Mesoscale Discussion 1392

Issued

Jul 29, 2021, 6:34 PM EDT (22:34 UTC)

Expired

Jul 29, 2021, 8:30 PM EDT

In force

116 min

Issued by

the Storm Prediction Center

Concerning

Severe thunderstorm watch 403

The Cincinnati radar (KILN), 120 km from the middle of the area, began a volume at 22:37 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

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299 
ACUS11 KWNS 292234
SWOMCD
SPC MCD 292234 
PAZ000-WVZ000-OHZ000-KYZ000-INZ000-300030-

Mesoscale Discussion 1392
NWS Storm Prediction Center Norman OK
0534 PM CDT Thu Jul 29 2021

Areas affected...Southern Ohio into southwest Pennsylvania

Concerning...Severe Thunderstorm Watch 403...

Valid 292234Z - 300030Z

The severe weather threat for Severe Thunderstorm Watch 403
continues.

SUMMARY...The severe thunderstorm threat continues across much of
the Ohio River Valley. Damaging winds and hail remain the primary
concern, but brief tornadoes are possible across southeastern OH and
southwest PA over the next couple of hours.

DISCUSSION...Recent radar imagery from southeastern OH/southwest PA
shows several discrete storms that have taken on supercellular
characteristics. While most updrafts have been fairly transient (per
GOES IR imagery and lightning trends), they have been strong enough
to support brief, weak tornadoes. Storm motions should continue to
favor discrete to semi-discrete storms in the near term, and an
environment featuring 100-150 m2/s2 0-1 km SRH (sampled by the KPBZ
VWP) with 7-8 C/km low-level lapse rates will remain supportive of a
brief/weak tornado threat for the next couple of hours prior to
sunset. Recent CAM guidance suggest additional convective
development is possible across eastern OH into the overnight hours,
though the severe threat may be conditional on the degree of
convective overturning associated with the ongoing storms.

Further west, a convective line driven by cold-pool propagation
continues to surge southward into south-central OH. IR imagery and
lightning trends show a few stronger updrafts embedded within the
line, suggesting that a damaging wind/hail threat will persist for
the near term. A gradual weakening trend is possible over the next
2-3 hours as the line moves into an environment with weaker
deep-layer shear. However, an instability gradient is noted from
southwest OH into central KY that may allow storms to propagate
southward. Trends will be monitored for the need for a downstream
watch.

..Moore.. 07/29/2021

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

ATTN...WFO...PBZ...RLX...CLE...ILN...IND...

LAT...LON   39898445 39758300 39698242 39848195 40148158 40518142
            40828113 40768049 40447982 39897943 39467966 39268031
            39168115 38908189 38758249 38668307 38788389 39058505
            39378549 39788557 40038534 39898445

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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.