Alert archive / Wisconsin / Mesoscale Discussions in 2021

Mesoscale Discussion 2069

December 28, 20215 counties in Minnesota; 6 counties in Wisconsin

The Storm Prediction Center issued this mesoscale discussion at Dec 28, 2021, 5:40 PM CST for 5 counties in Minnesota; 6 counties in Wisconsin. It was in force for 4 hr.

The area

The outline as issued.

The facts

Issued: Dec 28, 2021, 5:40 PM CST (23:40 UTC)
Expired: Dec 28, 2021, 9:45 PM CST
In force: 4 hr
Issued by: the Storm Prediction Center
Concerning: Heavy snow

Counties Aitkin County, MN, Carlton County, MN, Itasca County, MN, Lake County, MN, Saint Louis County, MN, Ashland County, WI, Bayfield County, WI, Douglas County, WI, Iron County, WI, Sawyer County, WI, Washburn County, WI

The radar

The Duluth radar (KDLH), 35 km from the middle of the area, began a volume at 23:39 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.

The nearest sounding before it

International Fa, MN (KINL), launched 12:00Z, 11.7 hours before the alert went out and 215 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 707 m above ground
0-6 km bulk shear: 38 kt
0-1 km storm-relative helicity: 60 m²/s²
0-3 km storm-relative helicity: 63 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

901 
ACUS11 KWNS 282341
SWOMCD
SPC MCD 282340 
MIZ000-WIZ000-MNZ000-290345-

Mesoscale Discussion 2069
NWS Storm Prediction Center Norman OK
0540 PM CST Tue Dec 28 2021

Areas affected...Northern Wisconsin into northeast Minnesota

Concerning...Heavy snow 

Valid 282340Z - 290345Z

SUMMARY...Snow banding is probable over the next few hours across
northern Wisconsin into northeast Minnesota. Moderate to heavy
snowfall rates up to 1 inch/hour are possible. Lake-enhanced
snowfall is also likely along the North Shore of MN.

DISCUSSION...Regional radar mosaics over the past hour have shown a
gradual weakening of the stratiform precipitation over
central/southern WI with a corresponding increase across northern
portions of the state into northeast MN. Surface observations under
this precipitation show occasional visibility reductions to 1/2 to
1/4 mile. This uptick in snowfall is likely the result of increasing
 ascent ahead of an approaching vorticity maxima (noted in
water-vapor and radar imagery over south-central MN), as well as
more focused ascent within a swath of warm air advection between
850-700 mb. Forecast soundings from northeast MN show a gradual
deepening of the dentritic growth zone in the coming hours with much
of this layer residing within a favorable zone of lift.
Additionally, transient frontogenesis may further augment and
organize mesoscale ascent. The combined result will be the potential
for at least a loosely organized snow band that will support
moderate to heavy snowfall rates up to 1 inch/hour. With Lake
Superior surface temperatures in the upper 30s/low 40s and
east/southeast winds, lake-effect enhancement is likely along the
North Shore where heavier snowfall rates are probable.

..Moore.. 12/28/2021

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

ATTN...WFO...MQT...GRB...DLH...

LAT...LON   45929216 46569336 47059405 47729413 48159370 48449288
            48339173 47969071 47439018 46668977 46298982 46019005
            45789052 45749124 45929216

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Dec 28, 8:59 AM CST	Mesoscale Discussion	SPC	Dodge, Fillmore, Freeborn, Houston, Mower, Olmsted and 3 more	5 hr

Nearby

Mesoscale Discussions in Wisconsin, 2021 Mesoscale Discussions in Minnesota, 2021 Every mesoscale discussion in 2021

Sources

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.