SPC AC 151730

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1230 PM CDT Wed Jul 15 2020

   Valid 161200Z - 171200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   EASTERN OH INTO WESTERN PA/NY...

   ...SUMMARY...
   Strong to severe storms will be possible Thursday from the Ozarks
   into the Ohio Valley and western Pennsylvania/New York. Additional
   isolated strong to severe storms may occur across parts of the
   central Plains.

   ...Ozarks into the Ohio Valley and Western Pennsylvania/New York...
   A large-scale upper trough will move slowly eastward across parts of
   central Canada, the Upper Midwest, and Great Lakes region on
   Thursday. A convectively enhanced shortwave trough embedded within
   this regime should shift quickly northeastward from parts of the OH
   Valley into the Northeast through the day. At the surface, a weak
   low initially over IN is forecast to likewise develop toward Lakes
   Erie/Ontario by Thursday evening. A cold front trailing
   southwestward from this low across the OH Valley into the Mid-South
   and Ozarks will serve as a focus for strong to severe storm
   development across these regions.

   Generally weak/non-severe storms will likely be ongoing at the start
   of the period Thursday morning across OH and vicinity in association
   with the previously mentioned shortwave trough. There is some
   concern that this precipitation and/or cloud debris may limit
   diurnal destabilization across eastern OH into parts of western
   PA/NY. Regardless, modestly enhanced (30-40 kt) mid-level flow
   coupled with even weak destabilization along/ahead of the front
   should prove sufficient for storm organization by early Thursday
   afternoon. Multicells and small bowing line segments should be the
   primary storm mode given the linear nature of the low-level forcing
   mechanism (front), but an embedded supercell or two cannot be ruled
   out with 30-40 kt of effective bulk shear expected.

   Strong to damaging winds should be the main threat as low-level
   lapse rates modestly steepen ahead of the morning storms/clouds.
   Some enhancement to the low-level flow suggests a brief tornado
   cannot be ruled out either, mainly across eastern OH and western
   PA/NY vicinity. These strong to severe storms should quickly weaken
   into central PA/NY by Thursday evening as low-level moisture and
   related instability decrease with eastward extent.

   With weak large-scale forcing behind the lead shortwave trough,
   generally isolated storm coverage is expected along the length of
   the cold front from the lower OH Valley into the Mid-South and
   Ozarks. One exception may be across parts of northern/central AR and
   vicinity Thursday afternoon/evening, where a remnant MCV from prior
   storms may act to increase convective potential. Isolated instances
   of both large hail and damaging wind gusts may occur given the large
   degree of instability forecast, although deep-layer shear should
   remain rather modest.

   ...Central Plains...
   At least isolated storms are expected to once again develop across
   the higher terrain of the central Rockies, and subsequently spread
   slowly eastward across the central High Plains through Thursday
   evening. Additional storms may also form farther east across parts
   of northern/central NE and vicinity along/ahead of a weak front.
   Mid-level flow will be modestly enhanced across NE owing to somewhat
   closer proximity to the upper-level trough farther north. Even
   through large-scale ascent will remain nebulous, a couple of
   supercells may ultimately form across NE owing to marginally
   sufficient effective bulk shear and strong instability. Isolated
   large hail and severe wind gusts should be the main threats with any
   storms that can form in this regime across the central Plains.

   ...Minnesota Arrowhead...
   Weak destabilization appears possible ahead of a cold front across
   the MN Arrowhead region Thursday afternoon. There remains
   considerable uncertainty regarding overall storm coverage across
   this region, as stronger ascent will likely remain displaced to the
   north in Ontario. Will defer possible inclusion of 5% wind
   probabilities to a later outlook pending better confidence in storm
   development.

   ..Gleason.. 07/15/2020

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