A weak front will drop southward across NC during the day, with
   strong heating and a deepening surface trough to the south. A very
   moist air mass will be in place with lower 70s F dewpoints resulting
   in around 3000 J/kg MLCAPE by afternoon. Storms are expected to
   initiate along the front in far southeast NC, and propagate
   south/southwestward across SC during the late afternoon into early
   evening. Locally damaging downbursts, or even marginal hail, will be
   possible.

   ..Jewell/Bentley.. 06/15/2018

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z