Area Forecast Discussion
Issued by NWS Portland, ME

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870
FXUS61 KGYX 270723
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
323 AM EDT Thu Jul 27 2017

.SYNOPSIS...
A cold front moves across the area today bringing scattered
showers in the morning and possible thunderstorms in the
afternoon. High pressure will nose into the region Friday and
into the weekend as a low pressure slips south of the area.
This high will remain established over the Northeast through
early next week with an extended period of pleasant weather.

&&

.NEAR TERM /THROUGH TODAY/...
A more uncertain forecast than usual in the near term this
morning...as it looks like we have a couple rounds of precip in
store. The first will continue crossing the region this morning.
A lead s/wv trof is forcing an area of mainly light showers thru
the Northeast. It is likely many locations will see rain
falling...but less likely that they will see measurable precip.
This shower activity will linger into the mid
morning...especially farther S where the front will begin to lag
as flow becomes more and more parallel to it.

This all complicates the forecast...because the second round of
potential precip is heavily dependent on daytime heating. A
secondary s/wv trof is forecast to spark scattered thunderstorms
after the morning clouds/showers move off. The more sunshine we
see...I expect the better chance for and greater coverage of
thunderstorms. At this time it looks like significant cloud
cover may linger into the afternoon...so I shied away from
likely PoP and this reflects the uncertainty.

That being said...with a decent jet streak overhead sufficient
shear will be in place for storm organization. If we can get
some pockets of sun...a stronger storm or two is possible. With
the uncertainty about that sun...SPC has pulled the remainder of
the forecast area from the marginal risk. I have also trimmed
the enhanced wording back to mainly Srn NH. If storms do
form...gusty winds and small hail are possible...mainly in the
18 to 22 or 23z window.

&&

.SHORT TERM /TONIGHT THROUGH 6 PM FRIDAY/...
Trof axis swings across the area tonight...bringing an end to
the showers and storms as it shoves the cold front off the
coast. Farther S the flow is more or less parallel to the
front...so the tail end should stall in the vicinity of Srn New
England. This may keep some clouds and possibly a stray shower
around Srn NH.

Surface ridging tries to nose into the region...but we remain in
cyclonic flow aloft into Fri. This should keep the boundary
layer fairly mixed overnight...and allow for diurnal cloud cover
increases Fri afternoon.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
A coastal low develops over DELMARVA Fri night then moves east
northeast along the southern New England coast Sat into Sat
night. Models continue in good agreement of the track and in
keeping the northern fringe of the precipitation shield just
south of the ME/NH coastline. An overcast day expected Saturday
along southern and coastal areas while further north partly to
mostly sunny skies expected. A light northeast breeze will keep
temps mostly in the 70s Sat. By Sunday the coastal low will
have exited well to the east allowing high pressure to build
over the area allowing mostly sunny skies and seasonable temps
mostly in the 75-80 degree range. A more zonal west to southwest
flow aloft develops early to mid week allowing warmer temps to
spread across the region. Generally dry conditions expected
early to midweek except for maybe a few air mass afternoon
showers or thunderstorms mainly in the mountains and foothills.

&&

.AVIATION /07Z THURSDAY THROUGH MONDAY/...
Short Term...VFR conditions are expected to prevail thru Fri. An
area of SHRA will move thru the forecast area this morning...the
heaviest of which may bring a brief period of MVFR conditions.
Ahead of the cold front this afternoon scattered TSRA are
possible. These may bring MVFR or lower conditions...but
coverage is uncertain enough to preclude mention in the TAFs at
this time. Tonight into Fri high pressure tries to nose back
into the region...and widespread VFR conditions return.

Long Term...VFR conditions through the weekend and into next
week.

&&

.MARINE...
Short Term...Winds and seas are expected to remain below SCA
thresholds. The exception may be near 25 nm where a few 5 ft
seas are possible late today in Sly flow ahead of the front.

Long Term...SCA conditions may develop over the outer waters
Saturday into Saturday evening as the coastal low passes
southeast of the area, otherwise winds and seas to remain below
SCA criteria.

&&

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

&&

$$

NEAR TERM...Legro
SHORT TERM...Legro
LONG TERM...Marine
AVIATION...Legro/Marine
MARINE...Legro/Marine



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