SPC MD 681

MD 0681 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR PORTIONS OF SOUTHERN IA...NORTHERN MO...CENTRAL/NORTHERN IL

Mesoscale Discussion 0681
NWS Storm Prediction Center Norman OK
1205 PM CDT Wed May 10 2017

Areas affected...Portions of southern IA...northern
MO...central/northern IL

Concerning...Severe potential...Watch possible 

Valid 101705Z - 101930Z

Probability of Watch Issuance...60 percent

SUMMARY...The area is being monitored for an increasing
severe-thunderstorm risk this afternoon. While there is some
uncertainty regarding the timing of more substantial increase in
severe risk, Watch issuance will be possible within the next few
hours.

DISCUSSION...A persistent thunderstorm cluster, enhanced by ascent
accompanying a long-lived MCV, is tracking eastward near a
quasi-stationary front draped from far southern IA into northern
parts of central IL. Surface-based destabilization continues near
and south of this boundary owing to diurnal heating amid surface
dewpoints in the lower/middle 60s -- supporting MLCAPE around 1000
J/kg and minimal inhibition. As buoyancy for inflow supporting the
thunderstorm cluster continues to increase, storms may experience
gradual intensification -- especially given 40-50 kt of
west-southwesterly flow in the mid levels indicted by area VAD wind
profiles offering moderate deep shear. At least isolated damaging
wind gusts may accompany this activity as it spreads generally
eastward through the afternoon.

The arrival of a mid-level perturbation from the southwest may
encourage modest strengthening of deep shear through the afternoon,
resulting in increasing mesoscale organization to the thunderstorm
cluster. If this were to occur, the severe-wind risk could increase.
Furthermore, some increase in large-scale ascent, accompanying the
disturbance aloft, may support convective development ahead of and
south of the established thunderstorm cluster, perhaps briefly
exhibiting supercell characteristics. A brief tornado could occur,
especially near the surface boundary where low-level SRH/ambient
vertical vorticity will be enhanced. Otherwise, severe wind gusts
and hail (aided by moderately steep mid-level lapse rates) should be
the primary hazards.

..Cohen/Guyer.. 05/10/2017

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...LOT...ILX...LSX...DVN...DMX...EAX...

LAT...LON   41359314 41439127 41018841 40278802 39858856 39909029
            40139295 40599378 41049367 41359314 

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