Alert archive / South Dakota / Mesoscale Discussions in 2018

Mesoscale Discussion 366

May 7, 2018Emmons County, McIntosh County, North Dakota; 17 counties in South Dakota

The Storm Prediction Center issued this mesoscale discussion at May 7, 2018, 7:17 PM CDT for Emmons County, McIntosh County, North Dakota; 17 counties in South Dakota. It was in force for 118 min.

The area

The outline as issued.

The facts

Issued: May 7, 2018, 7:17 PM CDT (00:17 UTC)
Expired: May 7, 2018, 9:15 PM CDT
In force: 118 min
Issued by: the Storm Prediction Center
Chance of a watch: 20%

Counties Emmons County, ND, McIntosh County, ND, Campbell County, SD, Corson County, SD, Dewey County, SD, Edmunds County, SD, Faulk County, SD, Haakon County, SD, Hughes County, SD, Hyde County, SD, Jackson County, SD, Jones County, SD, Lyman County, SD, McPherson County, SD, Mellette County, SD, Potter County, SD, Stanley County, SD, Sully County, SD, Walworth County, SD

The radar

The Aberdeen radar (KABR), 174 km from the middle of the area, began a volume at 00:20 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 nearest sounding before it

Aberdeen, SD (KABR), launched 00:00Z, 0.3 hours before the alert went out and 168 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 2739 m above ground
0-6 km bulk shear: 30 kt
0-1 km storm-relative helicity: 134 m²/s²
0-3 km storm-relative helicity: 306 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

098 
ACUS11 KWNS 080018
SWOMCD
SPC MCD 080017 
SDZ000-NDZ000-NEZ000-080215-

Mesoscale Discussion 0366
NWS Storm Prediction Center Norman OK
0717 PM CDT Mon May 07 2018

Areas affected...Much of central South Dakota and adjacent North
Dakota

Concerning...Severe potential...Watch unlikely 

Valid 080017Z - 080215Z

Probability of Watch Issuance...20 percent

SUMMARY...At least a risk for localized strong surface gusts is
expected to persist with thunderstorm activity spreading eastward
across the region through the 7-10 PM CDT time frame.  A short-lived
period with increasing thunderstorm organization and more widespread
strong gusts is possible, but it still seems unlikely that a severe
weather watch will be needed.

DISCUSSION...Thunderstorm activity, including isolated strong to
severe cells, continues to develop east of the higher plains and
Black Hills, perhaps associated with at least one smaller scale
perturbation embedded within the broad/low amplitude mid/upper wave
progressing across and east of the Rockies.  Aided by forcing
associated with lower/mid tropospheric warm advection, in the
presence of modest mixed-layer CAPE (up to around 1000 J/kg), this
may persist across much of central South Dakota and adjacent
portions of North Dakota through the 01-03Z time.

Deep layer shear is also fairly modest across the region, but the
lingering relatively strongly heated and deeply mixed boundary layer
probably will remain favorable to localized strong surface gusts
approaching or briefly exceeding severe limits.  Some coincidental
further strengthening of a southerly 850 mb jet from 30-40 kt is
forecast, and this could provide a window of opportunity for
increasing convective organization with a consolidating cold pool. 
However, any such development is generally expected to be
short-lived, before activity begins to ingest more stable and/or
stabilizing boundary layer across the lower Plains later this
evening.

..Kerr/Hart.. 05/08/2018

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...FSD...ABR...BIS...LBF...UNR...

LAT...LON   45470150 46320052 46419931 45379868 43699940 42980144
            44070191 45470150

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 8, 2:58 PM CDT	Mesoscale Discussion	SPC	Sargent	2 hr

Nearby

Mesoscale Discussions in South Dakota, 2018 Mesoscale Discussions in North Dakota, 2018 Every mesoscale discussion in 2018

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.