MD 1254 CONCERNING SEVERE POTENTIAL…WATCH POSSIBLE FOR NORTHERN AND CENTRAL IN INTO PARTS OF NORTHWEST AND WEST-CENTRAL OH
Mesoscale Discussion 1254
NWS Storm Prediction Center Norman OK
0751 AM CDT Fri Jul 07 2017
Areas affected...northern and central IN into parts of northwest and
west-central OH
Concerning...Severe potential...Watch possible
Valid 071251Z - 071445Z
Probability of Watch Issuance...40 percent
SUMMARY...Storms are expected to become more widespread through this
morning into the early afternoon across northern into central IN and
parts of northwest to west-central OH. The probability for an
increase in severe storm coverage should increase, with large hail
and damaging winds being the primary severe-weather threats.
Convective trends will be monitored across this region, with the
potential for WW issuance later this morning.
DISCUSSION...Morning time-lapse of radar imagery and lightning
intensities showed a small cluster of storms increasing in intensity
across far northern IN (Porter County to Elkhart County), with IR
satellite imagery indicating cooling cloud tops. These storms
formed in an environment consisting of steep midlevel lapse rates
(7-8 C/km in the 3-5 km layer per 12Z RAOBS at ILX/DVN), moderate
instability, and effective bulk shear of 35-45 kt. 1.75 inch hail
was reported with a storm in Porter County at 1207Z.
The 06Z NAM/09Z ESRL HRRR, while slow with convective initiation
across northern IN, suggest storm coverage will increase across the
rest of northern IN into northwest OH through the late morning and
spread into central IN and west-central OH by or after Noon.
Visible satellite imagery indicated strong surface heating will
occur today, further destabilizing the environment with mixed-layer
CAPE exceeding 2000 J/kg. This combined with an increase in
effective bulk shear to 40-50 kt this afternoon suggests organized
severe storm coverage should increase later this morning into the
early afternoon, with large hail and damaging winds the primary
severe-weather threats. Although stronger forcing for ascent is
expected to arrive into the Midwest later today, the trailing
portion of a shortwave trough moving through southern Lower MI at
this time may continue to provide sufficient upward vertical motion
for additional storm development into this afternoon across the
discussion area.
..Peters/Guyer.. 07/07/2017
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...ILN...IWX...IND...LOT...
LAT...LON 41478712 41648658 41578583 41558503 41448438 41098396
40598391 40138406 39988440 40008534 39978627 40108668
40308697 40788717 41478712
from SPC Mesoscale Discussions http://bit.ly/2tPPmCN
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