Area Forecast Discussion
Issued by NWS Portland, ME

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FXUS61 KGYX 250132
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
932 PM EDT Sat Sep 24 2016

.SYNOPSIS...
High pressure moving out of Canada will bring cooler temperatures
and drier air to the region through Sunday night. Many towns in
the area may see their first frost or freezing temperatures
tonight or Sunday night. Gradually moderating temperatures are
expected Monday before another approaching cold front brings the
threat for showers for Monday night and Tuesday. Cool weather will
return for Wednesday.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
930 PM Update...Just a few minor adjustments to temperatures based
on latest trends in observational data. The forecast remains on
track with frost and freeze headlines remaining in place.

640 PM Update...Little change to the going forecast. Have adjusted
sky cover and temperatures a little bit based on latest trends in
observational data. Otherwise, a cool and mostly clear night is
expected. Frost/Freeze headlines remain in effect across the
north.

Previously...

Only issue for tonight will be frost/freeze potential, mainly in
the northern zones. Any clouds this afternoon will diminish with
loss of daylight, and winds will slacken some on the coastal
plain, but will become light in sheltered areas. This will allow
for good radiational cooling and the development of fog or frost
in the mountain valleys. The question remains as to weather fog of
frost forms first, and indications are that fog would be favored
over frost, but some uncertainty remains. Either way there`s a
good chance that even with fog temps fall below freezing in the
far north, and so the freeze warning remains in place here as
well. Overall lows will range from around 30 in the far north to
the low 40s along the coast and in urban southern NH.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
Sunday morning will see the passage of a weak 500mb wave which
will help intensify surface low over the maritimes and tighten up
the pressure gradient making for a cool and breezy day...with
gusts of around 25 mph at times. Should see more clouds in the
first part of the day with sunnier skies in the afternoon as drier
air works in and highs in the mid to upper 50s north...the low 60s
south.

Sunday night will bring good radiational cooling conditions with
cold air aloft, and will see a better possibility of frost in all
areas but the immediate coast with lows ranging from the upper 30s
in the north to around 40 in the south.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
High amplitude ridge moves into New England from the west on
Monday with surface high pressure shifting offshore. Temperatures
warm into the 60s with increasing high clouds arriving from the
west later in the day as the next upper trough approaches. This
trough will begin spreading showers into the area along its cold
front late Monday night into Tuesday with the front and showers
pushing offshore Tuesday evening.

Models continue to diverge in how to handle the upper trough from
Wednesday onward as is typical with cut off lows. As a result,
there is a high degree of forecast uncertainty. The GFS sends the
trough eastward rather quickly, evolving it more as a sharp open
wave which crosses the area by early Friday and is replaced by
ridging through the weekend. The ECMWF however maintains a cut
off low which dives southward into the southern Appalachians
before drifting northward toward the eastern Great Lakes early
next week. Such dramatic differences lead to low forecaster
confidence this weekend. Much of the current forecast involves a
blend of the available forecast models with neither solution
particularly favored over another.

Wednesday and Thursday look dry no matter which model is
preferred as high pressure shifts toward the region. Have decided
to include a low chance for showers beginning on Friday to account
for the possibility of energy rotating around the cut off low
envisioned by the ECMWF. This chance of showers lingers into next
weekend. Daytime temperatures seem likely to be in the 60s through
the period, though it could be a little cooler if the low lingers
and brings showers. Nighttime temperatures mainly in the 40s to
low 50s, though it could be cooler if the drier GFS is correct.

&&

.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
Short Term...Mainly VFR conditions expected. Winds will gust to
25 mph on Sunday at many of the airports. Valley fog likely
tonight at KHIE/KLEB.

Long Term...Increasing cloud cover expected from west to east late
Monday, with conditions becoming MVFR or IFR in showers late
Monday night through Tuesday. A cold front will push through on
Tuesday, ending the showers but it could take a little while for
the low level moisture to clear out and conditions to go VFR
again. Morning fog is a possibility at LEB and HIE Wednesday and
Thursday morning as is typical this time of year.

&&

.MARINE...
Short Term...Winds and seas will continue near SCA criteria, but
should remain below those levels through Sunday night.

Long Term...Increasing southerly flow ahead of the cold front on
Tuesday could approach 25 KT. The prolonged fetch will allow wave
heights to build from 5 to 8 FT Tuesday night. Should see
conditions calm down again on Wednesday with high pressure moving
toward the area. There is a high degree of uncertainty in the
forecast from Thursday onward with winds generally from the NNE at
10 to 15 KT the most likely result. It is possible that low
pressure could form off the mid Atlantic coast bringing more of an
easterly component to the winds and perhaps some stronger wind
speeds and higher wave heights.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Freeze Warning from 2 AM to 8 AM EDT Sunday for MEZ007-008.
     Frost Advisory from 2 AM to 8 AM EDT Sunday for MEZ009-012-013.
NH...Freeze Warning from 2 AM to 8 AM EDT Sunday for NHZ001-002.
     Frost Advisory from 2 AM to 8 AM EDT Sunday for NHZ003-004.
MARINE...None.

&&

$$

NEAR TERM UPDATE...Ekster
SHORT TERM...Cempa
LONG TERM...Kimble


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