Area Forecast Discussion
Issued by NWS Portland, ME-- Highlight Changed Discussion --
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FXUS61 KGYX 081338 AAA
Area Forecast Discussion...UPDATED
National Weather Service Gray ME
838 AM EST Thu Dec 8 2016
A slow moving broad upper trough over the Great Lakes will move
through southern Canada today and Friday, spreading snow showers
into the mountains as it approaches. Ahead of this broad upper
trough, a weak cold front will cross the area later today and
then followed by an arctic cold front through the region on
Friday bringing gusty northwest winds and much colder temperatures
that will continue through the weekend. The next potential storm
system will approach late Sunday night and Monday.
.NEAR TERM /Today/...
-- Changed Discussion --Update...First cold front is approaching New England at this
hour...and I have tweaked PoP to start increasing in the mtns
quicker than previous forecast. Lake effect streamers are already
reaching the Green Mtns...and as CAA increases we should see some
of this reach the White Mtns too. Secondary cold front is back
across Lake Superior...and will arrive late this evening with much
Areas of early morning fog will dissipate by 12z. Otherwise a
general westerly flow develops today as an upper trof over the
Great Lakes approaches. This will spread orographically induced
snow showers in the mountains with some light accumulations
expected. Elsewhere in the downsloping areas just some clouds can
be expected. Used a blend of models for max temps which should
range from the 30s to lower 40s.
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.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/...
Tonight and Friday the snow showers will continue in the
mountains with additional accumulations expected in the more
favored exposed mountain areas to the northwest flow. Elsewhere
downsloping will continue with partly cloudy skies although a few
stray flurries may try to reach southern areas. The broad upper
trof moves thru the region Friday and exits to the east by later
in the day. It will drag an arctic cold front thru the area in the
afternoon so northwest winds will become gusty and temps will be
colder especially later in the afternoon.
Total snow accumulations in the mountains thru Friday will range
from 2-5 inches.
.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Cold northwest flow will be the rule Friday night and Saturday
with wind chill values in the single digits at most locations,
with those readings below zero in the mountains. Upslope snow
showers will continue in the Whites Friday night.
High pressure moves in Saturday night with very cold low
The 00z deterministic runs of the GFS and ECMWF are in better
agreement with the progression of short wave troughs and resultant
winter weather potential Sunday and Monday. Overall, the
consensus is generally for a weak short wave passage late Sunday.
With limited moisture and forcing for ascent, we aren`t expecting
much in the way of precipitation Sunday afternoon and evening -
perhaps a period of very light snow or flurries.
Another dampening short wave trough is expected to approach later
Sunday night and Monday allowing to relatively weak low pressure
to pass to the south of New England. The latest 00z runs of the
ECMWF and GFS generally concur with how things will pan out
through Monday with a period of accumulating snow, mainly across
the southern half of the CWA. However, it is worth noting that
uncertainty remains high as many GFS and ECMWF ensemble members
show considerable spread in low pressure timing and track.
Therefore, we expect continued bouncing around in upcoming
deterministic runs over the next day or two until the strength,
track, and speed of short wave troughs can be better resolved and
agreed upon. For example, the 00z deterministic GFS dries us out
Tuesday, but the ECMWF has another short wave trough approaching
with a good shot of snow...while the GFS builds ridging. The
bottom line is a low confidence forecast for the Monday- Wednesday
timeframe as far as any wintry weather impacts go.
.AVIATION /14Z THURSDAY THROUGH MONDAY/...
Short Term...Variable conditions from VFR to IFR in areas of fog thru
12z this morning. After 12z VFR conditions except MVFR conditions
in the mountains in scattered snow showers thru Fri.
Long Term...VFR conditions are expected Friday night through
Saturday night. Periods of MVFR conditions possible late Sunday
and Sunday evening in some very light snow. IFR conditions will
then be possible on Monday in Snow.
Short Term...A cold front will cross the waters this afternoon and
in its wake increasing west SCA winds can be expected that will
continue into Friday. During the day Friday the west to northwest
flow will increase further and may reach Gale force winds as an
upper trof moves thru the region, thus a Gale watch remains in
effect for during the day Friday into Friday night.
Long Term...Gale watch remains in effect for Friday night for
potential NW gales. SCA conditions then continue through Saturday
and subside for Sunday and Monday.
MARINE...Gale Watch from Friday morning through late Friday night for
Small Craft Advisory from 3 PM this afternoon to 10 AM EST
Friday for ANZ150>152-154.