Area Forecast Discussion
Issued by NWS Portland, ME

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FXUS61 KGYX 282249
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
649 PM EDT Wed Jun 28 2017

.SYNOPSIS...
A warm front will approach on Thursday and bring increasing
chances of rain during the afternoon and especially the
nighttime hours. Another low pressure system may affect the
region on Saturday and possibly Sunday with more showers and
thunderstorms.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
640 pm...Widely scattered showers and t-storms moving along what
looks like weak sfc boundary extending from Coos county SE to
Penobscot Bay. This will likely be the focus for any addl
showers into early evening, as daytime heating fades. But even
these should diminish mid-late evening. Otherwise skies stay
clear through midnight or so, Did tweak mins upward a bit as
clouds roll in from the west late, so low fall into the 50s.


At 18z...several weak surface troughs were located across
northern New England. These troughs combined with weak upper
support and daytime heating were producing showers and scattered
thunderstorms across the region. This activity will dissipate
this evening with loss of heating and as upper trough slides
offshore. For the balance of the night...skies will average
partly cloudy as we see some warm air advection clouds move into
the region from the west. Along the international border area
there may even be a few showers towards morning. Lows tonight
will range from the upper 40s to mid 50s.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
On Thursday...a warm front will lift north and east into the
region. We`ll see thicker clouds along with an increasing chance
of showers and a few thunderstorms as we head through the day.
The heaviest and most persistent precipitation should be found
over the northern half of New Hampshire eastward into Maine.
Highs tomorrow will be mainly in the 70s. Showers and thunderstorm
activity will taper from south to north as the warm front lifts
northward across the area. Lows will range from the upper 50s
to mid 60s.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
The first in a series of two surface low pressure systems will
pass to our north, crossing over the Saint Lawrence River Valley
on Friday. Ahead of this system, a warm front will enter and
gradually cross New Hampshire and then Maine. A very warm and
tropical airmass will accompany this system. Warm air advection
will lead to H8 temperatures near +15C over southern areas,
leading to heat index values between 90 and 95 degrees over
extreme southwestern Maine and southern New Hampshire. Have
highlighted this heat in the HWO and DSS slide.

Surface dew points will climb through the 60s as precipitable
water values climb to nearly 2 inches. Showers will be likely
during the day with scattered thunderstorms. A few of these
showers and storms will be strong as CAPE values increase to
over 1000 J/Kg and boundaries will be in place during the day.
Locally heavy rains are possible as well.

The precipitation retreats northward to the mountains Friday
night near the proximity of the warm front. It will be a warm,
muggy night with patchy fog.

On Saturday, temperatures climb to between 75 and 85 degrees,
however it will fell warmer due to the increased dew point
values. Temperatures over southern New Hampshire may reach 90
degrees during the afternoon.

More showers with scattered thunderstorms will be on tap for
Saturday as an upper level trough approaches from the west.
Again, a few of these storms could be strong with gusty winds
and areas of very heavy rain.

A trough of low pressure will cross the region on Sunday with a
few more showers and thunderstorms possible. However, this
trough will shift the winds aloft to the west, gradually
advecting in cooler and slightly drier air into the region.

An upper level trough will allow for cold air advection to
continue early next week. An upper level trough will situate
itself north of the region, triggering a few diurnally driven
showers and possibly a thunderstorm or two. However, this
precipitation will be much less widespread in nature.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
Short Term /through Thursday Night/...lcl MVFR psb through 23z
in -shra/-tsra otw VFR with some patchy valley fog with lcl IFR
conditions psb late tonight. Areas of MVFR Thu and Thu night in
shra/tsra with lcl IFR psb vcnty mid coast Maine in fog and
stratus.

Long Term...Areas of IFR with local IFR conditions possible in
overnight fog Saturday night and Sunday night as a moist,
tropical airmass remains in place over the region. There will be
scattered thunderstorms as well over the weekend, some of which
may contain heavy rainfall. Scattered showers are possible next
week, but it is a drier airmass in place and
ceilings/visibilities will be improved.

&&

.MARINE...
Short Term /through Thursday Night/...winds and seas will remain
below small craft through the day Thursday. Strengthening southerly
flow behind a warm front Thursday Night will push winds and seas
to near SCA threshold outside the bays.

Long Term...Conditions will likely remain below SCA thresholds.
However, will need to monitor for a brief period Saturday
afternoon as the gradient wind may combine with a sea breeze for
a brief period of gusty winds.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...None.

&&

$$
SYNOPSIS...Schwibs
NEAR TERM...Cempa/Schwibs
SHORT TERM...Schwibs
LONG TERM...Cannon
AVIATION...Schwibs
MARINE...Cannon/Schwibs


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