SPC AC 070630

   Day 2 Convective Outlook CORR 1
   NWS Storm Prediction Center Norman OK
   0130 AM CDT Tue Jul 07 2020

   Valid 081200Z - 091200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE UPPER
   MIDWEST INTO THE CENTRAL PLAINS...

   CORRECTED FOR INCORRECT OUTLOOK LINE DIRECTION

   ...SUMMARY...
   Severe thunderstorms are expected from the northern/central Plains
   into the Upper Midwest Wednesday. Isolated severe thunderstorms are
   also possible across New England.

   ...Upper Midwest into the Central Plains...
   A shortwave trough is expected to be over southern 
   Saskatchewan/Manitoba at the beginning of the period. This shortwave
   is expected continue northeastward into central Manitoba/western
   Ontario while the parent cyclone matures into a closed system over
   southern Saskatchewan. Another shortwave trough is expected to move
   through the base of this cyclone, from the northern High Plains
   eastward/northeastward into southern Manitoba. 

   Showers and thunderstorms will likely be ongoing early Wednesday
   morning across central/eastern MN, supported by enhanced low-level
   southeasterly flow across a warm front. These storms are expected to
   gradually diminish throughout the morning as the low-level flow and
   resulting warm-air advection weaken. At the same time, a surface
   low, which was centered near the ND/MN/MB border intersection at the
   beginning of the period, will move northeastward. This evolution
   will encourage the eastward/southeastward progression of a cold
   front from the eastern Dakotas into NE and the Upper Midwest. 

   Dewpoints ahead of this front are forecast to be in the upper
   60s/low 70s, contributing to moderate to strong buoyancy. The
   strongest buoyancy is anticipated across eastern SD and southwest MN
   where the best combination of low-level moisture and steep mid-level
   lapse rates is forecast. Thunderstorm development is expected along
   the length of the front, which will extend from far northwest MN
   southwestward through central SD and into western NE by Wednesday
   afternoon. The better vertical shear will lag behind the front,
   likely limiting storm organization and promoting primarily
   outflow-dominant storm structures across much of the region. The
   only exception to this is across portions of central NE where more
   southerly surface winds may contribute to enough low-level shear for
   more persistent storm organization and a greater tornado threat.
   Additionally, the low-level jet is expected to strengthen south of
   this area during the evening, resulting in an environment that could
   support an organized convective line. Confidence in that scenario is
   increasing, which prompt the southward and eastward expansion of the
   severe probabilities. However, further expansion, and potentially
   higher probabilities, may be needed in later outlooks if this
   scenario appears likely.

   ...Mid-Atlantic into New England...
   Scattered to numerous thunderstorms are possible from the
   northern Mid-Atlantic into the Northeast as a result of pre-frontal
   confluence amid ample low-level moisture and modest buoyancy. Weak
   vertical shear should preclude organized severe thunderstorms across
   the majority of the region. The only exception is across New England
   where slightly stronger flow aloft attendant to a low-amplitude
   shortwave trough will increase vertical shear. This increased shear
   could result in a few stronger storms capable of hail and/or
   damaging wind gusts. Hail risk is greater with earlier, more
   discrete development. Wind damaging risk will be greater later after
   the storms have transitioned to bowing line segments.

   ...Carolinas...
   Widespread thunderstorm activity is anticipated from GA through the
   Carolinas in the vicinity of a surface low and associated upper
   cyclone that is expected to move slowly over the region. Some
   enhancement of the low-level flow is possible along the eastern
   periphery of the system, but this is currently expected to be
   offshore. Resulting weak vertical shear over land will keep any
   severe threat low.

   ..Mosier.. 07/07/2020

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