248
FXUS61 KGYX 141504
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
1104 AM EDT Wed Aug 14 2024

.SYNOPSIS...
Comfortable temperatures and valley fog this morning will give
way to increasing clouds and showers and thunderstorms this
afternoon. Especially across western Maine, a few of these
storms could be strong and contain small hail and gusty winds.
Another round of showers and storms is expected Thursday before
some improvement Friday. After Friday, more unsettled weather
is possible through this weekend and potentially even into early
next week. Hurricane Ernesto passes offshore late this weekend
and early next week, bringing an increasing swell and dangerous
rip currents by late this weekend and early next week.

&&

.NEAR TERM /UNTIL 7 PM THIS EVENING/...
1100am Update...High smoke cast brought a red sunrise this
morning. Reduction in vis is apparent on the higher summits, and
have added a bit of haze to the forecast there. So far, surface
obs have not been impacted visibility wise. No changes to
shower/storms this afternoon at this time. CAMs are jockeying
with the idea of a multicell initiation and perhaps a transition
to one or two linear segments that could bring the
gusty/stronger winds. SHIP values are also nearing 1 in a few
sampled model soundings across western ME this afternoon. Storm
behavior is expected to be pulse initially due to minimal shear
(just 12kt 0-6 shear on 12z GYX RAOB). Mid level lapse rates
look to cooperate today once lifting mechanism arrives. Storms
that take root and pulse quickly may be able to produce a few
larger hailstones before transitioning to predominantly windy
outflow, but entrainment may also counter this theory.

615am Update...Minor changes to reflect latest observational
trends.

Previous discussion...Valley fog this morning will lift shortly
after sunrise with daytime mixing. It will be another warm day
with sun early. An approaching S/WV trof will help increase
clouds and convection by this afternoon. Storms will develop
along the higher terrain and drift south with the S/WV. Forecast
soundings still show decent lapse rates aloft and ample CAPE
for stronger storms. Lack of shear will preclude a widespread
severe weather threat...but an isolated storm with small hail
and gusty winds will be possible. I have not included that
wording in the forecast grids at this time since the coverage of
severe weather threat is not anticipated to be that great.
Subsequent updates may put that wording in...mainly from the
mtns into most of western ME.

&&

.SHORT TERM /7 PM THIS EVENING THROUGH 6 PM THURSDAY/...
CLearing skies will allow for radiational cooling and valley fog
once again. Given the increased chances of rain today I do have
more widespread coverage of fog tonight. Thu will also remain
under the influence of the upper trof...giving us another
afternoon of increasing convection. Showers and storms should
focus midday to early afternoon in the mtns...and drift south
thru the afternoon and evening. Still cannot rule out a stronger
storm or two...with machine learning guidance showing a low
probability of small hail.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Overview...

A series of troughs move through the Northeast late this week
and through the weekend, bringing multiple chances for showers
and storms, as well as near average to seasonably cool
temperatures. Tropical storm Ernesto is expected to strengthen
into a Hurricane and pass offshore this weekend and early next
week, bringing an increasing swell and dangerous rip currents
starting this weekend.

Details...
A weak shortwave ridge moves through on Friday, bringing a
brighter and relatively drier day. However, with the cutoff low
and cold pool aloft still nearby, some scattered showers are
still possible Friday afternoon, especially across northern and
eastern areas.

By Saturday, the next trough begins to dig in through the Great
Lakes. This brings an increasing chance of showers late in the
day, especially across western and northern areas. These
continue to spread eastward overnight as low pressure develops
through the Great Lakes and slowly drifts eastward. A ridge
develops and remains nearly stationary across Atlantic Canada
over the weekend. This slows and nearly stalls the system in the
Great Lakes from making much eastward progress, allowing
eastern areas to stand a better chance at remaining drier. This
pattern continues through Monday, with another reinforcing
shortwave transiting the trough going into Tuesday.

While all this is going on across the Northeast, Ernesto is
expected to become a hurricane and pass offshore this weekend
and early next week, likely passing close to Bermuda this
weekend. An increasing swell from the system is expected to
begin arriving by Saturday, with waves gradually building
through Monday, and then slowly lowering from Tuesday through
midweek next week. There remains some question as to how much
the trough across the Northeast will interact with Ernesto and
affect its track. While it`s expected to remain offshore, this
interaction will determine how close Ernesto will pass by to
New England, and the angle that it will be tracking while
offshore. These factors impact how large the waves will build
to, and the strength of the rip currents. Regardless, the long
period swell begins to arrive by Saturday, likely starting as a
2ft swell with a 16 second period, and then gradually build
through Monday. To how large remains in question and dependent
on the track distance and direction, which will be the main
question to solve over the next few days. Regardless, rip
currents begin to strengthen by Saturday and remain a concern
through at least midweek next week.

&&

.AVIATION /15Z WEDNESDAY THROUGH SUNDAY/...
Short Term...SHRA/TSRA develop by mid afternoon and drift south
thru the evening hours. Local MVFR or lower conditions are
possible in any convection, and some may contain gusty winds and
small hail. After showers dissipate local LIFR conditions will
once again by possible in valley fog tonight. Another round of
local MVFR or lower conditions will be possible Thu in
SHRA/TSRA.

Long Term...Mainly VFR conditions are expected, but periods of
MVFR ceilings and showers are likely at times through early
next week, especially across interior terminals during the
afternoon and evening. Nighttime valley fog is also likely at
LEB and HIE each night.

&&

.MARINE...
Short Term...Winds and seas are expected to remain below SCA
thresholds. Later this evening showers and storms may drift over
the coastal waters with locally gusty winds possible.

Long Term...Weak pressure patterns prevail as broad high
pressure gives way to broad low pressure late this week through
the weekend. Hurricane Ernesto likely passes east of the Gulf of
Maine late this weekend and early next week, bringing an
increasing southeasterly swell starting by Saturday. The swell
may build to greater than 5ft by Sunday.

&&

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

&&

$$


NEAR TERM...Cornwell
SHORT TERM...Legro
LONG TERM...Clair