000
ACUS11 KWNS 222009
SWOMCD
SPC MCD 222009
WIZ000-MIZ000-MNZ000-222215-

Mesoscale Discussion 1396
NWS Storm Prediction Center Norman OK
0309 PM CDT Sat Jul 22 2017

Areas affected...portions of northeast MN...northwest WI...adjacent
portions of Lake Superior

Concerning...Severe potential...Watch possible

Valid 222009Z - 222215Z

Probability of Watch Issuance...40 percent

SUMMARY...Thunderstorms are expected to increase in coverage and
intensity through the remainder of this afternoon and early evening,
with a risk for large hail and locally strong wind gusts.  If
confidence regarding likely storm coverage increases then a watch
would be possible.

DISCUSSION...Visible satellite imagery shows areas of deepening
cumulus clouds in the vicinity of a surface trough/confluence zone
that extends from a surface low over southeast Manitoba southward
across eastern MN as of 20Z/3 pm CDT.  Additional deepening cumulus
were also noted in the vicinity of a lake breeze boundary around the
western portion of Lake Superior.  Beneath cool mid-level
temperatures, diurnal heating of mid-upper 60s surface dew points
has resulted in MLCAPE averaging 1000-locally 1500 J/kg.
Large-scale forcing for ascent associated with a pronounced
shortwave trough over southern Manitoba will develop across the
area, and combined with minimal CINH should result in thunderstorm
development over the next few hours.  Moderate westerly mid-level
flow will contribute to effective shear of 35-45 kts, with straight
hodographs favoring a few splitting storms capable of large hail.
Isolated strong wind gusts will also be possible, especially where
storms can congeal into clusters with time.

The primary uncertainty is the coverage of severe storms, and
convective trends/high-resolution guidance will be monitored for
increasing confidence in greater storm coverage that would warrant a
Severe Thunderstorm Watch.

..Bunting/Grams.. 07/22/2017

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

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

LAT...LON   44579218 44809261 46729319 47199337 48129362 48539324
            48479276 48269210 48109160 48169089 48139019 47928986
            47229042 46879037 46408988 45968921 44918950 44539097
            44579218