SPC AC 101627

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1127 AM CDT Tue Aug 10 2021

   Valid 101630Z - 111200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
   INTO EARLY TONIGHT FOR EASTERN IA...NORTHERN IL...AND SOUTHERN WI...

   ...SUMMARY...
   Severe thunderstorms capable of wind damage and isolated large hail
   will be possible across a broad portion of the Midwest and Great
   Lakes region, especially this afternoon and evening. Locally severe
   wind gusts will also be possible in parts of the Ohio Valley and
   central Appalachians/Northeast States.

   ...Parts of the upper/middle MS Valley through tonight...
   A complex scenario is expected today, with corresponding
   predictability concerns.  On the larger scale, a midlevel shortwave
   trough will eject east-northeastward over northern MN today, as an
   upstream trough digs southeastward over SK/MB.  A surface front/wind
   shift associated with the ejecting trough will move
   eastward/southeastward across MN/IA before stalling late today. 
   Farther south, a convectively-enhanced midlevel trough approaching
   southwest IA will continue eastward today, and a loosely organized
   cluster of storms is ongoing along I-70 in MO.  It is possible that
   outflow with this cluster will be the impetus for more intense
   convection this afternoon farther east in northeast MO/west central
   IL, as well as with the convectively-enhanced wave interacting with
   the stalling front later this afternoon toward northeast IA.

   A reservoir of large buoyancy (MUCAPE greater than 4000 J/kg) is
   present across the Corn Belt per 12z soundings, based on 7.5-9 C/km
   midlevel lapse rates and lowest 100-mb mean mixing ratios of 17-19
   g/kg (near-surface dewpoints in the mid-upper 70s).  Given the
   aforementioned possibilities of more than one storm cluster and the
   area of large to extreme CAPE, have expanded the higher damaging
   wind probabilities farther south into MO/IL.  Lapse rate profiles
   will favor both intense updrafts and downdrafts, with the potential
   for a swath or two of damaging winds (possibly up to 75-80 mph),
   though rather modest vertical shear casts some doubt on the
   organization and longevity of any storm clusters.

   ...Eastern OH/PA/NY this afternoon/evening...
   A midlevel trough with embedded perturbations will continue eastward
   today from the lower Great Lakes toward PA/NY.  Convection is
   ongoing in a band across east central OH, where there is some
   potential for a few damaging outflow gusts in the short term. 
   However, the storms are moving toward and area of weaker buoyancy,
   which casts doubt on the damaging-wind potential through the
   afternoon (refer to MD 1459 for additional details).  Otherwise, a
   few loosely organized storm clusters/bands are expected in advance
   of these embedded perturbations into NY/PA, where MLCAPE near 1000
   J/kg and a modest increase in flow/shear in the 850-500 mb layer
   will support multicell clusters capable of producing isolated wind
   damage.

   ..Thompson/Bentley.. 08/10/2021

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 2000Z