SPC AC 071650

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1150 AM CDT Fri Sep 07 2018

   Valid 081200Z - 091200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE NORTHERN HIGH PLAINS...

   ...SUMMARY...
   Isolated severe storms capable of damaging winds or hail are
   possible over the northern High Plains Saturday afternoon and
   evening. A few strong wind gusts cannot be ruled out over parts of
   the lower Ohio and mid Mississippi Valleys as well.

   ...Synopsis...
   High pressure will move from Ontario into Quebec, with a front
   extending roughly along the I-70 corridor from MO to the Mid
   Atlantic with a moist air mass supporting scattered storms. Weak
   cyclogenesis will occur across the lower OH Valley, in association
   with the remnants of Gordon as it interacts with the front. This too
   will provide a focus for numerous thunderstorms and heavy rain, from
   eastern MO across IL, IN, and western KY. 

   To the west, a low-amplitude progressive shortwave trough will move
   east across the northern Rockies, with an associated lee-trough from
   SK southward across the northern High Plains which will provide a
   focus for at least isolated afternoon and evening thunderstorms.

   ...Northern High Plains...
   Strong heating will occur near the developing lee-trough, with steep
   lapse rate profiles resulting in weak instability and a narrow zone
   of uncapped air mass. This may support a few high-based storms
   capable of gusty winds, or support mainly small hail with any
   cellular activity.  Given a strong southerly low-level jet, a storm
   or two may persist into the night across the western Dakotas.

   ...Mid MS/Lower OH Valleys...
   Widespread rain and storms are expected to be ongoing across
   southeast MO Saturday morning, and will develop into IL during the
   day and across parts of IN and KY by evening. This activity will be
   associated with a gradually deepening surface low as the warm moist
   air mass interacts with the synoptic front. While flow aloft will be
   weak, substantial low-level warm advection will develop over this
   area, with increasing SRH mainly along and north of the front where
   most of the diurnal and evening storms are expected to be
   concentrated. More isolated afternoon activity may occur south of
   the main east-west cold front, most likely in close proximity to the
   surface low. Thus, a short lived strong storm or two cannot be ruled
   out, with either damaging wind gust or weak/brief tornado potential.
   An upgrade to Marginal risk for isolated severe storms could be
   added in later outlooks as predictability issues related to early
   convection, potential outflow, air mass quality and low-level shear
   are better known.

   ...MAXIMUM RISK BY HAZARD...
   Tornado:  <2%     - None
   Wind:      5%     - Marginal
   Hail:      5%     - Marginal

   ..Jewell.. 09/07/2018

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