Flash Flooding and Hail in Oklahoma, August 17 to 18, 2009

Name: Flash Flooding and Hail in Oklahoma, August 17 to 18, 2009
Start: 2009-08-17T17:43
End: 2009-08-18T03:30
Location: Oklahoma

August 17 to 18, 2009 · NWS OUN · 15 events in 8 counties and zones

Where it happened

Every event with a place to put it. Tap one for its entry below.

Tornadoes
Tropical storms and surge
Floods
Wind
Hail
Winter weather
Heat and drought
Cold
Fire, smoke and dust
Marine and coastal
Other

Open the live radar over this ground

The toll

Deaths: 0
Injuries: 0
Property damage: $900,000
Crop damage: None recorded
Events: 15

Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.

What happened

The episode as NWS OUN wrote it up.

A stationary frontal boundary was located from the Texas panhandle, into west central and central Oklahoma Oklahoma during the late afternoon hours. Very unstable air was in place along and south of the boundary. Thunderstorms developed over the Texas panhandle and developed eastward along the boundary. The combination of the very unstable air and decent vertical wind shear allowed for some of the thunderstorms to become better organized, with severe weather reported over parts of west central into central Oklahoma. Later in the evening, additional thunderstorms developed north of the boundary as the low-level jet developed. Severe weather was reported over parts of northern Oklahoma, mainly in the form of strong winds and very heavy rainfall.

What forecasters said that day

The local office's own words before the first event, 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 the first event at Aug 17, 5:30 PM CST, 13 minutes earlier.

Area forecast discussion, Aug 17, 5:30 PM CST, 13 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORMAN OK
630 PM CDT MON AUG 17 2009

.AVIATION...
OUTFLOW BOUNDARY EXTENDS FROM NEAR KOKC TO SOUTH OF KGAG.
SCATTERED THUNDERSTORMS ARE EXPECTED MAINLY NORTH OF THIS BOUNDARY
ALTHOUGH THE SPECIFIC TIMING FOR AFFECTING SPECIFIC TAF SITES IS
QUITE UNCERTAIN GIVEN THE SCATTERED NATURE OF THE CONVECTION. THE
OUTFLOW BOUNDARY WILL ALSO GIVE SOME VARIABLE WIND DIRECTION OVER
TIME AT THE NORTHERN AND CENTRAL OKLAHOMA TAF SITES.

&&

.PREV DISCUSSION... /ISSUED 259 PM/

DISCUSSION...TODAY OUR FOCUS IS ON THE SHORT TERM POTENTIAL FOR
HEAVY RAINFALL. THERE ARE NUMEROUS INGREDIENTS IN PLACE...INCLUDING
A STATIONARY FRONT BENEATH PARALLEL UPPER FLOW...AND ABUNDANT
MOISTURE. ACTIVITY IS EXPECTED INITIALLY ALONG AN OUTFLOW BOUNDARY
FROM THE OKLAHOMA CITY AREA...WESTWARD TO NEAR ARNETT. STEEP LAPSE
RATES SUPPORT THE THREATS OF DAMAGING WINDS AND SOME LARGE
HAIL...ESPECIALLY DURING THE EVENING. THESE LAPSE RATES WOULD TEND
TO FAVOR COLD POOLS TO KEEP STORMS MOVING...BUT THE COLD POOLS WILL
MEET RESISTANCE FROM AN EASTERLY TO SOUTHERLY LOW LEVEL JET.
THIS...ALONG WITH SLOW MOTION OF INDIVIDUAL CELLS...AND INCREASING
SYNOPTIC SCALE LIFT OVER NORTHERN OKLAHOMA...SUGGESTS REPEATED HEAVY
RAIN MAY OCCUR ALONG AND NORTH OF THE INITIAL LINE OF THUNDERSTORMS.

THIS REASONING LED TO THE FLASH FLOOD WATCH FOR COUNTIES ALONG AND
NORTH OF INTERSTATE 40. THE LARGE SCALE PATTERN WILL REMAIN IN PLACE
THROUGH TUESDAY NIGHT...AND THE FLOOD WATCH WILL NEED TO BE
REVISITED AND POSSIBLY EXTENDED IN TIME AFTER SEEING THE OUTCOME OF
THE MONDAY NIGHT CONVECTION.

