A Mesodiscussion is issued by the National Weather Service's Storm Prediction Center when there is a chance of a significant weather event impacting an area. These are routinely issued before weather watches or as updated to weather watches.

SPC MD 1124

MD 1124 CONCERNING SEVERE THUNDERSTORM WATCH 301... FOR EASTERN MONTANA...WESTERN NORTH DAKOTA...NORTHEAST WYOMING...AND NORTHWEST SOUTH DAKOTA
MD 1124 Image

Mesoscale Discussion 1124
NWS Storm Prediction Center Norman OK
0618 PM CDT Sat Jul 21 2018

Areas affected...Eastern Montana...Western North Dakota...Northeast
Wyoming...and Northwest South Dakota

Concerning...Severe Thunderstorm Watch 301...

Valid 212318Z - 220045Z

The severe weather threat for Severe Thunderstorm Watch 301
continues.

SUMMARY...The severe threat continues across severe thunderstorm
watch 301. The greatest threat will likely continue to be with the
large storm on the Montana/North Dakota border entering McKenzie
county as it continues southeast.

DISCUSSION...Numerous storms have developed along the front in
eastern Montana and eastern Wyoming. Additional storm development is
possible along the front in the next few hours. A large storm has
developed in far northeast Montana with reports of hail up to 2
inches and damage from wind blown hail. An expanding cumulus field
in western North Dakota where MLCAPE is around 2000 J/kg combined
with effective shear around 40 to 50 knots would suggest this storm
will maintain intensity through the evening as it continues
southeast. The mean wind will tend to advect this storm cluster east
into an increasingly stable airmass, but deviant right motion and
continued development on the southwestern flank of the cluster
should continue the threat along the instability gradient towards
Dickinson, ND. 

Further south along the front, storms have struggled to maintain
their intensity, likely due to weak subsidence from slight height
rises aloft. This will likely limit a more organized threat in this
area through the evening. However, brief strong updrafts before the
storms begin to weaken will continue to pose a large hail and
damaging wind threat.

..Bentley.. 07/21/2018

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

ATTN...WFO...ABR...BIS...UNR...CYS...BYZ...GGW...

LAT...LON   48070517 48270466 48420419 48390362 48250262 47840229
            47000209 45670194 44710186 43800191 43480253 43360336
            43400453 43480520 44170564 46600534 48070517 

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