Alert archive / Oklahoma / Severe Thunderstorm Warnings in 2008

Severe Thunderstorm Warning 291, NWS Norman, OK

April 21, 20084 counties in Oklahoma

NWS Norman, OK issued this severe thunderstorm warning at Apr 21, 2008, 9:11 PM CDT for 4 counties in Oklahoma. It was in force for 34 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
Apr 21, 2008, 9:11 PM CDT (02:11 UTC)
Expired
Apr 21, 2008, 9:45 PM CDT
In force
34 min
Issued by
NWS Norman, OK
Area
Storm-based polygon

Counties Cleveland County, OK, Lincoln County, OK, Pottawatomie County, OK, Seminole County, OK

The radar

The Norman radar (KTLX), 30 km from the middle of the area, began a volume at 02:12 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.

IssuedProductOfficeLasted
Apr 21, 8:56 PM CDTTornado WatchSPC5 hr

The nearest sounding before it

Lamont, OK (KLMN), launched 00:00Z, 2.2 hours before the alert went out and 152 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-pSkew-T log-p diagram, Lamont, OK at 00:00Z on 2008-04-22Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1716 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Lamont, OK at 00:00Z on 2008-04-22The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 18 square meters per square second.19395878Sfc1 km3 km6 km9 kmRMLM
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
1716 J/kg
Mixed-layer CIN
-20 J/kg
Mixed-layer LCL
1734 m above ground
0-6 km bulk shear
32 kt
0-1 km storm-relative helicity
18 m²/s²
0-3 km storm-relative helicity
169 m²/s²
Significant tornado parameter
0.2
Supercell composite
6.3

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 Norman, OK wrote its last area forecast discussion before this severe thunderstorm warning went out at Apr 21, 3:37 PM CDT, 5 hours 34 minutes earlier.

Area forecast discussion, Apr 21, 3:37 PM CDT, 5 hours 34 minutes before
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Hazardous weather outlook, Apr 21, 7:50 PM CDT, 1 hour 21 minutes before
HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE NORMAN OK
750 PM CDT MON APR 21 2008

OKZ004>048-050>052-TXZ083>090-221200-
HARPER-WOODS-ALFALFA-GRANT-KAY-ELLIS-WOODWARD-MAJOR-GARFIELD-NOBLE-
ROGER MILLS-DEWEY-CUSTER-BLAINE-KINGFISHER-LOGAN-PAYNE-BECKHAM-
WASHITA-CADDO-CANADIAN-OKLAHOMA-LINCOLN-GRADY-MCCLAIN-CLEVELAND-
POTTAWATOMIE-SEMINOLE-HUGHES-HARMON-GREER-KIOWA-JACKSON-TILLMAN-
COMANCHE-STEPHENS-GARVIN-MURRAY-PONTOTOC-COAL-COTTON-JEFFERSON-
CARTER-JOHNSTON-ATOKA-LOVE-MARSHALL-BRYAN-HARDEMAN-FOARD-WILBARGER-
WICHITA-KNOX-BAYLOR-ARCHER-CLAY-
1200 PM CDT MON APR 21 2008

THIS HAZARDOUS WEATHER OUTLOOK COVERS NORTHERN...WESTERN...
CENTRAL...AND SOUTHERN OKLAHOMA...AND WESTERN NORTH TEXAS.

.DAY ONE...TONIGHT...

THUNDERSTORM OUTLOOK...
THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF
CENTRAL OKLAHOMA.

LOCATION...
THE SLIGHT RISK AREA IS EAST AND NORTH OF A LINE FROM ALFALFA...TO
MARLOW...TO PAULS VALLEY...TO HOLDENVILLE.

TIMING...
THE MOST LIKELY TIME FOR SEVERE THUNDERSTORMS WILL BE BETWEEN 8 PM
AND 12 AM.

RECOMMENDED ACTIONS...
STORM SPOTTER GROUPS AND EMERGENCY MANAGEMENT PERSONNEL ACROSS THE
RISK AREA SHOULD PLAN FOR SEVERE WEATHER THIS EVENING.

DISCUSSION...
THE COLD FRONT WHICH MOVED INTO NORTHERN AND WESTERN OKLAHOMA
EARLIER TODAY HAS BECOME NEARLY STATIONARY FROM NORTH CENTRAL INTO
WEST CENTRAL OKLAHOMA. A DRY LINE EXTENDED FROM THE FRONT IN WEST
CENTRAL OKLAHOMA SOUTHWARD INTO WESTERN NORTH TEXAS. A STRONG CAP
SUPPRESSED THUNDERSTORM DEVELOPMENT THROUGH MUCH OF THE DAY. HOWEVER
EVENING UPPER AIR SOUNDINGS SHOW THAT THE CAP HAD SIGNIFICANTLY
WEAKENED. AS A RESULT THUNDERSTORM DEVELOPMENT WILL BE POSSIBLE THIS
EVENING IN THE VICINITY OF THE FRONT AND DRYLINE...MAINLY ACROSS
PARTS OF CENTRAL OKLAHOMA. MODERATE INSTABILITY AND FAVORABLE DEEP
LAYER SHEAR WILL FAVOR SEVERE STORM DEVELOPMENT. LARGE HAIL AND
DAMAGING WINDS WILL BE THE MAIN THREAT. ISOLATED TORNADOES CAN NOT
BE RULED OUT.

PROBABILITY TABLE...
VALID THROUGH 700 AM CDT TUESDAY APR 22.
PROBABILITY OF THUNDERSTORMS OCCURRING IN THE
              NWS NORMAN COUNTY WARNING AREA...60 PERCENT.
PROBABILITY OF SEVERE STORMS IF STORMS OCCUR...80 PERCENT.

OTHER HAZARDOUS WEATHER...
NONE.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY...

THUNDERSTORM OUTLOOK...
THUNDERSTORM CHANCES WILL RETURN LATE TUESDAY... AND CONTINUE
THROUGH THE REST OF THE WORK WEEK. SEVERE THUNDERSTORMS WILL BE
POSSIBLE... WITH THE BEST CHANCE OF SEVERE WEATHER OVER WESTERN
OKLAHOMA AND WESTERN NORTH TEXAS ON WEDNESDAY.

OTHER HAZARDOUS WEATHER...
NONE.

THE NEXT SCHEDULED HAZARDOUS WEATHER OUTLOOK WILL BE ISSUED AT 7 AM
TUESDAY.

24

In the hours before

Local storm report, Apr 21, 8:31 PM CDT, 40 minutes before
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Local storm report, Apr 21, 8:38 PM CDT, 33 minutes before
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The office that day

Everything else NWS Norman, OK issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Apr 21, 8:12 PM CDTSevere Thunderstorm WarningOUNGarvin, McClain48 min
Apr 21, 8:37 PM CDTSevere Thunderstorm WarningOUNCleveland, McClain, Pottawatomie38 min
Apr 21, 8:55 PM CDTSevere Thunderstorm WarningOUNGarvin, McClain, Pottawatomie50 min
Apr 21, 9:19 PM CDTSevere Thunderstorm WarningOUNKay26 min
Apr 21, 9:37 PM CDTSevere Thunderstorm WarningOUNGarvin, McClain, Pottawatomie20 min

Nearby

Severe Thunderstorm Warnings in Oklahoma, 2008Every severe thunderstorm warning in 2008

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.