Scientific Forecaster Discussion

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Area forecast discussion 
National Weather Service Caribou ME
347 PM EDT Wednesday Apr 23 2014

Synopsis...
low pressure will slowly move southeast away from the region into
the open Atlantic overnight through Thursday. High pressure will
build east later Thursday night into Friday night...then move east
on Saturday. Another low from the Great Lakes will approach
Saturday night.
&&

Near term /through Thursday/...
a cold upper low that crossed eastern Massachusetts this morning
with thunderstorms will move into the Gulf of Maine this evening.
The upper low is expected to be just far enough south such that
only coastal Hancock and Washington counties are vulnerable to any
thunderstorms this evening. Surface low pressure will deepen ahead
of the upper trough overnight. The low will deepen well to the
south of Nova Scotia which will reduce precipitation in the
forecast area. However...the upper trough will develop a negative
tilt overnight and send Atlantic moisture streaming northward
along an inverted surface trough into New Brunswick and along the
eastern Maine border later tonight into Thursday. Precipitation
totals through the period should be limited to a maximum of just
over a half inch along the eastern Maine border. While
precipitation moves northward along the eastern Maine border
overnight...colder air arrives from the northwest. The result will
be snow in northwestern Maine later in the night with one to three
inches of snow...mostly for elevations above 1000 feet where the
warm boundary layer will not be as big a factor. Any snow will
change back to rain Thursday morning. Overnight lows will be in
the low 30s north and middle to upper 30s elsewhere.

During Thursday...Bangor will be on the western fringe of
precipitation but will be cloudy with strong northwesterly wind
gusts over 35 miles per hour. Further east...the trade-off will be less
wind...but steadier rain through the day. It will be a chilly day
with highs in the low 40s for most of the area. The exception will
be the Bangor area where upper 40s are forecast.
&&

Short term /Thursday night through Saturday/...
the last of the low level moisture with the slowly departing surface/upper
low S of Nova Scotia will gradually move east of the region Thursday night.
Scattered rn and snow showers Thursday evening should then dissipate by Friday morning.
Despite this...with not much in the way of strong low level subsidence...
broken-overcast SC conditions will likely hold well into the day
Friday...especially across the NE and far northwest portions of the forecast area...before
giving way to partial clearing Friday evening. Otherwise southern and western portions of
the forecast area should experience more in the way of sunshine especially by the
afternoon hours.

After a brief clearing overnight Friday for all of the forecast area...clouds ahead of
another advcg surface low and shortwave aloft from the Great Lakes will move
ewrd into the forecast area late Friday night into Erly say morning. Clouds will continue
to thicken through the day Sat...with increasing rn shower/steady rainfall
probability of precipitation to the region Sat afternoon.

Low temperatures Thursday night and to a lesser xtnt...Friday night will be held up
by wind...and or cloud cover. Otherwise...cloud cover and low level cool advcn
will hold hi temperatures a few degree below normal on Friday...while increasing
clouds and the potential of afternoon rn will also keep hi temperatures few degree
below normal on Sat.
&&

Long term /Saturday night through Wednesday/...
a pattern of fast moving lows that move from the Western Plains
through the mid-west...into the Gulf of Maine. Will keep the
northeast in an unsettled weather pattern through much of the
period. Brief periods of drying as a weak high pressure ridge
builds south out of Canada between lows. The GFS...ECMWF...and Gem
are in good general agreement...however there are minor difference
in timing and intensity of the lows. General pattern continues wet
and cool conditions through much of the period.

Loaded superblend through period. Used diurnal tool for hrly
temperatures through the period. Nawave 4 for seas in the coastal waters.
Added 15 percent to winds for gusts over land...25 percent for
gusts over coastal waters.
&&

Aviation /18z Wednesday through Monday/...
near term: MVFR for bhb and bgr into Thursday afternoon when VFR
conditions are expected. A low-top embedded thunderstorm is
possible for bhb this evening. From hul northward...IFR is
expected to linger through the night and transition to MVFR in the
morning. Snow is possible for car and fve later tonight into early
Thursday morning with an inch or so possible at fve. Winds will be
a significant issue for bgr and bhb Thursday with gusts to 35 kts
possible. These winds will be from the northwest.

Short to long term: MVFR clgs and occasionally visibilities expeceted for northern taf
sites with broken-overcast SC and occasional light rn/snow showers Thursday night into Friday
morning while downeast sites hold VFR. All sties then VFR Friday afternoon
through Sat. The next chance of MVFR and perhaps attms IFR clgs and
visibilities will be Sat night through Monday showers/rainfall associated with another
low pressure system from the upper Great Lakes.
&&

Marine...
near term: have maintained the Small Craft Advisory in place. Cannot rule out a few
gusts to 35 kts later Thursday as mixing will extend to a greater
height...but will not go with gale at this time.

Short term: Small Craft Advisory conditions with north to northwest wind gusts and WV heights will
continue from the near term through most of the night Thursday night...before
subsiding by Friday morning. Then winds and WV heights will remain below Small Craft Advisory
thresholds Friday through Sat.
&&

Car watches/warnings/advisories...
ME...none.
Marine...Small Craft Advisory from 2 am Thursday to 5 am EDT Friday for
anz050>052.
&&

$$
Near term...mcw
short term...vjn
long term...Norton
aviation...mcw/vjn
marine...mcw/vjn