Mesoscale Discussion 142

Issued

Feb 6, 2017, 11:20 PM CST (05:20 UTC)

Expired

Feb 7, 2017, 1:15 AM CST

In force

115 min

Issued by

the Storm Prediction Center

Chance of a watch

5%

The Indianapolis radar (KIND), 125 km from the middle of the area, began a volume at 05:20 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

505 
ACUS11 KWNS 070520
SWOMCD
SPC MCD 070520 
KYZ000-INZ000-ILZ000-IAZ000-070715-

Mesoscale Discussion 0142
NWS Storm Prediction Center Norman OK
1120 PM CST Mon Feb 06 2017

Areas affected...Portions of IL...IN...northwest KY

Concerning...Severe potential...Watch unlikely 

Valid 070520Z - 070715Z

Probability of Watch Issuance...5 percent

SUMMARY...Thunderstorms developing from parts of the middle MS
Valley to the lower/middle OH Valley through the late evening/early
overnight hours may produce small hail. A few instances of
marginally severe hail cannot be ruled out. Watch issuance is not
anticipated.

DISCUSSION...VAD wind profiles across the region are suggesting a
broad strengthening of low-level southwesterly flow from the middle
MS Valley to the lower OH Valley, downstream of weakly phased
midlevel perturbations over the Central States. Related mass
convergence within the exit region of a consolidating low-level jet,
coupled with isentropic ascent along the jet, should promote an
increase in the coverage/intensity of elevated convection through
the overnight hours. Isolated thunderstorm activity has already been
increasing across portions of the region, and further increase is
expected during the next few hours.

While inflow layers are forecast to remain rooted above a
modifying/moistening cool dome at the surface, 00Z soundings across
the Central U.S. indicate that an elevated mixed layer will continue
to be advected into the region, before increasingly widespread
convection overturns related elevated buoyancy. Generally small hail
may accompany the more robust updrafts, given modest effective shear
(generally 25-35 kt). The presence of 700-500-mb lapse rates around
6.5-7.5 C/km may support a few instances of marginally several hail
with the more discrete cells. The lack of stronger effective shear,
and lack of stronger elevated buoyancy, will tend to limit the
severe risk. Also, as interacting convective elements tend to grow
upscale into small clusters, the severe-hail risk may tend to
lessen.

..Cohen/Hart.. 02/07/2017

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

ATTN...WFO...ILN...LMK...IWX...IND...PAH...LOT...ILX...LSX...
DVN...

LAT...LON   37788681 39138954 39899097 40599144 40939052 40888839
            40628673 40138589 39328514 38278477 37748531 37788681

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The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.