Alert archive / Minnesota / Mesoscale Discussions in 2012

Mesoscale Discussion 652

May 1, 20124 states

The Storm Prediction Center issued this mesoscale discussion at May 1, 2012, 6:11 PM CDT for 4 states. It was in force for 94 min.

The area

The outline as issued.

The facts

Issued: May 1, 2012, 6:11 PM CDT (23:11 UTC)
Expired: May 1, 2012, 7:45 PM CDT
In force: 94 min
Issued by: the Storm Prediction Center

All 71 counties

Clay County, IA, Dickinson County, IA, Emmet County, IA, Kossuth County, IA, Lyon County, IA, O'Brien County, IA, Osceola County, IA, Palo Alto County, IA, Sioux County, IA, Anoka County, MN, Benton County, MN, Blue Earth County, MN, Brown County, MN, Carver County, MN, Chippewa County, MN, Chisago County, MN, Cottonwood County, MN, Dakota County, MN, Faribault County, MN, Goodhue County, MN, Hennepin County, MN, Isanti County, MN, Jackson County, MN, Kanabec County, MN, Kandiyohi County, MN, Le Sueur County, MN, Lincoln County, MN, Lyon County, MN, Martin County, MN, McLeod County, MN, Meeker County, MN, Mille Lacs County, MN, Murray County, MN, Nicollet County, MN, Nobles County, MN, Pipestone County, MN, Ramsey County, MN, Redwood County, MN, Renville County, MN, Rice County, MN, Rock County, MN, Scott County, MN, Sherburne County, MN, Sibley County, MN, Stearns County, MN, Steele County, MN, Waseca County, MN, Washington County, MN, Watonwan County, MN, Wright County, MN, Yellow Medicine County, MN, Brookings County, SD, Hanson County, SD, Hutchinson County, SD, Lake County, SD, Lincoln County, SD, McCook County, SD, Minnehaha County, SD, Moody County, SD, Turner County, SD, Yankton County, SD, Barron County, WI, Burnett County, WI, Chippewa County, WI, Dunn County, WI, Pierce County, WI, Polk County, WI, Rusk County, WI, Saint Croix County, WI, Sawyer County, WI, Washburn County, WI

The radar

The Minneapolis radar (KMPX), 72 km from the middle of the area, began a volume at 23:13 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 224May 1, 9:30 PM CDT

The nearest sounding before it

Minneapolis, MN (KMPX), launched 12:00Z, 11.2 hours before the alert went out and 70 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: 1291 m above ground
0-6 km bulk shear: 45 kt
0-1 km storm-relative helicity: 163 m²/s²
0-3 km storm-relative helicity: 196 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.

317 
ACUS11 KWNS 012312
SWOMCD
SPC MCD 012311
WIZ000-MNZ000-IAZ000-SDZ000-020045-

MESOSCALE DISCUSSION 0652
NWS STORM PREDICTION CENTER NORMAN OK
0611 PM CDT TUE MAY 01 2012

AREAS AFFECTED...PORTIONS SERN SD...WRN WI...EXTREME NWRN
IA...CENTRAL/SRN MN.

CONCERNING...TORNADO WATCH 220...

VALID 012311Z - 020045Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 220 CONTINUES.

SUMMARY...ANOTHER WW...223...IS BEING ISSUED E OF WW 220 ACROSS
ADJACENT PORTIONS ERN MN AND WRN WI.  SVR THREAT CONTINUES IN WW 220
WITH BAND OF TSTMS FROM CENTRAL MN SWWD ACROSS SERN SD. WW MAY BE
CLEARED BEHIND SFC LOW AND COLD FRONT.

DISCUSSION...22Z SFC MESOANALYSIS SHOWS TRIPLE-POINT LOW BETWEEN
GHW-FFM...WARM FRONT SEWD FROM THERE MKT/OTM AREAS.  WARM FRONT WILL
LIFT NEWD ACROSS SERN MN AROUND 10-15 KT.  THIS IS SLOWER THAN PACE
OF INDIVIDUAL TSTMS MOVING ACROSS FRONT...BUT MAXIMIZING AMOUNT OF
TIME CELLS SPEND IN BAROCLINIC ZONE FOR SUCH STRONGLY ORTHOGONAL
CONVECTIVE TRANSLATION COMPONENT. TORNADO THREAT WILL REMAIN
RELATIVELY ENHANCED IN WARM FRONTAL ZONE...WHERE
1. TRANSITION FROM SFC-BASED TO ELEVATED EFFECTIVE-INFLOW PARCELS IS
GRADUAL WITH SW-NE EXTENT...
2. LOW-LEVEL STORM-RELATIVE INFLOW...VERTICAL SHEAR AND HODOGRAPH
SIZE ALL WILL REMAIN MAXIMIZED.

MEANWHILE LOW SHOULD MOVE ENEWD TO NEWD ACROSS NRN MN..WHILE
TRAILING COLD FRONT MOVES SEWD OVER SWRN MN AND SERN SD.  COLD FRONT
IS CLOSE TO TSTMS EVIDENT AT 23Z FROM NW BKX TO MHE...AND SHOULD
CATCH UP TO PRIMARY CONVECTIVE BAND OVER SERN SD DURING NEXT 2-3
HOURS.  MODIFIED FCST SOUNDINGS SUGGEST MLCAPE INCREASES FROM AROUND
500 J/KG IN WARM-FRONTAL ZONE TO AROUND 200 J/KG OVER SERN SD...WITH
35-40 KT EFFECTIVE SHEAR MAGNITUDES.  BKN AND SEGMENTED TO
QUASI-LINEAR STRUCTURES SHOULD PREDOMINATE NEAR COLD FRONT GIVEN
NEARLY PARALLEL ALIGNMENT OF MEAN WIND AND DEEP-SHEAR VECTORS.
INCREASE IN LLJ ACROSS IA THROUGH LATE EVENING WILL SUPPORT
POTENTIAL FOR UPSCALE GROWTH OF CONVECTION INTO BETTER-ORGANIZED
MCS...AND MORE OF IA IN SVR THREAT ALSO.

..EDWARDS.. 05/01/2012

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

ATTN...WFO...DLH...ARX...MPX...DMX...FSD...ABR...

LAT...LON   43759803 46069414 46119240 45879109 45329087 44529199
            44119294 43129433 42909513 42979762 43759803

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 1, 2:30 PM CDT	Mesoscale Discussion	SPC	Cherokee, Clay, Dickinson, Emmet, Lyon, O'Brien and 4 more	60 min
May 1, 2:59 PM CDT	Tornado Watch	SPC	Clay, Dickinson, Lyon, O'Brien, Osceola, Sioux	6 hr
May 1, 4:58 PM CDT	Severe Thunderstorm Watch	SPC	Buena Vista, Cherokee, Ida, Monona, Plymouth, Woodbury	4 hr
May 1, 6:10 PM CDT	Tornado Watch	SPC	Anoka, Blue Earth, Brown, Carver, Chisago, Dakota and 16 more	6 hr
May 1, 6:57 PM CDT	Mesoscale Discussion	SPC	Kittson, Lake of the Woods, Marshall, Pennington, Polk, Roseau	2 hr

Nearby

Mesoscale Discussions in Minnesota, 2012 Mesoscale Discussions in South Dakota, 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.