Mesoscale Discussion 1587

Issued

Aug 24, 2021, 3:00 AM CDT (08:00 UTC)

Expired

Aug 24, 2021, 5:00 AM CDT

In force

2 hr

Issued by

the Storm Prediction Center

Concerning

01z outlook upgrade

The Minneapolis radar (KMPX), 101 km from the middle of the area, began a volume at 08:02 UTC, the scan nearest the moment this went out.

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680 
ACUS11 KWNS 240800
SWOMCD
SPC MCD 240800 
WIZ000-MNZ000-SDZ000-NDZ000-241000-

Mesoscale Discussion 1587
NWS Storm Prediction Center Norman OK
0300 AM CDT Tue Aug 24 2021

Areas affected...Portions of western/central MN into far
west-central WI

Concerning...01Z Outlook upgrade 

Valid 240800Z - 241000Z

SUMMARY...The 01Z Day 1 Convective Outlook has been effectively
upgraded to a Slight Risk through 12Z this morning across recently
issued Severe Thunderstorm Watch 460. Scattered damaging wind gusts
up to 70 mph should be the main threat with a line of storms moving
eastward.

DISCUSSION...An organized MCS with a history of producing sporadic
severe wind gusts across eastern ND/SD will continue to move
eastward over parts of western/central MN this morning. A surface
front and corresponding instability gradient is generally draped
east to west across this region. Rich low-level moisture and steep
mid-level lapse rates are supporting substantial MUCAPE (2000-3000+
J/kg) along and south of the front. 30-40 kt of deep-layer shear
will likely prove sufficient for continued organization of this MCS
through the early morning hours, with some evidence of a rear-inflow
jet present per recent velocity data from KABR. The northern portion
of the line may tend to stay on the cool side of the surface front,
but the southern portion along/south of the boundary may have a
tendency to strengthen over the next few hours as the line develops
east-southeastward along the instability gradient. Given the large
reservoir of buoyancy already available, and continued low-level
warm advection which may further destabilize the environment ahead
of the line across central MN, there should be an increased
potential for mainly scattered severe/damaging downdraft wind gusts
up to 70 mph as the southern flank of the MCS strengthens.
Occasional large hail may also occur with discrete storms developing
across southern/central MN in the low-level warm advection regime.
The past several HRRR runs have been consistent in depicting this
scenario. Severe Thunderstorm Watch 460 has recently be issued to
address this threat, and the 01Z Day 1 Convective Outlook has
effectively been upgraded to a Slight Risk through 12Z for the
counties within the watch.

..Gleason/Thompson.. 08/24/2021

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

ATTN...WFO...DLH...ARX...MPX...FGF...FSD...ABR...

LAT...LON   44119518 44259563 44499601 44639645 45619686 46639678
            46639678 46689618 46629552 46369455 46159308 45699214
            44569214 44199255 44139396 44089455 44109498 44119518

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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.