Area Forecast Discussion
Issued by NWS Portland, ME

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FXUS61 KGYX 251623
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
1223 PM EDT Sun Jun 25 2017

.SYNOPSIS...
A series of upper level disturbances will cross the area today
into next week bringing chances for showers or thunderstorms,
especially in the mountains. Otherwise temperatures will be near
normal with lower humidity into mid week. Warmer and more humid
conditions move in at the end of the week, with a chance of
showers and thunderstorms by Friday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Update...
Convection continues to fire over eastern New York State as
short wave approaches the region from the west. Precipitation
should reach portions of western New Hampshire by around 18Z.
Have made minor adjustments to Pops and have raised maximum
temperatures for the rest of this afternoon.

Have issued a Beach Hazard Statement for high paddle craft risk
after coordination with WFO Caribou and the United States Coast
Guard. Otherwise, only minor changes to the forecast for today.
Cu will continue to build, initially over northern sections with
scattered showers and thunderstorms developing this afternoon.

Latest mesoscale models suggest these storms will cross northern
areas between 19Z and 23Z, with less activity further to the
south. Greatest instability remains to our west, however a few
of the storms this afternoon could contain gusty winds and small
hail for a brief period.

Prev Disc...
5 AM Update... Only minor changes to the forecast
database this morning. Quiet weather continues with temperatures
in the 50s to near 60 and low dew points. An area of stratus
remains over the northern NH and western ME mountains this
morning and should dissipate within a couple hours.


Previous discussion...
The first half of today will be nice and fair for much of the
area with drier air still working in from the WSW. Cloud cover
gradually builds this morning however as a front begins to near
the international border as an ejecting short wave swings
through the Great Lakes. Lapse rates and wind fields are better
to our west, but we could see a brief window with a few widely
scattered rotating strong storms...mainly across northern NH and
the western ME mtns. Have included small hail and gusty winds
for a few hours in these areas this afternoon. Again not
expecting most of the area to see anything outside of the
higher terrain.

Temperatures should warm into the 70s north to upper 70s to mid
80s across the interior with west winds in place.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...
Precipitation will come to an end in the evening hours with the
loss of instability and as the main short wave moves east.
Downsloping winds will allow for clearing for the coastal plain
and support additional drying and cooling into the 50s areawide
with cooler spots across the north. A frontal zone remains in
the region and expect more showers and thunderstorms Monday as
surface heating ensues. Again this will mainly be over the
mountains but we will probably see more showers in the
foothills. Westerly winds will bring temperatures up once again
but cloud cover and overall falling thicknesses will bring
readings down a few degrees compared to today.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
Upper trough over the Great Lakes shifts east across New England
on Tuesday. This will bring another round of showers and
possibly a few thunderstorms during the day Tuesday, this time a
little more widespread than prior days. Overall instability is
fairly weak given pretty dry low levels, but better forcing
arriving with the trough axis should trigger more widespread
afternoon convection. Although the trough moves to the east
Tuesday night, another one slides in behind it for Wednesday,
triggering another round of showers and possible thunderstorms
mainly in the northern half of the forecast area.

After a brief break Wednesday night, the next wave approaches
the area from the west on Thursday. This will be a better
developed pressure system with a developing warm front lifting
out ahead of a surface low tracking through the northern Great
Lakes. Models are showing some differences in the track of this
low and the preceding warm front with some increasing
uncertainty as to whether the warm front will lift north into
our area on Thursday (if at all). This would have a substantial
effect on temperature and precipitation forecasts for Thursday
and Friday. To the south of the warm front, temperatures will
warm well into the 80s. But as is typical for our area, a
preceding onshore flow to the north of the warm front sucks in
the cool maritime air and delays or prevents the northward
advance of the warmth. Because of this, we have decided to lower
high temperatures a bit along the coast of Maine on Thursday,
generally into the 60s, while still offering some 80 degree
readings to southern New Hampshire.

Surface low pressure tracks east along the warm front Thursday
night, with rain expected mainly along and to the north of the
warm front. While the low moves east on Friday, another stronger
low will be forming to the west over the Great Lakes. This will
prevent the trailing cold front from getting a good push
through our area, leaving the remnant boundary near our area.
This could provide the focus for some showers and possibly a
thunderstorm on Friday. This Great Lakes low then tracks
northeast into Canada on Saturday sending a front eastward
through New England providing another chance of showers.

&&

.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
Short Term...
Pockets of MVFR conditions are occurring this morning in
portions of the mountains where low level moisture is trapped.
Expect increasing cloud cover to arrive late with a frontal
boundary sagging into the mountains this afternoon and evening
and triggering widely scattered -TSRA. HIE and LEB have the
highest chances of being affected out of the TAF sites in NH and
ME. Heavy downpours and gusty winds are also possible with the
stronger storms. Some gusty SW winds are likely this afternoon.

Long Term...
Expect prevailing VFR conditions this week, but there will be
occasional chances for showers. The best chance of showers will
be each afternoon, primarily across the interior. An onshore
flow ahead of a warm front on Thursday could bring some IFR
ceilings to much of western Maine.

&&

.MARINE...
Short Term...Westerly winds are expected today with some
showers and thunderstorms crossing the waters. Fog may occur
tonight but winds and seas will stay below SCA criteria.

Long Term...Winds over the Gulf of Maine will be fairly light
out of the west or southwest for the next several days. A
stronger pressure gradient will develop on Thursday as a warm
front approaches, leading to southerly winds increasing to as
high as 25 KT.

&&

.TIDES/COASTAL FLOODING...
Another high astronomical tide will occur tonight around 1 AM at
Portland. The total tide will likely come in around 12 feet MLLW
with a light WSW wind in place. Very minor coastal flooding is
possible along the most vulnerable low lying side streets near
the wharfs in Portland, as well as Granite Point road in
Biddeford and the Backbay area of Hampton, New Hampshire.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Beach Hazards Statement until 8 PM EDT this evening for
     MEZ023>028.
NH...Beach Hazards Statement until 8 PM EDT this evening for NHZ014.
MARINE...None.

&&

$$
JC


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