Mesoscale Discussion 1007

Issued

Jul 4, 2018, 9:56 AM CDT (14:56 UTC)

Expired

Jul 4, 2018, 12:00 PM CDT

In force

2 hr

Issued by

the Storm Prediction Center

Chance of a watch

20%

The Duluth radar (KDLH), 177 km from the middle of the area, began a volume at 14:59 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.

521 
ACUS11 KWNS 041457
SWOMCD
SPC MCD 041456 
MIZ000-WIZ000-MNZ000-IAZ000-041700-

Mesoscale Discussion 1007
NWS Storm Prediction Center Norman OK
0956 AM CDT Wed Jul 04 2018

Areas affected...Upper Michigan...Wisconsin...southeastern
Minnesota...northeastern Iowa

Concerning...Severe potential...Watch unlikely 

Valid 041456Z - 041700Z

Probability of Watch Issuance...20 percent

SUMMARY...Severe weather potential appears limited across much of
the Upper Midwest through midday, but a gradual increase in
thunderstorm development and intensification is at least possible by
early afternoon.

DISCUSSION...Synoptic forcing for the overnight mesoscale convective
system is now spreading northeastward into/through northwestern
Ontario.  Although the large deep remnant composite surface cold
pool to the south appears to be in the process of weakening, lift
along or just above its leading edge is maintaining renewed
thunderstorm development in a narrow eastward advancing band.  The
northern flank of this activity seems likely to be negatively
impacted by cool boundary layer air off Lake Superior within the
next hour or two, however the environment to the south, across
western/central Wisconsin into Iowa is moist and characterized by
moderate instability.  

The mid-level environment across much of the Upper Midwest is fairly
warm, but insolation ahead of the ongoing convection will contribute
to at least a gradual weakening of inhibition and further increase
in CAPE into early afternoon.  Despite rather modest vertical shear,
in the presence of 20-30 kt southwesterly deep layer mean flow, and
the lack appreciable synoptic support, it may not be out of the
question that the increasing instability may be enough to contribute
to continuing convective development and intensification supportive
of an increase in severe weather potential by this afternoon.

..Kerr/Hart.. 07/04/2018

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

ATTN...WFO...MQT...GRB...MKX...DLH...ARX...MPX...DMX...

LAT...LON   48759101 48668925 46598871 44258955 43429034 42839147
            43139275 43719321 44909227 48759101

Mesoscale Discussions in Wisconsin, 2018Mesoscale Discussions in Minnesota, 2018Mesoscale Discussions in Iowa, 2018Every mesoscale discussion in 2018

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.