SPC AC 280658

   Day 1 Convective Outlook CORR 1
   NWS Storm Prediction Center Norman OK
   0158 AM CDT Tue May 28 2019

   Valid 281200Z - 291200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   SOUTHEAST NEBRASKA...EASTERN KANSAS...NORTHEAST OKLAHOMA...NORTHERN
   AND WESTERN MISSOURI...SOUTHERN IOWA...AND PARTS OF WESTERN ILLINOIS
   AS WELL AS ACROSS OHIO/PENNSYLVANIA...

   CORRECTED FOR ENHANCED RISK HEADLINE

   ...SUMMARY...
   Severe storms, capable of producing large hail, damaging wind and a
   few tornadoes, are possible Tuesday from the central Plains vicinity
   eastward to the Midwest.  Severe storms with large hail, damaging
   wind and a couple of tornadoes are also expected from the Ohio
   Valley into a portion of the Northeast States Tuesday afternoon and
   early evening.

   ...Synopsis...
   An upper trough/low over the West will make slow eastward progress
   toward/into the Plains today.  Meanwhile, a large ridge will remain
   over the Southeast; between the two features, a belt of enhanced
   west-northwesterly flow aloft will remain over the Ohio Valley and
   Northeast.

   At the surface, a weak low is progged to cross the Lower Great Lakes
   and Northeast, eventually departing the New England coast overnight.
    Trailing westward, a quasi-stationary front should become aligned
   west-to-east across the Ohio Valley states, and westward to the
   central Plains.  Here, a frontal low is progged to move slowly east
   across Kansas, while a cold front trailing from the low advances
   southeastward across Kansas/Oklahoma, and the Texas Panhandle.  

   ...Central Plains/Oklahoma east to the mid Mississippi Valley...
   Ongoing storms are forecast to be moving eastward across the mid
   Missouri Valley and then into/across Iowa through the morning, with
   likelihood that outflow reinforces the west-to-east front lying
   across the area.  As the aforementioned/weak surface low crosses
   Kansas and the trailing cold front shifts slowly southeastward, this
   boundary -- and the convectively reinforced front extending east
   across the northern Missouri/southern Iowa vicinity -- should serve
   as foci for new afternoon storm development.

   With a moist/moderately unstable airmass progged across the warm
   sector, and favorably strong/veering flow with height anticipated,
   organized/rotating storms -- and associated, all-hazard severe risk
   -- will likely evolve through the afternoon, most concentrated near
   the outflow and then likely in a more isolated manner southward into
   the southern Plains.  Development may extend as far southwest as the
   Concho Valley vicinity in Texas, though most likely after dark.

   Greatest tornado risk is expected near the outflow boundary, during
   the afternoon and evening, with threat likely transitioning to
   include damaging winds as convection grows upscale into the
   overnight hours.  This risk should spread across the mid Mississippi
   Valley into the Midwest through the end of the period.

   ...Ohio to New Jersey...
   Convection and associated cloud cover is progged to be ongoing
   across portions of the risk area at the start of the period, ahead
   of a surface low moving slowly east across the Lake Erie vicinity. 
   The convection should move eastward/diminish through midday,
   allowing some heating/destabilization to occur -- fueling new storm
   development, likely by early afternoon.  Storms development may be
   focused by the presence of remnant outflow associated with the
   earlier storms, though coherence -- and location -- of this possible
   boundary remains uncertain, dependent upon evolution of the ongoing
   convection.

   With fast/weakly veering west to west-northwesterly flow with height
   progged atop the region, clusters of organized/fast-moving storms
   are expected to evolve.  At this time, damaging winds would appear
   to be the primary severe risk, along with hail.  Tornado threat
   should be somewhat limited by only modest veering of the flow with
   height, but ample low-level speed shear suggests low-probability
   tornado risk during the afternoon.

   With regeneration of successive bands of storms possible, within the
   west-northwesterly flow regime, severe risk will likely linger
   through the evening and possibly into the overnight hours.

   ..Goss/Squitieri.. 05/28/2019

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