SPC AC 170723

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0223 AM CDT Wed May 17 2017

   Valid 191200Z - 201200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE SOUTHERN PLAINS TO THE OZARKS...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE SOUTHERN AND CENTRAL PLAINS TO THE LOWER OH VALLEY AND CENTRAL
   APPALACHIANS...

   ...SUMMARY...
   Severe thunderstorms capable of large hail and strong wind gusts
   will be possible across parts of central Texas into central and
   eastern Oklahoma, southern Missouri and northern Arkansas Friday
   afternoon and evening. Additional isolated strong storms may occur
   over portions of the lower Ohio Valley and central Appalachians
   regions.

   ...Synopsis...
   The upper low over the Rockies will lift northeast on Friday into
   the northern/central Plains. Downstream from this...an upper ridge
   will amplify from the southeastern U.S. to the upper Great Lakes.
   Strong deep-layer southwesterly flow will continue to stream over
   the Plains to the mid-MS Valley. A dryline will extend southward
   from western/central KS into western OK and west-central TX while a
   cold front is draped west-to-east from near the KS/NE state line
   into the lower OH Valley and mid-Atlantic states during the late
   afternoon. Thunderstorm activity is expected along the dryline as
   well as ahead of the southward sagging cold front. 

   ...Southern Plains to portions of the Ozarks...

   Quite a bit of uncertainty exists this period as there is likely to
   be areas of ongoing convection across parts of KS/MO/OK/TX. This
   will have implications on surface boundary locations and how the
   boundary layer may or may not recover by afternoon. That being said,
   various guidance is in agreement that rich boundary layer moisture
   will remain given strong south/southeasterly low-level flow
   persisting ahead of the ejecting upper low/trough. Additionally,
   steep lapse rates will remain across the region. Where
   boundary-layer recovery and destabilization can occur, kinematic and
   thermodynamic parameter space would support strong to severe
   convection. The best chance for this occurring appears to be across
   the slight risk area from central TX into parts of central and
   eastern OK, eastward to southern MO and northern AR. This area could
   change in coming outlooks depending on convective and model trends
   and lower-end severe probs will be maintained from previous Day 4
   outlook given quite a bit of uncertainty.

   ...Lower OH Valley to Central Appalachians Vicinity...

   Isolated strong storms will be possible ahead of the
   southward-advancing cold front in a moist and unstable environment.
   Deep-layer forcing will be rather weak, but steep lapse rates
   combined with weak to moderate instability could sustain storms
   capable of some hail and strong wind gusts.

   ..Leitman.. 05/17/2017

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