SPC AC 170730

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0230 AM CDT Fri Jul 17 2020

   Valid 191200Z - 201200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE GREAT LAKES/OH VALLEY INTO THE MID MS VALLEY AND CENTRAL
   PLAINS...

   ...SUMMARY...
   Isolated strong to severe thunderstorms may occur Sunday from
   portions of the Great Lakes/Ohio Valley regions into the mid
   Mississippi Valley and central Plains.

   ...Great Lakes/Ohio Valley into the Mid Mississippi Valley and
   Central Plains...
   An upper trough with enhanced mid-level westerly winds should move
   quickly northeastward from the Upper Midwest into Canada on Sunday.
   At the surface, a related area of low pressure should develop from
   Ontario into Quebec, with a trailing cold front moving slowly
   east-southeastward across the Great Lakes/OH Valley. The western
   portion of this front should stall over the mid MS Valley and parts
   of the central Plains. A very moist low-level airmass characterized
   by upper 60s to mid 70s F dewpoints will be present along/south of
   the front. Moderate to potentially very strong instability should
   develop across the warm sector given diurnal heating and the
   favorable low-level moisture.

   Primary uncertainty will be locations with greater convective
   coverage, as the large-scale ascent associated with the upper trough
   shifts quickly into Canada through the day. Stronger mid-level flow
   may also tend to remain displaced north of the surface warm sector,
   which should limit deep-layer shear and potential storm organization
   to some degree. Still, the favorable thermodynamic environment
   along/ahead of the front and some signal for convective development
   along its length suggests 5% severe probabilities are warranted. A
   nocturnal severe risk may develop across parts of the Lower Great
   Lakes region as low-level moisture and flow increases Sunday night
   ahead of the front.

   Farther west, a low-level upslope regime across parts of the central
   High Plains may support an isolated severe risk Sunday evening/night
   as a low-level jet modestly strengthens. Given the inherent
   uncertainties with prior days' convection and the general
   displacement of stronger mid-level flow into Canada, will defer
   possible inclusion of greater severe probabilities to a later
   outlook.

   ..Gleason.. 07/17/2020

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   NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 0730Z