Alert archive / Ohio / Mesoscale Discussions in 2021

Mesoscale Discussion 1125

June 29, 202120 counties in New York; 23 counties in Ohio; 14 counties in Pennsylvania

The Storm Prediction Center issued this mesoscale discussion at Jun 29, 2021, 2:33 PM EDT for 20 counties in New York; 23 counties in Ohio; 14 counties in Pennsylvania. It was in force for 117 min.

The area

The outline as issued.

The facts

Issued: Jun 29, 2021, 2:33 PM EDT (18:33 UTC)
Expired: Jun 29, 2021, 4:30 PM EDT
In force: 117 min
Issued by: the Storm Prediction Center
Concerning: Severe potential...watch unlikely
Chance of a watch: 5%

All 57 counties

Allegany County, NY, Cattaraugus County, NY, Cayuga County, NY, Chautauqua County, NY, Chemung County, NY, Cortland County, NY, Erie County, NY, Genesee County, NY, Livingston County, NY, Madison County, NY, Onondaga County, NY, Ontario County, NY, Schuyler County, NY, Seneca County, NY, Steuben County, NY, Tioga County, NY, Tompkins County, NY, Wayne County, NY, Wyoming County, NY, Yates County, NY, Ashland County, OH, Ashtabula County, OH, Carroll County, OH, Columbiana County, OH, Crawford County, OH, Cuyahoga County, OH, Delaware County, OH, Geauga County, OH, Holmes County, OH, Huron County, OH, Knox County, OH, Mahoning County, OH, Marion County, OH, Medina County, OH, Morrow County, OH, Portage County, OH, Richland County, OH, Stark County, OH, Summit County, OH, Trumbull County, OH, Union County, OH, Wayne County, OH, Wyandot County, OH, Butler County, PA, Cameron County, PA, Clarion County, PA, Crawford County, PA, Elk County, PA, Erie County, PA, Forest County, PA, Jefferson County, PA, Lawrence County, PA, McKean County, PA, Mercer County, PA, Potter County, PA, Venango County, PA, Warren County, PA

The radar

The Buffalo radar (KBUF), 146 km from the middle of the area, began a volume at 18:31 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 nearest sounding before it

Buffalo Intl Airport, NY (KBUF), launched 12:00Z, 6.6 hours before the alert went out and 146 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: 627 J/kg
Mixed-layer CIN: -58 J/kg
Mixed-layer LCL: 1039 m above ground
0-6 km bulk shear: 24 kt
0-1 km storm-relative helicity: 101 m²/s²
0-3 km storm-relative helicity: 122 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 1.1

Open this sounding in Storm Lab

The text

As transmitted.

790 
ACUS11 KWNS 291834
SWOMCD
SPC MCD 291833 
NYZ000-PAZ000-OHZ000-292030-

Mesoscale Discussion 1125
NWS Storm Prediction Center Norman OK
0133 PM CDT Tue Jun 29 2021

Areas affected...Northeast Ohio...Northwest Pennsylvania...and far
southwest New York

Concerning...Severe potential...Watch unlikely 

Valid 291833Z - 292030Z

Probability of Watch Issuance...5 percent

SUMMARY...Thunderstorms developing along the Lake Erie and Lake
Ontario lake breezes and across central Ohio may produce occasional
strong to damaging downburst winds. This threat will be limited in
nature, and a watch is not expected.

DISCUSSION...Thunderstorms have gradually developed along the lake
breeze on the southern shores of Lake Erie and Lake Ontario and
across central OH over the past 1-2 hours. The mean flow over the
region is aligned well with the lake breeze boundaries, making storm
propagation off the boundaries difficult and mitigating storm
coverage for the time being. This has allowed temperatures across
east/northeast OH and into northwest PA/southwest NY to warm into
the upper 80s and low 90s with nearly 20 degree dewpoint depressions
noted - indicative of a potentially well-mixed boundary layer with
steep low-level lapse rates. Recent mesoanalysis estimates and RAP
forecast soundings support this idea with around 8 C/km lapse rates
noted in the lowest 1-2 km. Although deep-layer shear over the
region is modest, 1500-2000 J/kg MLCAPE combined with these
low-level profiles may support a few downbursts with strong winds.
Storms initially confined to the boundaries and across central OH
will likely propagate to the east/southeast due to a combination of
mean flow and cold pool propagation, though confidence in the
southeastern extent of convection area is uncertain, and a watch is
not expected.

..Moore/Thompson.. 06/29/2021

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

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

LAT...LON   41348269 41458194 41578161 41848106 42197998 42527928
            42757880 43027868 43147810 43237742 43297662 43397610
            43167555 42747550 42037628 41787744 41317804 41027895
            40658077 40278241 40158352 40438369 40828353 41198301
            41348269

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jun 29, 7:17 PM EDT	Mesoscale Discussion	SPC	Albany, Columbia, Fulton, Greene, Montgomery, Rensselaer and 4 more	88 min
Jun 29, 12:54 PM EDT	Mesoscale Discussion	SPC	Defiance, Fulton, Henry, Lucas, Paulding, Putnam and 3 more	2 hr

Nearby

Mesoscale Discussions in Ohio, 2021 Mesoscale Discussions in New York, 2021 Mesoscale Discussions in Pennsylvania, 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.