Alert archive / Minnesota / Mesoscale Discussions in 2012

Mesoscale Discussion 656

May 1, 201215 counties in Minnesota; 8 counties in Wisconsin

The Storm Prediction Center issued this mesoscale discussion at May 1, 2012, 10:48 PM CDT for 15 counties in Minnesota; 8 counties in Wisconsin. It was in force for 87 min.

The area

The outline as issued.

The facts

Issued: May 1, 2012, 10:48 PM CDT (03:48 UTC)
Expired: May 2, 2012, 12:15 AM CDT
In force: 87 min
Issued by: the Storm Prediction Center

All 23 counties

Blue Earth County, MN, Dakota County, MN, Dodge County, MN, Faribault County, MN, Fillmore County, MN, Freeborn County, MN, Goodhue County, MN, Le Sueur County, MN, Mower County, MN, Olmsted County, MN, Rice County, MN, Steele County, MN, Wabasha County, MN, Waseca County, MN, Winona County, MN, Barron County, WI, Buffalo County, WI, Chippewa County, WI, Dunn County, WI, Eau Claire County, WI, Pepin County, WI, Pierce County, WI, Trempealeau County, WI

The radar

The Minneapolis radar (KMPX), 91 km from the middle of the area, began a volume at 03:49 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

Minneapolis, MN (KMPX), launched 00:00Z, 3.8 hours before the alert went out and 94 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: 279 J/kg
Mixed-layer CIN: -111 J/kg
Mixed-layer LCL: 1279 m above ground
0-6 km bulk shear: 44 kt
0-1 km storm-relative helicity: 227 m²/s²
0-3 km storm-relative helicity: 393 m²/s²
Significant tornado parameter: 0.2
Supercell composite: 4.9

Open this sounding in Storm Lab

The text

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

344 
ACUS11 KWNS 020348
SWOMCD
SPC MCD 020348 
WIZ000-MNZ000-IAZ000-020515-

MESOSCALE DISCUSSION 0656
NWS STORM PREDICTION CENTER NORMAN OK
1048 PM CDT TUE MAY 01 2012

AREAS AFFECTED...PORTIONS SERN MN...WRN WI.

CONCERNING...TORNADO WATCH 223...

VALID 020348Z - 020515Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 223 CONTINUES.

SUMMARY...WW MAY BE CLEARED BEHIND MAIN CONVECTIVE BAND.  PRIMARY
SVR THREAT IS FROM DAMAGING GUSTS...WITH ISOLATED HAIL ALSO
EXPECTED.  BRIEF TORNADO OR TWO STILL MAY OCCUR FROM EITHER
BOOKEND/BOW VORTICES OR MISOCIRCULATIONS ALONG LEADING EDGE OF QLCS.
OVERALL SVR POTENTIAL SHOULD CONTINUE TO LESSEN WITH EWD EXTENT
ACROSS WW AREA.  HOWEVER...SMALL PORTION OF SERN MN AND NERN IA SE
OF WW MAY EXPERIENCE THREAT FOR SVR GUSTS BEFORE MCS NOW ALONG MN/IA
BORDER WEAKENS.

DISCUSSION...EARLIER WARM FRONT HAS BECOME QUASISTATIONARY ACROSS
THIS REGION...AND WAS ANALYZED AT 3Z FROM W-CENTRAL IL NEAR
OTM...MCW AND S-CENTRAL MN SW OF TWIN CITIES.  NARROW CORRIDOR OF
N-CENTRAL/NERN IA AND IMMEDIATE MN BORDER REGION W OF FRONT IS
CHARACTERIZED BY MLCAPE 500-1000 J/KG AND EFFECTIVE SHEAR 40-50
KT...BASED ON MODIFIED FCST SOUNDINGS.  MCS SHOULD CONTINUE TO MOVE
EWD AROUND 30 KT...WHICH VIA EXTRAPOLATION WOULD MOVE IT EWD OUT OF
WW AROUND 5Z.  LOCAL ACCELERATIONS OF COLD POOL CAUSED BY BOWING MAY
HASTEN THAT PROCESS SLIGHTLY.  AS THIS OCCURS...WARM SECTOR
EFFECTIVELY WILL SHRINK FROM S-N...AS MN PORTION OF COMPLEX GOES
ATOP FRONTAL SFC THEN PROCEEDS EWD OVER PROGRESSIVELY DEEPER AND
MORE STABLE LAYER OF LOW THETAE.  SVR THREAT THEREFORE WILL BE
DISPLACED SWD INTO WW 224 WITH TIME.

..EDWARDS.. 05/02/2012

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

ATTN...WFO...ARX...MPX...DMX...

LAT...LON   43489429 44469393 44789277 45509178 45109116 44149138
            43509199 43489429

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 1, 9:18 PM CDT	Severe Thunderstorm Watch	SPC	Cottonwood, Jackson	7 hr
May 2, 3:34 PM CDT	Mesoscale Discussion	SPC	Blue Earth, Brown, Cottonwood, Dodge, Faribault, Freeborn and 16 more	86 min
May 2, 5:25 PM CDT	Severe Thunderstorm Watch	SPC	Blue Earth, Brown, Cottonwood, Dodge, Faribault, Freeborn and 14 more	4 hr

Nearby

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