Alert archive / South Dakota / Mesoscale Discussions in 2017

Mesoscale Discussion 939

June 2, 201712 counties in South Dakota

The Storm Prediction Center issued this mesoscale discussion at Jun 2, 2017, 1:48 PM MDT for 12 counties in South Dakota. It was in force for 87 min.

The area

The outline as issued.

The facts

Issued: Jun 2, 2017, 1:48 PM MDT (19:48 UTC)
Expired: Jun 2, 2017, 3:15 PM MDT
In force: 87 min
Issued by: the Storm Prediction Center
Chance of a watch: 20%

Counties Bennett County, SD, Campbell County, SD, Dewey County, SD, Haakon County, SD, Hughes County, SD, Jackson County, SD, Jones County, SD, Mellette County, SD, Potter County, SD, Stanley County, SD, Sully County, SD, Walworth County, SD

The radar

The Rapid City radar (KUDX), 178 km from the middle of the area, began a volume at 19:49 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

Rapid City, SD (KRAP), launched 12:00Z, 7.8 hours before the alert went out and 184 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: 18 J/kg
Mixed-layer CIN: -194 J/kg
Mixed-layer LCL: 2851 m above ground
0-6 km bulk shear: 22 kt
0-1 km storm-relative helicity: 14 m²/s²
0-3 km storm-relative helicity: 20 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

928 
ACUS11 KWNS 021949
SWOMCD
SPC MCD 021948 
SDZ000-NDZ000-NEZ000-022115-

Mesoscale Discussion 0939
NWS Storm Prediction Center Norman OK
0248 PM CDT Fri Jun 02 2017

Areas affected...Central SD

Concerning...Severe potential...Watch unlikely 

Valid 021948Z - 022115Z

Probability of Watch Issuance...20 percent

SUMMARY...Isolated damaging wind gusts and hail possible this
afternoon across central SD. Low severe coverage is expected to
preclude the need for a watch.

DISCUSSION...Recent visible satellite imagery shows an increasingly
agitated cu field across central SD. Strengthening updrafts within
this cu field have resulted in lightning over the last 30 mins.
Current surface analysis indicates this development is just ahead of
a pre-frontal trough and within a broad area of pre-frontal
confluence. Overall look of the cu field and recent surface
observations and model soundings suggest this develop is based quite
high, likely over 10kft. Expectation is for the areal extent of this
activity to increase over the next hour or so while moving
north-northeastward. Weak shear will likely preclude anything but
modest storm organization but near dry adiabatic low-level lapse
rates and high storm bases will result in the potential damaging
wind gusts within the strongest storms. Some hail is also possible,
particularly as storms move north-northeastward into a more unstable
airmass across north-central SD. Anticipated severe coverage is
expected to be low, precluding higher watch probabilities, but
convective trends across the area will be monitored closely.

..Mosier/Weiss.. 06/02/2017

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

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

LAT...LON   44890144 45720092 45870059 45949996 45739953 44979944
            43350047 42980167 43450235 44890144

Nearby

Mesoscale Discussions in South Dakota, 2017 Every 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.