Alert archive / Kentucky / Mesoscale Discussions in 2017

Mesoscale Discussion 618

April 30, 201720 counties in Kentucky

The Storm Prediction Center issued this mesoscale discussion at Apr 30, 2017, 3:58 PM CDT for 20 counties in Kentucky. It was in force for 92 min.

The area

The outline as issued.

The facts

Issued: Apr 30, 2017, 3:58 PM CDT (20:58 UTC)
Expired: Apr 30, 2017, 5:30 PM CDT
In force: 92 min
Issued by: the Storm Prediction Center
Chance of a watch: 20%

Counties Adair County, KY, Barren County, KY, Boyle County, KY, Casey County, KY, Clinton County, KY, Cumberland County, KY, Edmonson County, KY, Garrard County, KY, Green County, KY, Hardin County, KY, Hart County, KY, Larue County, KY, Lincoln County, KY, Marion County, KY, Metcalfe County, KY, Nelson County, KY, Russell County, KY, Taylor County, KY, Washington County, KY, Wayne County, KY

The radar

The Louisville radar (KLVX), 95 km from the middle of the area, began a volume at 21:01 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

Nashville Metro, TN (KBNA), launched 12:00Z, 9.0 hours before the alert went out and 145 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: 329 J/kg
Mixed-layer CIN: -20 J/kg
Mixed-layer LCL: 815 m above ground
0-6 km bulk shear: 41 kt
0-1 km storm-relative helicity: 231 m²/s²
0-3 km storm-relative helicity: 284 m²/s²
Significant tornado parameter: 0.3
Supercell composite: 2.0

Open this sounding in Storm Lab

The text

As transmitted.

729 
ACUS11 KWNS 302058
SWOMCD
SPC MCD 302058 
KYZ000-302230-

Mesoscale Discussion 0618
NWS Storm Prediction Center Norman OK
0358 PM CDT Sun Apr 30 2017

Areas affected...Central KY

Concerning...Severe potential...Watch unlikely 

Valid 302058Z - 302230Z

Probability of Watch Issuance...20 percent

SUMMARY...Isolated damaging wind gusts are possible for the next
hour or so across portions of central KY.

DISCUSSION...Recent radar imagery shows a well-defined line of
thunderstorms moving across TN and AL moving generally
northeastward. Estimated speed along the northern portion this line
is around 45 to 50 kt and BNA reported a 44 kt gusts around 20Z.
This storm motion takes the northern portion of the line into
south-central KY soon. The low-level environment across the region
is a bit drier than areas farther south (i.e. dewpoints in the upper
50s and low 60s across central KY versus mid to upper 60s in TN and
AL). This is mitigating the overall instability and is expected to
result in a general downward/diminishing trend in storm strength
over the next few hours. However, the well-developed nature of the
convective line and favorable line-parallel orientation to the bulk
shear suggests sporadic damaging wind gusts are possible for the
next hour or so. Limited/marginal nature of the severe risk is
expected to preclude watch issuance but convective trends across the
region will be monitored closely.

..Mosier/Thompson.. 04/30/2017

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

ATTN...WFO...JKL...LMK...

LAT...LON   36748610 37148641 37948581 37748448 36698473 36748610

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Apr 30, 12:54 AM CDT	Mesoscale Discussion	SPC	Ballard, Carlisle, Fulton, Graves, Hickman	96 min
Apr 30, 1:10 AM CDT	Severe Thunderstorm Watch	SPC	Calloway, Carlisle, Fulton, Graves, Hickman	6 hr
Apr 30, 2:58 AM CDT	Mesoscale Discussion	SPC	Ballard, Calloway, Carlisle, Fulton, Graves, Hickman and 3 more	92 min
Apr 30, 1:21 PM CDT	Mesoscale Discussion	SPC	Simpson	54 min
Apr 30, 1:58 PM CDT	Mesoscale Discussion	SPC	Greenup	2 hr

Nearby

Mesoscale Discussions in Kentucky, 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.