ZCZC SPCSWOMCD ALL
ACUS11 KWNS 281706 
SPC MCD 281706 
NYZ000-PAZ000-OHZ000-281900-

Mesoscale Discussion 0450
NWS Storm Prediction Center Norman OK
1206 PM CDT Wed Apr 28 2021

Areas affected...Portion of northwest Pennsylvania...southwest New
York...northeast Ohio

Concerning...Severe potential...Watch possible 

Valid 281706Z - 281900Z

Probability of Watch Issuance...40 percent

SUMMARY...The severe threat is gradually increasing across eastern
portions of the Lower Great Lakes region. Damaging wind gusts and
large hail are expected to be the primary severe threats. Conditions
are currently being monitored for the possibility of a Severe
Thunderstorm Watch issuance.

DISCUSSION...Diurnal heating, and the northeastward advection of
modest low-level moisture (characterized by near 60F dewpoints per
latest METAR observations) are resulting in increased instability
across eastern portions of the Lower Great Lakes this afternoon.
Modifying RAP forecast soundings to current surface
temperature/dewpoint fields yields 500/1000 J/kg of SBCAPE/MLCAPE.
The 1630Z BUF-VWP shows modestly curved low-level hodographs, with
over 200 m2/s2 0-3 km SRH and 30+ kts of deep-layer shear present.
Current MRMS Mosaic radar data shows organized convection crossing
Lake Erie and is poised to reach Erie and Chautauqua Counties in NY
within the hour. Additional convective development is also possible
over the next few hours.

Storms that can mature and become sustained in the current
environment will likely be multicellular in nature, with one or two
of the stronger, longer lived complexes potentially supporting the
development of transient supercellular or small-scale bowing
structures. With continued surface heating, a well-mixed sfc-850 mb
layer will likely support damaging gusts with the stronger storms.
Latest Mesoanalysis also shows 7-7.5 C/km mid-level lapse rates
present, supporting the risk for large hail, especially with any
bowing segments or supercells that develop. Given the modest
low-level veering with height, a brief tornado also cannot be
completely ruled out.

Convective coverage and subsequent severe remains a bit uncertain at
this time. Trends will continue to be monitored for the need of a
Severe Thunderstorm Watch issuance.

..Squitieri/Hart.. 04/28/2021

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

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

LAT...LON   41818105 43087873 43417680 43267597 42397595 41577660
            40847775 40747893 40947996 41418098 41818105 

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