SPC MD 1101

MD 1101 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PORTIONS OF FAR EASTERN IA...NORTHERN/CENTRAL IL...AND NORTHWESTERN IN

Mesoscale Discussion 1101
NWS Storm Prediction Center Norman OK
0205 PM CDT Tue Jun 20 2017

Areas affected...Portions of far eastern IA...northern/central
IL...and northwestern IN

Concerning...Severe potential...Watch unlikely 

Valid 201905Z - 202130Z

Probability of Watch Issuance...20 percent

SUMMARY...An isolated large hail and damaging wind threat may
develop this afternoon. Watch issuance is unlikely.

DISCUSSION...A shortwave trough over WI is embedded within
large-scale troughing over much of the eastern CONUS. Ascent
associated with this shortwave trough is encouraging convective
development along a surface front located across central/eastern IA
into northern IL as of 19Z. Although low-level moisture remains
limited across northern/central IL and vicinity, it should prove
sufficient in combination with strong diurnal heating to maintain
convection as it moves quickly southeastward through the remainder
of the afternoon and into this evening. Southwesterly low-level
winds both strengthen and veer to northwesterly with height, and
resultant effective bulk shear values of 40-50 kt will support
organized updrafts.

Instability should remain limited to around 500-1000 J/kg through
peak heating, mainly owing to warm mid-level temperatures centered
around 500 mb per 12Z soundings from DVN and ILX. But, steep low and
mid-level lapse rates below 500 mb should enhance convective
downdrafts, with an isolated strong to locally damaging wind threat
possible with expected scattered thunderstorms. A few instances of
marginally severe hail may also occur. The previously mentioned warm
mid-level temperatures may limit more robust updraft intensities,
and the corresponding severe threat will probably remain too
isolated/marginal to warrant a watch.

..Gleason/Hart.. 06/20/2017

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

ATTN...WFO...IWX...IND...LOT...ILX...LSX...DVN...

LAT...LON   40749145 42139074 42088902 41678758 41048626 39738775
            38919003 39869130 40749145 

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