[Weather] [2019.12.28 PM] NWS Boston EM Briefing: Significant Higher Elevation Icing Threat and Wintry Mix Tonight - Tuesday

Sun Dec 29 11:04:23 UTC 2019

Good morning everyone,

Here is the latest forecast information on a complicated storm system
bringing concerns for significant higher-elevation icing and wintry mix of
precipitation types for Southern New England tonight into Tuesday.

*What Has Changed:*

*Winter Headlines (In Effect Tonight through Tuesday AM, All Areas):*

Ice Storm Warnings *for the eastern slopes of the Berkshires.* Predominantly
freezing rain of a prolonged-duration is expected here, with the *most
significant icing and impacts* expected for these locations.

*Winter Storm Warning* *for northern Worcester County into northwest
Middlesex County in MA. *Wintry mixture of freezing rain and sleet here,
though greatest impact from freezing rain. *Significant icing and impacts*
expected.

Winter Weather Advisories *for most of the remainder of Southern New
England (except southern RI, southern Plymouth & Bristol Counties in MA
into Cape Cod and the Islands)*. Mix of precip types for these areas, with
lesser though still impactful accretions of freezing rain and sleet (with
snow possible northern MA).

*Marine Headlines:*

*Gale Warnings* for southern coastal offshore waters. In effect Monday 7 AM
into early Tuesday.

*Gale Watches* for eastern coastal and offshore waters. In effect Monday
Night into Tuesday.

===============================================

*Main Weather Concerns:  *

1) *Higher Elevation Significant Icing in* *western MA (eastern slopes of
the Berkshires) and north-central MA (Worcester County hills into northwest
Middlesex County) developing tonight thru Monday night*.  Icing is expected
to begin in tonight and continue into Monday evening, with temperatures
around 30 degrees. There is now high confidence in icing accumulations of a
half-inch or greater in each area, with *local amounts up to one inch
possible in the eastern slopes of the Berkshires where freezing rain is
expected to predominate*.

2)* Lower Elevations: Lesser amounts of sleet and freezing rain develop
tonight and continue through Monday. *Accumulations of freezing rain and
sleet will affect the Monday morning commute. While freezing rain is still
expected to continue across interior MA and northern CT for the afternoon
commute, a wintry mix of sleet to rain is expected towards the MA East
Coast. Icing amounts range from a light glaze to a quarter-inch, though *may
locally be near a half-inch in spots N/W of I-84 and I-495 if freezing rain
can remain more prolonged*.

3)  A* brief period of snow* is possible at the end of the storm late
Monday night into Tuesday, especially in northern Massachusetts near the
New Hampshire border.  Up to a couple inches of snow is expected in these
areas.

4)  *Strong east to northeast winds* are expected over the coastal waters
and along the South Coast Monday night. Limited impact expected.

===============================================

*Confidence...and what could still change:*

We have high confidence that this storm system will occur and produce a
wintry mix. Confidence has also increased on the potential for significant
icing and impact in higher-elevation areas (e.g. those areas currently in
Ice Storm and Winter Storm Warnings).

Confidence on the distribution/duration of precipitation types is moderate
outside of the two Ice Storm and Winter Storm Warning areas. This may
result in further significant change in snow/sleet and ice accumulations -
especially across northeast MA, southern interior MA on into northern CT.

Supporting graphics are attached, including the current Winter headlines,
Storm Total Icing, Onset, peak wind gusts tonight into Monday afternoon
(e.g. period when icing is greatest), and peak wind gusts for Monday
evening.

Meteorologists: Andrew Loconto and Frank Nocera

If you have any questions or would like more information, don't hesitate to
contact us via this email address, on NWSChat <https://nwschat.weather.gov/>,
or at the following:

National Weather Service Boston/Norton, MA
46 Commerce Way
Norton, MA 02766
508.622.3280
Website <http://www.weather.gov/boston> | Facebook
<http://www.facebook.com/NWSBoston> | Twitter
<http://www.twitter.com/NWSBoston>
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