SPC AC 081729

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1129 AM CST Wed Mar 08 2017

   Valid 091200Z - 101200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE OZARK PLATEAU REGION AND ADJACENT PORTIONS OF THE CENTRAL PLAINS
   AND MIDDLE MISSISSIPPI VALLEY...

   ...SUMMARY...
   Strong thunderstorms may impact parts of the Ozark Plateau region
   Thursday afternoon and evening, accompanied by at least some risk
   for severe hail and strong wind gusts.

   ...Synopsis...
   Models indicate that the upper flow pattern will undergo at least
   some amplification during this forecast period, particularly east of
   the Rockies through the Atlantic Seaboard.  Within the stronger belt
   of westerlies emanating from the mid-latitude Pacific, broad upper
   ridging appears likely to build across the eastern Pacific through
   the Rockies and Plains, Thursday into Thursday night, while
   downstream troughing digs east of the Mississippi Valley through the
   western Atlantic.

   A vigorous short wave impulse within this latter (cyclonic) regime
   is forecast to dig across parts of the Upper Midwest and Great Lakes
   region, accompanied by a substantive reinforcing intrusion of cold
   air to the lee of the Rockies.  The leading edge of this air mass is
   expected to reach the Mid Atlantic Coast, Ohio Valley, Ozark Plateau
   and south central Plains by 12z Friday.  Ahead of this front, modest
   moisture return in the wake of a preceding front may contribute to
   considerable destabilization beneath a plume of steep mid-level
   lapse rates, from the vicinity of the lower Rio Grande Valley
   northeastward into the Ozark Plateau region.  Despite an increase in
   potential instability, forcing sufficient to overcome mid-level
   inhibition and support the initiation of storms remains unclear at
   this time, aside from terrain related forcing near/west of the Rio
   Grande River, and a zone of enhanced lower/mid tropospheric warm
   advection expected to develop and shift southeastward across parts
   of the Ozark Plateau region by Thursday evening.

   ...Ozark Plateau and surrounding areas...
   Based on latest model output, at least scattered thunderstorm
   development appears likely within an east southeastward developing
   zone of enhanced lower/mid tropospheric warm advection, as it
   encounters a better low-level moisture return.  This may initiate as
   early as late afternoon across parts of southeast Kansas
   (particularly near/north of Chanute), before increasing while
   spreading east southeastward across the Missouri Ozarks, into south
   central Missouri, by late Thursday evening.

   Near the southwestern edge of the stronger cyclonic mid-level flow
   (50+ kt at 500 mb), deep layer vertical shear probably will be more
   than sufficient for organized severe storm potential.  Given the
   likely presence of at least steep mid-level lapse rates, the
   magnitude of the low-level moisture return and its influence on
   destabilization remains the primary uncertainty concerning the
   extent of the convective potential.  This is a point of considerable
   model spread.  Taking into consideration a most probable solution
   somewhere between that currently depicted by the aggressive NAM and
   much more modest GFS (with respect to destabilization), there is
   support for at least some severe weather potential with anticipated
   thunderstorm development.

   Activity may remain mostly rooted within the elevated warm advection
   regime, with severe hail and locally strong surface gusts the
   primary severe threats.  It is possible that this could spread into
   upper portions of the lower Mississippi Valley by late Thursday
   night.

   ..Kerr.. 03/08/2017

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