WE ADJUSTED GFS GUIDANCE POPS UPWARD IN DAYS 1-3...BUT MOST
SIGNIFICANTLY FOR TONIGHT...WHERE THE NAM AND LOCAL WRF HAD A BETTER
HANDLE ON THE OUTFLOW BOUNDARY AND MORE SOUTHERLY SWATH OF
PRECIPITATION. MUCH LIKE TODAY...THERE SHOULD BE A THUNDERSTORM
COMPLEX ONGOING IN NORTHERN OKLAHOMA TUESDAY MORNING. MODELS HAVE A
CONSISTENT SIGNAL FOR STRONG LIFT AND ANOTHER ASSOCIATED COMPLEX IN
NORTHWEST OKLAHOMA WEDNESDAY MORNING. THE GFS GUIDANCE FOR HIGH
TEMPERATURES DID NOT REFLECT THE CONVECTION WELL...SO WE ADJUSTED
TEMPERATURES DOWNWARD ALONG A GRADIENT FROM INTERSTATE 40 NORTHWARD.

A COLD FRONT WILL SWEEP THROUGH LATE WEDNESDAY INTO THURSDAY...WITH
A CONTINUED CHANCE FOR STORMS ALONG THE FRONT...AND DRIER...MORE
STABLE AIR BEHIND IT.

&&

.PRELIMINARY POINT TEMPS/POPS...
OKLAHOMA CITY OK  72  90  74  95 /  40  20  20  20
HOBART OK         75  94  75 100 /  20  20  30  10
WICHITA FALLS TX  75 100  77 102 /  10  10  10  10
GAGE OK           66  82  68  93 /  70  30  60  20
PONCA CITY OK     72  81  76  92 /  70  50  40  30
DURANT OK         74  99  75  95 /  10  10  10  20

&&

.OUN WATCHES/WARNINGS/ADVISORIES...
OK...FLASH FLOOD WATCH THROUGH TUESDAY MORNING FOR OKZ004>020-024>026.

TX...NONE.
&&

Hazardous weather outlook, Aug 17, 11:00 AM CST, 6 hours 43 minutes before

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE NORMAN OK
1200 PM CDT MON AUG 17 2009

OKZ004>048-050>052-TXZ083>090-181000-
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 AUG 17 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 THROUGH TONIGHT
ACROSS PORTIONS OF OKLAHOMA.

LOCATION...
THE SLIGHT RISK AREA IS NORTH OF INTERSTATE 40.

TIMING...
THE MOST LIKELY TIME FOR SEVERE THUNDERSTORMS WILL BE FROM LATE
AFTERNOON THROUGH EARLY TUESDAY MORNING.

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

DISCUSSION...
MODERATE INSTABILITY... COMBINED WITH SURFACE BOUNDARIES... AN UPPER
LEVEL TROUGH... AND MODERATE VERTICAL WIND SHEAR... WILL BRING A
CHANCE OF SEVERE THUNDERSTORMS TO NORTHERN OKLAHOMA LATER TODAY. INSOLATION
AND AN OUTFLOW BOUNDARY ACROSS CENTRAL OKLAHOMA WILL PROVIDE
SUFFICIENT LIFT FOR THUNDERSTORMS LATER THIS AFTERNOON.
THUNDERSTORMS WILL BE CAPABLE OF PRODUCING VERY HEAVY RAIN AND
LOCALIZED FLOODING. A FEW THUNDERSTORMS MAY ALSO MAKE LARGE HAIL AND
DAMAGING WINDS.

PROBABILITY TABLE...
VALID THROUGH 700 AM CDT TUESDAY AUG 18.
PROBABILITY OF THUNDERSTORMS OCCURRING IN THE
              NWS NORMAN COUNTY WARNING AREA...100 PERCENT.
PROBABILITY OF SEVERE STORMS IF STORMS OCCUR...70 PERCENT.

OTHER HAZARDOUS WEATHER...
A FLOOD WATCH IS EFFECTIVE FOR THE NORTHERN HALF OF OKLAHOMA FROM
LATE THIS AFTERNOON THROUGH MID-DAY TUESDAY.

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

THUNDERSTORM OUTLOOK...
SEVERE THUNDERSTORMS ARE POSSIBLE TUESDAY AND TUESDAY NIGHT.
THUNDERSTORM CHANCES RECEDE BEYOND WEDNESDAY MORNING.

