Alert archive / Indiana / Mesoscale Discussions in 2017

Mesoscale Discussion 804

May 20, 201737 counties in Indiana

The Storm Prediction Center issued this mesoscale discussion at May 20, 2017, 7:07 PM EDT for 37 counties in Indiana. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: May 20, 2017, 7:07 PM EDT (23:07 UTC)
Expired: May 20, 2017, 9:30 PM EDT
In force: 2 hr
Issued by: the Storm Prediction Center
Chance of a watch: 20%

All 37 counties

Adams County, IN, Benton County, IN, Blackford County, IN, Boone County, IN, Carroll County, IN, Cass County, IN, Clinton County, IN, Delaware County, IN, Fountain County, IN, Fulton County, IN, Grant County, IN, Hamilton County, IN, Hancock County, IN, Hendricks County, IN, Henry County, IN, Howard County, IN, Huntington County, IN, Jasper County, IN, Jay County, IN, Madison County, IN, Marion County, IN, Miami County, IN, Montgomery County, IN, Newton County, IN, Parke County, IN, Pulaski County, IN, Putnam County, IN, Randolph County, IN, Shelby County, IN, Starke County, IN, Tippecanoe County, IN, Tipton County, IN, Vermillion County, IN, Wabash County, IN, Warren County, IN, Wells County, IN, White County, IN

The radar

The Indianapolis radar (KIND), 67 km from the middle of the area, began a volume at 23:09 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

Lincoln, IL (KILX), launched 12:00Z, 11.1 hours before the alert went out and 198 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: 734 m above ground
0-6 km bulk shear: 42 kt
0-1 km storm-relative helicity: 347 m²/s²
0-3 km storm-relative helicity: 347 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.3

Open this sounding in Storm Lab

The text

As transmitted.

112 
ACUS11 KWNS 202307
SWOMCD
SPC MCD 202307 
INZ000-ILZ000-210130-

Mesoscale Discussion 0804
NWS Storm Prediction Center Norman OK
0607 PM CDT Sat May 20 2017

Areas affected...North-central Indiana

Concerning...Severe potential...Watch unlikely 

Valid 202307Z - 210130Z

Probability of Watch Issuance...20 percent

SUMMARY...An isolated severe threat will be possible early this
evening across parts of north-central Indiana. Strong wind gusts,
hail and perhaps a brief tornado will be possible. Due to the
isolated nature of the threat, weather watch issuance is not
expected.

DISCUSSION...The latest surface analysis shows a frontal boundary
extending from northern Illinois southeastward into central Indiana.
A moist and unstable airmass is located to the south of the boundary
where surface dewpoints are generally in the upper 60s to lower 70s
F. This is contributing to a pocket of moderate instability with
MLCAPE estimated to be between 500 and 1500 J/kg. In addition, the
Indianapolis WSR-88D VWP shows 0-6 km shear around 45 kt with some
gradual veering of the winds with height in the lowest 2 Km AGL.
This should be enough for storm rotation and hail with the stronger
cells. As thunderstorms move northeastward across the warm front, a
brief tornado will be possible. Strong wind gusts will also be
possible. The severe threat is expected to be short-lived due to the
relatively stable airmass located to the north of the front.

..Broyles/Hart.. 05/20/2017

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

ATTN...WFO...ILN...IWX...IND...LOT...ILX...

LAT...LON   39968492 39528574 39488690 39698741 40158770 40968767
            41378688 41158577 40878483 39968492

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 20, 12:13 PM EDT	Mesoscale Discussion	SPC	Bartholomew, Brown, Clark, Crawford, Dearborn, Decatur and 22 more	92 min
May 20, 4:23 PM EDT	Severe Thunderstorm Watch	SPC	Clark, Crawford, Floyd, Harrison, Jefferson, Orange and 3 more	7 hr
May 20, 6:42 PM EDT	Mesoscale Discussion	SPC	Bartholomew, Brown, Clark, Crawford, Dearborn, Decatur and 22 more	2 hr

Nearby

Mesoscale Discussions in Indiana, 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.