Alert archive / Oklahoma / Severe Thunderstorm Watches in 2017

Severe Thunderstorm Watch 152

April 20, 201726 counties in Oklahoma; 18 counties in Texas

The Storm Prediction Center issued this severe thunderstorm watch at Apr 20, 2017, 9:33 PM CDT for 26 counties in Oklahoma; 18 counties in Texas. It was in force for 7 hr.

The area

The outline as issued.

The facts

Issued
Apr 20, 2017, 9:33 PM CDT (02:33 UTC)
Expired
Apr 21, 2017, 5:00 AM CDT
In force
7 hr
Issued by
the Storm Prediction Center
Largest hail expected
2 in
Strongest gust expected
50 kt
All 44 counties

Beckham County, OK, Blaine County, OK, Caddo County, OK, Canadian County, OK, Carter County, OK, Cleveland County, OK, Comanche County, OK, Cotton County, OK, Custer County, OK, Dewey County, OK, Garvin County, OK, Grady County, OK, Greer County, OK, Harmon County, OK, Jackson County, OK, Jefferson County, OK, Kingfisher County, OK, Kiowa County, OK, Logan County, OK, McClain County, OK, Murray County, OK, Oklahoma County, OK, Roger Mills County, OK, Stephens County, OK, Tillman County, OK, Washita County, OK, Archer County, TX, Baylor County, TX, Briscoe County, TX, Childress County, TX, Clay County, TX, Collingsworth County, TX, Cottle County, TX, Donley County, TX, Foard County, TX, Gray County, TX, Hall County, TX, Hardeman County, TX, Hemphill County, TX, Motley County, TX, Roberts County, TX, Wheeler County, TX, Wichita County, TX, Wilbarger County, TX

The radar

The Altus AFB radar (KFDR), 128 km from the middle of the area, began a volume at 02:33 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 SPC expected

The probabilities SPC published with the watch, for the watch area over its life.

Two or more tornadoes
5%
One or more EF2 to EF5 tornadoes
2%
Ten or more severe wind reports
20%
One or more gusts of 65 knots or more
10%
Ten or more severe hail reports
40%
One or more hailstones of 2 inches or more
30%
Six or more combined severe hail and wind reports
60%

Warnings issued inside it

28 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.

IssuedProductOfficeCountiesLasted
Apr 20, 9:48 PM CDTSevere Thunderstorm WarningLUBCottle27 min
Apr 20, 9:53 PM CDTSevere Thunderstorm WarningOUNHarmon, Jackson52 min
Apr 20, 10:13 PM CDTSevere Thunderstorm WarningOUNFoard, Hardeman47 min
Apr 20, 10:37 PM CDTSevere Thunderstorm WarningOUNJackson, Tillman38 min
Apr 20, 10:52 PM CDTSevere Thunderstorm WarningOUNFoard, Hardeman, Wilbarger38 min
Apr 20, 11:08 PM CDTSevere Thunderstorm WarningOUNJackson, Tillman67 min
Apr 20, 11:23 PM CDTSevere Thunderstorm WarningOUNJackson, Kiowa52 min
Apr 20, 11:25 PM CDTSevere Thunderstorm WarningOUNBaylor, Foard, Wilbarger50 min
Apr 20, 11:46 PM CDTSevere Thunderstorm WarningOUNCuster, Washita44 min
Apr 21, 12:00 AM CDTSevere Thunderstorm WarningOUNCaddo, Comanche, Kiowa45 min
Apr 21, 12:07 AM CDTSevere Thunderstorm WarningOUNArcher, Baylor, Wichita, Wilbarger53 min
Apr 21, 12:08 AM CDTSevere Thunderstorm WarningOUNCotton, Tillman53 min
Apr 21, 12:15 AM CDTSevere Thunderstorm WarningOUNBlaine45 min
Apr 21, 12:25 AM CDTSevere Thunderstorm WarningOUNCuster17 min
Apr 21, 12:27 AM CDTSevere Thunderstorm WarningOUNCanadian, Kingfisher33 min
Apr 21, 12:36 AM CDTSevere Thunderstorm WarningOUNCaddo, Comanche39 min
Apr 21, 12:55 AM CDTSevere Thunderstorm WarningOUNArcher, Wichita50 min
Apr 21, 1:09 AM CDTSevere Thunderstorm WarningOUNGarfield, Kingfisher, Logan, Noble, Payne28 min
Apr 21, 1:12 AM CDTSevere Thunderstorm WarningOUNCaddo, Comanche, Grady29 min
Apr 21, 1:21 AM CDTSevere Thunderstorm WarningOUNClay39 min
Apr 21, 1:54 AM CDTSevere Thunderstorm WarningOUNClay32 min
Apr 21, 2:36 AM CDTSevere Thunderstorm WarningOUNLincoln, Logan, Oklahoma39 min
Apr 21, 3:47 AM CDTSevere Thunderstorm WarningOUNBeckham, Roger Mills43 min
Apr 21, 3:49 AM CDTSevere Thunderstorm WarningOUNCuster, Washita41 min
Apr 21, 4:02 AM CDTSevere Thunderstorm WarningOUNCuster, Washita43 min
Apr 21, 4:23 AM CDTSevere Thunderstorm WarningOUNDewey25 min
Apr 21, 4:27 AM CDTSevere Thunderstorm WarningOUNCuster, Dewey, Roger Mills24 min
Apr 21, 4:40 AM CDTSevere Thunderstorm WarningAMAHansford, Hutchinson, Ochiltree, Roberts80 min

