Area Forecast Discussion
Issued by NWS Portland, ME

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FXUS61 KGYX 150732
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
332 AM EDT Tue May 15 2018

.SYNOPSIS...
A strong cold front will cross the area this afternoon preceded
by showers and a few thunderstorms. Some of the thunderstorms
over extreme southern New Hampshire into adjacent southwest
Maine could be strong to severe this afternoon with strong winds,
hail, and very heavy rain. High pressure with cooler and drier
weather follows the front tonight and Wednesday. Another cold
front will drop south across the area early Thursday with a few
clouds and widely scattered showers. High pressure and drier air
follows for the remainder of Thursday and Friday. A complex
frontal system will cross the region with showers this upcoming
weekend.

&&

.NEAR TERM /THROUGH TODAY/...
At 06z...a wavy east-west frontal boundary extended from
southern Quebec through the upper Great Lakes. Shortwave impulse
evident on GOES water vapor imagery over the western Great Lakes
will race eastward and help drive the front southward across the
forecast area by afternoon. Area of convection on NWS Doppler
radar mosaic associated with this feature across the eastern
Great Lakes will move east into the forecast area by midday.
Strengthening southwest flow will introduce higher dewpoints
into the area in advance of the front with dewpoints rising into
the lower 60s across southern New Hampshire into adjacent
southwest Maine by early afternoon. Warmest temperatures and
highest CAPE values will be realized over southern New
Hampshire with values by afternoon near 1000 j/kg. HREF model
output and forecast soundings suggest line segments and isolated
supercells with primary threat damaging winds as environmental
wind field quickly strengthens by afternoon. Activity will
quickly end from northwest to southeast by early evening as the
cold front rushes offshore.

&&

.SHORT TERM /TONIGHT AND WEDNESDAY/...
High pressure and drier air builds across the area tonight with
mainly clear skies and patchy fog developing. On
Wednesday...the high builds by to our north with easterly flow
keeping the coastal plain cool with highs limited to the 50s
even with the strong May sunshine. Warmest readings will be
found across the Connecticut Valley with temperatures
approaching 70.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
The annual Battle of Spring continues with warm, moist air
building over southern North America while there remains a fair
amount of cold, dry air over the Canadian Arctic and Hudson Bay
which has yet to be vanquished. The battle in our region will,
as usual, be most obvious in the fight between building daytime
warmth and the still-cold Gulf of Maine. A warm ridge will
build over the eastern part of the continent late this week into
the weekend, but a remnant tropical wave from the Gulf of
Mexico rotating around the Bermuda High will end up bringing
rain and an onshore wind that will rob us of our warmth for at
least one day. By early next week the ridge is replaced by a
trough dropping southeast out of Hudson Bay bringing a cool, dry
flow out of the Arctic.

A northern stream wave will track east through the Gulf of Saint
Lawrence Wednesday night, sending a cold front southward into
northern New England. The best chance of precipitation will be
further to the north in Canada, but there is a chance of some
showers crossing the border into the northern parts of Maine.
There are some timing differences between the models on when
this front will arrive, but there is agreement that this air
mass will be quite dry when it arrives on Thursday, with high
pressure sliding toward the area into Friday morning possibly
bringing another freeze to the northeastern part of the forecast
area. The GFS is the quickest with bringing the dry air in and
nudging the high into our region during the overnight hours, so
if it were to verify then a broader area of frost/freeze
conditions will be possible than what is indicated in the
current forecast, possibly extending into the coastal plain of
Maine. As the high slides to the east on Friday, expect
temperatures fairly cool, especially near the coast, with
moisture gradually increasing.

The remnants of a tropical disturbance currently lurking off the
Florida Gulf Coast will begin moving into New England Friday
night, spreading through New Hampshire and Maine on Saturday. It
will be very disorganized as it moves through, so it`s unclear
how much rain will fall and in what areas, but at this point
coastal areas seem likely to get the best chance of rain from
this event. With the uncertainty on organization and track of
this feature, rainfall amounts could range from a tenth of an
inch to more than an inch. An onshore flow ahead of this low
will keep a cooling influence from the Gulf of Maine dominant on
Saturday, so expect highs only in the 50s, possibly colder than
that along the Midcoast.

We might get a brief break on Sunday between the departing
tropical low and an approaching cold front. Temperatures will be
warmer as winds become westerly, but there could be some showers
or possibly a thunderstorm as the front arrives, especially if
it arrives during the daytime hours on Sunday. Cooler and drier
air will be moving in on Monday behind the front, but a
downsloping wind on the coastal plain will keep temperatures
warmer.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
Short Term /through Wednesday/...Localized IFR and LIFR
conditions early this am, especially along the ME Midcoast
region in fog, stratus, and drizzle. Otherwise VFR with areas
of MVFR and local IFR developing after 16z in shra and tsra. A
few thunderstorms may contain hail and damaging winds over the
southern third of NH into adjacent SW ME this afternoon. VFR
returns aft 23z following a cold frontal passage. Sct MVFR
tonight in valley fog otherwise VFR expected through the day
Wednesday.

Long Term...Could see some MVFR conditions north of the
mountains Wednesday night into early Thursday as a cold front
drops in from the north. Otherwise expect VFR conditions on
Thursday and Friday. Widespread IFR or lower conditions expected
on Saturday as a tropical low brings clouds and showers. With
the tropical moisture arriving and a cool breeze from the Gulf
of maine, there could be some very low clouds and fog developing
as well. This should clear out at some point on Sunday.

&&

.MARINE...
Short Term /through Wednesday/...Areas of fog over the coastal
waters, especially over eastern areas. We will see a brief
period of SCA or near SCA winds and seas outside the bays this
afternoon and early evening as a cold front drops south across
the waters. Given water temps near 50F and borderline SCA
conditions expected...have gone with An SCA for this period.
Expect winds and seas to drop quickly below SCA tonight and on
Wednesday as high pressure builds by to our northern.

Long Term...Another cold front will drop through from the
northwest on Thursday, but winds should be fairly light with it.
High pressure builds in behind it through Friday. A weak wave of
low pressure moves in from the southwest on Saturday, but again
winds should remain light.

&&

.FIRE WEATHER...
Showers and thunderstorms today as a cold front crosses the
area. Dry weather returns tonight through Friday. The next
chance for a more widespread rainfall event will this weekend.

&&


.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...Small Craft Advisory from 2 PM this afternoon to 9 PM EDT this
     evening for ANZ150-152-154.

&&

$$
NEAR TERM...Schwibs
SHORT TERM...Schwibs
LONG TERM...Kimble



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