SPC AC 202258

   Day 1 Convective Outlook AMEND 1
   NWS Storm Prediction Center Norman OK
   0558 PM CDT Thu Jun 20 2019

   Valid 202300Z - 211200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE EASTERN U.S....

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE MID MISSOURI VALLEY AND GREAT PLAINS...

   AMENDED FOR GRAPHIC LINES

   ...SUMMARY...
   Damaging wind risk continues from southern Virginia to eastern
   Georgia this afternoon. The risk for very large hail with a few
   tornadoes also persists across parts of the Mid-Missouri Valley this
   afternoon into early evening.  Otherwise, scattered severe storms
   are expected across a broad portion of the central and northern
   Great Plains, and over the eastern states.

   ...Discussion...
   No substantive changes are being made to the ongoing outlook, as
   forecast reasoning, and general areas of greater risk, remain on
   track.  The greatest change to the existing areas is a decrease in
   the expanse of both the MRGL risk area and thunder area over the
   southern Plains, where capping is expected to largely hinder
   convective risk.

   Otherwise, severe risk continues over portions of the Southeast,
   where ongoing watches and warnings are in effect.  Meanwhile, severe
   storms are expected to develop from the central and northern high
   Plains eastward across the central Plains region later this
   afternoon and evening.

   ..Broyles.. 06/20/2019

   .PREV DISCUSSION... /ISSUED 1116 AM CDT Thu Jun 20 2019/

   ...Southeast and Mid Atlantic States...
   A progressive shortwave trough is evident in morning water vapor
   imagery over AL, with other minor MCVs farther north over east TN
   and WV.  These features will track eastward today across much of the
   Southeast states and Mid Atlantic region.  Strong daytime heating is
   occurring over this region, where dewpoints in the 70s will yield
   afternoon MLCAPE values of 1000-2000 J/kg.  Strong westerly flow
   aloft, steep low-level lapse rates, and favorable large-scale
   forcing will combine for an active strong/severe thunderstorm event
   for this region.  Multiple lines and clusters of storms will
   traverse the area this afternoon and evening, posing a risk of
   damaging winds and some hail.  

   ...Northern PA/NJ/NY into New England...
   Persistent cloud cover is limiting heating/destabilization from
   northern PA/NJ northward into New England.  Despite the limited
   thermodynamic environment, model guidance and recent radar trends
   suggest the potential for scattered afternoon thunderstorms. 
   Forecast soundings show very favorable vertical shear profiles for
   organized or even rotating storms capable of gusty winds and perhaps
   a tornado.  However, given the weak CAPE profiles, it appears that
   the severe risk in this area will remain widely spaced and primarily
   marginal. Nevertheless, have extended the SLGT risk area northward
   into central NY ahead of ongoing strong activity.

   ...NE/IA/KS/MO...
   A well-defined shortwave trough is moving across SD/NE this morning.
    12z model guidance provides continued confidence that a cluster of
   intense storms will continue to develop/evolve with this feature
   over northeast NE and track southeastward into parts of IA/MO/KS. 
   These storms may produce very large hail and damaging winds.  This
   corridor may require an upgrade to ENH at 20z once mesoscale details
   become more clear on the evolution of the cluster of storms.

   ...Northern and Central High Plains...
   Strong heating is occurring today from southeast MT into eastern WY
   and far eastern CO, where dewpoints in the mid 40s to lower 50s and
   steep mid-level lapse rates are present.  Scattered thunderstorms
   are expected to develop along this axis by mid/late afternoon -
   spreading eastward through the evening. Forecast soundings show
   favorable vertical shear profiles for a few supercells capable of
   large hail and damaging winds.  An isolated tornado or two is also
   possible.  The activity which forms in eastern CO/western KS appears
   to have the best chance of persisting deep into the evening and
   spreading farther east across KS.

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