SPC AC 202047

   Day 1 Convective Outlook AMEND 1
   NWS Storm Prediction Center Norman OK
   0347 PM CDT Mon May 20 2024

   Valid 202000Z - 211200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS THE
   CENTRAL HIGH PLAINS...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   NORTHERN ILLINOIS AND SOUTHERN WISCONSIN...

   AMENDED FOR LOWER MICHIGAN

   ...SUMMARY...
   The primary threat for severe thunderstorms today will be over parts
   of the central Plains, with large hail, damaging wind gusts, and a
   few tornadoes possible.

   ...20z Update...
   No changes to forecast reasoning and outlook thresholds for the
   Plains severe risk -- see previous discussion below. Some spatial
   adjustments made across southern Wisconsin and northern Illinois for
   an eastward-shifting severe risk, which includes upward-adjusted
   probabilities (Slight Risk) across parts of Lower Michigan.

   ..Guyer.. 05/20/2024

   .PREV DISCUSSION... /ISSUED 1133 AM CDT Mon May 20 2024/

   ...Central High Plains...
   A large upper trough will slowly deepen across the western United
   States today, with strengthening southwesterly mid/upper level flow
   spreading across the Plains states.  A band of mid-level moisture
   and instability will result in scattered high-based thunderstorms
   across northern CO/southern WY by mid-afternoon, capable of locally
   damaging wind gusts.  Other discrete supercell storms may form in
   vicinity of the DCVZ as southeasterly low-level winds and elevated
   terrain aid in initiation.  These storms will track
   east-northeastward into a progressively more moist/unstable air
   mass, with the risk of very large hail and a few tornadoes through
   the evening.  By mid-evening, coverage of storms will increase over
   southwest NE as a southerly low-level jet strengthens, with storms
   progressing across the central Plains overnight with a continued
   risk of large hail and damaging winds.

   ...IL/WI...
   A well-defined remnant MCV from overnight convection over KS is
   currently over northeast IA.  A surface boundary extends eastward
   from the low across northern IL.  Broken clouds and partial
   afternoon heating will aid in the development of thunderstorms near
   the MCV later today as it tracks across southern WI/northern IL. 
   Any storm that can interact with the boundary would have the
   potential to become a supercell and pose a risk of a tornado or two.
    Otherwise, hail and gusty winds could occur with the strongest
   cells.

   ...Southeast FL...
   Widely scattered afternoon thunderstorms are possible across
   southeast FL.  Ample low-level moisture, strong heating, cyclonic
   midlevel flow, and relatively steep lapse rates could result in a
   strong storm or two capable of gusty winds and hail.

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