Mesoscale Discussion 1456

Issued

Aug 9, 2021, 9:52 PM CDT (02:52 UTC)

Expired

Aug 9, 2021, 11:15 PM CDT

In force

83 min

Issued by

the Storm Prediction Center

Concerning

Severe thunderstorm watch 418

Counties Kittson County, MN, Marshall County, MN, Norman County, MN, Pennington County, MN, Polk County, MN, Red Lake County, MN, Roseau County, MN, Cavalier County, ND, Grand Forks County, ND, Griggs County, ND, Nelson County, ND, Pembina County, ND, Ramsey County, ND, Steele County, ND, Traill County, ND, Walsh County, ND

The Fargo/Grand Forks radar (KMVX), 67 km from the middle of the area, began a volume at 02:54 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.

832 
ACUS11 KWNS 100252
SWOMCD
SPC MCD 100252 
MNZ000-NDZ000-100415-

Mesoscale Discussion 1456
NWS Storm Prediction Center Norman OK
0952 PM CDT Mon Aug 09 2021

Areas affected...eastern north Dakota northwestern Minnesota

Concerning...Severe Thunderstorm Watch 418...

Valid 100252Z - 100415Z

The severe weather threat for Severe Thunderstorm Watch 418
continues.

SUMMARY...Additional storm development across WW418 will likely
continue tonight as the main band of convection continues eastward.
Damaging winds and hail appear to be the main threats though a
tornado cannot be ruled out.

DISCUSSION...Ahead of a cold front across eastern North Dakota a
band of deep convection a couple of supercells continue to pose a
risk for severe weather. Recent radar trends suggest additional
storm development taking place along the cold front will continue as
deep ascent from an upper trough over the northern Plains continues
eastward. As nocturnal stabilization progresses, cold pool
development may favor a more linear storm mode supportive of
damaging wind gusts as storms approach the Minnesota border. Latest
HRRR guidance supports this showing additional storm development
south and east of the main band merging into a more linear
configuration.  

Ahead of the main band of storms, a likely tornadic supercell in the
vicinity of Grand Forks has been able to remain isolated as it
tracks along a warm frontal zone. Enhanced helicity (200-300 m2/s2
ESRH) owing to backed surface flow along the front may continue to
support a tornado threat over the next hour or so before nocturnal
inhibition increases substantially hindering low-level mesocyclone
maintenance. 

As storms approach the eastern edge of WW418 expiring at 0400z, a
general decrease in severe potential is expected. While some severe
risk may exist to the east of the current watch, a downstream watch
appears unlikely given an increasingly stable boundary layer.
Nevertheless, local watch extensions across northeastern North
Dakota and northwestern Minnesota are possible.

..Lyons/Hart.. 08/10/2021

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

ATTN...WFO...FGF...BIS...

LAT...LON   47299870 48419915 49009899 49129785 49099649 48999592
            48799558 48369535 47859532 47519556 47319600 47179689
            47069759 47299870

Mesoscale Discussions in North Dakota, 2021Mesoscale Discussions in Minnesota, 2021Every mesoscale discussion in 2021

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.