Mesoscale Discussion 1090
NWS Storm Prediction Center Norman OK
0945 AM CDT Mon Jun 19 2017
Areas affected...Parts of the northern Mid Atlantic Coast region
into New England
Concerning...Severe potential...Watch likely
Valid 191445Z - 191715Z
Probability of Watch Issuance...95 percent
SUMMARY...Increasing thunderstorm activity is expected into and
through the 1-4 PM EDT time frame, accompanied by a risk for
potentially damaging wind gusts. At least a couple of severe
weather watches appear likely within the next hour or two.
DISCUSSION...Ahead of lingering pre-frontal convection, insolation
within a seasonably high moisture content boundary layer (surface
dew points near/above 70F) is contributing to moderately large CAPE
and weakening inhibition. This is occurring from the lee of the
Allegheny Mountains through much of the Hudson/Champlain Valleys
into the mountains of northern New England, where lower/mid
tropospheric flow is already cyclonic and modest in strength.
Although large-scale upstream troughing is only very slowly
progressing eastward, weak mid-level height falls associated with
subtle embedded perturbations may aid storm development into the
17-20Z time frame.
The initiation of thunderstorms already appears underway across the
Poconos, Catskills into and northeast of the Berkshires, and a
gradual increase in coverage/intensification seems probable into
early afternoon. Eventually, in the presence of soundings that
appear characterized by high precipitable water and 30-40 kt south
to southwesterly lower/mid tropospheric flow, heavy precipitation
loading and downward momentum transfer may contribute to increasing
potential for downbursts. Consolidating and strengthening cold
pools may also contribute to organizing convection accompanied by
strong, potentially damaging wind gusts.
...Please see www.spc.noaa.gov for graphic product...
LAT...LON 46317018 45996884 44636944 42887161 41847291 41107398
39717604 39857746 40837723 41927614 42827488 43947365
44767292 45287237 46317018