Alert archive / Minnesota / Severe Thunderstorm Warnings in 2002

Severe Thunderstorm Warning 342, NWS Grand Forks, ND

September 2, 2002Clay County, Minnesota; Cass County, North Dakota

NWS Grand Forks, ND issued this severe thunderstorm warning at Sep 2, 2002, 5:55 AM CDT for Clay County, Minnesota; Cass County, North Dakota. It was in force for 50 min. 2 reports came from inside the area while it was in force.

The area

The counties it named, with what was reported inside it.

The facts

Issued: Sep 2, 2002, 5:55 AM CDT (10:55 UTC)
Expired: Sep 2, 2002, 6:45 AM CDT
In force: 50 min
Issued by: NWS Grand Forks, ND
Area: Counties, with a storm outline in the text

Counties Clay County, MN, Cass County, ND

The radar

The Fargo/Grand Forks radar (KMVX), 77 km from the middle of the area, began a volume at 10:55 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 was reported inside it

Time	Report	Where	Remark
Sep 2, 6:00 AM CDT	Hail 0.75	Horace, ND
Sep 2, 6:05 AM CDT	Thunderstorm Wind	Sabin, MN	Tree branches were downed by the wind.

NCEI Storm Data entries that began inside the alert's area while it was in force. Before 2003 the local storm report archive is thin, so this is the record of what happened rather than what was phoned in.

Did it verify

Not verified. The Iowa Environmental Mesonet's Cow found no qualifying storm report inside this severe thunderstorm warning while it was in force. That is not proof nothing happened: reports are thin where few people live.

Cow counts a report within 15 km of the polygon while the warning was in force: a tornado for a tornado warning; hail of 1 inch or more, a gust of 58 mph or more or wind damage for a severe thunderstorm warning; a flash flood report for a flash flood warning.

The nearest sounding before it

Aberdeen, SD (KABR), launched 00:00Z, 10.9 hours before the alert went out and 253 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: 1557 J/kg
Mixed-layer CIN: -90 J/kg
Mixed-layer LCL: 1182 m above ground
0-6 km bulk shear: 36 kt
0-1 km storm-relative helicity: 32 m²/s²
0-3 km storm-relative helicity: 103 m²/s²
Significant tornado parameter: 0.1
Supercell composite: 0.4

Open this sounding in Storm Lab

What forecasters said that day

The local office's own words before this severe thunderstorm warning went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Grand Forks, ND wrote its last area forecast discussion before this severe thunderstorm warning went out at Sep 2, 1:50 AM CDT, 4 hours 5 minutes earlier.

Area forecast discussion, Sep 2, 1:50 AM CDT, 4 hours 5 minutes before

FORECAST DISCUSSION FOR EASTERN NORTH DAKOTA AND NORTHWEST MINNESOTA
NATIONAL WEATHER SERVICE EASTERN ND/GRAND FORKS ND
150 AM CDT MON SEP 2 2002

...MAIN FORECAST CHALLENGE THIS PACKAGE CENTERS ON LINGERING POP
THREAT THIS MORNING AND WIND POTENTIAL WITH STRENGTHENING NORTHWEST
PRESSURE GRADIENT IN WAKE OF FRONT REMAINDER OF DAY...

.CURRENT OBSERVATIONAL OVERVIEW...
06Z MSAS ANALYSIS DEPICTED LOW PRESSURE OVER EXTREME WESTERN
MANITOBA PROVINCE WITH ASSOCIATED PRE-FRONTAL TROUGH AXIS ACROSS
CENTRAL NORTH DAKOTA. FURTHER UPSTREAM PARENT COLD FRONT WAS
SITUATED FROM EXTREME SOUTHEAST SASK PROVINCE TO WESTERN NORTH
DAKOTA. LATEST PRESSURE TENDENCY FIELDS SUGGESTS GOOD RISE/FALL
COUPLE ASSOCIATED WITH FEATURE. LATEST RADAR MOSAIC INDICATED SOME
CONVECTIVE TYPE MAINLY HIGH BASED SHOWER ACTIVITY (LITTLE IF ANY
LIGHTNING STRIKES) IN VICINITY OF ENHANCED MOISTURE FLUX CONVERGENCE
AHEAD OF COLD FRONT.

.FORECAST DETAILS...
FINALLY LIGHT AT THE END OF THE TUNNEL WITH RESPECT TO CONVECTIVE
THREAT ACROSS THE REGION. EXPECT STRONG UPSTREAM SHORTWAVE TROUGH TO
FINALLY KICK PARENT COLD FRONT THROUGH AREA THIS MORNING. REVIEW OF
FORECASTED SOUNDINGS SUGGESTS THE POTENTIAL FOR ELEVATED CONVECTION
WITH FROPA...PER INVERTED V SOUNDING (STEEP LAPSE RATES 850-700MB
LAYER) FOR AREAS FROM THE RED RIVER VALLEY EAST EARLY TODAY. IN
WAKE OF FRONT GOOD NORTHWESTERLY PUNCH OF DRIER AIR ADVECTS INTO THE
REGION. TIGHTENING NORTHWESTERLY PRESSURE GRADIENT COUPLED WITH
UNIDIRECTIONAL FLOW WITH HEIGHT AND ADIABATIC MIXING LAYER TO ALMOST
700MB SHOULD RESULT IN WINDY CONDITIONS. BASED ON LATEST GUIDANCE
FEEL WINDS WILL STAY JUST BELOW WIND ADVISORY CRITERIA. EXPECT WINDS
TO ABATE AND DECOUPLE TONIGHT AS HIGH PRESSURE OVER THE CENTRAL
PLAINS RIDGES INTO THE DAKOTAS. FRIENDLY CONFINES OF HIGH SHOULD
SLOWLY ERODE AND SLIP AWAY LATE TUESDAY INTO TUESDAY NIGHT AS
SOUTHERLY FLOW BECOMES ESTABLISHED ONCE AGAIN ACROSS THE NORTHERN
PLAINS AHEAD DEEPENING NORTHWEST CONUS UPPER LEVEL TROUGH. NO
CHANGES PLANNED TO EXTENDED PACKAGE PENDING NO REAL SURPRISES WITH
NEW MRF.

.FGF...NONE.

BERG

The office that day

Everything else NWS Grand Forks, ND issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Sep 2, 7:51 AM CDT	Severe Thunderstorm Warning	FGF	Otter Tail	39 min
Sep 2, 8:19 AM CDT	Severe Thunderstorm Warning	FGF	Wadena	41 min
Sep 2, 8:34 AM CDT	Tornado Warning	FGF	Wadena	41 min
Sep 2, 3:38 AM CDT	Severe Thunderstorm Warning	FGF	Barnes	52 min

Nearby

Severe Thunderstorm Warnings in Minnesota, 2002 Severe Thunderstorm Warnings in North Dakota, 2002 Every severe thunderstorm warning in 2002

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; verification from NCEI's Storm Data; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.