Alert archive / Wisconsin / Mesoscale Discussions in 2012

Mesoscale Discussion 2185

December 20, 2012Allamakee County, Clayton County, Winneshiek County, Iowa; Houston County, Minnesota; 24 counties in Wisconsin

The Storm Prediction Center issued this mesoscale discussion at Dec 20, 2012, 3:12 AM CST for Allamakee County, Clayton County, Winneshiek County, Iowa; Houston County, Minnesota; 24 counties in Wisconsin. It was in force for 4 hr.

The area

The outline as issued.

The facts

Issued: Dec 20, 2012, 3:12 AM CST (09:12 UTC)
Expired: Dec 20, 2012, 7:15 AM CST
In force: 4 hr
Issued by: the Storm Prediction Center

All 28 counties

Allamakee County, IA, Clayton County, IA, Winneshiek County, IA, Houston County, MN, Adams County, WI, Clark County, WI, Columbia County, WI, Crawford County, WI, Grant County, WI, Green Lake County, WI, Iowa County, WI, Jackson County, WI, Juneau County, WI, La Crosse County, WI, Marathon County, WI, Marquette County, WI, Monroe County, WI, Outagamie County, WI, Portage County, WI, Richland County, WI, Sauk County, WI, Shawano County, WI, Trempealeau County, WI, Vernon County, WI, Waupaca County, WI, Waushara County, WI, Winnebago County, WI, Wood County, WI

The radar

The La Crosse radar (KARX), 105 km from the middle of the area, began a volume at 09:12 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

Green Bay/Straub, WI (KGRB), launched 00:00Z, 9.2 hours before the alert went out and 155 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: 582 m above ground
0-6 km bulk shear: 60 kt
0-1 km storm-relative helicity: 10 m²/s²
0-3 km storm-relative helicity: 36 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

645 
ACUS11 KWNS 200913
SWOMCD
SPC MCD 200912
WIZ000-IAZ000-MNZ000-201315-

MESOSCALE DISCUSSION 2185
NWS STORM PREDICTION CENTER NORMAN OK
0312 AM CST THU DEC 20 2012

AREAS AFFECTED...FAR NERN IA...FAR SERN MN...SRN/CNTRL WI

CONCERNING...BLIZZARD

VALID 200912Z - 201315Z

SUMMARY...HEAVY SNOWFALL RATES OF 1-2 IN PER HR COUPLED WITH N-NELY
WIND GUSTS UP TO 35 MPH /PRIMARILY AFTER 11Z/ WILL RESULT IN
BLIZZARD CONDITIONS DEVELOPING NEWD INTO SRN/CNTRL WI THROUGH 13Z.

DISCUSSION...DEEPENING CYCLONE CONTINUES TO DEVELOP NEWD OUT OF
N-CNTRL MO INTO W-CNTRL IL...WITH PRESSURE FALLS AS HIGH AS 4 MB/2
HR OBSERVED ACROSS PARTS OF NERN IL. STRONG LOW-LEVEL WAA PRECEDING
THE CYCLONE IS FORECAST TO RESULT IN A SLIGHT N-NWWD SHIFT IN THE
SFC FREEZING LINE ACROSS SRN/ERN WI. FORCING FOR ASCENT ASSOCIATED
WITH MIDLEVEL DCVA/HEIGHT FALLS AND UPPER DIVERGENCE...COUPLED WITH
PERSISTENT LOW-LEVEL ISENTROPIC LIFT...WILL CONTINUE TO MAINTAIN
SNOWFALL RATES OF 1-1.5 IN PER HR ACROSS SRN AND PARTS OF CNTRL WI.
ADDITIONALLY...BOTH SLANTWISE AND UPRIGHT CONVECTIVE INSTABILITY /AS
EVIDENCED BY OCCASIONAL ISOLATED LIGHTNING STRIKES/ COULD LEAD TO
LOCALIZED ENHANCEMENT OF SNOWFALL RATES. LATEST HIGH-RESOLUTION
MODEL GUIDANCE /INCLUDING 07Z WRF-HRRR AND 07Z RAP/ SUPPORTS THIS
SCENARIO...SHOWING A NWD EXPANSION OF HEAVIER SNOW RATES INTO PARTS
OF CNTRL WI.

THE POTENTIAL FOR BLIZZARD CONDITIONS IS EXPECTED TO CONTINUE TO LAG
ONGOING AREA OF SNOW OVER WI. THE SFC PRESSURE GRADIENT WILL TIGHTEN
ACROSS SRN WI IN RESPONSE TO THE DEEPENING CYCLONE...WITH SFC WINDS
ANTICIPATED TO SLOWLY BACK TOWARDS THE NNE AND EVENTUALLY THE N. AS
SUCH...WIND GUSTS UP TO 35 MPH WILL BECOME MORE COMMON AFTER
11-12Z...RESULTING IN SIGNIFICANT VISIBILITY REDUCTIONS.

..ROGERS.. 12/20/2012

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...GRB...MKX...DVN...ARX...MPX...

LAT...LON   44288832 43678864 43338902 42919003 42649092 42609148
            42959190 43579203 44299157 44779073 45018969 45028915
            44958841 44688812 44288832

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Dec 19, 9:32 PM CST	Mesoscale Discussion	SPC	Adair, Adams, Audubon, Black Hawk, Boone, Bremer and 24 more	5 hr
Dec 20, 7:49 AM CST	Mesoscale Discussion	SPC	Appanoose, Cedar, Davis, Des Moines, Henry, Jefferson and 10 more	4 hr
Dec 20, 10:52 AM CST	Mesoscale Discussion	SPC	Clinton, Des Moines, Scott	6 hr
Dec 20, 11:28 AM CST	Mesoscale Discussion	SPC	Adams, Brown, Calumet, Columbia, Crawford, Dane and 31 more	6 hr

Nearby

Mesoscale Discussions in Wisconsin, 2012 Mesoscale Discussions in Iowa, 2012 Mesoscale Discussions in Minnesota, 2012 Every mesoscale discussion in 2012

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.