Mesoscale Discussion – Severe T-storm Watch possible in west-central and SW Illinois this afternoon

Weather
Mesoscale Discussion 1442
   NWS Storm Prediction Center Norman OK
   1140 AM CDT Sun Aug 08 2021

   Areas affected...Portions of central/eastern MO and western/southern
   IL

   Concerning...Severe potential...Watch possible 

   Valid 081640Z - 081915Z

   Probability of Watch Issuance...60 percent

   SUMMARY...A threat for scattered damaging winds and severe hail
   should increase this afternoon. Watch issuance is possible.

   DISCUSSION...Widespread cloudiness is present across much of western
   MO this morning, which has limited heating across this area so far.
   Less cloud cover over central/eastern MO into IL has allowed surface
   temperatures to generally warm into the 80s as of 1630Z. A very
   moist low-level airmass depicted on the 12Z SGF sounding and
   evidenced by low to mid 70s surface dewpoints from various
   observations sites is present across this region. Continued diurnal
   heating will likely allow 2000-3000 J/kg of MLCAPE to develop by
   peak afternoon heating. A shortwave trough evident in water vapor
   satellite imagery will move eastward from the central Plains towards
   the mid MS Valley through the rest of the day. Large-scale ascent
   preceding this feature will likely encourage the development of
   scattered to numerous thunderstorms this afternoon across much of
   central/eastern MO and eventually into western IL.

   Initial storms will probably focus along a differential heating zone
   and remnant outflow boundary present across south-central MO as
   small-scale perturbations embedded within the shortwave trough
   overspread this area. Mid-level flow is not expected to be overly
   strong, but marginal deep layer shear around 25-30 kt should be
   enough to support some storm organization. Convection will probably
   tend to form into multiple clusters with time. As low-level lapse
   rates continue to steepen, damaging downdraft wind gusts should
   become the primary threat. But, isolated severe hail may also occur
   with initially more discrete development. Trends will be monitored
   for signs of increasing convective coverage and intensity, with
   watch issuance possible early this afternoon.
Current Regional Weather Radar Mosaic

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