Area Forecast Discussion
Issued by NWS Portland, ME

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FXUS61 KGYX 220139

Area Forecast Discussion
National Weather Service Gray ME
939 PM EDT Sat Oct 21 2017

High pressure will gradually shift off to the east tonight and
and Monday. A slow moving cold front will approach from the
west Monday night and Tuesday and will stall over the region
Tuesday night. Several waves of low pressure will ride north
along this boundary through Thursday as the front pushes east.
High pressure will build in from the southwest on Friday.


940 pm Update: No changes needed to forecast. High clouds
continue to spill across the region. Input latest mesonet data.

7 pm Update: High level moisture spilling through the large
upper ridge axis. Have made adjustments to sky grid forecast for
a partly cloudy night due to the high clouds. Input latest obs
data with no discernable changes to temps at this time.

Previous Discussion:
High pressure center will remain off shore tonight...but plenty
of surface ridging in place for radiational cooling. Started
with low temps from this morning and blended in MOS guidance and
bias corrected MOS guidance. This raised temps a few degrees
from this morning...which makes sense given dew points are
higher this afternoon and suggest mainly upper 30s at the
coolest spots. Those increased dew points may also help valley
fog form...especially across Wrn zones.


With high center off shore flow will be more Ely Sun...keeping
temps a little cooler especially on the Wrn ME coast and
Seacoast NH. Mixed down H9 temps and then blended in the MET
guidance to show the cooler onshore temps.

Sun night increasing dew points and deeper return flow will keep
temps more mild than previous nights. This may also allow for
some more widespread radiation fog.


High pressure will continue to slide off to the east on Monday.
After a sunny start to the day increasing onshore flow will
bring scattered to broken ocean stratus into southern New
Hampshire and Maine in the afternoon. Temperatures on Monday
will again top out well above normal ranging from the mid 60s in
the north and mid coast to the lower 70s in southern New
Hampshire and southwest Maine.

Slow moving cold front approaching from the west will increase
onshore flow Monday night spreading ocean stratus into most of
the forecast area. Showers ahead of this boundary may edge into
the Connecticut Valley by daybreak but expect most of the area
to see a dry night. Clouds will keep temps from falling off much
with lows overnight ranging through the 50s.

Cold front will gradually stall over the Hudson Valley on
Tuesday with showers ahead of the front shifting east into New
Hampshire and western Maine over the course of the day. Will
see another warm day with highs ranging through the 60s.

Frontal boundary will continue its slow eastward progress
Tuesday night and Wednesday as several waves of low pressure
ride north along it. Tropical connection will provide plenty
moisture in advance of this system so several inches of much
needed rain will fall across the region. Jackpot for rainfall
still appears focused in eastern Maine but 2 to 3 inches across
New Hampshire and western Maine looking more likely with both
the ECMWF and GFS both showing these amounts if not slightly
more. Lows Tuesday night will be almost summer-like with
readings only dropping into the upper 50s to lower 60s. Highs
on Wednesday will range through the 60s.

Focus of heavy rainfall will shift east Wednesday night as the
front pushes into western Maine. Looking for rain in the
evening to taper to showers with areas of drizzle. Lows
overnight will range through the 40s to near 50 in coast and
midcoast areas.

Deep upper trough will swing in from the west on Thursday
keeping conditions unsettled through the day. Looking for
mostly cloudy skies with scattered showers and much cooler
temps. Expect highs ranging through the 50s.

Upper trough will lift out to the northeast Thursday night as
shallow ridging builds in from the west. Expect evening
showers to give way to partial clearing after midnight. Fair
weather will return on Friday as high pressure builds south
of New England.


Short Term...Widespread VFR conditions will continue thru Sun.
Higher dew points and high pressure tonight will likely help
valley fog form in the CT River Valley. LIFR after 06z for LEB
and HIE...lifting at HIE first and LEB around 13z. Onshore flow
Sun night may allow more widespread IFR fog to develop...though
confidence is low at this time.

Long Term...VFR Monday with areas of MVFR ceilings developing in
the south during the afternoon. IFR/LIFR ceilings Monday night
through Wednesday. MVFR ceilings Thursday.


Short Term...Wind and seas will remain below SCA thresholds with
high pressure in place thru Sun night.

Long Term...SCA`s may be needed Monday night. Gales possible on




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