Mesoscale Discussion 0511
NWS Storm Prediction Center Norman OK
1147 AM CDT Mon Apr 21 2025
Areas affected...parts of nern OH...nwrn PA...swrn NY State
Concerning...Severe potential...Watch unlikely
Valid 211647Z - 211915Z
Probability of Watch Issuance...20 percent
SUMMARY...Strengthening low-topped thunderstorm development appears
probable by 3-5 PM EDT, including isolated to widely scattered
supercells accompanied by small to marginally severe hail and at
least some risk for a tornado. It is not clear that a severe
weather watch will be needed, but trends are being monitored.
DISCUSSION...Within the warm sector of an occluding cyclone
migrating northeastward across the upper peninsula of Michigan,
boundary-layer destabilization is ongoing within at least a narrow
corridor across eastern Ohio into the lower Great Lakes vicinity.
Closely trailing an initial band of weak mid-level warm advection
driven convection, which has contributed to saturation of initially
dry lower/mid-tropospheric profiles, boundary-layer moisture
characterized by dew points near 60f, is rapidly advecting
northeastward. This is occurring beneath the leading edge of a
mid-level dry slot, which is allowing for increasing insolation.
The NAM and Rapid Refresh suggest that this will contribute to
mixed-layer CAPE on the order of 500 J/kg, prior to the passage of
the cold front.
This is also occurring beneath a 30-50 kt south-southwesterly 850 mb
jet axis, where forecast soundings indicate enlarged low-level
hodographs may include modest clockwise curvature of the shear
vector with height by peak destabilization. As mid/upper forcing
for ascent (downstream of the base of a negatively tilted short wave
advancing toward the region) supports deepening convective
development, there appears a window of opportunity for scattered
low-topped supercell development by 19-21Z. This may be accompanied
by a risk for small to marginally severe hail, locally strong
surface gusts, and at least potential for a tornado or two.
..Kerr/Hart.. 04/21/2025
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...BUF...CTP...PBZ...CLE...
LAT...LON 42887905 42497783 41857867 40827995 40408114 40938153
41898069 42887905
MOST PROBABLE PEAK TORNADO INTENSITY...85-115 MPH
MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN
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