SPC MD 1



MD 0001 CONCERNING WINTER MIXED PRECIPITATION FOR PORTIONS OF VERMONT AND NEW HAMPSHIRE…MUCH OF MAINE

MD 0001 Image

Mesoscale Discussion 0001
NWS Storm Prediction Center Norman OK
0915 PM CST Mon Dec 31 2018

Areas affected...Portions of Vermont and New Hampshire...much of
Maine

Concerning...Winter mixed precipitation 

Valid 010315Z - 010915Z

SUMMARY...A wintry mix of precipitation is expected for the next
several hours. A mix of sleet and freezing rain are most likely in
the southern portions of the region, with heavy snow (with rates up
to 1 in/hr) likely in the northern most areas. Heavy snow is also
possible in the higher elevations. Throughout tonight, a transition
to rain is expected, starting from the south, moving northward.

DISCUSSION...Widespread moderate to occasionally heavy precipitation
has been noted in advance of a well-defined cyclone (currently over
Lower Michigan) and associated upper-level trough, which is
currently promoting 925-700 mb WAA and large-scale ascent across the
northeast CONUS. 

PFC RAP soundings indicate a sub-freezing troposphere ahead of the
widespread precipitation across portions of New England, where near
freezing surface temperatures have also been observed (mainly from
central Vermont/New Hampshire, northward). As the aforementioned WAA
continues to warm the low levels of the troposphere, temperatures
aloft will climb above freezing in some spots (as also supported by
latest high-resolution model guidance), promoting a mix of rain
(perhaps some freezing rain), sleet, and snow, particularly in the
lower elevations, as already indicated by KENX and KCXX
dual-polarimetric radar data within the past hour. The higher
elevations in portions of Vermont and New Hampshire, as well as both
higher and lower elevations in central/northern Maine, will likely
see longer periods of snow, with up to 1 in/hr snowfall rates in the
lower elevations and up to 2 in/hr rates in the higher elevations. 

As the aforementioned surface low continues northeastward,
above-freezing temperatures will continue to advect northward both
at the surface and aloft, resulting in a transition to all rain.
This transition is expected to start across the southernmost
portions of the area first, and progress northeast with time, with
portions of central and northern Maine likely remaining below
freezing at the surface and throughout a deep layer, hence a snow
threat lingering in this region.

..Squitieri.. 01/01/2019

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

ATTN...WFO...CAR...GYX...BTV...

LAT...LON   43487047 43397101 44187308 44657321 44877262 45037110
            46057015 46267001 46476980 46456890 46416842 45956784
            45876777 45706780 45656788 45146807 43487047 

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