Alert archive / Ohio / Severe Thunderstorm Watches in 2017

Severe Thunderstorm Watch 151

April 20, 201712 counties in Indiana; 13 counties in Michigan; 28 counties in Ohio

The Storm Prediction Center issued this severe thunderstorm watch at Apr 20, 2017, 2:08 PM EDT for 12 counties in Indiana; 13 counties in Michigan; 28 counties in Ohio. It was in force for 6 hr.

The area

The outline as issued.

The facts

Issued: Apr 20, 2017, 2:08 PM EDT (18:08 UTC)
Expired: Apr 20, 2017, 8:00 PM EDT
In force: 6 hr
Issued by: the Storm Prediction Center
Largest hail expected: 1.5 in
Strongest gust expected: 60 kt

All 53 counties

Adams County, IN, Allen County, IN, Blackford County, IN, DeKalb County, IN, Grant County, IN, Huntington County, IN, Jay County, IN, LaGrange County, IN, Noble County, IN, Steuben County, IN, Wells County, IN, Whitley County, IN, Branch County, MI, Calhoun County, MI, Hillsdale County, MI, Jackson County, MI, Kalamazoo County, MI, Lenawee County, MI, Livingston County, MI, Macomb County, MI, Monroe County, MI, Oakland County, MI, Saint Joseph County, MI, Washtenaw County, MI, Wayne County, MI, Allen County, OH, Ashland County, OH, Auglaize County, OH, Crawford County, OH, Defiance County, OH, Erie County, OH, Fulton County, OH, Hancock County, OH, Hardin County, OH, Henry County, OH, Huron County, OH, Logan County, OH, Lorain County, OH, Lucas County, OH, Marion County, OH, Mercer County, OH, Morrow County, OH, Ottawa County, OH, Paulding County, OH, Putnam County, OH, Richland County, OH, Sandusky County, OH, Seneca County, OH, Shelby County, OH, Van Wert County, OH, Williams County, OH, Wood County, OH, Wyandot County, OH

The radar

The Detroit radar (KDTX), 136 km from the middle of the area, began a volume at 18:08 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.

What SPC expected

The probabilities SPC published with the watch, for the watch area over its life.

Two or more tornadoes: 10%
One or more EF2 to EF5 tornadoes: 2%
Ten or more severe wind reports: 40%
One or more gusts of 65 knots or more: 10%
Ten or more severe hail reports: 30%
One or more hailstones of 2 inches or more: 10%
Six or more combined severe hail and wind reports: 70%

Warnings issued inside it

6 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.

Issued	Product	Office	Counties	Lasted
Apr 20, 2:23 PM EDT	Severe Thunderstorm Warning	DTX	Livingston	23 min
Apr 20, 2:28 PM EDT	Severe Thunderstorm Warning	IWX	Noble	34 min
Apr 20, 3:38 PM EDT	Severe Thunderstorm Warning	IWX	Defiance	21 min
Apr 20, 4:06 PM EDT	Severe Thunderstorm Warning	IWX	Branch, Cass, Saint Joseph	39 min
Apr 20, 4:54 PM EDT	Severe Thunderstorm Warning	IWX	Putnam	36 min
Apr 20, 5:27 PM EDT	Severe Thunderstorm Warning	CLE	Hancock	39 min

Discussions around it

SPC mesoscale discussions over the same counties from four hours before the watch to its end.

The nearest sounding before it

Detroit, MI (KDTX), launched 12:00Z, 6.1 hours before the alert went out and 139 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: 543 m above ground
0-6 km bulk shear: 68 kt
0-1 km storm-relative helicity: 595 m²/s²
0-3 km storm-relative helicity: 665 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 2.4

Open this sounding in Storm Lab

The text

As transmitted.

995 
WWUS20 KWNS 201805
SEL1  
SPC WW 201805
INZ000-MIZ000-OHZ000-LEZ000-210000-

URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 151
NWS Storm Prediction Center Norman OK
205 PM EDT Thu Apr 20 2017

The NWS Storm Prediction Center has issued a

* Severe Thunderstorm Watch for portions of 
  Northeast Indiana
  South central and southeast Lower Michigan
  Northwest Ohio
  Lake Erie

* Effective this Thursday afternoon and evening from 205 PM until
  800 PM EDT.

* Primary threats include...
  Scattered damaging wind gusts to 70 mph possible
  Isolated large hail events to 1.5 inches in diameter possible

SUMMARY...Clusters of strong/severe storms will continue to develop
through the afternoon from Indiana into southern Lower Michigan and
northwestern Ohio.  Occasional damaging gusts and large hail will be
the main concerns through the afternoon and into this evening.

The severe thunderstorm watch area is approximately along and 80
statute miles east and west of a line from 15 miles northwest of
Detroit MI to 50 miles south southwest of Findlay OH. For a complete
depiction of the watch see the associated watch outline update
(WOUS64 KWNS WOU1).

PRECAUTIONARY/PREPAREDNESS ACTIONS...

REMEMBER...A Severe Thunderstorm Watch means conditions are
favorable for severe thunderstorms in and close to the watch area.
Persons in these areas should be on the lookout for threatening
weather conditions and listen for later statements and possible
warnings. Severe thunderstorms can and occasionally do produce
tornadoes.

&&

AVIATION...A few severe thunderstorms with hail surface and aloft to
1.5 inches. Extreme turbulence and surface wind gusts to 60 knots. A
few cumulonimbi with maximum tops to 450. Mean storm motion vector
26030.

...Thompson

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Apr 20, 1:36 PM EDT	Mesoscale Discussion	SPC	Adams, Allen, Blackford, DeKalb, Delaware, Elkhart and 15 more	84 min
Apr 20, 4:31 PM EDT	Mesoscale Discussion	SPC	Adams, Allen, Blackford, Boone, Carroll, Cass and 37 more	119 min
Apr 20, 7:01 PM EDT	Mesoscale Discussion	SPC	Adams, Allen, Blackford, DeKalb, Jay, Steuben and 1 more	59 min
Apr 20, 2:40 PM EDT	Mesoscale Discussion	SPC	Ashtabula, Belmont, Carroll, Columbiana, Coshocton, Cuyahoga and 19 more	65 min

Nearby

Severe Thunderstorm Watches in Ohio, 2017 Severe Thunderstorm Watches in Michigan, 2017 Severe Thunderstorm Watches in Indiana, 2017 Every severe thunderstorm watch 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.