Alert archive / Minnesota / Severe Thunderstorm Watches in 2012

Severe Thunderstorm Watch 539

July 29, 20129 counties in Minnesota

The Storm Prediction Center issued this severe thunderstorm watch at Jul 29, 2012, 7:51 PM CDT for 9 counties in Minnesota. It was in force for 6 hr.

The area

The outline as issued.

The facts

Issued: Jul 29, 2012, 7:51 PM CDT (00:51 UTC)
Expired: Jul 30, 2012, 2:13 AM CDT
In force: 6 hr
Issued by: the Storm Prediction Center
Largest hail expected: 2 in
Strongest gust expected: 60 kt

Counties Beltrami County, MN, Itasca County, MN, Kittson County, MN, Koochiching County, MN, Lake County, MN, Lake of the Woods County, MN, Marshall County, MN, Roseau County, MN, Saint Louis County, MN

The radar

The Fargo/Grand Forks radar (KMVX), 198 km from the middle of the area, began a volume at 00:55 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.

What SPC expected

The probabilities SPC published with the watch, for the watch area over its life.

Two or more tornadoes: 20%
One or more EF2 to EF5 tornadoes: 5%
Ten or more severe wind reports: 30%
One or more gusts of 65 knots or more: 30%
Ten or more severe hail reports: 30%
One or more hailstones of 2 inches or more: 20%
Six or more combined severe hail and wind reports: 70%

Warnings issued inside it

4 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.

Issued	Product	Office	Counties	Lasted
Jul 29, 9:13 PM CDT	Severe Thunderstorm Warning	FGF	Lake of the Woods, Roseau	62 min
Jul 29, 9:46 PM CDT	Severe Thunderstorm Warning	FGF	Roseau	29 min
Jul 29, 10:14 PM CDT	Severe Thunderstorm Warning	FGF	Beltrami, Lake of the Woods, Marshall, Roseau	61 min
Jul 29, 11:48 PM CDT	Severe Thunderstorm Warning	DLH	Itasca, Koochiching, Saint Louis	42 min

Discussions around it

SPC mesoscale discussions over the same counties from four hours before the watch to its end.

The nearest sounding before it

International Fa, MN (KINL), launched 00:00Z, 0.9 hours before the alert went out and 124 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: 1490 J/kg
Mixed-layer CIN: -31 J/kg
Mixed-layer LCL: 1732 m above ground
0-6 km bulk shear: 37 kt
0-1 km storm-relative helicity: 71 m²/s²
0-3 km storm-relative helicity: 119 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.

010 
WWUS20 KWNS 300052
SEL9
SPC WW 300052
MNZ000-300800-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 539
NWS STORM PREDICTION CENTER NORMAN OK
750 PM CDT SUN JUL 29 2012

THE NWS STORM PREDICTION CENTER HAS ISSUED A
SEVERE THUNDERSTORM WATCH FOR PORTIONS OF

       NORTHERN MINNESOTA

EFFECTIVE THIS SUNDAY NIGHT AND MONDAY MORNING FROM 750 PM UNTIL
300 AM CDT.

HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 70
MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.

THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 40
STATUTE MILES NORTH AND SOUTH OF A LINE FROM 15 MILES SOUTH
SOUTHWEST OF HALLOCK MINNESOTA TO 20 MILES SOUTH SOUTHEAST OF ELY
MINNESOTA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU9).

REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE
FAVORABLE FOR SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
AND POSSIBLE WARNINGS. SEVERE THUNDERSTORMS CAN AND OCCASIONALLY
DO PRODUCE TORNADOES.

DISCUSSION...MCS OVER SERN MANITOBA IS EXPECTED TO CONTINUE SEWD
ACROSS THE INTERNATIONAL BORDER TONIGHT WITH PREFERRED STORM
DEVELOPMENT ALONG SRN/SWRN FLANK OF SYSTEM IN RESPONSE TO THE
FORMATION OF A NOCTURNAL LOW-LEVEL WIND MAXIMUM.  FARTHER E...A
SEPARATE CLUSTER OF TSTMS ONGOING ALONG OUTFLOW BOUNDARY NNE OF DLH
MAY ALSO PERSIST AS INFLOW IS ENHANCED BY THE ABOVE-MENTIONED LLJ.
SEVERE HAIL AND DAMAGING WIND GUSTS WILL BE THE PRIMARY HAZARDS WITH
THESE STORMS.

AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
TO 2 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60
KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 550. MEAN STORM
MOTION VECTOR 30030.


...MEAD

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 29, 7:37 PM CDT	Mesoscale Discussion	SPC	Kittson, Koochiching, Lake of the Woods, Marshall, Roseau	53 min
Jul 29, 11:03 PM CDT	Mesoscale Discussion	SPC	Beltrami, Itasca, Koochiching, Lake, Saint Louis	117 min

Nearby

Severe Thunderstorm Watches in Minnesota, 2012 Every severe thunderstorm watch 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.