Alert archive / Wisconsin / Mesoscale Discussions in 2012

Mesoscale Discussion 1883

September 4, 20125 states

The Storm Prediction Center issued this mesoscale discussion at Sep 4, 2012, 6:39 PM CDT for 5 states. It was in force for 66 min.

The area

The outline as issued.

The facts

Issued
Sep 4, 2012, 6:39 PM CDT (23:39 UTC)
Expired
Sep 4, 2012, 7:45 PM CDT
In force
66 min
Issued by
the Storm Prediction Center
All 54 counties

Allamakee County, IA, Black Hawk County, IA, Bremer County, IA, Buchanan County, IA, Butler County, IA, Chickasaw County, IA, Clayton County, IA, Delaware County, IA, Dubuque County, IA, Fayette County, IA, Floyd County, IA, Grundy County, IA, Howard County, IA, Mitchell County, IA, Winneshiek County, IA, Jo Daviess County, IL, Gogebic County, MI, Ontonagon County, MI, Cook County, MN, Fillmore County, MN, Houston County, MN, Lake County, MN, Saint Louis County, MN, Winona County, MN, Adams County, WI, Ashland County, WI, Bayfield County, WI, Buffalo County, WI, Chippewa County, WI, Clark County, WI, Crawford County, WI, Eau Claire County, WI, Grant County, WI, Iowa County, WI, Iron County, WI, Jackson County, WI, Juneau County, WI, La Crosse County, WI, Lafayette County, WI, Lincoln County, WI, Marathon County, WI, Monroe County, WI, Oneida County, WI, Portage County, WI, Price County, WI, Richland County, WI, Rusk County, WI, Sauk County, WI, Sawyer County, WI, Taylor County, WI, Trempealeau County, WI, Vernon County, WI, Vilas County, WI, Wood County, WI

The radar

The La Crosse radar (KARX), 121 km from the middle of the area, began a volume at 23:42 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 watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

The nearest sounding before it

Minneapolis, MN (KMPX), launched 12:00Z, 11.7 hours before the alert went out and 192 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-pSkew-T log-p diagram, Minneapolis, MN at 12:00Z on 2012-09-04Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1446 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Minneapolis, MN at 12:00Z on 2012-09-04The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 172 square meters per square second.19395878Sfc1 km3 km6 km9 kmRMLM
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
1446 J/kg
Mixed-layer CIN
-171 J/kg
Mixed-layer LCL
1471 m above ground
0-6 km bulk shear
28 kt
0-1 km storm-relative helicity
172 m²/s²
0-3 km storm-relative helicity
221 m²/s²
Significant tornado parameter
0.0
Supercell composite
7.8

Open this sounding in Storm Lab

The text

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

695 
ACUS11 KWNS 042339
SWOMCD
SPC MCD 042339 
MIZ000-WIZ000-MNZ000-ILZ000-IAZ000-050045-

MESOSCALE DISCUSSION 1883
NWS STORM PREDICTION CENTER NORMAN OK
0639 PM CDT TUE SEP 04 2012

AREAS AFFECTED...FAR NERN MN...CNTRL WI...FAR NERN IA

CONCERNING...SEVERE THUNDERSTORM WATCH 614...

VALID 042339Z - 050045Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 614
CONTINUES.

SUMMARY...STRONG TO SEVERE TSTMS ARE EXPECTED TO CONTINUE AS A COLD
FRONT PROGRESSES ACROSS THE UPPER MS VALLEY.

DISCUSSION...NUMEROUS STRONG TO SEVERE TSTM HAVE DEVELOPED AHEAD OF
A COLD FRONT PROGRESSING THROUGH THE UPPER MS VALLEY. GIVEN THE
MODERATELY SHEARED AND UNSTABLE ENVIRONMENT ACROSS CNTRL WI
/CHARACTERIZED BY EFFECTIVE BULK SHEAR AROUND 35 KT AND MLCAPE 2000
J PER KG/...THE CURRENT ACTIVITY IN AND AROUND THIS AREA IS EXPECTED
TO CONTINUE. THESE SUPERCELLS WILL CONTINUE TO POSE A SEVERE
WIND/HAIL THREAT. 

FARTHER N /IN AND AROUND CLARK CO/...RECENT RADAR TRENDS REVEAL THIS
ACTIVITY HAS BEGUN TO EXHIBIT MORE FORWARD-PROPAGATION AS IT BECOMES
OUTFLOW DOMINANT. AS A RESULT...THE PRIMARY THREAT WILL THIS STORMS
IS SEVERE WIND GUSTS ALTHOUGH SOME SEVERE HAIL IS STILL POSSIBLE.

..MOSIER.. 09/04/2012

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

ATTN...WFO...MQT...GRB...MKX...DVN...DLH...ARX...MPX...DMX...

LAT...LON   42189301 43509302 43499244 43849241 43859206 44199207
            44189186 44429209 44609202 44609161 45219166 45219155
            46759156 46689182 46719204 46729213 46669221 46669233
            46749233 46799309 48589309 48309217 48089167 48099123
            48109011 47968857 47238862 47038893 45468905 45468940
            45148945 45108919 44248923 44248961 43408959 43198984
            42538982 42518999 42208994 42209031 42399052 42399067
            42299066 42299275 42209277 42189301

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Sep 4, 3:27 PM CDTSevere Thunderstorm WatchSPCJo Daviess8 hr
Sep 4, 1:33 PM CDTMesoscale DiscussionSPCAllamakee, Bremer, Chickasaw, Clayton, Delaware, Fayette and 2 more117 min
Sep 4, 5:08 PM CDTMesoscale DiscussionSPCHarrison, Monona97 min

Nearby

Mesoscale Discussions in Wisconsin, 2012Mesoscale Discussions in Iowa, 2012Mesoscale Discussions in Minnesota, 2012Every 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.