OTHER HAZARDOUS WEATHER...
A FLOOD WATCH IS EFFECTIVE FOR THE NORTHERN HALF OF OKLAHOMA UNTIL
MID-DAY TUESDAY. THUNDERSTORMS TUESDAY MORNING WILL LIKELY GENERATE
VERY HEAVY RAINFALL.

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

In the hours before

Special weather statement, Aug 17, 4:47 PM CST, 56 minutes before

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE NORMAN OK
547 PM CDT MON AUG 17 2009

OKZ015-017-172330-
DEWEY OK-BLAINE OK-
547 PM CDT MON AUG 17 2009

...SIGNIFICANT WEATHER ADVISORY...

THIS SIGNIFICANT WEATHER ADVISORY IS FOR BLAINE AND DEWEY COUNTIES.

A STRONG THUNDERSTORM WAS LOCATED 5 MILES SOUTHWEST OF EAGLE CITY AT
546 PM CDT...MOVING EAST AT 15 MPH. SMALL HAIL AND WINDS AROUND 50
MPH ARE LIKELY. ADDITIONAL THUNDERSTORMS WERE FORMING ON AN OUTFLOW
BOUNDARY EXTENDING WEST TOWARD TALOGA. SEVERE WEATHER IS POSSIBLE AS
STORM STRENGTHEN THIS EVENING.

LAT...LON 3577 9821 3585 9890 3599 9905 3616 9862
      3616 9822

BURKE

Special weather statement, Aug 17, 5:36 PM CST, 7 minutes before

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE NORMAN OK
636 PM CDT MON AUG 17 2009

OKZ007-172350-
GRANT OK-
636 PM CDT MON AUG 17 2009

...SIGNIFICANT WEATHER ADVISORY...

THIS SIGNIFICANT WEATHER ADVISORY IS FOR GRANT COUNTY.

A STRONG THUNDERSTORM WAS LOCATED 5 MILES NORTHWEST OF LAMONT AT 636
PM CDT...MOVING NORTHEAST AT 10 MPH.

SMALL HAIL AND WINDS AROUND 50 MPH ARE POSSIBLE.

PEOPLE IN GRANT COUNTY SHOULD MONITOR THE WEATHER SITUATION CLOSELY.
LISTEN FOR WARNINGS AND REMAIN ALERT FOR THREATENING WEATHER
CONDITIONS.

LAT...LON 3691 9762 3681 9746 3675 9746 3661 9760
      3671 9778

..SPEG.

The radar

The Vance AFB radar (KVNX), 94 km away, was scanning. The volume nearest the first event began at 23:44 UTC.

Open the radar archive at this moment

Event by event

7 thunderstorm wind, 5 hail, 3 flash flood. Local standard time, as filed.

Hail, Blaine

When: August 17, 5:43 PM CST
Where: Blaine County, Roman Nose St Park
Measured: 1 in hail
Reported by: Park/Forest Service
Coordinates: 35.930, -98.430

Hail, Grant

When: August 17, 6:25 PM CST
Where: Grant County, Nash
Measured: 1 in hail
Reported by: Public
Coordinates: 36.670, -98.050

Hail, Kay

When: August 17, 7:05 PM CST
Where: Kay County, Blackwell
Measured: 0.88 in hail
Reported by: Emergency Manager
Coordinates: 36.800, -97.280

Thunderstorm Wind, Custer

When: August 17, 7:05 PM CST
Where: Custer County, 5 mi SW of Butler
Measured: 52 kt (60 mph) measured gust
Reported by: Mesonet
Coordinates: 35.589, -99.253

Thunderstorm Wind, Washita

When: August 17, 7:30 PM CST
Where: Washita County, 4 mi WNW of Bessie
Measured: 50 kt (58 mph) measured gust
Reported by: Mesonet
Coordinates: 35.402, -99.056

Flash Flood, Grant

When: August 17, 7:45 PM CST to 9:45 PM CST
Where: Grant County, 3.37 mi SSW of Medford to 3.03 mi NNE of Medford
Cause: Heavy Rain
Reported by: Law Enforcement
Coordinates: 36.767, -97.759

Flash flooding was reported near the One Oak Plant, two to three miles southwest of Medford on Highway 81. Additional flooding was reported on CR M and M.

