SPC AC 211731

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1231 PM CDT Tue May 21 2019

   Valid 221200Z - 231200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
   EASTERN KANSAS/NORTHWESTERN MISSOURI...

   ...SUMMARY...
   Thunderstorms capable of mainly large hail are possible Wednesday
   night into early Thursday morning from the central Plains into the
   middle Mississippi Valley, and possibly southwestward across
   Oklahoma to the southern High Plains. A few strong storms with gusty
   winds and hail will also be possible over a portion of the Ohio
   Valley.

   ...Synopsis...
   As an upper low initially progged over the northern Plains weakens
   and drifts northeast across the upper Mississippi Valley toward the
   Upper Great Lakes/Ontario with time, a second low is forecast to
   expand/deepen over the Intermountain West with time.  As this
   evolution occurs, height rises are progged across much of the
   eastern half of the U.S. as ridging over the southeastern U.S./Gulf
   of Mexico expands in the wake of the departing northern Plains low.

   At the surface, a weakening baroclinic zone is forecast to linger
   from the Midwest west-southwestward to the Texas Panhandle vicinity
   as the old/occluded low drifts toward the upper Mississippi Valley. 
   Otherwise, a broad area of low pressure is progged over the west in
   conjunction with the upper low, while high pressure prevails over
   the east.

   ...Southern High Plains northeast to the mid Mississippi Valley
   area...
   In the wake of the departing upper low, and ahead of the
   second/developing low over the West, ridging/subsidence will largely
   prevail over the southern Plains and vicinity.  Still, returning
   moisture combined with daytime heating will result in substantial
   destabilization -- though capping, stemming from the aforementioned
   ridging/subsidence -- will most likely preclude daytime convective
   development.  Some hints that a few storms could initiate over the
   Oklahoma vicinity are indicated -- apparently tied to a very weak
   mid-level disturbance moving through the otherwise anticyclonic flow
   -- but this appears very low probability at this time.  Should a
   storm or two initiate however, the background CAPE/shear environment
   would be quite supportive for supercell storms -- and all severe
   hazards.  At this time, will expand the 5% risk across Oklahoma, for
   what still appears to be a highly conditional scenario at best.

   Later in the evening/overnight, increasing warm advection should
   support storm development a bit farther northeast, as the
   aforementioned disturbances moves into eastern Kansas/western
   Missouri.  With storms most likely to develop in the zone of warm
   advection to the cool side of the remnant front, large hail with a
   few of the stronger/rotating storms would appear the most likely
   risk.

   ...Upper Ohio Valley...
   Weakening/remnant convection is progged to be moving across the
   Midwest/mid Mississippi Valley at the start of the period, ahead of
   the weak surface front.  As some heating/destabilization of a
   relatively moist boundary layer over the mid and upper Ohio Valley
   occurs, an afternoon uptick in convective coverage/intensity may
   occur, though likely tempered to some degree by background ridging
   aloft.  Still, with amply strong mid-level west-southwesterlies
   supportive of some organization and fast-moving storms, risk for
   locally damaging winds -- and possibly hail -- will exist with a
   couple of the strongest cells, from afternoon into the evening. 
   Convection should weaken as it reaches the Appalachians during the
   evening.

   ...MAXIMUM RISK BY HAZARD...
   Tornado:   2%     - Marginal
   Wind:      5%     - Marginal
   Hail:     15%     - Slight

   ..Goss.. 05/21/2019

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