Alert archive / Texas / Mesoscale Discussions in 2017

Mesoscale Discussion 538

April 21, 20178 counties in Arkansas; 11 counties in Oklahoma; 39 counties in Texas

The Storm Prediction Center issued this mesoscale discussion at Apr 21, 2017, 3:09 PM CDT for 8 counties in Arkansas; 11 counties in Oklahoma; 39 counties in Texas. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued
Apr 21, 2017, 3:09 PM CDT (20:09 UTC)
Expired
Apr 21, 2017, 5:15 PM CDT
In force
2 hr
Issued by
the Storm Prediction Center
Chance of a watch
80%
All 58 counties

Hempstead County, AR, Howard County, AR, Lafayette County, AR, Little River County, AR, Miller County, AR, Pike County, AR, Polk County, AR, Sevier County, AR, Atoka County, OK, Bryan County, OK, Carter County, OK, Choctaw County, OK, Coal County, OK, Jefferson County, OK, Johnston County, OK, Love County, OK, Marshall County, OK, McCurtain County, OK, Pushmataha County, OK, Archer County, TX, Baylor County, TX, Bowie County, TX, Camp County, TX, Cass County, TX, Clay County, TX, Collin County, TX, Cooke County, TX, Dallas County, TX, Delta County, TX, Denton County, TX, Ellis County, TX, Fannin County, TX, Franklin County, TX, Grayson County, TX, Gregg County, TX, Harrison County, TX, Hood County, TX, Hopkins County, TX, Hunt County, TX, Jack County, TX, Johnson County, TX, Kaufman County, TX, Lamar County, TX, Marion County, TX, Montague County, TX, Morris County, TX, Palo Pinto County, TX, Parker County, TX, Rains County, TX, Red River County, TX, Rockwall County, TX, Tarrant County, TX, Titus County, TX, Upshur County, TX, Van Zandt County, TX, Wise County, TX, Wood County, TX, Young County, TX

The radar

The Dallas/Ft Worth radar (KFWS), 119 km from the middle of the area, began a volume at 20:06 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

Fort Worth, TX (KFWD), launched 12:00Z, 8.2 hours before the alert went out and 98 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, Fort Worth, TX at 12:00Z on 2017-04-21Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 106 joules per kilogram.LCLLFCEL10008507005003002001001 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, Fort Worth, TX at 12:00Z on 2017-04-21The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 86 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
106 J/kg
Mixed-layer CIN
-396 J/kg
Mixed-layer LCL
1056 m above ground
0-6 km bulk shear
32 kt
0-1 km storm-relative helicity
86 m²/s²
0-3 km storm-relative helicity
85 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.1

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, 3:54 PM CDTMesoscale DiscussionSPCBenton, Boone, Carroll, Crawford, Franklin, Johnson and 8 more66 min
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
Apr 21, 1:07 AM CDTMesoscale DiscussionSPCCooke, Denton, Grayson, Montague, Wise113 min

Nearby

Mesoscale Discussions in Texas, 2017Mesoscale 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.