Area Forecast Discussion
Issued by NWS Portland, ME

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FXUS61 KGYX 172330
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
730 PM EDT Sat Jun 17 2017

.SYNOPSIS...
A warm front will slowly push east of the region tonight. A
warm and humid airmass will prevail on Sunday. A cold front will
approach from the Great Lakes Region on Monday and will stall
along the coast Monday night. On Tuesday, the cold front will
gradually dissipate. The next cold front will move in on
Wednesday and exit the region on Wednesday night. High pressure
will build in on Thursday.

&&

.NEAR TERM /TONIGHT/...
7PM UPDATE...
Have updated the forecast mainly to adjust sky cover and
precipitation chances overnight. Not seeing much forcing for
precipitation overnight, though it will be cloudy, foggy, and
possibly drizzly at times over the coastal plain to the east of
the mountains. Model forecasts show patchy areas of light
precipitation which is likely just a representation of this low
cloud layer and possible drizzle. Thus have reduced rain
chances, but kept mention of fog and drizzle. It`s quite clear
to the northwest of the mountains at the moment, and if this
continues expect fog to commence in the valleys this evening as
low level moisture is quite rich. Fog may also occur along the
coastal plain where dewpoint depressions are already only about
5 degrees, but considering the low clouds already in place there
and the limited cooling this time of year radiation fog may be
harder to accomplish here. But with some cooling and added
moisture, we certainly could see the fog again.

ORIGINAL DISCUSSION...
Plenty of low level moisture will remain in place. This will
allow fog to develop overnight, especially along and near the
coastline. Low clouds will keep temperatures fairly uniform
across the region with lows in the upper 50s to mid 60s from
north to south. There could be some cooler locations in the far
north if this area remains cloud- free through late this
evening.

There will be a low chance for a passing shower overnight as the
warm front lifts north of our area.

&&

.SHORT TERM /SUNDAY AND SUNDAY NIGHT/...
On Sunday, fog will gradually dissipate during the morning
hours. Plenty of cloud cover will remain, especially in the
south. There is a lack of a focusing mechanism for
precipitation, but there will be a low chance of a passing,
quick shower or two. Where there is any sunshine, daytime
heating will lead to increased instability, allowing for
thunderstorms as well. It will be warmer and more muggy than
today with dew points on the increase and temperatures in the
lower to mid 80s in some areas away from the coast.

By Sunday night, a cold front will slowly be approaching from
the northwest. The steadier, heavier precipitation will remain
outside our forecast area through the night, leading to the
threat of heavy, tropical rainfall in the extended portion of
the forecast.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
The combination of a large bermuda high anchored off the east coast
and a trof over the Great Lakes will allow a warm and very
moist southwest flow along the east coast to be transported
north into the region Mon into Tue. The source region will be
straight from the Gulf of Mexico so high PWATS will prevail.
During Mon the air mass will destabilize as the trof over the
Great Lakes slowly pushes east. Heavy showers and some strong
scattered thunderstorms are expected Mon through Mon night. QPF
amounts of 1.5 to 2 inches is expected in the mountains with
lesser amounts further south. Have opted to hold off on issuing
a Flash Flood Watch for the mountains and foothills until we
have a higher confidence for even higher amounts, which is
certainly possible considering the source region of the air
mass, and also some training of convection possible. Some of the
scattered thunderstorms may approach severe limits in the
afternoon and evening as per SPC suggests. Due to the high
dewpoints over the cooler waters expect fog to be an issue at
times...especially along the coast.

By late Tuesday a trof moves across the area allowing a more
westerly flow and clearing out much of the precipitation by late
in the day. Some low level moisture will remain and areas of fog
may redevelop Tue night. Wednesday through Friday could see
scattered showers as weak impulses move swiftly along the west
to southwest flow aloft. Temps will remain near seasonal levels.

&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
Short Term.../00Z TAFS/
MVFR cloud deck currently over the coastal plain from southern
New Hampshire right through central Maine will gradually lower
in height overnight as cooling occurs. Conditions are likely to
go IFR again for most of the coastal plain, while LIFR
conditions are possible near the coast and across much of Maine.
Some fog is also possible. Further to the north across the
mountains, Whitefield has been reporting HZ all day which seems
erroneous given no other observations reporting this. However,
as the sun goes down up there, nighttime cooling may lead to
valley fog through the morning, possibly as far south as
Lebanon.

Long Term...A tropical southerly flow will allow for plenty of
low level moisture that will produce areas of fog into Mon and
then numerous showers and scattered thunderstorms Mon into early Tue.
Mainly MVFR to IFR conditions can be expected across the area
Mon through early Tue. Conditions slowly improve to VFR by late
Tue into Wed except MVFR in any scattered lingering showers.

&&

.MARINE...
Short Term...Wave guidance continues to run a tad high today.
Have capped off seas no higher than four feet for the night.
Gradient continues to increase out of the south on Sunday, with
gradually building waves. Therefore, have hoisted a Small Craft
Advisory beginning Sunday morning.

Long Term...SCA`s will be needed through Monday and probably
extended into Tue due to the increasing southerly flow keeping
seas above 5 feet.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...Small Craft Advisory from 8 AM Sunday to 6 PM EDT Monday for
     ANZ150>154.

&&

$$

NEAR TERM UPDATE...Kimble
SHORT TERM...Cannon
LONG TERM...Marine
AVIATION...Kimble



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