Alert archive / Wisconsin / Mesoscale Discussions in 2012

Mesoscale Discussion 1669

August 1, 2012Gogebic County, Iron County, Michigan; 12 counties in Minnesota; 32 counties in Wisconsin

The Storm Prediction Center issued this mesoscale discussion at Aug 1, 2012, 1:07 PM CDT for Gogebic County, Iron County, Michigan; 12 counties in Minnesota; 32 counties in Wisconsin. It was in force for 23 min.

The area

The outline as issued.

The facts

Issued: Aug 1, 2012, 1:07 PM CDT (18:07 UTC)
Expired: Aug 1, 2012, 1:30 PM CDT
In force: 23 min
Issued by: the Storm Prediction Center
Chance of a watch: 80%

All 46 counties

Gogebic County, MI, Iron County, MI, Anoka County, MN, Carver County, MN, Chisago County, MN, Dakota County, MN, Goodhue County, MN, Hennepin County, MN, Ramsey County, MN, Rice County, MN, Scott County, MN, Wabasha County, MN, Washington County, MN, Winona County, MN, Barron County, WI, Buffalo County, WI, Chippewa County, WI, Clark County, WI, Dunn County, WI, Eau Claire County, WI, Florence County, WI, Forest County, WI, Iron County, WI, Jackson County, WI, La Crosse County, WI, Langlade County, WI, Lincoln County, WI, Marathon County, WI, Menominee County, WI, Monroe County, WI, Oneida County, WI, Pepin County, WI, Pierce County, WI, Polk County, WI, Portage County, WI, Price County, WI, Rusk County, WI, Saint Croix County, WI, Sawyer County, WI, Shawano County, WI, Taylor County, WI, Trempealeau County, WI, Vilas County, WI, Washburn County, WI, Waupaca County, WI, Wood County, WI

The radar

The Duluth radar (KDLH), 178 km from the middle of the area, began a volume at 18:07 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.

Severe Thunderstorm Watch 544Aug 1, 2:20 PM CDT

The nearest sounding before it

Minneapolis, MN (KMPX), launched 12:00Z, 6.1 hours before the alert went out and 224 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: 670 J/kg
Mixed-layer CIN: -340 J/kg
Mixed-layer LCL: 1367 m above ground
0-6 km bulk shear: 24 kt
0-1 km storm-relative helicity: 246 m²/s²
0-3 km storm-relative helicity: 292 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 2.1

Open this sounding in Storm Lab

The text

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

794 
ACUS11 KWNS 011808
SWOMCD
SPC MCD 011807 COR
WIZ000-MIZ000-MNZ000-011830-

MESOSCALE DISCUSSION 1669
NWS STORM PREDICTION CENTER NORMAN OK
0107 PM CDT WED AUG 01 2012

AREAS AFFECTED...PARTS OF CENTRAL AND NRN WI/WRN UPPER MI/PARTS OF
EAST CENTRAL MN

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY

VALID 011807Z - 011830Z

CORRECTED FOR WORDING IN FIRST SENTENCE OF DISCUSSION.

PROBABILITY OF WATCH ISSUANCE...80 PERCENT

SUMMARY...THE POTENTIAL EXISTS FOR ELEVATED STORMS CURRENTLY LOCATED
OVER NWRN WI AND FAR WRN UPPER MI TO TURN SEWD WITHIN NWLY FLOW
ALOFT AND POSE A THREAT FOR DAMAGING WINDS AS THIS ACTIVITY BECOMES
SURFACE BASED OVER NRN INTO CENTRAL WI.  ISOLATED HAIL WILL REMAIN A
THREAT...ESPECIALLY WITH THE ONGOING ELEVATED STORMS.

DISCUSSION...TRENDS IN LATE MORNING-EARLY AFTERNOON REGIONAL RADAR
IMAGERY INDICATED ISOLATED STRONGER STORMS PROGRESSING EWD/ESEWD
THROUGH NRN WI AND ADJACENT COUNTIES OF WRN UPPER MI.  OBJECTIVE
ANALYSES SUGGEST THIS ACTIVITY CURRENTLY REMAINS AT LEAST MARGINALLY
ELEVATED DUE TO SOME INHIBITION OVER THIS AREA.  HOWEVER...THE
MODIFIED 12Z GRB SOUNDING WITH CURRENT CENTRAL WI READINGS IN THE
LOWER-MID 80S REDUCES THIS INHIBITION SUGGESTING SURFACE BASED
STORMS COULD EVOLVE FAIRLY SOON. A FEED OF MODERATE INSTABILITY PER
A 30 KT WLY LLJ WILL BE MAINTAINED INTO NRN WI. THIS COMBINED WITH
LOWER TROPOSPHERIC WAA...STEEP MIDLEVEL LAPSE RATES AND EFFECTIVE
BULK SHEAR OF 35-40 KT WILL SUPPORT AN ENVIRONMENT FAVORABLE FOR
ADDITIONAL TSTMS AND AN INCREASE IN THE SEVERE WEATHER THREAT.

STEEPENING LOW LEVEL LAPSE RATES PER SURFACE HEATING WILL BOOST
DCAPE VALUES WHICH ARE ALREADY RANGING FROM 1500-1700 J/KG.  12Z
NSSL-WRF 4 KM SUGGESTS THE ONGOING ELEVATED STORMS AND NEW ACTIVITY
DEVELOPING OVER WEST CENTRAL WI INTO CENTRAL MN WILL TURN SEWD WITH
AN INCREASING POTENTIAL FOR DAMAGING WINDS.  THIS TREND APPEARS TO
BE STARTING AS ONGOING STORMS ARE TRANSITIONING INTO A LINEAR
MODE...AND A WATCH WILL BE NEEDED SHORTLY.

..PETERS/CARBIN.. 08/01/2012

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

ATTN...WFO...MQT...GRB...DLH...ARX...MPX...

LAT...LON   46469065 46588989 46748954 46768883 46498830 45728810
            44698849 44258901 43819089 44059271 44269362 44749382
            45139389 45519312 45899224 46329154 46469065

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 1, 4:14 PM CDT	Mesoscale Discussion	SPC	Anoka, Benton, Brown, Carver, Chippewa, Chisago and 24 more	91 min
Aug 1, 5:12 PM CDT	Severe Thunderstorm Watch	SPC	Anoka, Blue Earth, Brown, Carver, Chippewa, Cottonwood and 28 more	5 hr
Aug 1, 2:19 PM CDT	Severe Thunderstorm Watch	SPC	Clark, Forest, Langlade, Lincoln, Marathon, Marinette and 7 more	4 hr

Nearby

Mesoscale Discussions in Wisconsin, 2012 Mesoscale Discussions in Minnesota, 2012 Mesoscale Discussions in Michigan, 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.