SPC MD 391

MD 0391 CONCERNING HEAVY SNOW FOR PARTS OF EAST-CENTRAL AND NORTHEAST MA...SOUTHEAST NH...AND SOUTHWEST ME

Mesoscale Discussion 0391
NWS Storm Prediction Center Norman OK
0620 AM CDT Sat Apr 01 2017

Areas affected...Parts of east-central and northeast MA...southeast
NH...and southwest ME

Concerning...Heavy snow 

Valid 011120Z - 011615Z

SUMMARY...Moderate to heavy snowfall rates (up to around 1
inch/hour) will be possible through the morning across a portion of
eastern New England from east-central/northeast MA into southeast NH
and extreme southwest ME.  While snow will remain the main
precipitation type north of MA, ongoing rain in east-central and
northeast MA early this morning should transition to snow around
mid-morning and persist into the afternoon.

DISCUSSION...Trends in water vapor imagery early this morning remain
consistent with most of the deterministic models, showing the
shortwave trough that moved off the Mid-Atlantic Coast during the
night will remain progressive today, and take on some negative tilt
with east-northeastward movement.  The attendant surface low (per
10Z surface analysis) was located approximately 70 nm south of the
RI coast, with strongest pressure falls located over Cape Cod and
the Islands off the southeast MA coast.  These trends suggest the
low should track to the east-northeast, reaching 40N/70W around 18Z.

Given the track of this storm system, low-level flow extending into
southern New England this morning will back to easterly and maintain
an influx of Atlantic moisture.  Meanwhile, surface winds will
subsequently back to a more northerly trajectory across the
discussion area.  These factors combined with diffluent flow aloft
across southeast New England and warm air advection within the nose
of the backing low-level jet will maintain forcing for ascent.  09Z
RAP soundings indicated the vertical thermal profile in locations
across east-central and northeast MA will cool below 0 C such that
precipitation will change from rain to snow, or a mix of rain and
snow.  These soundings also suggested sufficient forcing for ascent
within a 500-570 mb dendritic growth layer by 15Z to potentially
enhance snowfall rates.  As the shortwave trough and surface low
shift east of the longitude of 70W, the heavier snowfall rates
should diminish by or after 18Z.

..Peters.. 04/01/2017

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...GYX...BOX...

LAT...LON   42377022 42257090 42227157 42527197 43147159 43427083
            43537036 43227018 42736996 42377022 

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