Discussions around it

SPC mesoscale discussions over the same counties from four hours before the watch to its end.

The nearest sounding before it

Amarillo Airport, TX (KAMA), launched 00:00Z, 2.6 hours before the alert went out and 167 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, Amarillo Airport, TX at 00:00Z on 2017-04-21Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Amarillo Airport, TX at 00:00Z on 2017-04-21The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 2 square meters per square second.193958Sfc1 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
0 J/kg
Mixed-layer CIN
No buoyant parcel
Mixed-layer LCL
2129 m above ground
0-6 km bulk shear
63 kt
0-1 km storm-relative helicity
2 m²/s²
0-3 km storm-relative helicity
278 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Apr 20, 11:30 PM CDTMesoscale DiscussionSPCBeckham, Blaine, Caddo, Canadian, Carter, Cleveland and 19 more60 min
Apr 21, 3:44 AM CDTMesoscale DiscussionSPCBeckham, Blaine, Caddo, Canadian, Carter, Cleveland and 26 more2 hr
Apr 21, 4:20 AM CDTSevere Thunderstorm WatchSPCAlfalfa, Atoka, Beaver, Beckham, Blaine, Bryan and 42 more8 hr
Apr 21, 7:54 AM CDTMesoscale DiscussionSPCAlfalfa, Beckham, Blaine, Caddo, Canadian, Carter and 27 more2 hr
Apr 21, 9:45 AM CDTMesoscale DiscussionSPCAdair, Atoka, Cherokee, Cleveland, Coal, Creek and 23 more2 hr
Apr 21, 10:04 AM CDTSevere Thunderstorm WatchSPCAdair, Cherokee, Choctaw, Creek, Haskell, Latimer and 11 more5 hr
Apr 21, 1:12 PM CDTMesoscale DiscussionSPCLeFlore93 min
Apr 21, 3:09 PM CDTMesoscale DiscussionSPCAtoka, Bryan, Carter, Choctaw, Coal, Jefferson and 5 more2 hr
Apr 21, 3:54 PM CDTMesoscale DiscussionSPCAdair, Cherokee, Coal, Creek, Delaware, Haskell and 17 more66 min
Apr 21, 4:40 PM CDTTornado WatchSPCAtoka, Bryan, Carter, Choctaw, Coal, Haskell and 11 more8 hr
Apr 21, 1:07 AM CDTMesoscale DiscussionSPCCooke, Denton, Grayson, Montague, Wise113 min

Nearby

Severe Thunderstorm Watches in Oklahoma, 2017Severe Thunderstorm Watches in Texas, 2017Every severe thunderstorm watch in 2017

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.