Mesoscale Discussion 19

Issued

Jan 14, 2021, 8:44 PM CST (02:44 UTC)

Expired

Jan 15, 2021, 1:45 AM CST

In force

5 hr

Issued by

the Storm Prediction Center

Concerning

Blizzard

The Sioux Falls radar (KFSD), 33 km from the middle of the area, began a volume at 02:47 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.

717 
ACUS11 KWNS 150244
SWOMCD
SPC MCD 150244 
MNZ000-IAZ000-NEZ000-SDZ000-150745-

Mesoscale Discussion 0019
NWS Storm Prediction Center Norman OK
0844 PM CST Thu Jan 14 2021

Areas affected...Southeastern South Dakota...southwest
Minnesota...northeastern Nebraska...and northwestern Iowa

Concerning...Blizzard 

Valid 150244Z - 150745Z

SUMMARY...Increasing winds with concurrent snowfall should lead to
scattered to widespread blizzard conditions along the I-29 corridor
through portions of South Dakota, Nebraska, and Iowa heading into
early Friday morning.

DISCUSSION...Surface observations from along the I-29 corridor in
the SD/MN/NE/IA region show sustained winds between 20-30 mph with
temperatures in the upper 20s and low 30s. Blowing snow model output
suggests that isolated blizzard conditions may be ongoing. This idea
is supported  by recent visibility observations and regional web
cams, which mostly show visibilities above a mile (with the
exception of a few localized areas where stronger winds and moderate
snowfall are concurrent).

While widespread blizzard conditions are not yet ongoing, conditions
should begin to deteriorate heading into the early morning hours. A
stalled, but slowly deepening surface low across east/northeastern
IA will help strengthen the pressure gradient along the I-29
corridor. Snowfall amounts through 08 UTC are forecast to generally
be less than a couple of inches for this area, but increasing winds
coupled with this falling snow will increase the probability of
visibility falling to one-quarter mile or less. Blowing snow model
probabilities suggest that persistent/widespread blizzard conditions
will be most likely for locations that see a combination of
temperatures in the 20s, sustained wind speeds above 35 mph, and
concurrent snowfall. For locations that do not see sustained winds
at this magnitude, frequent gusts up to 50-60 mph with concurrent
light to moderate snowfall will likely result in at least transient
visibility reductions to one-quarter mile or less. 

Blizzard conditions should gradually begin across the SD/MN/NE/IA
region between 03-08 UTC (where temperatures have already fallen
below freezing, snow is ongoing, and recent guidance suggests winds
are most likely to begin increasing through 08 UTC). Blizzard
conditions should gradually spread south and east through 12 UTC
Friday morning as temperatures continue to fall and sustained 35+
mph winds increase in coverage.

..Moore.. 01/15/2021

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

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

LAT...LON   43239736 43879757 44689762 45109711 45109659 44739587
            43969560 43789553 42939514 42369525 42109553 41999586
            42059644 42279681 42799720 43239736

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