Mesoscale Discussion 1452

Issued

Aug 9, 2021, 2:56 PM CDT (19:56 UTC)

Expired

Aug 9, 2021, 5:00 PM CDT

In force

2 hr

Issued by

the Storm Prediction Center

Concerning

Severe potential...watch likely

Chance of a watch

80%

The Fargo/Grand Forks radar (KMVX), 128 km from the middle of the area, began a volume at 19:59 UTC, the scan nearest the moment this went out.

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• Severe Thunderstorm Watch 418Aug 9, 3:55 PM CDT

391 
ACUS11 KWNS 091957
SWOMCD
SPC MCD 091956 
MNZ000-NDZ000-092200-

Mesoscale Discussion 1452
NWS Storm Prediction Center Norman OK
0256 PM CDT Mon Aug 09 2021

Areas affected...Portions of central and eastern North Dakota.

Concerning...Severe potential...Watch likely 

Valid 091956Z - 092200Z

Probability of Watch Issuance...80 percent

SUMMARY...Severe thunderstorm development is expected within the
next 1 to 2 hours. Large hail, damaging winds, and perhaps a tornado
are all possible.

DISCUSSION...19Z surface analysis shows a ~1006mb surface low near
Sheridan, North Dakota. Extending east front this surface low is a
stationary front which extends into northwest Minnesota. This
boundary has been reinforced by precipitation for much of the
morning, but now that convection is waning, may begin to lift north
as a warm front through the afternoon and evening. In addition, a
cold front extends from near this surface low southward to central
South Dakota. 

Deep-layer ascent has started to spread eastward ahead of an
approaching upper-level low with expanding cloud cover and some
elevated convection across northwest North Dakota. In the last 30
minutes, some low-level cumulus has started to develop near the
low-pressure center and extending southward along the cold front.
Vertical development currently appears limited, and SPC mesoanalysis
still shows inhibition across the region. However, expect this
inhibition to erode over the next 1 to 2 hours as stronger ascent
arrives. The environment is favorable for supercells given around
1500 J/kg MLCAPE (forecast to increase above 2000 J/kg) and
effective shear around 40 to 50 knots per SPC mesoanalysis. 

Large hail will likely be the primary threat given the storm mode,
steep mid-level lapse rates, and storm motion which will likely
cause storms to move to the cool side of the stationary front and
perhaps become elevated. However, there will also be a threat for
severe wind and perhaps a tornado or two. The best tornado potential
would likely be along or maybe slightly on the northern side of the
stationary front where enough warming has occurred for surface based
storm development in a region with significantly backed surface
winds. Weak winds (<20 knots) in the lowest 2km per regional RAOBs
will also be a limiting factor to a greater tornado threat. 

A watch is likely within the hour.

..Bentley/Thompson.. 08/09/2021

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

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

LAT...LON   48110124 49020053 49089718 48499716 47079698 46599706
            46319920 46650051 48110124

Mesoscale Discussions in North Dakota, 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.