Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Caribou ME
1020 am EST Monday Dec 22 2014
high pressure will move east into the Maritimes this afternoon and
tonight. A large area of low pressure will approach Tuesday night
and track to our west Wednesday into Thursday.
Near term /through tonight/...
930 am update...temperatures needed adjustment upwards for this
afternoon. The mesoscale NAM is doing a fine job in capturing the
inversion still in place and showing the warming trends.
another day under the subsidence inversion is expected with cloudy
skies and gradually moderating temperatures. A weak norlun trough
just west of the Hancock County coast...but is expected to remain
west of the forecast area today. The other synoptic scale change
today will be that the high will finally move east into the
Canadian Maritimes. This means that a low level southeasterly flow
will develop tonight and advect Atlantic moisture northwestward
into the state. This moisture will cause light snow showers in the
upslope areas of southern Piscataquis County this evening and
possibly spread to far northern Penobscot later in the night. Any
accumulations in southern Piscataquis should be under a half inch.
Highs today will rise to the middle 20s north and lower 30s south.
Temperatures will only fall a few degrees tonight under the
continued cloud cover and stagnant conditions.
Short term /Tuesday through Wednesday/...
weak high pressure will slide into the Maritimes on Tuesday as
moisture well ahead of a large storm system moving into the Midwest
begins to overspread the area. Rain will spread across the region
late Tuesday into Tuesday night. Temperatures will likely be cold
enough across central and northern areas for the rain to begin as
sleet and freezing rain. Models seems to differ on how cold the
surface air will be Wednesday morning. The NAM has a weak wave of
low pressure near the coast which holds cold air across the north
and would allow freezing rain to continue over the North Well into
Wednesday morning. The GFS is much weaker with the wave near the
coast allowing warm air to lift across the area which would give
predominantly plain rain for Wednesday. With cold air remaining near
the surface in a strong low level inversion, it appears at least a
period of freezing rain is likely across the north late Tuesday
night into Wednesday morning. Precipitation should be plain rain
across the area by Wednesday afternoon as warmer air pushes north
over the area.
Long term /Wednesday night through Sunday/...
low pressure tracking to our west will bring rain and fog Wednesday
night into Thursday. Latest forecast guidance is not showing as much
wind ahead of the system as previous models with the storm tracking
to our west a little weaker, and some secondary reflections of low
pressure closer to the coast modifying the gradient a bit. However,
if the GFS is right, coastal areas may have a period of gusty winds
early Thursday morning as the occluded front approaches. Rain should
taper off to a few showers Thursday afternoon following the frontal
passage and some strong gusty winds may follow the front late
Thursday into Friday as the low consolidates to our north. Dry
weather is then expected Friday into Saturday as high pressure
builds south of the region. A cold front on Sunday may then bring a
few snow showers, mainly across the north, before ushering in a
colder air mass later Sunday.
Aviation /15z Monday through Friday/...
near term: mostly MVFR ceilings from hul northward. Ceilings will
occasionally drop just below 1000ft. Towards bgr and bhb...VFR
conditions will gradually give way to MVFR ceilings this evening
through tonight. The MVFR ceilings could arrive as early as this
morning for bgr.
IFR conditions will persist Tuesday through Wednesday night. In low
clouds, and some rain, freezing rain over the north, and fog Tuesday
into Wednesday. Conditions will likely improve to VFR downeast and
MVFR over the north late Thursday following a frontal passage. VFR
conditions are likely on Friday. Some low level wind shear is
possible Wednesday night into Thursday for a low level southerly jet
bringing strong south winds a couple thousand feet above the
near term: light winds and seas around 2 to 3 feet are expected
through the period.
a gale will likely be needed Wednesday night into Thursday for
strong winds associated with low pressure lifting to our west. Seas
will build in response to the southeasterly winds, possibly up to
12- 15 feet in response to a long fetch. Fog will likely limit
visibilities as warmer air advects across the waters.
warmer scenario expected Christmas eve(wednesday) into Christmas
day west/the potential for some heavy rainfall west/low pressure forecast to
pass by to our west. The heaviest rainfall looks to be across
eastern Maine including the Penobscot and St. Croix basins west/1-2
inches of rainfall. Across northern and western areas, rainfall of
1+ inches is possible. The combination of melting snow, heavy
rainfall and winds will lead to substantial runoff and rises on
the rivers. Any ice will likely melt/breakup and move. The ice jam
on the Aroostook River is a concern as it could break up and move
west/the above scenario expected.
concern over relatively high astronomical tide (perigean Spring
tide) high tide at Bar Harbor will occur approximately 25th/0530z
(11.76 feet mllw)... 25th/1800z (12.73 feet mllw) and 26/0624z (11.80
ft). Latest wave model continues to develop fetch... on 24th to
25... extending from coast to 600 nm to south. Latest wave model
guidance continues to suggest wave heights around 15 feet and
periods ranging from 9 to 11 seconds during these high tides.
Wave heights and long periods still sufficient for minor
overtopping issues. Also will strong onshore winds expected and
elevated astronomical tide some flooding issues still possible.