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016
FXUS61 KGYX 182217 CCA
AFDGYX

Area Forecast Discussion...CORRECTED
National Weather Service Gray ME
617 PM EDT Thu Apr 18 2019

.SYNOPSIS...
A warm front will lift north through the region this evening.
While this front stalls in southern Canada, a moist southerly
flow will persist over New England through the weekend. Several
rounds of showers will be possible as low pressure tracks
northward to the west of New England. A cold front on Sunday
will finally bring the wet weather to an end. Another cold front
drops in from the northwest Monday night and Tuesday. High
pressure will briefly build over the region Wednesday. A weak
weather disturbance will cross the region Thursday.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
615 PM Update...Minor adjustments to temps and PoPs at this time
based on latest trends in observational data as well as latest
mesoscale model output. Drizzle is setting in across the coastal
plain and should continue overnight along with the development of
fog. Otherwise, shower activity should move in from the west
shortly, before moving off to the northeast after midnight.

Previously...

High Impact Weather Potential: Areas of fog possible overnight.

Pattern: Longwave trough is marching east across the central portion
of the continent with an impressive moisture plume lifting from the
Gulf north and east across the eastern half of the United States.
The leading edge of increasing moisture has manifested itself as a
band of showers /along an elevated warm front/ that has moved across
the region today. This is the very beginning of the transition to a
warm and unsettled period of weather.  Forecast concerns for tonight
include continued shower chances in the broad warm/moist advection
region...as well as the potential for drizzle and fog.

Through this evening: Earlier showers/sprinkles are pulling
east of the region with surface warm front still well south of
the region. As this lifts north...expect weak shower activity
over southern New England will continue to move north and
east...with southeastern areas likely to see renewed
sprinkle/shower activity through 8pm. Temperatures will not move
much through this evening...with most locations in the 40s at
8pm.

Tonight: Deep southwest flow continues through the night with
surface warm front lifting north of the region and allowing both
temperatures and dewpoints to climb. As the aformentioned shower
activity south of our region continues to lift north and east...
moist isentropic ascent will likely allow it to continue to
expand...with increasing coverage/intensity to these showers as
they reach our eastern zones. Otherwise...with impressive
moisture advection resulting in a profile with moisture
increasing with height suggests fog and drizzle development and
have included that potential in the forecast overnight. Behind
the initial batch of showers along the warm front...could see a
few other isolated showers...but no significant precipitation is
expected overnight. With the strong warm advection...expect
temperatures to slowly climb overnight...reaching near 50 in the
mountains...with temps climbing through the 50s to near 60 in
the south.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
High Impact Weather Potential:

* Locally heavy rain possible near the international border Friday
  night.
* Areas of fog possible again Friday night.

Pattern: Upstream longwave trough cuts off to our west and slows
as it becomes removed from the stronger westerlies over Canada.
At the surface...an area of low pressure over the Ohio Valley
12 UTC Friday morning will occlude and fill as it moves slowly
north and east to a position over western Pennsylvania by 12 UTC
Saturday. To the north of this low...connected by a slow moving
cold front...will be another surface wave north of New England.
This feature will push east with the aforementioned front
sinking towards the international border during the day Friday
and into our northern zones Friday night. This feature will be
the first focus for potentially heavier rainfall activity and
will be the focus of this forecast period. A secondary focus
will be how much warmth we achieve on Friday in the warm sector
as well as the potential for a renewed round of fog Friday
night.

Friday: With the warm sector overhead...Friday has the potential to
be rather warm as T9s warm into the lower teens south of the now
stalled frontal boundary to our north that will begin to sink back
south behind a departing wave of low pressure.  There is little in
the way of forcing for ascent through the day...with the mid levels
remaining rather dry.  Thus...will continue to focus PoPs on our far
northern zones...closest to the southward sinking cold front.  Even
here...the best chances for significant precipitation will likely
hold off until Friday night.  South of the mountains...would expect
that we/ll slowly erode the morning stratus and may in fact be able
to see a few sunny breaks.  With the aforementioned warm
temperatures aloft...expect that southern areas will make a run at
/or even above/ 70...with 75 in reach given enough sun.  Closer to
the mountains...low to middle 60s are expected given more cloud
cover.

