Alert archive / Minnesota / Mesoscale Discussions in 2018

Mesoscale Discussion 992

July 2, 201820 counties in Minnesota; Cass County, Richland County, North Dakota; 7 counties in South Dakota

The Storm Prediction Center issued this mesoscale discussion at Jul 2, 2018, 11:32 PM CDT for 20 counties in Minnesota; Cass County, Richland County, North Dakota; 7 counties in South Dakota. It was in force for 88 min.

The area

The outline as issued.

The facts

Issued: Jul 2, 2018, 11:32 PM CDT (04:32 UTC)
Expired: Jul 3, 2018, 1:00 AM CDT
In force: 88 min
Issued by: the Storm Prediction Center

All 29 counties

Becker County, MN, Big Stone County, MN, Cass County, MN, Chippewa County, MN, Clay County, MN, Douglas County, MN, Grant County, MN, Hubbard County, MN, Kandiyohi County, MN, Lac qui Parle County, MN, Mahnomen County, MN, Norman County, MN, Otter Tail County, MN, Pope County, MN, Stevens County, MN, Swift County, MN, Todd County, MN, Traverse County, MN, Wadena County, MN, Wilkin County, MN, Cass County, ND, Richland County, ND, Clark County, SD, Codington County, SD, Deuel County, SD, Grant County, SD, Hamlin County, SD, Roberts County, SD, Spink County, SD

The radar

The Aberdeen radar (KABR), 107 km from the middle of the area, began a volume at 04:31 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.

Severe Thunderstorm Watch 258Jul 3, 1:55 AM CDT

The nearest sounding before it

Aberdeen, SD (KABR), launched 00:00Z, 4.5 hours before the alert went out and 142 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: 2124 J/kg
Mixed-layer CIN: -10 J/kg
Mixed-layer LCL: 1720 m above ground
0-6 km bulk shear: 49 kt
0-1 km storm-relative helicity: 113 m²/s²
0-3 km storm-relative helicity: 157 m²/s²
Significant tornado parameter: 0.4
Supercell composite: 8.5

Open this sounding in Storm Lab

The text

As transmitted.

404 
ACUS11 KWNS 030432
SWOMCD
SPC MCD 030432 
MNZ000-SDZ000-NDZ000-030600-

Mesoscale Discussion 0992
NWS Storm Prediction Center Norman OK
1132 PM CDT Mon Jul 02 2018

Areas affected...Portions of northeastern SD...southeastern ND...and
western/central MN

Concerning...Severe Thunderstorm Watch 256...

Valid 030432Z - 030600Z

The severe weather threat for Severe Thunderstorm Watch 256
continues.

SUMMARY...Mainly an isolated large hail risk continues across
eastern portions of WW 256 and into parts of western/central MN.
Downstream watch issuance into more of MN appears unlikely at this
time.

DISCUSSION...04Z RAP mesoanalysis indicates a southwesterly 35-45 kt
low-level jet is present across eastern SD and southern/central MN.
Multiple bands of thunderstorms have formed across this area in the
low-level warm air advection regime. The best instability and
potential for surface-based convection is located across
northeastern SD, where surface dewpoints in the upper 60s to lower
70s and modestly steep mid-level lapse rates are supporting around
1500-2500 J/kg MLCAPE per RAP mesoanalysis estimates. A belt of
strong mid-level westerlies will remain over the Dakotas and MN, and
related effective bulk shear of 40-50 kt will continue to organize
thunderstorms. Large hail should remain the primary threat over the
next several hours, with storms likely remaining elevated with
eastward extent into MN due to more marginal instability. Current
expectations are for the overall severe threat to remain too
isolated/marginal to warrant a downstream Severe Thunderstorm Watch
into more of MN, although convective trends will continue to be
monitored.

..Gleason.. 07/03/2018

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

ATTN...WFO...DLH...MPX...FGF...ABR...

LAT...LON   44679797 44679918 44889914 45059847 45459729 46009706
            46539719 46649791 46799790 47419716 47509444 47449368
            44979495 44659684 44679797

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 2, 7:36 PM CDT	Severe Thunderstorm Watch	SPC	Big Stone, Traverse, Wilkin	9 hr
Jul 2, 9:50 PM CDT	Mesoscale Discussion	SPC	Traverse, Wilkin	115 min
Jul 3, 1:59 AM CDT	Severe Thunderstorm Watch	SPC	Big Stone, Clay, Norman, Traverse, Wilkin	7 hr
Jul 3, 4:15 AM CDT	Mesoscale Discussion	SPC	Big Stone, Clay, Norman, Traverse, Wilkin	90 min
Jul 3, 7:01 AM CDT	Mesoscale Discussion	SPC	Becker, Cass, Clay, Clearwater, Douglas, Grant and 8 more	119 min
Jul 3, 6:16 PM CDT	Mesoscale Discussion	SPC	Big Stone, Lac qui Parle, Lincoln, Traverse, Wilkin	2 hr
Jul 3, 12:01 AM CDT	Mesoscale Discussion	SPC	Adams, Bowman, Golden Valley, Grant, Hettinger, Slope and 1 more	89 min
Jul 3, 3:25 PM CDT	Mesoscale Discussion	SPC	Lawrence	2 hr
Jul 3, 5:42 PM CDT	Severe Thunderstorm Watch	SPC	Bennett, Butte, Custer, Fall River, Haakon, Harding and 7 more	7 hr
Jul 3, 6:42 PM CDT	Severe Thunderstorm Watch	SPC	Brown, Clark, Day, Edmunds, Faulk, Hand and 8 more	4 hr

Nearby

Mesoscale Discussions in Minnesota, 2018 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.