SPC MD 643


MD 0643 Image

Mesoscale Discussion 0643
NWS Storm Prediction Center Norman OK
0714 PM CDT Thu May 16 2019

Areas affected...Southern and Eastern Iowa...Northern Illinois

Concerning...Severe potential...Watch possible 

Valid 170014Z - 170215Z

Probability of Watch Issuance...60 percent

SUMMARY...An isolated severe threat is likely to continue developing
across parts of southern and eastern Iowa eastward into northern
Illinois. Wind damage and hail will be the primary threats. Weather
watch issuance may be needed especially as uncertainty concerning
convective coverage decreases.

DISCUSSION...The latest surface analysis has a cold front from
eastern Nebraska extending eastward across central Iowa into
northern Illinois. An axis of maximized low-level moisture and
enhanced convergence near an outflow boundary exists across northern
Illinois where convective initiation has occurred in the last hour.
Storm development in this area should remain relatively isolated,
moving southeastward across north-central Illinois over the next
hour or two. A wind damage and hail threat will be possible with
this convection.

Further to the west, An axis of moderate instability is analyzed
across southern and eastern Iowa. The RAP is estimating MLCAPE
values in the 1500 to 2500 J/kg range and shows 0-3 km lapse rates
exceeding 8.0 C/km along this corridor. As a capping inversion
decreases and low-level convergence becomes enhanced along the
front, cell initiation is expected to occur. The latest short-term
guidance suggests that scattered surface-based initiation will take
place by 01Z to 02Z. In addition to the instability, the WSR-88D VWP
at Davenport, Iowa shows 0-6 km shear near 35 kt suggesting that a
severe threat may develop as cells increase in coverage. Wind damage
and hail will likely be the primary threats.

..Broyles/Guyer.. 05/17/2019

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


LAT...LON   42209173 42829056 42788979 42228886 41438815 40608797
            40548825 40958880 41128951 41159146 40989334 41019414
            41409423 41789315 42209173 

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