|Mesoscale Discussion 1209|
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Mesoscale Discussion 1209
NWS Storm Prediction Center Norman OK
1132 AM CDT Sat Jul 01 2017
Areas affected...portions of central/eastern New York...much of
Vermont/New Hampshire...southwest Maine...western Massachusetts
Concerning...Severe potential...Watch likely
Valid 011632Z - 011830Z
Probability of Watch Issuance...80 percent
SUMMARY...An increase in thunderstorm coverage and intensity is
anticipated through early/mid afternoon. Damaging winds will be the
primary threat with a tornado or two possible. Isolated instances
of large hail can also be expected. Short-term trends are being
monitored and a watch is likely prior to 18Z.
DISCUSSION...A expansive area of rain and thunderstorms extended
from central New York northeast through the North Country region and
northern Vermont at 16Z, with most of the thunderstorms confined to
the southern periphery of the precipitation area. Along and
south/east of this precipitation area, diurnal heating through
layered clouds has allowed temperatures to warm into the 80s.
Continued heating of this very moist air mass (PW values in excess
of 1.75 inches) will contribute to weak/pockets of moderate
surface-based instability this afternoon.
Modest large-scale ascent will develop over the discussion area this
afternoon associated with a mid-level impulse moving northeast
across the lower Great Lakes/Ohio Valley. This will contribute to
an increase in thunderstorm coverage over the next few hours along
the southwest-northeast oriented zone of differential heating, and
along a surface trough/confluence zone over central New York.
Short-term guidance continues to suggest that strengthening 850-mb
flow beneath 40-50 kt mid-level flow will result in a risk for
damaging winds, isolated large hail and perhaps a tornado or two
given some low-level hodograph curvature noted on forecast
soundings. With time, a more linear storm mode should become
established with a continued risk for damaging winds.
Observational and short-term model trends will be monitored and a
watch is likely prior to 18z.
...Please see www.spc.noaa.gov for graphic product...
LAT...LON 43317476 43267481 43737416 44227320 44667226 44887124
44727094 44137078 43197145 42507225 42117300 42057386
42127437 42377490 42667501 42957500 43317476
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