SPC AC 190049

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0749 PM CDT Tue Sep 18 2018

   Valid 190100Z - 191200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM A PORTION
   OF THE CENTRAL AND NORTHERN PLAINS INTO THE UPPER MISSISSIPPI VALLEY
   REGION...

   ...SUMMARY...
   Isolated large hail remains possible tonight from South Dakota,
   Nebraska into Iowa.

   ...Central and northern Plains area through the upper Mississippi
   Valley region...

   Early this evening a quasi-stationary front (a portion of which has
   been convectively reinforced) extends from the OH Valley westward
   through northern MO to along the KS/NE border. A weakening cluster
   of warm advection storms continues southeast through MO into IL.
   Farther upstream across western NE new storms are in the process of
   developing in response to the next in a series of vorticity maxima
   moving through a low amplitude synoptic upper ridge. The low-level
   jet will strengthen tonight, partly in response to this feature.
   Increasing isentropic ascent north of the front will contribute to
   fairly widespread thunderstorm development spreading eastward
   through tonight. Updrafts will remain elevated, but given 7-7.5 C/km
   mid-level lapse rates, moderate instability and 35-45 kt effective
   bulk shear, a few storms may become capable of producing hail.

   ..Dial.. 09/19/2018

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