Alert archive / Oklahoma / Severe Thunderstorm Warnings in 2009

Severe Thunderstorm Warning 276, NWS Norman, OK

April 30, 2009Canadian County, Oklahoma County, Oklahoma

NWS Norman, OK issued this severe thunderstorm warning at Apr 30, 2009, 11:59 PM CDT for Canadian County, Oklahoma County, Oklahoma. It was in force for 46 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 30, 2009, 11:59 PM CDT (04:59 UTC)
Expired: May 1, 2009, 12:45 AM CDT
In force: 46 min
Issued by: NWS Norman, OK
Area: Storm-based polygon

Counties Canadian County, OK, Oklahoma County, OK

The radar

The Norman radar (KTLX), 45 km from the middle of the area, began a volume at 05:00 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
Apr 30, 7:54 PM CDT	Severe Thunderstorm Watch	SPC	5 hr

The nearest sounding before it

Norman, OK (KOUN), launched 00:00Z, 5.0 hours before the alert went out and 45 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: 1831 J/kg
Mixed-layer CIN: -60 J/kg
Mixed-layer LCL: 1271 m above ground
0-6 km bulk shear: 39 kt
0-1 km storm-relative helicity: 66 m²/s²
0-3 km storm-relative helicity: 197 m²/s²
Significant tornado parameter: 0.6
Supercell composite: 6.5

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 30, 11:19 PM CDT, 40 minutes earlier.

Area forecast discussion, Apr 30, 11:19 PM CDT, 40 minutes before

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Hazardous weather outlook, Apr 30, 11:55 AM CDT, 12 hours 4 minutes before

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE NORMAN OK
1155 AM CDT THU APR 30 2009

OKZ004>048-050>052-TXZ083>090-011000-
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-
1155 AM CDT THU APR 30 2009

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

.DAY ONE...THIS AFTERNOON AND TONIGHT...

THUNDERSTORM OUTLOOK...
THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THIS AFTERNOON
INTO TONIGHT ACROSS ALL OF OKLAHOMA AND WESTERN NORTH TEXAS.

TIMING...
THE MOST LIKELY TIME FOR SEVERE THUNDERSTORMS WILL BE FROM 4 PM
THROUGH THE NIGHT.

IMPACTS...
SOME DAMAGE TO VEGETATION...AUTOMOBILES...AND HOMES...FROM HAIL TO
THE SIZE OF TENNIS BALLS.

LOCALLY SIGNIFICANT WIND DAMAGE FROM 75 MPH WINDS.

A LOW CHANCE OF TORNADOES.

RECOMMENDED ACTIONS...
STORM SPOTTER GROUPS AND EMERGENCY MANAGEMENT PERSONNEL ACROSS THE
RISK AREA SHOULD PLAN FOR SEVERE WEATHER OPERATIONS FROM LATE THIS
AFTERNOON UNTIL LATE TONIGHT.

