MD 0389 CONCERNING WINTER MIXED PRECIPITATION FOR PORTIONS OF NEW ENGLAND

Mesoscale Discussion 0389
NWS Storm Prediction Center Norman OK
0717 PM CDT Fri Mar 31 2017
Areas affected...Portions of New England
Concerning...Winter mixed precipitation
Valid 010017Z - 010615Z
SUMMARY...Pockets of freezing rain up to 0.05 inches per hour will
continue/expand this evening into the overnight hours across parts
of southern/central New England (especially over higher elevations).
Freezing rain may mix with sleet at times as well. Farther north,
snowfall rates up to 1 inch per hour will be possible across
southern New Hampshire and vicinity later this evening into tonight.
DISCUSSION...Recent surface analysis depicts pressure falls of
around 1-1.5 mb/hr along and offshore the New Jersey and Long Island
coasts this evening. In turn, a surface cyclone currently near the
Mid-Atlantic coast will advance northeast towards the New York Bight
as it deepens. Concurrently, enhanced 850-700-mb flow and related
warm advection/isentropic ascent will spread eastward towards
southern New England, maintaining a broad shield of precipitation
over the region.
Surface observations indicate a mixture of sleet and freezing rain
occurring at several sites across Massachusetts and northern
Connecticut presently, and forecast soundings suggest winter
precipitation is likely more prominent in locations above 500-700 ft
in elevation. As the offshore low further deepens and shifts
northeast, backing near-surface winds will allow near/sub-freezing
temperatures to expand across parts of northern Connecticut
northward into Massachusetts. Thus, pockets of freezing rain upwards
of 0.05 inches per hour should persist/expand through the overnight,
while occasionally mixing with/changing to sleet.
Farther north, KBOX dual-pol data illustrate the northeastern extent
of the melting layer extending from far southern New Hampshire
southeastward to Cape Cod. While the low-level jet/warm advection
will further amplify, diabatic cooling effects from melting
hydrometeors and adiabatic cooling from broad ascent should preclude
much movement of this transition zone tonight. In turn, north of
this boundary, snowfall rates may increase up to 1 inch per hour
late this evening.
..Picca.. 04/01/2017
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...GYX...BOX...BTV...ALY...
LAT...LON 42367138 41997204 41717313 41677344 42687332 43347308
43827183 43837109 43627079 43277075 42727074 42367138
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