Mesoscale Discussion 1331
NWS Storm Prediction Center Norman OK
0257 PM CDT Mon Jul 17 2017
Areas affected...Portions of the northern Plains and upper
Concerning...Severe potential...Watch likely
Valid 171957Z - 172100Z
Probability of Watch Issuance...80 percent
SUMMARY...Thunderstorms will continue to develop across the region
through this evening, with an attendant threat of damaging winds,
large hail, and perhaps a tornado. Watch issuance is likely within
the next hour.
DISCUSSION...A cumulus field continues to organize across portions
of NE South Dakota, SE North Dakota, and western Minnesota this
afternoon, as a cold front and associated low pressure shift across
the region. Surface heating (i.e., temperatures in the 90s) has
combined with sufficient boundary-layer moisture and instability
aloft to promote MLCAPE values upwards of 1500-2500 J/kg this
afternoon. While mid-level westerly flow remains modest, veering of
winds with height has provided around 30-40 kt of effective shear.
Combined with ample mid-level buoyancy, a mixture of supercells and
multicell clusters will likely organize over the next few hours,
with a resultant threat of damaging winds and large hail.
Additionally, while low-level flow remains relatively weak, ample
boundary-layer moisture and backed flow with eastward extent may
favor a tornado or two as well this evening. As such, watch issuance
is expected within the next hour.
...Please see www.spc.noaa.gov for graphic product...
LAT...LON 45199575 45189698 45509747 46309777 46659766 46819738
47209646 47569451 47529304 47479248 47059216 46309220
45619236 45269418 45199575