Area Forecast Discussion
Issued by NWS Caribou, ME

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FXUS61 KCAR 192001

Area Forecast Discussion
National Weather Service Caribou ME
301 PM EST Mon Feb 19 2018

High pressure will remain to our southeast tonight. A frontal
boundary will form across the region late tonight into Tuesday
as warm high pressure remains to our southeast and cold high
pressure builds to our north.

Tonight will be mild as high pressure remains to our southeast
and moisture wrapping over the ridge pushes into the area. Some
light rain may push across central and downeast areas this
evening and some light sleet, snow and freezing rain could push
into the north late tonight. Overnight into Tuesday a frontal
boundary will become increasingly well defined across our
region. Cold high pressure over Quebec will push cooler air in
across far northern areas while the high out in the Atlantic
continues to push warm air north across the southern part of our
region. Moisture continuing to push east along this front will
bring spotty light rain to Downeast and central areas while some
freezing rain and sleet will be likely over the far north as
the subfreezing air seeps into the low levels from Canada. A
winter weather advisory will be issued for northern Aroostook
county for the freezing rain late tonight into Tuesday night.

On Tuesday night, the cold front will sag southward towards the
coast with a shallow wedge of cold air due to a large 1040mb
high anchored in Quebec. The cold air damming won`t have a lot
of time to get established. Strong warm air advection associated
with an anomalously powerful 596 decameter H500 high off the
Carolina coast will push the front back northward later in the
night. Throughout the entire night, warming at H850 to H700
occurs and creates a progressively steeper frontal inversion. In
terms of precipitation, the frontal boundary will cause rain for
most of the area. The only areas that will dip below freezing
will be in Aroostook County and it won`t be much below freezing.
Furthermore, wet bulbs will also be near freezing. Thus, it`s a
marginal set-up for freezing rain, with worse case accretions
around a tenth of an inch. A Winter Weather Advisory will be
issued for northern Aroostook where confidence is highest in the
cold surface temps. Zone 5, southeastern Aroostook, will need
another look as the event gets closer. Fog will be an issue
Tuesday night for most of the area.  On Wednesday, a LLJ and
strong southwest winds are expected to make quick work of the
frontal inversion for Bangor and the coastal zones...propelling
highs into 60s. High temperature records stand a good chance of
being broken at Bangor, not only for the date, but the entire
month. Further north, the clouds and inversion will hang on
until the cold front draws closer, but highs around 50F at
Caribou will be near record territory. Furthermore, dew points
will reach the 50s and promote rapid snowmelt for the entire
area. The cold front crosses later Wednesday afternoon into
early evening with isolated to scattered showers. On Wednesday
night, cold air will filter into the area with a fairly rapid
freeze in northern zones that could produce some slick roadways.
Further south, temperatures will remain above freezing until
later in the night. On Thursday, high pressure builds with
temperatures still above normal, but substantially cooler than
Wednesday. Went on the higher side of guidance due to the
expected sunshine and increased insolation of late Feb. Rivers
will require watch into Thursday night at least. See the hydro
section for detail.

On Thursday night, a 1040mb high pressure crests over the area.
Lows were adjusted downward due to good potential for strong
radiational cooling. On Friday, clouds increase with a weak
overrunning event that will produce light snow Friday night.
This will be a fast-moving system in the southern stream with a
relatively flat upper level shortwave. Sub-advisory snowfall is
expected with precipitation ending as rain in southern zones.
Temperatures will be warmer behind this system on Saturday with
highs in the upper 30s to lower 40s. Somewhat cooler air arrives
Saturday night into Sunday and sets the stage for snow Sunday
night into Monday. This system remains a wild card with a wide
variety of configurations shown in guidance and questions as to
whether northern and southern streams phase. Nonetheless, it
looks like a viable threat to produce advisory or warning snow. With
respect to the coast, higher astronomical tides will be
returning and strong east or southeast winds could cause some

NEAR TERM: Ceilings will drop to IFR tonight in lowering clouds,
and remain IFR through Tuesday in low clouds, some spotty rain
and fog Downeast, and light mixed precipitation over the far

SHORT TERM: The prognosis is for VLIFR on Tuesday night with
freezing rain for HUL north to FVE. The VLIFR lifts to IFR and
MVFR by Wednesday afternoon. VFR returns Wednesday evening and
continues until later Friday when IFR in snow arrives. Snow ends
by Saturday way to MVFR cigs from HUL northward
and VFR further south.

NEAR TERM: A SCA will be up for south southwesterly winds
tonight. Winds should diminish below SCA late tonight as the
strongest gradient shifts south with the frontal boundary
forming across our area.

SHORT TERM: Fog is expected Tuesday night into Wednesday. An SCA
for the outer waters seems likely later Wednesday into Thursday.
Another SCA for the outer waters is possible Friday night. An
SCA or Gale Warning may be needed later Sunday into Sunday

In the Bangor area, a prolonged period of above freezing
temperatures capped by the potentially highest temp ever
recorded in Feb on Wednesday heightens hydro concerns. Fog on
Tuesday night and dew points exceeding 50F on Wednesday will
accelerate snowmelt. While precipitation amounts will be light,
snowmelt could cause rivers to rise just enough for ice break
up...and the potential for subsequent jamming. The areas for
concern are the Piscataquis Basin, lower Penobscot Basin,
Kenduskeag in well as other small streams in
Hancock, Washington, southern Penobscot and southern Piscatquis

The relatively short duration of the record the 50s and 60s...and lack of significant rainfall
does alleviate hydro concerns somewhat at this time and no Flood
Watch will be issued right now. Nonetheless, the situation will
require close watch. GEFS, NAEFS, and SREF hydrographs do not
show the potential for significant river rises to flood stage,
but they do show enough of a rise...2-3.5 promote ice
break-up worries.

Record high temperatures are possible Wednesday, 2/21. The
record highs are as follows, with forecast highs in parenthesis:

Bangor: 60F, 1937 (63F)
Millinocket: 62F, 1994 (57F)
Houlton: 50F, 1953 (53F)
Caribou: 50F, 1994 (49F)

The all-time record for the month of February in Bangor is 60F.

ME...Winter Weather Advisory from 9 AM Tuesday to 4 AM EST
     Wednesday for MEZ001-002.
     Winter Weather Advisory from 9 PM this evening to 1 PM EST
     Tuesday for MEZ003-004-010.
MARINE...Small Craft Advisory until 5 AM EST Tuesday for ANZ050>052.



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