Mesoscale Discussion 1020

Issued

Jun 19, 2021, 7:07 PM EDT (23:07 UTC)

Expired

Jun 19, 2021, 8:30 PM EDT

In force

83 min

Issued by

the Storm Prediction Center

Concerning

Severe potential...watch possible

Chance of a watch

40%

Counties Carroll County, OH, Columbiana County, OH, Geauga County, OH, Jefferson County, OH, Mahoning County, OH, Portage County, OH, Stark County, OH, Summit County, OH, Trumbull County, OH, Allegheny County, PA, Armstrong County, PA, Beaver County, PA, Butler County, PA, Lawrence County, PA, Mercer County, PA, Venango County, PA, Washington County, PA, Brooke County, WV, Hancock County, WV

The Pittsburgh radar (KPBZ), 54 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.

828 
ACUS11 KWNS 192307
SWOMCD
SPC MCD 192307 
PAZ000-WVZ000-OHZ000-200030-

Mesoscale Discussion 1020
NWS Storm Prediction Center Norman OK
0607 PM CDT Sat Jun 19 2021

Areas affected...eastern Ohio and western Pennsylvania

Concerning...Severe potential...Watch possible 

Valid 192307Z - 200030Z

Probability of Watch Issuance...40 percent

SUMMARY...Ongoing thunderstorms have shown greater organization and
increasing severe potential over the last 30 minutes. A few
supercells have recently evolved and may pose a risk for strong
winds, hail, or a brief tornado into this evening. Uncertainty on
storm evolution and longevity remains high. A weather watch is
possible, but uncertain.

DISCUSSION...Along a diffuse frontal zone from eastern Ohio and
western Pennsylvania, several small storms have developed early this
evening. RADAR and satellite obs suggest these storms have become
better organized over the last 30 minutes, with a couple of
supercells noted east of Cleveland and north of Pittsburgh. Severe
potential may be increasing as convection continues through an
environment characterized by weak to moderate buoyancy (500-1000
J/kg) and sufficient (40-50 kts) deep-layer shear for supercells.
Locally backed surface winds along the front were contributing to
somewhat enlarged low-level hodographs with 0-1km SRH around 100
m2/s2. While not overly supportive of severe weather, storms may
pose a risk for damaging wind gusts, hail, or a brief tornado across
far eastern OH and western PA this evening. 

Farther to the east, the airmass remains much less favorable for
severe weather owing to persistent cloud cover and cooler
temperatures. Any severe threat that does evolve will likely be
confined spatial and temporally. Convective trends will be monitored
for a possible weather watch, though high uncertainty in storm
evolution remains.

..Lyons/Guyer.. 06/19/2021

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

ATTN...WFO...PBZ...CLE...

LAT...LON   41378165 41678083 41598025 41427977 40977941 40577939
            40197977 40098027 40228069 40568110 40728138 41068184
            41378165

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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.