Area Forecast Discussion
Issued by NWS Caribou, ME

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000
FXUS61 KCAR 121120
AFDCAR

Area Forecast Discussion
National Weather Service Caribou ME
620 AM EST Tue Dec 12 2017

.SYNOPSIS...
Low pressure across the eastern Great Lakes will deepen today
and tonight and track across Maine tonight into Wednesday
morning and will pull away to the north of the region Wednesday
afternoon. High pressure will build to the south of the area
Friday.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
6:20 am update: Snow is spreading into southern Maine and to
the Mid Coast as of 6 am. The snow will develop over the next
few hours across much of the Central Highlands, Bangor Region,
and Downeast. The snow is still expected to reach the Saint John
Valley by around noon. Only minor tweaks to the forecast based
on the latest observations, but the start time of the
snow still looks to be on track.

Previous discussion...
Low pressure with multiple centers across the eastern Great
Lakes south to western PA early this morning will track into NY
State today and to near Portland, Maine by 00z this evening. The
low is expected to deepen tonight and track into northern Maine
by Wednesday morning, and then gradually pull away to the north
during the day. Snow will rapidly overspread the area today,
starting first in southwest Piscatquis County by 8 or 9 am, and
reaching far northeast Maine and the eastern Saint John Valley
by around noon. A strong onshore flow and ocean temperatures in
the upper 40s will allow the snow to rapidly change to rain
after an hour or two along the immediate coast with any
accumulation an inch or less. In the Greater Bangor Region,
expect a period of snow for several hours with the snow to
change to rain by late afternoon or early evening after a few
inches of snow. The warm surge works rapidly to the north during
the night, and by 09-12z the snow may mix with or change to
rain all the way north to Caribou as there is layer above
freezing between 800-900H. Temperatures at the surface will
likely be below freezing, so there could be a bit of freezing
rain; however, it is unlikely to be a major issue after several
inches of snow. Most of the significant precipitation lifts out
of far northern Maine Wednesday morning with the deformation
zone to generally set up along or just west of western
Maine/Quebec border. Colder air sweeps back into the area from
the southwest during the day. Current thoughts are that the
snowfall totals look very good across the Downeast area, but are
likely a bit high in the north and will trim them back a bit.
Also, will end the last of the warnings by 21Z Wednesday and not
have them extend into Wed night with this update. There will
also be a fairly strong jet along the coast later this afternoon
into this evening with gusts to 45 mph possible, and will issue
a wind advisory for late this afternoon into this evening for
coastal Hancock and coastal Washington Counties.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY/...
The model guidance is in good agreement through the short term
period of the forecast. An upper level low will be moving
across northern Maine at the start of the period, an associated
surface low will be centered near the mouth of the St Lawrence.
Wrap around precipitation will extend into northern Maine.
Thursday morning the upper low will regress north over central
Quebec, a weak ridge of higher pressure will build into Maine as
another low move into the north Atlantic along the NJ coast.
This low will track across the Gulf of Maine through the end of
the period bringing a chance for some snowshowers to Downeast
Maine Thursday.

Loaded a blend of the GFS/NAM/ECMWF to smooth out the minor
differences in the models. Loaded NAWAVE4 for seas in the
coastal waters. Loaded windgust by factor tool. For QPF used
GFS.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
The extended models are in good general agreement at the start
of the period. An active weather pattern will continue through
the extended period as an upper low over Northern Canada will
spin off troughs and clipper system about 12 to 18 hrs apart
through the period. At this time most appear to only support 1
to around 3 inches of snow.

Loaded a blend to smooth out the differences in the models,
however the solution leans more towards the GFS solution. Used
NAWAVE4 for seas in the coastal waters. Used windgust by factor
tool.

&&

.AVIATION /11Z TUESDAY THROUGH SATURDAY/...
NEAR TERM: Conditions will lower to LIFR at Downeast terminals by
late morning, and by early to mid afternoon at the northern
terminals. LIFR will improve to MVFR late tonight at the
Downeast terminals, and during the day Wednesday at the northern
terminals; although IFR and LIFR still possible at times in
snow showers.

SHORT TERM: MVFR conditions across northern Maine with scattered
snowshowers. VFR conditions for Southeastern Maine today. High
pressure builds into the area this afternoon bring clearing
conditions. MVFR condition will remain across northern Maine as
an upper level low over central Quebec bring wrap around
snowshowers to northern Maine. These conditions will continue
unto Friday morning when the upper low begins to move NE toward
the Maritimes and higher pressure builds across the whole state.
Condition will fall to IFR from south to north on Saturday
morning as a low and associated frontal system moves into the
state. IFR condition will remain through the end of the period.

&&

.MARINE...
NEAR TERM: A gale warning is in effect from 3 pm this afternoon until
midnight tonight.  Conditons will lower to SCA overnight, but
another period of gales is likely Wednesday.

SHORT TERM: A Gale Warning may be required through much of the
period as a low pressure system moves through the Gulf of Maine
waters.

&&

.CLIMATE...
The low yesterday at Caribou of -8F was the first
sub-zero temperature of the season. The average date of the
first sub-zero temperature at Caribou is December 12th.

&&

.CAR WATCHES/WARNINGS/ADVISORIES...
ME...Winter Storm Warning from 11 AM this morning to 1 PM EST
     Wednesday for MEZ002.
     Winter Storm Warning until 7 PM EST Wednesday for MEZ001-003-
     004-010.
     Winter Weather Advisory until 5 AM EST Wednesday for MEZ005-
     006-011-031-032.
     Winter Weather Advisory until 7 PM EST this evening for
     MEZ015>017.
     Wind Advisory from 4 PM this afternoon to 11 PM EST this
     evening for MEZ029-030.
MARINE...Gale Warning from 3 PM this afternoon to midnight EST tonight
     for ANZ050>052.

&&

$$

Near Term...CB
Short Term...Norton
Long Term...Norton
Aviation...CB/Norton
Marine...CB/Norton
Climate...CB


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