Hail, Blaine

When: August 17, 7:45 PM CST
Where: Blaine County, 3 mi E of Greenfield
Measured: 0.75 in hail
Reported by: Public
Coordinates: 35.730, -98.326

Thunderstorm Wind, Custer

When: August 17, 7:55 PM CST
Where: Custer County, 4 mi WSW of Weatherford
Measured: 50 kt (58 mph) measured gust
Reported by: Mesonet
Coordinates: 35.508, -98.766

Thunderstorm Wind, Caddo

When: August 17, 8:30 PM CST to 8:35 PM CST
Where: Caddo County, 7 mi W of Hinton
Measured: 54 kt (62 mph) measured gust
Reported by: Mesonet
Coordinates: 35.470, -98.484

A wind gust of 58 mph was measured at 2130 cdt, another gust of 62 mph was measured at 2135 cdt, and another gust to 66 mph was measured at 2140 cdt.

Hail, Grant

When: August 17, 8:35 PM CST
Where: Grant County, 6 mi N of Lamont
Measured: 1.25 in hail
Reported by: Public
Coordinates: 36.777, -97.560

Thunderstorm Wind, Canadian

When: August 17, 8:40 PM CST
Where: Canadian County, 9.41 mi WSW of Calumet
Measured: 61 kt (70 mph) estimated gust
Reported by: Amateur Radio
Coordinates: 35.560, -98.280

A tractor trailer was blown over on eastbound Highway 281, three miles northwest of Interstate 40, off of exit 108. Significant tree damage was also reported at this location. Monetary damage estimates were not available.

Thunderstorm Wind, Caddo

When: August 17, 8:45 PM CST to 8:47 PM CST
Where: Caddo County, 3.13 mi ESE of Bridgeport
Measured: 61 kt (70 mph) estimated gust
Reported by: Amateur Radio
Coordinates: 35.530, -98.330

A tractor trailer was blown over on Interstate 40 near mile marker 103. Tree damage was also reported at this location. Monetary damage estimates were not available.

Flash Flood, Kay

When: August 17, 10:00 PM CST to August 18, 1:00 AM CST
Where: Kay County, 2.86 mi NW of Blackwell to 2.51 mi N of Blackwell
Cause: Heavy Rain
Reported by: Emergency Manager
Coordinates: 36.827, -97.320

Several streets in Blackwell were closed due to water running over top of them. Several county roads west of town were also impassable.

Thunderstorm Wind, Kay

When: August 17, 10:45 PM CST to 10:47 PM CST
Where: Kay County, 1.78 mi NNE of Ponca City to 0.91 mi S of Ponca City
Measured: 65 kt (75 mph) estimated gust
Property damage: $900,000
Reported by: County Official
Coordinates: 36.724, -97.069

Widespread wind damage was reported over the southeast parts of Ponca City. The damage area was from S. 8th to S. 13th from South Ave north about 4 to 5 blocks. Numerous trees and power lines were blown down. Several houses reported at least minor damage, with one home blown off its foundation and losing its roof. Monetary damage is estimated based on figures from Ponca City Emergency Management.

Flash Flood, Garfield

When: August 18, 12:00 AM CST to 3:30 AM CST
Where: Garfield County, 3.85 mi SW of Kremlin to 4.09 mi NE of North Enid
Cause: Heavy Rain
Reported by: Emergency Manager
Coordinates: 36.506, -97.873

Highways 45 and 81, north and west of Enid, were closed due to water running over top of them. Several county roads were also closed in these areas due to high water.

What these are

Hail: Hail three-quarters of an inch or larger, or smaller hail that caused damage, filed with the largest stone measured.
Thunderstorm Wind: Winds from a thunderstorm of 50 knots (58 mph) or more, or lower winds that caused damage or casualties. Measured gusts are marked MG, estimated EG.
Flash Flood: Flooding that begins within six hours of the rain that causes it, or of a dam or levee failure or ice jam release, often with deadly speed.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

Every storm in Oklahoma in 2009 Every state in 2009 This day in weather history Warnings in Oklahoma, August 2009

Sources

NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 193112, 193113, 193114, 193115, 193116, 193117, 193118, 193119, 193120, 193121, 193123, 193124, 193125, 193127, 193128.