Alert archive / Iowa / Severe Thunderstorm Warnings in 2015

Severe Thunderstorm Warning 203, NWS Omaha, NE

September 6, 2015Shelby County, Iowa

NWS Omaha, NE issued this severe thunderstorm warning at Sep 6, 2015, 6:30 PM CDT for Shelby County, Iowa. It was in force for 45 min. No storm report in the archive falls inside the area while it was in force.

The area

The counties it named.

The facts

Issued: Sep 6, 2015, 6:30 PM CDT (23:30 UTC)
Expired: Sep 6, 2015, 7:15 PM CDT
In force: 45 min
Issued by: NWS Omaha, NE
Area: Storm-based polygon
Hail: 1.0 in
Wind: 60.0 mph

County Shelby County, IA

The radar

The Omaha radar (KOAX), 97 km from the middle of the area, began a volume at 23:30 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 watch it was issued in

The SPC watch in force over the same counties when this warning went out.

Issued	Product	Office	Lasted
Sep 6, 6:02 PM CDT	Severe Thunderstorm Watch	SPC	7 hr

The nearest sounding before it

Omaha, NE (KOAX), launched 12:00Z, 11.5 hours before the alert went out and 97 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: 648 J/kg
Mixed-layer CIN: -347 J/kg
Mixed-layer LCL: 1274 m above ground
0-6 km bulk shear: 32 kt
0-1 km storm-relative helicity: 387 m²/s²
0-3 km storm-relative helicity: 389 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.1

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 Omaha, NE wrote its last area forecast discussion before this severe thunderstorm warning went out at Sep 6, 6:20 PM CDT, 10 minutes earlier.

Area forecast discussion, Sep 6, 6:20 PM CDT, 10 minutes before

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Hazardous weather outlook, Sep 6, 5:07 PM CDT, 1 hour 23 minutes before

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
507 PM CDT SUN SEP 6 2015

IAZ043-055-056-069-079-080-090-091-NEZ011-012-015>018-030>034-
042>045-050>053-065>068-078-088>093-071215-
MONONA-HARRISON-SHELBY-POTTAWATTAMIE-MILLS-MONTGOMERY-FREMONT-
PAGE-KNOX-CEDAR-THURSTON-ANTELOPE-PIERCE-WAYNE-BOONE-MADISON-
STANTON-CUMING-BURT-PLATTE-COLFAX-DODGE-WASHINGTON-BUTLER-
SAUNDERS-DOUGLAS-SARPY-SEWARD-LANCASTER-CASS-OTOE-SALINE-
JEFFERSON-GAGE-JOHNSON-NEMAHA-PAWNEE-RICHARDSON-
507 PM CDT SUN SEP 6 2015

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHWEST
IOWA...WEST CENTRAL IOWA...EAST CENTRAL NEBRASKA...NORTHEAST
NEBRASKA AND SOUTHEAST NEBRASKA.

.DAY ONE...TONIGHT AND LABOR DAY

THERE IS A CHANCE FOR SEVERE THUNDERSTORMS TONIGHT...SOME CAPABLE
OF PRODUCING DAMAGING WINDS...LOCALLY HEAVY RAIN...AND LARGE HAIL.
THE BEST POTENTIAL FOR SEVERE STORMS WOULD BE ALONG AND SOUTH OF
INTERSTATE 80.

A FLASH FLOOD WATCH IS IN EFFECT THROUGH MONDAY MORNING FOR PARTS
OF SOUTHWEST IOWA.

ADDITIONAL THUNDERSTORMS WILL BE POSSIBLE MONDAY AFTERNOON WITH
STRONG TO SEVERE STORMS POSSIBLE ALONG WITH LOCALIZED HEAVY RAIN.

TEMPERATURES HAVE WARMED WELL INTO THE 90S AHEAD OF THE COLD FRONT
FRONT AND THE WARM MID LEVEL TEMPERATURES HAVE HELD BACK ANY
SIGNIFICANT DEVELOPMENT. AN UPPER LEVEL WEATHER DISTURBANCE
COMBINED WITH THE HEATING SHOULD PROMOTE SCATTERED THUNDERSTORMS
DEVELOPING THROUGH THIS EVENING AHEAD OF AND ALONG THE FRONT.
MODERATE INSTABILITY...ABUNDANT MOISTURE AND SUFFICIENT SHEAR SUGGEST
THE POTENTIAL FOR DAMAGING WINDS...HEAVY RAIN...AND LARGE HAIL
WITH THE STRONGER STORMS.

THE FRONT STALLS OVER SOUTHEAST NEBRASKA AND SOUTHWEST IOWA...WITH
MOISTURE POOLED ALONG THE FRONT WITH STORMS DIMINISHING BY MONDAY
MORNING.  ALTHOUGH NOT AS HOT AS TODAY...ANOTHER UPPER LEVEL
WEATHER DISTURBANCE MONDAY AFTERNOON SHOULD PROMOTE THUNDERSTORM
RE-DEVELOPMENT WITH ANOTHER ROUND OF HEAVY RAIN...POSSIBLY OVER
AREAS THAT RECEIVE LOCALIZED HEAVY RAIN TONIGHT.

.DAYS TWO THROUGH SEVEN...MONDAY NIGHT THROUGH SUNDAY

THUNDERSTORMS SHOULD CONTINUE MONDAY NIGHT WITH HEAVY RAIN
POSSIBLE FOR PARTS OF SOUTHEAST NEBRASKA AND SOUTHWEST IOWA. A FEW
STORMS MAY LINGER INTO TUESDAY. THE NEXT CHANCE FOR THUNDERSTORMS
WILL BE WEDNESDAY NIGHT.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED THIS EVENING IN SOUTHWEST
IOWA...AND PARTS OF EAST CENTRAL AND SOUTHEAST NEBRASKA.

ZAPOTOCNY

In the hours before

Special weather statement, Sep 6, 6:18 PM CDT, 12 minutes before

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Local storm report, Sep 6, 6:25 PM CDT, 5 minutes before

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Local storm report, Sep 6, 6:30 PM CDT, 0 minutes before

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The office that day

Everything else NWS Omaha, NE issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Sep 6, 4:24 AM CDT	Flash Flood Watch	OAX	Cass, Gage, Johnson, Lancaster, Nemaha, Otoe and 2 more	24 hr
Sep 6, 5:54 PM CDT	Severe Thunderstorm Warning	OAX	Lancaster	51 min
Sep 6, 6:34 PM CDT	Severe Thunderstorm Warning	OAX	Cass, Lancaster, Sarpy, Saunders	41 min
Sep 6, 6:44 PM CDT	Severe Thunderstorm Warning	OAX	Lancaster	46 min
Sep 6, 6:56 PM CDT	Severe Thunderstorm Warning	OAX	Douglas, Sarpy, Saunders	49 min
Sep 6, 6:18 PM CDT	Special Weather Statement	OAX	Shelby	57 min

Nearby

Severe Thunderstorm Warnings in Iowa, 2015 Every severe thunderstorm warning in 2015

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.