SPC AC 031959

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0259 PM CDT Wed Jun 03 2020

   Valid 032000Z - 041200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE CENTRAL
   HIGH PLAINS VICINITY EASTWARD TO THE MID ATLANTIC COAST...

   ...SUMMARY...
   Scattered clusters of strong to severe storms will continue to
   develop through tonight from the central Great Plains through the
   Midwest and Mid-Atlantic States. Damaging winds and large hail will
   be the primary hazards.

   ...Discussion...
   Little change appears necessary with respect to the ongoing outlook,
   as convection continues to evolve as expected.  The ENH risk area
   has been removed from the Mid Atlantic region, as the prior line of
   severe storms has moved well offshore.  SLGT risk is being
   maintained across the area however -- in tandem with newly issued WW
   244, as new storms develop as anticipated in the wake of the earlier
   MCS.  Damaging winds will be the primary risk into this evening.

   Elsewhere, storms continue to develop across the central High Plains
   and into South Dakota, where WW 243 is now in effect, with this
   convection expected to expand and progress southeastward with time.
   Additional storm development is also expected farther east, into the
   MO/IL vicinity later this afternoon/evening.  Hail and locally
   damaging winds will be possible across these areas.

   ..Goss.. 06/03/2020

   .PREV DISCUSSION... /ISSUED 1131 AM CDT Wed Jun 03 2020/

   ...Mid-Atlantic States...
   Fast-moving line segment over far eastern PA should progress
   east-southeast off the NJ coast in the next couple hours. While
   buoyancy is scant, steep low-level lapse rates and
   MCV-enhanced/rear-inflow jet 2-5 km AGL winds greater than 70 kt
   will support severe gusts with a pronounced swath of damaging winds
   until it exits the coast.

   Destabilization in the wake of this activity is underway amid low to
   mid 60s surface dew points with potential for redevelopment towards
   peak heating along the trailing outflow of the ongoing MCS. 30-40 kt
   effective shear and weak forcing for ascent should yield a few
   discrete cells with mid-level updraft rotation capable of producing
   locally strong gusts and marginally severe hail. 

   ...Mid-MS to Upper OH Valleys...
   With ample heating underway to the south/southeast of lingering
   stratiform across northern IL, scattered convective development is
   expected in a west/east-orientation during the late afternoon along
   a convergent surface front. On the fringe of modest mid-level
   westerlies generally paralleling the initiation boundary, multicell
   clusters will be the dominant mode with general risks of isolated
   damaging winds and hail. 

   A longer-lived cluster/MCS this evening into tonight is anticipated
   across parts of IL/MO which should backbuild southwestward given
   modest low-level warm advection beneath increasingly weak northwest
   mid-level flow with southern extent. Regenerative updrafts on the
   western flank on the periphery of the central Great Plains EML will
   pose the best chance for severe hail, otherwise strong to isolated
   severe gusts should be the main threat. A broader merging of MCSs
   may occur overnight with consolidation of upstream activity
   spreading east in NE/KS.

   ...SD/NE/KS...
   A low-amplitude mid-level impulse near the Black Hills should
   continue east-southeast. The primary severe risk should initially
   develop by mid to late afternoon across south-central South Dakota
   southwest towards the CO/KS/NE border area as very steep
   mid-level lapse rates atop mid to upper 50s surface dew points
   support moderate buoyancy. 

   A few supercells are likely in the presence of 35-40 kt effective
   shear where significant severe hail will be possible. With time,
   upscale growth into multiple clusters that may evolve into a broader
   southeast-moving MCS tonight is depicted by several CAMs towards the
   plume of strong buoyancy over eastern KS and MO, despite only weak
   low-level warm advection. This would yield potential for severe
   wind/isolated hail persisting overnight.

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