Mesoscale Discussion 0134
NWS Storm Prediction Center Norman OK
1112 AM CST Tue Jan 24 2017
Areas affected...Much of Maine and vicinity
Concerning...Winter mixed precipitation
Valid 241712Z - 242315Z
SUMMARY...A mix of winter precipitation -- ranging from
sleet/freezing rain to the south and snow to the north -- will
continue shifting northward/northwestward across northern New
DISCUSSION...Latest radar loop shows widespread wintry precipitation
across central and northern Maine at this time, with scattered
patches of winter precipitation farther west and south. Meanwhile,
temperatures across southern New England -- outside of
isolated/higher terrain locales and protected valleys -- continue to
rise above freezing.
The precipitation is being supported by strong ascent driven by
intense warm advection, as a 60 kt easterly/east-southeasterly
low-level jet is observed to the north of a vertically-stacked low
now residing off the mid-Atlantic coast and shifting slowly
north-northeastward with time.
Snow continues to fall across northern and western portions of Maine
at this time, where low-level warm advection has not yet pushed
temperatures above freezing in the lower troposphere. Rates
averaging 1/2" to locally 1" per hour will persist into the
afternoon, though an eventual changeover to sleet/freezing rain is
expected from south to north as warm advection persists.
Farther south and east across Maine, temperatures remain below
freezing at the surface at this hour, away from coastal areas.
However, an above-freezing warm nose in a roughly 850 mb to 700 mb
layer (as revealed by the morning GYX RAOB and progged by point
soundings from the models) is yielding a mix of freezing rain and
sleet, with substantial accumulations occurring in some areas
(reports of 1.5" of sleet accumulation, and .25" freezing rain
accretion have been received).
The heaviest band of precipitation is now occurring across central
Maine, including Piscataquis, Penobscot, southern Aroostook, and
Washington counties. The latest MLT observation (Millinocket
Municipal Airport) has transitioned from snow to freezing rain in
the past 90 minutes or so, reflective of the expected precipitation
trend across central and northern Maine through the afternoon hours.
LAT...LON 45236693 44846736 45006813 44886918 44847023 45037090
45287085 46777006 47546914 47466830 47086760 45736768