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ACUS11 KWNS 311900
SWOMCD
SPC MCD 311900
MNZ000-NDZ000-312130-

Mesoscale Discussion 1397
NWS Storm Prediction Center Norman OK
0200 PM CDT Fri Aug 31 2018

Areas affected...extreme eastern ND into northern MN

Concerning...Severe potential...Watch possible

Valid 311900Z - 312130Z

Probability of Watch Issuance...40 percent

SUMMARY...Sporadic strong storms may produce hail this afternoon.
With uncertainty in the evolution of the severe threat, a watch is
not expected in the near-term, but may be needed later this
afternoon or early evening.

DISCUSSION...Severe threat continues to be uncertain across far
eastern ND into northern MN early this afternoon. Timing and
coverage forecast has been complicated by widespread cloud cover,
limiting heating and reinforcing strong inhibition across much of
the area. Over the last hour or two, some pockets of stronger
heating have occurred over northern MN and billowing cumulus has
been noted in visible satellite imagery. Isolated thunderstorms have
developed in isentropic upglide ahead of the surface front across
northwest MN and in the vicinity of an impulse related to early
morning convection tracking northeast out of SD into west-central
MN. Based on modified RAP/HRRR/NAM 4km soundings, this activity
should be elevated with a stout EML noted between 850-700 mb. Above
this EML, steep lapse rates and plenty of elevated instability exist
per 12z regional RAOBs. However, convection across northwest MN may
become surface based as it moves toward the area of aforementioned
clearing where surface inhibition is much lower. Additionally, deep
layer shear on the order of 40 kt favors organized cells.

Initial convection should mostly remain elevated, and sporadic
instances of severe hail are possible. The threat should initially
remain rather sparse until later this evening when stronger forcing
for ascent overspreads the area as the main upper trough ejects
eastward and the surface cold front begins to advance east/southeast
across the region. This should also allow for storms to become more
surface based as the low level cap erodes. At that time, the severe
threat may increase sufficiently to warrant a severe thunderstorm
watch. In the short-term, uncertainty and the isolated nature of
the threat should precluding a watch issuance for at least another
couple of hours.

..Leitman/Grams.. 08/31/2018

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

ATTN...WFO...DLH...FGF...

LAT...LON 48789286 48429236 48209236 47879253 47609297 46439568
46259658 46439692 46879696 47999705 48629617 48959562
49239504 49289491 48929402 48789286



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