Area Forecast Discussion
Issued by NWS Caribou, ME

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FXUS61 KCAR 121834
AFDCAR

Area Forecast Discussion
National Weather Service Caribou ME
134 PM EST Tue Dec 12 2017

.SYNOPSIS...
Low pressure will track from the Great Lakes toward southern
Maine today then lift across Maine tonight into Wednesday.
&&

.NEAR TERM /THROUGH WEDNESDAY/...
Update...
Intensifying low pressure will track from the eastern Great
Lakes toward southern Maine today. Snow will persist across
much of the region through the afternoon. However, developing
onshore winds will begin to draw warmer air inland from the Gulf
of Maine. The will allow the snow to transition to rain along
the Downeast coast during the afternoon. Across interior
Downeast areas, the snow should begin to transition to a wintry
mix later this afternoon. Have not made any changes to the
Winter Storm Warning/Winter Weather Advisory or Wind Advisory
headlines. Have updated the forecast to adjust for current
conditions.

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 /18Z TUESDAY THROUGH SUNDAY/...
NEAR TERM: IFR/LIFR conditions are expected across the region
this afternoon into tonight, with local VLIFR conditions across
central and northern areas. LIFR will improve to MVFR late
tonight at the Downeast terminals, and during the day Wednesday
at the northern terminals, although IFR and LIFR is still
possible at times in snow showers. Low level wind shear will
also be a concern Downeast early tonight.

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: Winds will increase across the waters this afternoon
along with building seas. A Gale Warning remains in effect for
the waters from 3 PM this afternoon until midnight tonight.
Conditons will lower to SCA overnight, but another period of
gales is likely Wednesday. Visibilities will be reduced in rain
this afternoon into tonight.

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.
&&

.CAR WATCHES/WARNINGS/ADVISORIES...
ME...Winter Storm Warning until 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 until 11 PM EST this evening for MEZ029-030.
MARINE...Gale Warning until midnight EST tonight for ANZ050>052.

&&

$$

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


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