DISCUSSION...
RICH GULF MOISTURE WAS IN PLACE. DEWPOINTS WILL RISE INTO THE MIDDLE
AND LOCALLY UPPER 60S...WHILE A COLD FRONT APPROACHES FROM THE
NORTHWEST. FROM MIDDAY INTO THE AFTERNOON...A SMALL COMPLEX OF
THUNDERSTORMS WILL MOVE JUST EAST OF STILLWATER...DOWN TO INTERSTATE
40. THIS WILL PRODUCE AN OUTFLOW BOUNDARY ORIENTED NORTHWEST TO
SOUTHEAST ACROSS CENTRAL AND NORTH CENTRAL OKLAHOMA. ELSEWHERE...THE
ENTIRE REGION WILL RECEIVE PLENTY OF HEATING...RESULTING IN STRONG
INSTABILITY...WITH CAPE VALUES GREATER THAN 2500...AND POSSIBLY
APPROACHING 3500 LATE THIS AFTERNOON. CAP STRENGTH WILL BE GREATEST
TO THE WEST...AND WEAKEST NEAR THE OUTFLOW BOUNDARY. THE FRONT WILL
MOVE INTO NORTHWEST OKLAHOMA...AND A WIND SHIFT...OR TROUGH AHEAD OF
THE FRONT IS EXPECTED TO BECOME THE FOCUS FOR THUNDERSTORM
DEVELOPMENT LATE THIS AFTERNOON. THE TROUGH WILL EXTEND FROM NEAR
PONCA CITY TO WATONGA AND MANGUM. THE MOST NUMEROUS STORMS ARE
EXPECTED WHERE THE TROUGH OVERTAKES THE OUTFLOW BOUNDARY IN NORTH
CENTRAL AND CENTRAL OKLAHOMA. INITIALLY...MODERATE WIND SHEAR AND
STRONG INSTABILITY MAY RESULT IN SUPERCELLS...WITH A RISK OF VERY
LARGE HAIL...AND AT LEAST A LOW CHANCE OF TORNADOES. THE STORMS MAY
QUICKLY GROW INTO A COMPLEX...HOWEVER...AND BEGIN TO MOVE SOUTH AND
SOUTHEAST...WITH AN INCREASING THREAT OF DAMAGING WINDS...IN
ADDITION TO LARGE HAIL.

FARTHER TOWARD WESTERN OKLAHOMA AND WESTERN NORTH TEXAS...A STRONG
CAP WILL LIMIT THE NUMBER OF STORMS...BUT ANY STORMS THAT DO FORM
MAY BRIEFLY EXHIBIT SUPERCELL STRUCTURE. VERY LARGE HAIL AND
DAMAGING WINDS WILL BE POSSIBLE.

PROBABILITY TABLE...
VALID THROUGH 500 AM CDT FRIDAY MAY 1.
PROBABILITY OF THUNDERSTORMS OCCURRING IN THE
              NWS NORMAN COUNTY WARNING AREA...70 PERCENT.
PROBABILITY OF SEVERE STORMS IF STORMS OCCUR...90 PERCENT.

OTHER HAZARDOUS WEATHER...
THROUGH EVENING...HEAVY RAIN AND LOCAL FLOODING SHOULD BE FOCUSED
WITH INDIVIDUAL STORMS IN THE WEST...OR WITH A DEVELOPING COMPLEX OF
STORMS IN NORTHERN AND CENTRAL OKLAHOMA. EVENTUALLY... HOWEVER..
THERE IS A LOW TO MODERATE CHANCE THAT HEAVY RAIN COULD MOVE BACK
INTO SOUTHERN OKLAHOMA AND CLAY COUNTY TEXAS BY LATE EVENING AND
OVERNIGHT. AFTER RECEIVING 8 TO 13 INCHES OF RAIN YESTERDAY...THOSE
AREAS WILL FLOOD QUICKLY...IF ADDITIONAL RAIN ARRIVES.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY...

THUNDERSTORM OUTLOOK...
SEVERE STORMS ARE POSSIBLE ALONG A SLOW MOVING COLD FRONT ON FRIDAY.
IF SEVERE STORMS OCCUR THIS WEEKEND...THEY WILL BE MOST LIKELY IN
SOUTHEASTERN OKLAHOMA. THERE IS A CHANCE OF THUNDERSTORMS ON TUESDAY
AND WEDNESDAY AS A STRONG UPPER LEVEL STORM SYSTEM APPROACHES THE
AREA.

OTHER HAZARDOUS WEATHER...
HEAVY RAINFALL IS EXPECTED FROM FRIDAY NIGHT THROUGH SUNDAY ACROSS
MUCH OF OKLAHOMA AND WESTERN NORTH TEXAS...WHICH COULD LEAD TO BOTH
LOCALIZED AND MAINSTEM RIVER FLOODING.

UNSCHEDULED UPDATES TO THE HAZARDOUS WEATHER OUTLOOK WILL BE ISSUED
TODAY.

