Scientific Forecaster Discussion

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Area forecast discussion 
National Weather Service Caribou ME
120 am EDT Thursday Apr 24 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 today/...
update: precipitation continues to spread nwwrd across our eastern/northestern areas...
as this precipitation pushes into the colder air...expect some wet snow
to develop and already seeing that at kfve west/ a few inches possible later
tonight into Thursday am across the far north and northwest. Will need to monitor
accums but at this time forecast amounts of up to an inch over the NE and 1-3
over the far north and northwest appears reasonable. Current forecast appears on
track at this time west/ no changes needed.

Previous discussion... 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 /tonight 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 Thursday/...
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 /05z Thursday through Monday/...
near term: MVFR for kbhb and kbgr into Thursday afternoon when VFR
conditions are expected. From khul northward...IFR is expected through
middle morning Thursday and will then transition to MVFR by noon. Snow is
possible from kpqi to kfve later tonight into early Thursday
morning. Winds will be a significant issue for the downeast
terminals Thursday with gusts to 35 kts possible. These winds will be
from the northwest.

Short to long term: MVFR ceilings 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 ceilings and
visibilities will be Sat night through Monday showers/rainfall associated with another
low pressure system from the upper Great Lakes.

&&

Marine...
near term: the wind has picked up sooner than anticipated and is
gusting well into Small Craft Advisory levels as of 9 PM. Have thus started the Small Craft Advisory
as of this update time. 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.

&&

Hydrology...
rivers continue to run high from the recent snow melt
and rainfall. Rainfall amounts in the past 24 hours were highest
across the northeast corner of the hsa with amounts around an
inch. The rivers are expected to continue to see rises over the
next day or two...but main Stem river flooding is not expected at
this time. Add'l rainfall amounts overnight into Thursday of up
to one half of an inch are expected across the eastern half of the
hsa with lesser amounts to the west.

&&

Car watches/warnings/advisories...
ME...none.
Marine...Small Craft Advisory until 5 am EDT Friday for anz050>052.

&&

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