Mesoscale Discussion 0709
NWS Storm Prediction Center Norman OK
1220 PM CDT Sun May 23 2021
Areas affected...Southern New York...Northern Pennsylvania...and
Southern New England
Concerning...Severe potential...Watch unlikely=20
Valid 231720Z - 231915Z
Probability of Watch Issuance...5 percent
SUMMARY...Isolated storms capable of a few damaging wind gusts
possible this afternoon, watch issuance unlikely.
DISCUSSION...Visible satellite shows early morning clearing ahead of
an east-west oriented cold front moving into portions of southern
New York and vicinity has allowed for modest destabilization and
widespread cumulus development across the region, with a few higher
dBZ returns now showing up on KBGM. Surface temperatures have
already warmed into the mid-80s F, with surface dew point
temperatures in the low 60s F. This is yielding approximately
500-1000 J/kg of SBCAPE/MUCAPE despite marginal mid- and low-level
lapse rates. Effective shear ranges from 30-40 kt across the region,
increasing with eastern extent, amid a northwesterly unidirectional
As surface heating/destabilization continues, isolated thunderstorm
development is expected to continue along the advancing cold front.
Convection will be capable of mixing moderately strong flow aloft
toward the surface, as indicated by DCAPE values of 400-800 J/kg.
Thus a few isolated damaging wind gusts are possible this afternoon.
Storm cores may be a little more organized in/near the southern New
England area, given slightly higher values of deep-layer shear, and
thus, perhaps better potential for severe wind gusts. However, given
the expectation for isolated storm coverage, watch issuance is not
anticipated at this time.
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