SPC AC 101727

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1227 PM CDT Sat Oct 10 2020

   Valid 111200Z - 121200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PARTS OF THE
   NORTHERN/CENTRAL PLAINS INTO THE UPPER MIDWEST...

   ...SUMMARY...
   Isolated strong to severe thunderstorms may occur Sunday across
   parts of the northern/central Plains into the Upper Midwest, with
   marginally severe thunderstorms also possible across parts of the
   Southeast and Mid-Atlantic.

   ...Synopsis...

   ...Northern/Central Plains into the Upper Midwest...
   A strong shortwave trough is expected to move into the Plains on
   Sunday, contributing to the development of a mid-level cyclone
   across Saskatchewan by Sunday afternoon. This shortwave trough will
   also feature enhanced mid-level flow, which will spread across the
   Plains early Sunday and into the Upper Midwest by Sunday evening. 

   The deepening mid-level cyclone will be accompanied by an occluding
   surface low and attendant cold front. Early Sunday, this cold front
   will likely extend from central Saskatchewan south-southeastward to
   another low in central ND and then southwestward back across central
   WY. A surface trough/dryline will also extend south from the ND
   surface low into the TX Panhandle. This surface features are
   expected to push eastward throughout the day, with the faster motion
   of the cold front allowing it to eventually overtake the dryline
   Sunday evening. 

   Low 60s dewpoints will likely be in place ahead of the front from
   the central Plains into the Upper Midwest. A strong elevated mixed
   layer will likely cap convection throughout much of the afternoon.
   Even with this capping, ascent along the front, augmented by
   increasing large-scale forcing, should be able to overcome the
   convective inhibition as the front reaches far eastern
   Dakotas/middle MO Valley. This scenario favors quick linear
   development, with little opportunity ahead of the front for cellular
   convection. Even so, the presence of steep mid-level lapse rates
   suggest the possibility of severe hail in the strongest cores.
   Strong low to mid-level flow will also contribute to a damaging wind
   threat along the fast-moving cold front as it surges eastward.
   Limited instability casts doubt on how much the squall line can
   organize, with some undercutting of updrafts likely. However, this
   limited instability may be countered by the strong flow, and the
   general expectation is that strong, convectively augmented gusts are
   probable along the front for at least a few hours during the late
   afternoon and evening. Decreasing instability with eastern extent
   adds to uncertainty on the eastern extent of the damaging wind
   threat, but current thinking is that the line will outpace the
   instability ahead of it as it reaches central IA/MN.

   ...Southeast/Mid-Atlantic...
   Current NHC forecast of Tropical Depression Delta places it over
   central TN early Sunday morning, before the system then progresses
   northeastward throughout the day. Mid-level flow will gradually
   decrease as the overall system weakens. However, enough vertical
   shear will remain present over the warm, moist, and modestly
   unstable warm sector to support isolated strong to severe storms,
   particularly in areas where even modest heating can occur. Primary
   threat from any stronger storms is damaging wind gusts, but a
   tornado or two is also possible, especially near the warm front.

   ..Mosier.. 10/10/2020

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