SPC AC 160526

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1226 AM CDT Thu Jul 16 2020

   Valid 161200Z - 171200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM EASTERN OHIO
   INTO WESTERN NEW YORK STATE AND ACROSS WESTERN NEBRASKA...

   ...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 and parts of Minnesota.

   ...Synopsis...
   A broad mid-level anticyclone will remain nearly stationary from
   Texas into the Carolinas today,  On the periphery of this
   anticyclone, weak shortwave troughs will migrate from west to east
   across the central Plains and from east to west along the central
   Gulf Coast.  Farther north, a progressive upper air pattern will
   dominate, with a shortwave trough traversing the eastern Great Lakes
   in the morning and a longer-wave trough extending from western
   portions of Hudson Bay to Minnesota through the day.

   At the surface, a weak trough will accompany the mid-level shortwave
   trough across the eastern Great Lakes and portions of
   Ohio/Pennsylvania through the day.  This trough will extend
   southwestward through the Ozarks and into southern Kansas, where it
   will remain nearly stationary during peak heating hours.  Another
   weak trough will migrate eastward across northern and central
   Minnesota during the day and act as an effective dryline/cold front.
    Another trough will remain nearly stationary in the lee of the
   Rockies.

   ...Ohio/Pennsylvania into western New York...
   Showers and a few thunderstorms may be ongoing initially along the
   surface trough over southern Michigan/western Ohio as lift/ascent
   associated with both the trough and aforementioned mid-level
   shortwave traverse the region.  Through the day, convection will
   gradually intensify in response to surface heating, with 80s F
   surface temperatures and 70s F dewpoints resulting in around
   1000-1500 J/kg MUCAPE.  Shear profiles actually support
   supercellular storms - and 300-400 m2/s2 SRH values in the 0-3km
   layer support low-level mesocyclogenesis especially within
   persistent, discrete cells.  A couple of tornadoes are possible in
   addition to damaging wind gusts and isolated hail - though limiting
   factors include weakening ascent aloft with the departing shortwave
   trough and poor mid-level lapse rates. Any severe threat should
   spread into western New York state in the early evening before
   weakening after dark.

   ...Eastern Colorado into much of Nebraska...
   As surface heating commences, destabilization and steep tropospheric
   lapse rates will result in convection developing initially along
   higher terrain of central Colorado and migrating eastward through
   the Colorado Plains and Nebraska.  Storms may also focus along a
   weak surface boundary across northwestern/north-central Nebraska
   during the afternoon.  Models peak in convective coverage in the
   00-03Z timeframe across western Nebraska, where steep mid-level
   lapse rates and modest westerly mid-level flow will promote a few
   clusters/linear segments capable of damaging winds and large hail. 
   One or two forward-propagating linear segments may persist overnight
   from western Kansas into central Nebraska.

   ...Minnesota...
   The eastward-moving surface trough and lift associated with the
   approaching mid-level wave will result in a few thunderstorms
   developing from northern into central Minnesota during the afternoon
   through early evening.  Thermodynamic profiles are most impressive
   closer to the International Border area and along the surface
   trough, where mid-level cooling will promote 1500-2000 J/kg MLCAPE
   in the afternoon.  Shear profiles in the region support organization
   and perhaps updraft rotation in a few cells, with west-southwesterly
   flow veering to northwesterly and strengthening with height.  This
   should promote a risk of hail and damaging wind gusts, although an
   isolated tornado cannot be completely ruled out.  Concerns regarding
   convective coverage preclude any introduction of Slight Risk and
   associated probabilities at this time, though portions of northern
   Minnesota may need an upgrade in later outlooks.

   ...South-central Kansas into northern Arkansas...
   Surface heating along the nearly stationary surface boundary across
   the area will foster at least isolated surface-based convection
   during the afternoon amidst an environment characterized by strong
   buoyancy (high dewpoints beneath steep mid-level lapse rates). 
   Shear profiles are only marginally supportive of convective
   organization, though CAMs indicate some potential for small linear
   segments to develop and forward-propagate during the afternoon. The
   presence of a weak shortwave over central Kansas may also encourage
   afternoon convective development.  Large hail and damaging wind
   gusts are possible with any convection that can materialize.

   ...Western Tennessee into Kentucky...
   Mid-level lapse rates are less in magnitude compared to areas
   farther west.  However, surface convergence along a synoptic
   boundary draped across the region and any remnant surface boundaries
   from prior-day convection will likely result in isolated to
   scattered thunderstorm development within a weakly sheared
   environment.  2000-3000 J/kg MLCAPE and minimal inhibition suggests
   that loosely organized convection is possible, with isolated
   downbursts and hail being the primary threats.

   ..Cook.. 07/16/2020

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