SPC AC 181958

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0258 PM CDT Sat May 18 2024

   Valid 182000Z - 191200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR WESTERN
   PORTIONS OF THE UPPER PENINSULA OF MICHIGAN INTO CENTRAL
   WISCONSIN...

   ...SUMMARY...
   Large hail and damaging winds remain possible in the western Great
   Lakes region this afternoon.

   ...20Z Update...
   Cloud cover has remained across portions of southeast Georgia into
   North Florida. Furthermore, outflow from convection has surged south
   of Jacksonville. Storms are initiating on this boundary, but are
   quickly being undercut. Wind probabilities have been reduced in
   these areas as the environment has generally become more stable in
   the wake of the boundary.

   A few marginal supercells have develop both near/north of Orlando
   and along the sea breeze boundary in eastern Florida, the 5%
   wind/hail probabilities have been adjusted to account for this
   activity. The 15Z Cape Canaveral sounding showed 7.3 C/km mid-level
   lapse rates and 43 kts of effective shear. Marginally severe hail
   and damaging winds are possible, but weak mid-level ascent and
   warmer temperatures aloft (-7 C) should limit overall storm
   organization/intensity.

   Elsewhere, the outlook remains unchanged other than adjustments to
   the general thunderstorm areas to account for current observations.

   ..Wendt.. 05/18/2024

   .PREV DISCUSSION... /ISSUED 1129 AM CDT Sat May 18 2024/

   ...North FL/South GA...
   A persistent band of widespread showers and thunderstorms extends
   from the FL Panhandle into southern GA.  This band will sag
   southward through the day, with occasional intensification along the
   leading edge as daytime heating destabilizes the upstream
   environment.  Locally gusty/damaging winds appear to be the main
   threat.

   ...FL East Coast...
   Strong heating is occurring along the FL peninsula, where hot/humid
   conditions will be present this afternoon.  Westerly low-level flow
   will focus a rather strong sea-breeze circulation, with most CAM
   solutions suggesting scattered thunderstorm development.  It is
   uncertain whether the activity will be along the immediate
   coastline, or offshore.  However, sufficient vertical shear and CAPE
   profiles indicate a risk of supercells capable of large hail and
   perhaps a tornado/waterspout or two.


   ...Western Great Lakes into Central Plains...
   A surface cold front will extend from western WI into parts of
   IA/MO/KS by mid-afternoon.  Scattered thunderstorms are expected to
   form along the front from the MN Arrowhead southward into western
   WI, with more isolated convection from there southward into the
   Plains states.  Forecast soundings in MI/WI/Upper MI show favorable
   vertical shear profiles for a few supercell structures capable of
   hail and damaging wind gusts.  Therefore have added a SLGT risk area
   for that scenario.  From IA south, relatively weak winds in the
   lowest 6km and a deep sub-cloud layer suggest outflow dominant
   storms with a more marginal severe threat.

   ...CO/Western KS...
   Model guidance and water vapor imagery show a plume of mid-level
   moisture spreading into central CO.  This should result in a cluster
   of thunderstorms over the mountains by mid-afternoon, spreading
   eastward into the Plains this evening.  Inverted-v sounding profiles
   and favorable westerly flow aloft will promote gusty/damaging wind
   potential in some of this activity.

   ...MS/AL into the Carolinas...
   A relatively moist and unstable air mass is in place today across
   the TN Valley into the Carolinas.  Little cap and pockets of daytime
   heating will lead to scattered afternoon thunderstorms throughout
   the region - with some potential for locally gusty/damaging wind
   gusts.  Areas of slightly greater focus for concern of strong storms
   are 1) Ahead of the MCV currently over northern MS, and 2)  an axis
   from northern AL into central NC along the northern edge of slightly
   stronger winds aloft.

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