Alert archive / Ohio / Mesoscale Discussions in 2021

Mesoscale Discussion 1878

October 21, 20215 states

The Storm Prediction Center issued this mesoscale discussion at Oct 21, 2021, 2:39 PM EDT for 5 states. It was in force for 3 hr.

The area

The outline as issued.

The facts

Issued: Oct 21, 2021, 2:39 PM EDT (18:39 UTC)
Expired: Oct 21, 2021, 5:45 PM EDT
In force: 3 hr
Issued by: the Storm Prediction Center
Concerning: Severe potential...watch unlikely
Chance of a watch: 20%

All 68 counties

Greenup County, KY, Chautauqua County, NY, Erie County, NY, Adams County, OH, Ashland County, OH, Ashtabula County, OH, Athens County, OH, Belmont County, OH, Carroll County, OH, Columbiana County, OH, Coshocton County, OH, Cuyahoga County, OH, Fairfield County, OH, Gallia County, OH, Geauga County, OH, Guernsey County, OH, Harrison County, OH, Hocking County, OH, Holmes County, OH, Jackson County, OH, Jefferson County, OH, Knox County, OH, Lake County, OH, Lawrence County, OH, Licking County, OH, Mahoning County, OH, Medina County, OH, Meigs County, OH, Monroe County, OH, Morgan County, OH, Muskingum County, OH, Noble County, OH, Perry County, OH, Pickaway County, OH, Pike County, OH, Portage County, OH, Ross County, OH, Scioto County, OH, Stark County, OH, Summit County, OH, Trumbull County, OH, Tuscarawas County, OH, Vinton County, OH, Washington County, OH, Wayne County, OH, Allegheny County, PA, Beaver County, PA, Butler County, PA, Clarion County, PA, Crawford County, PA, Erie County, PA, Forest County, PA, Lawrence County, PA, Mercer County, PA, Venango County, PA, Warren County, PA, Washington County, PA, Brooke County, WV, Hancock County, WV, Jackson County, WV, Marshall County, WV, Mason County, WV, Ohio County, WV, Pleasants County, WV, Tyler County, WV, Wetzel County, WV, Wirt County, WV, Wood County, WV

The radar

The Pittsburgh radar (KPBZ), 72 km from the middle of the area, began a volume at 18:41 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

Pittsburgh, PA (KPIT), launched 12:00Z, 6.7 hours before the alert went out and 89 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: 1175 m above ground
0-6 km bulk shear: 48 kt
0-1 km storm-relative helicity: 105 m²/s²
0-3 km storm-relative helicity: 188 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

012 
ACUS11 KWNS 211840
SWOMCD
SPC MCD 211839 
PAZ000-NYZ000-WVZ000-OHZ000-KYZ000-212145-

Mesoscale Discussion 1878
NWS Storm Prediction Center Norman OK
0139 PM CDT Thu Oct 21 2021

Areas affected...northern Ohio...western Pennsylvania and New York

Concerning...Severe potential...Watch unlikely 

Valid 211839Z - 212145Z

Probability of Watch Issuance...20 percent

SUMMARY...Storms are likely to increase along the cold front in
Ohio, and may pose a marginal wind/small hail risk eastward into
western Pennsylvania and New York.

DISCUSSION...A potent shortwave trough continues to move rapidly
east across MI with a cold front from north-central OH into northern
KY. Substantial cloud cover currently exists over eastern OH and
western PA/NY, but limited heating earlier has warmed the boundary
layer somewhat. Still, instability is quite limited.

Evident on visible imagery is a plume of steeper low-level lapse
rates just ahead of the front from central KY into southwest/central
OH. Here, cold air aloft will continue to overspread the region,
aiding destabilization. MUCAPE on the order of 500-750 J/kg is
likely, and additional clearing may occur later today farther east.

Radar shows cells becoming more numerous along the OH portion of the
front, and this trend is expected to continue across northern OH
this afternoon. Given the cellular storm model, small hail will be
possible. Strong deep-layer shear may also support fast storm
movement with isolated strong gusts. A severe gust will be possible
with the strongest cells.

Further, a supercell is possible after 21Z and perhaps closer to
00Z, as low-level shear increases over eastern OH, western PA and
western NY, with effective values of 160-200 m2/s2. Trends in
boundary-layer destabilization will need to be monitored through
evening.

..Jewell/Bunting.. 10/21/2021

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

ATTN...WFO...BUF...CTP...PBZ...RLX...CLE...ILN...

LAT...LON   40597972 40138008 39498063 38978136 38468232 38428286
            38618368 38838384 39698307 40828248 41828190 42058172
            42278130 42408022 42747929 43087912 43217899 43197872
            43067868 42487868 41417915 40597972

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Oct 21, 3:50 PM EDT	Mesoscale Discussion	SPC	Bath, Bell, Breathitt, Carter, Clay, Clinton and 30 more	2 hr
Oct 21, 5:25 PM EDT	Mesoscale Discussion	SPC	Carroll, Columbiana, Coshocton, Geauga, Harrison, Jefferson and 5 more	2 hr
Oct 21, 7:56 PM EDT	Mesoscale Discussion	SPC	Allegheny, Armstrong, Butler, Cambria, Clarion, Clearfield and 6 more	2 hr

Nearby

Mesoscale Discussions in Ohio, 2021 Mesoscale Discussions in Pennsylvania, 2021 Mesoscale Discussions in West Virginia, 2021 Every mesoscale discussion in 2021

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.