Friday Night:  As a surface low occludes over the Ohio
Valley/eastern Great Lakes...associated triple point will push east
with cold/stationary front east of this feature draped over our
northern zones. Therefore...with forcing for ascent increasing from
both the north and west...expect shower activity to increase in
coverage and intensity overnight. PWATs increase to around
1.5"/+3-4 sigma with warm cloud depths making a run at 10kft.
This...and model sounding suggesting some potential for a bit of
elevated instability suggest some heavier showers and even an
embedded thunderstorm are possible. Still...in an area-wide
sense...QPF does not look tremendously heavy overnight...
especially over coastal areas which may not see much more than
an isolated showers and drizzle overnight. A very mild night is
in store...which will cause significant melting of remaining
snowpack over the foothills and mountains. While areas along and
north of the stalled front will be able to sneak back down into
the 40s...to the south of this 50s...and even lower 60s are
expected with dewpoints in the 50s. Sounding profiles are less
suggestive of fog...but would not be surprised to see
some...especially in areas of remaining snowpack.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
A warm front will become relatively stationary over northern
portions of the forecast area Saturday. This will allow for
warm, moist air and increasing precipitable water values to
ride quickly poleward on an increasing southerly flow. Rain will
be likely during the day with warm temperatures and snowmelt
continuing in the mountains. H8 temperatures reach +12C to +14C
fueling that warm air. This will allow for very warm surface
temperatures across portions of the interior. Dew points will
continue to be on the rise as well during this period adding to
the snowmelt. The resulting runoff will be compounded with over
an inch of rainfall over much of the region. There is the
potential for higher rainfall totals in north-central areas such
as the Presidentials in New Hampshire and the Foothills in
Maine.

Periods of rain and patchy fog will continue through Sunday as
the front becomes washed out during the period. There may be a
break in the precipitation over far western areas Sunday as best
dynamics and moisture shift towards eastern Maine.

12Z guidance in relatively good agreement bringing a focus for
precipitation back to the area Sunday night into Monday. Showers
will lift northward across our region in association with the
upper level low pressure system.

Models are then in disagreement as to whether a cold front will
cross the region late Tuesday and Tuesday night, potentially allowing
dryer air to enter the region from the north. The European
models is somewhat more pessimistic, triggering weak
cyclogenesis as additional upper level support enters the region
from the west. In fact, the Euro is marginally cold enough to
bring snow to some areas on Wednesday and Wednesday night.

&&

.AVIATION /22Z THURSDAY THROUGH TUESDAY/...
Short Term...

Summary:   A warm front will lift north of the region through
tonight with deteriorating flying conditions.  Low pressure will
pass north of the region overnight with a cold front then settling
into northern areas late Friday and Friday night.

Restrictions: Expect conditions to deteriorate this evening to
MVFR/IFR due to CIGS and potentially VSBYS throughout the
terminals. On Saturday...VSBYS will improve to VFR...but CIGS
will be slow to respond and may remain MVFR through much of the
day. Deterioration is likely again Friday night to IFR/LIFR in
fog/drizzle and an increasing threat for rain...particularly at
LEB-HIE-AUG.

Winds: Southeasterly winds 8-15kts will continue into this evening
before slowly shifting southerly overnight around 10kts with south
or southwesterly winds 12g20kts expected on Friday...continuing
through the night Friday night.

LLWS: Tonight...southwesterly winds at 1.5-2kft increase to over
40kts with LLWS likely throughout the terminals.  It is likely that
LLWS will again occur under similar conditions Friday night.

Long Term...Sat right through early Tuesday...MVFR with areas
of IFR in shra, and fog. An isolated thunderstorm is possible.
Southerly wind gusting up to 25 kt. Conditions gradually improve
during the midweek period.

Mon...Sct MVFR psb in -shra.

&&

.MARINE...
Short Term...

Southerly winds will strengthen ahead of an approaching low pressure
system with SCA conditions all waters and a few gusts to gale force
over the outer waters tonight.  SCAs will likely continue for all
waters through the end of the short term period Friday night with
occasional gusts to around 35kts in the outer waters.

Long Term...SCAs likely over the weekend with gale force gusts
possible as a southerly gradient continues over the region.

&&

.HYDROLOGY...
High river flows already in place will set the stage for
another possible flooding scenario this weekend. Warm, moist air
will move north into the region with several rounds of rain
possible. Through the weekend it is expected that much of the
remaining snow cover in northern New Hampshire and western Maine
will melt and run off into the rivers. Although the locations
and amounts of the heavier rainfall are still quite uncertain,
there is the potential for significant flooding to occur mainly
in the headwaters. This would most likely occur on Saturday into
Sunday, with any flooding possibly lasting into early next
week. The flood watch will remain unchanged this afternoon.

Minor flooding appears likely at many locations...with moderate
flooding possible...particularly in the Connecticut...
Pemigewasset...and Saco basins.

&&

.TIDES/COASTAL FLOODING...
High astronomical tides this weekend will combine with a
prolonged onshore southerly flow to bring a threat for beach
erosion, splashover, and coastal flooding. Tides during the
overnight hours on Saturday and Sunday reach 11 feet at
Portland and a modest increase in storm surge values may bring
water levels to near or above flood stage over the weekend.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Flood Watch from Saturday morning through Sunday afternoon for
     MEZ007>009-012>014-019>022-024>028.
NH...Flood Watch from Saturday morning through Sunday afternoon for
     NHZ001>009-011.
MARINE...Small Craft Advisory until 8 PM EDT Friday for ANZ150>154.

&&

$$

NEAR TERM...Arnott/Ekster
LONG TERM...Cannon