SPC AC 201937

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0237 PM CDT Sun Jun 20 2021

   Valid 202000Z - 211200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM PARTS OF
   EXTREME EASTERN IOWA ACROSS CHICAGOLAND TO NORTHWEST OHIO AND
   SOUTHERN LOWER MICHIGAN...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
   ENHANCED RISK...AND ALSO OVER PARTS OF GEORGIA AND THE CAROLINAS...

   ...SUMMARY...
   Scattered severe storms are expected across the Midwest into the
   lower Great Lakes/upper Ohio Valley. Large hail, severe/damaging
   winds, and a few tornadoes are possible. Damaging winds and a couple
   of tornadoes are also possible across the Southeast.

   ...20Z Update...

   ...Southeast Coast...
   Air mass downstream of Tropical Depression Claudette continues to
   destabilize amid modest heating and ample low-level moisture. As
   mentioned in MCD #1034, a couple of transient supercells may pose an
   isolated risk for a tornado or two through the afternoon. The
   highest conditional risk for a tornado appears to be over parts of
   eastern NC during the afternoon due to the larger hodographs.
   Additionally, based on recent trends and the location of center of
   TD Claudette, the severe risk across southeast GA has diminished
   enough to remove Slight Risk-equivalent probabilities. Isolated
   threat across southern GA/northern FL merits continued inclusion of
   5% wind probabilities. 

   ...Elsewhere...
   Forecast delineated outlined in the previous outlook (discussion
   below) remains valid and no changes are needed.

   ..Mosier.. 06/20/2021

   .PREV DISCUSSION... /ISSUED 1122 AM CDT Sun Jun 20 2021/

   ...MO to OH...
   Current water vapor loop shows a convectively augmented vort max
   over northern MO.  New thunderstorm development has occurred in the
   past couple of hours in this region, with a corridor of rapid
   heating/destabilization occurring to the east from northeast MO into
   northern IL.  Storms will likely intensify through the afternoon
   along this axis, with the risk of damaging winds, large hail, and
   isolated tornadoes.  12z CAM solutions differ on the handling of
   this cluster, but the potential appears to exist for a longer-lived
   bowing structure that would track all the way into northern OH this
   evening.  Please refer to MCD #1032 for short-term details.

   ...MN/WI/IA/IL...
   Latest surface analysis shows a low over west-central MN.  clearing
   skies ahead of the low, along with southerly low-level winds, will
   help to warm/moisten and destabilize this area by mid-afternoon.  A
   consensus of model guidance shows intense thunderstorm development
   later today over southeast MN, southwest WI, and parts of
   northern/eastern IA.  Large hail and damaging winds will be possible
   with these storms.  A combination of remnant cloud debris and
   outflow boundaries complicate the scenario, but also increase the
   conditional risk of supercells and perhaps a few tornadoes this
   evening.  If the storms over MO do not materialize into a
   longer-lived bow, then this area of storms may persist for several
   hours and track eastward across the ENH risk area.

   ...GA/SC/NC...
   The remnants of Claudette continue to affect parts of GA and the
   Carolinas today, with relatively strong low-level winds from
   southeast GA into southern SC.  Considerable daytime heating and
   ample low level moisture will provide favorable thermodynamics for a
   few intense afternoon thunderstorms capable of damaging wind gusts
   and a few tornadoes.

   ...Southeast CO into southern KS late tonight...
   A surface cold front will extend from eastern CO into southern KS
   tonight, providing the focus for a few evening/overnight
   thunderstorms.  Sufficient CAPE/shear along this zone will pose a
   risk of hail in the strongest storms.

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