Mesoscale Discussion 178

Issued

Mar 14, 2021, 6:20 PM CDT (23:20 UTC)

Expired

Mar 15, 2021, 12:15 AM CDT

In force

6 hr

Issued by

the Storm Prediction Center

Concerning

Heavy snow

The Sioux Falls radar (KFSD), 117 km from the middle of the area, began a volume at 23:23 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.

512 
ACUS11 KWNS 142320
SWOMCD
SPC MCD 142320 
IAZ000-MNZ000-NEZ000-SDZ000-WYZ000-150515-

Mesoscale Discussion 0178
NWS Storm Prediction Center Norman OK
0620 PM CDT Sun Mar 14 2021

Areas affected...Much of South Dakota into portions of
Iowa...Nebraska...and Minnesota.

Concerning...Heavy snow 

Valid 142320Z - 150515Z

SUMMARY...Heavy snow will gradually expand in coverage across the
Upper Midwest after 0000 UTC. Snowfall rates of 1-2 inches per hour
are expected and will likely continue into the overnight hours.

DISCUSSION...6 pm Radar and METAR observations showed a large comma
head band of stratiform precipitation across portions of the
Northern Plain into the Upper Midwest. Gradual expansion of the
precipitation shield is expected over the next several hours as
forcing for ascent from a 564 DAM closed low over western Kansas
shifts to the east. The heaviest corridor of snow currently located
over western South Dakota will develop eastward, mainly after 0000
UTC, in part due to strong mid-level warm advection ahead of the
surface cyclone over southeastern Colorado. Regional model soundings
show a deep and saturated dendritic growth zone above a shallow
surface warm layer. This warm air will gradually erode as increased
low-level cool advection and dynamic column cooling develop this
evening and into the overnight. The result should be the development
of moderate to heavy snow with rates of 1 to 2 inches per hour along
a corridor from eastern South Dakota and southwestern Minnesota into
northeastern Nebraska and west-central Iowa. While some uncertainty
in the exact time of change over exists, it appears likely that
heavy snow will become widespread between 0300 and 0600 UTC and
continue through the overnight.

..Lyons.. 03/14/2021

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

ATTN...WFO...MPX...DMX...FSD...OAX...ABR...LBF...UNR...

LAT...LON   42699865 42980046 43030305 43320389 44270407 45140357
            45650253 45710056 45559884 44999712 44529613 43789462
            42929347 42049293 41529321 41279407 41409503 41639586
            41929649 42319746 42699865

Mesoscale Discussions in South Dakota, 2021Mesoscale Discussions in Iowa, 2021Mesoscale Discussions in Nebraska, 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.