TAYLOR/BURKE/II

In the hours before

Local storm report, Apr 30, 9:32 PM CDT, 2 hours 27 minutes before

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Special weather statement, Apr 30, 9:33 PM CDT, 2 hours 26 minutes before

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Local storm report, Apr 30, 9:49 PM CDT, 2 hours 10 minutes before

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Special weather statement, Apr 30, 10:13 PM CDT, 1 hour 46 minutes before

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Special weather statement, Apr 30, 10:36 PM CDT, 1 hour 23 minutes before

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Local storm report, Apr 30, 10:50 PM CDT, 1 hour 9 minutes before

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The office that day

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

Issued	Product	Office	Counties	Lasted
Apr 30, 7:58 PM CDT	Severe Thunderstorm Warning	OUN	Custer	62 min
Apr 30, 8:27 PM CDT	Tornado Warning	OUN	Custer	48 min
Apr 30, 9:05 PM CDT	Tornado Warning	OUN	Custer, Washita	40 min
Apr 30, 9:42 PM CDT	Severe Thunderstorm Warning	OUN	Washita	16 min
Apr 30, 10:44 PM CDT	Severe Thunderstorm Warning	OUN	Kingfisher	46 min
Apr 30, 11:04 PM CDT	Severe Thunderstorm Warning	OUN	Kingfisher	41 min
Apr 30, 11:28 PM CDT	Severe Thunderstorm Warning	OUN	Kingfisher, Logan	55 min
Apr 30, 11:35 PM CDT	Severe Thunderstorm Warning	OUN	Garfield, Noble	25 min
Apr 30, 11:56 PM CDT	Severe Thunderstorm Warning	OUN	Noble	49 min
May 1, 12:44 AM CDT	Severe Thunderstorm Warning	OUN	Canadian, Oklahoma	46 min
May 1, 2:00 AM CDT	River Flood Warning	OUN	Atoka, Bryan	7 hr
May 1, 6:30 AM CDT	Severe Thunderstorm Warning	OUN	Alfalfa, Grant	45 min
May 1, 7:01 AM CDT	Severe Thunderstorm Warning	OUN	Alfalfa, Garfield, Grant	59 min
May 1, 7:46 AM CDT	Severe Thunderstorm Warning	OUN	Garfield, Grant, Kay, Noble	44 min
May 1, 8:16 AM CDT	Flash Flood Warning	OUN	Alfalfa, Garfield, Grant	3 hr
May 1, 8:30 AM CDT	Severe Thunderstorm Warning	OUN	Garfield, Grant, Kay, Noble, Payne	60 min
May 1, 8:58 AM CDT	Flash Flood Warning	OUN	Kay, Noble	3 hr
May 1, 9:27 AM CDT	Severe Thunderstorm Warning	OUN	Garfield, Grant, Kay, Noble	63 min
May 1, 5:40 PM CDT	Severe Thunderstorm Warning	OUN	Comanche, Cotton, Tillman	65 min
May 1, 6:18 PM CDT	Severe Thunderstorm Warning	OUN	Cotton, Tillman	44 min
May 1, 3:09 PM CDT	Severe Thunderstorm Warning	OUN	Knox	66 min
May 1, 3:44 PM CDT	Areal Flood Advisory	OUN	Knox	3 hr
May 1, 4:26 PM CDT	Severe Thunderstorm Warning	OUN	Baylor, Foard, Knox, Wilbarger	64 min
May 1, 5:14 PM CDT	Flash Flood Warning	OUN	Baylor, Foard, Knox	4 hr
May 1, 5:28 PM CDT	Severe Thunderstorm Warning	OUN	Baylor, Foard, Hardeman, Knox, Wilbarger	62 min
May 1, 5:53 PM CDT	Areal Flood Advisory	OUN	Wilbarger	3 hr
May 1, 6:23 PM CDT	Severe Thunderstorm Warning	OUN	Baylor	40 min

Nearby

Severe Thunderstorm Warnings in Oklahoma, 2009 Every severe thunderstorm warning in 2009

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.