Alert archive / Oklahoma / Mesoscale Discussions in 2017

Mesoscale Discussion 540

April 21, 201714 counties in Arkansas; 23 counties in Oklahoma

The Storm Prediction Center issued this mesoscale discussion at Apr 21, 2017, 3:54 PM CDT for 14 counties in Arkansas; 23 counties in Oklahoma. It was in force for 66 min.

The area

The outline as issued.

The facts

Issued
Apr 21, 2017, 3:54 PM CDT (20:54 UTC)
Expired
Apr 21, 2017, 5:00 PM CDT
In force
66 min
Issued by
the Storm Prediction Center
Chance of a watch
40%
All 37 counties

Benton County, AR, Boone County, AR, Carroll County, AR, Crawford County, AR, Franklin County, AR, Johnson County, AR, Logan County, AR, Madison County, AR, Newton County, AR, Pope County, AR, Scott County, AR, Sebastian County, AR, Washington County, AR, Yell County, AR, Adair County, OK, Cherokee County, OK, Coal County, OK, Creek County, OK, Delaware County, OK, Haskell County, OK, Hughes County, OK, Latimer County, OK, LeFlore County, OK, Mayes County, OK, McIntosh County, OK, Murray County, OK, Muskogee County, OK, Okfuskee County, OK, Okmulgee County, OK, Pittsburg County, OK, Pontotoc County, OK, Pottawatomie County, OK, Rogers County, OK, Seminole County, OK, Sequoyah County, OK, Tulsa County, OK, Wagoner County, OK

The radar

The Western Arkansas radar (KSRX), 65 km from the middle of the area, began a volume at 20:57 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 watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

The nearest sounding before it

Springfield, MO (KSGF), launched 12:00Z, 8.9 hours before the alert went out and 194 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, Springfield, MO at 12:00Z 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, Springfield, MO at 12:00Z on 2017-04-21The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -171 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
0 J/kg
Mixed-layer CIN
No buoyant parcel
Mixed-layer LCL
637 m above ground
0-6 km bulk shear
55 kt
0-1 km storm-relative helicity
-171 m²/s²
0-3 km storm-relative helicity
-150 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

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SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Apr 21, 9:45 AM CDTMesoscale DiscussionSPCCrawford, Franklin, Garland, Howard, Johnson, Logan and 12 more2 hr
Apr 21, 10:04 AM CDTSevere Thunderstorm WatchSPCClark, Crawford, Franklin, Garland, Hot Spring, Howard and 14 more5 hr
Apr 21, 1:12 PM CDTMesoscale DiscussionSPCArkansas, Cleburne, Conway, Crawford, Crittenden, Cross and 28 more93 min
Apr 21, 3:09 PM CDTMesoscale DiscussionSPCHempstead, Howard, Lafayette, Little River, Miller, Pike and 2 more2 hr
Apr 21, 4:40 PM CDTTornado WatchSPCHempstead, Howard, Little River, Logan, Miller, Montgomery and 6 more8 hr
Apr 20, 9:33 PM CDTSevere Thunderstorm WatchSPCBeckham, Blaine, Caddo, Canadian, Carter, Cleveland and 20 more7 hr
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

Nearby

Mesoscale Discussions in Oklahoma, 2017Mesoscale Discussions in Arkansas, 2017Every mesoscale discussion 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.