Area Forecast Discussion
Issued by NWS Portland, ME

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112
FXUS61 KGYX 241052
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
652 AM EDT Mon Apr 24 2017

.SYNOPSIS...
A cold front will drop south into northern New England today
and stall. Low pressure will slowly move up the Eastern Seaboard
Tuesday and Wednesday with rain. A cold front will slowly
approach from the west Thursday into Friday, before finally
crossing the region on Saturday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Patchy fog early this morning will dissipate around sunrise in
the valleys of south-central New Hampshire.

A weak cold front will continue to slowly press southward this
morning across the northern and central portions of our forecast
area. This front remains relatively moisture starved with little
if any precipitation expected and will likely dissipate later
today over the region.

With plenty of sunshire, especially over southern areas,
temperatures will climb through the 60s. A couple locations over
southern New Hampshire will nudge 70 degrees. Along the coast,
winds will become onshore leading to temperatures falling the
through 50s during the afternoon.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
Update...
Have updated the grids to account for current conditions. Some
patchy fog continues over southwest New Hampshire with patchy
fog being reported at times in Rockland as well. This fog will
mix out quickly this morning.

Have adjusted temperatures per current observations and raised
today`s forecast max readings by a couple degrees as plenty of
sunshine will allow for some readings in the lower 70s across
southern New Hampshire today. A sea breeze will lead to lowering
temperatures along the coast this afternoon.

Prev Disc...
A coastal low pressure system will reach the North
Carolina tonight. A large area of high pressure will remain over
the northern Maine acting as a blocking pattern and keeping
precipitation from advecting up the coast and into our area.

By Tuesday, this surface high will retreat to the Canadian
Maritimes as low pressure slowly moves towards the Mid Atlantic
region. 00Z model suite is in relatively good agreement with
the positioning of this system. Model ensembles are in very good
agreement as well with the upper level low pressure system
gradually opening up and moving northeast with time.

An onshore flow will allow for rain and perhaps some drizzle to
enter the region with the gradient being created by the exiting
surface high as much as the approaching weak area of low
pressure.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
A coastal low moving slowly northeast up the east coast of the
U.S. will bring rain Tue night into early Thu. All models agree
on the track of this system moving over eastern New England by
Thursday and spreading heavy rain at times with qpf totals to
range between 1-2 inches. An persistent onshore flow will keep
temps cool and damp through Thursday. See Tides/Coastal flooding
section below regarding coastal effects.

The system finally moves off to the east by late Thursday
slowly bringing an end to the rain from west to east. With lack
of any dry ventilation following this system, the low level
moisture will likely linger and not much in the way of clearing
expected into early Friday.

Some partial clearing should take place during the day Friday
with warmer temperatures as the flow aloft and in the lower
levels becomes southwest ahead of an approaching upper short
wave helping clear out much of the moisture. The short wave
moves through during the afternoon so some scattered convection should
develop.

A broad bermuda high setup develops over the weekend but along
its northern periphery over northern New England, models are
showing a broad area of overrunning rain to develop.

&&

.AVIATION /12Z MONDAY THROUGH FRIDAY/...
Short Term...VFR conditions are expected today and tonight. We
may start to see some MVFR cigs develop across southern NH and
coastal ME late Monday night.

Long Term...IFR to LIFR conditions expected Tue night into
early Thursday. Conditions improve by late Thu to MVFR from west
to east and then mainly VFR by Fri.

&&

.MARINE...
Short Term...A brief period of marginal SCA conditions will be
possible tonight in advance of a cold front. However,
probability is pretty low, so will hold off an advisory at this
time. Otherwise sub-sca conditions are expected through Monday
night.

Long Term...A prolonged weak onshore easterly flow will
generate wave heights 5 to 9 FT by Tuesday night into Wednesday
and potentially staying above 5 FT into Friday.

&&

.FIRE WEATHER...
RH values will be generally between 35 and 45 percent tonday
with relatively light winds. Rain is expected to develop Tue
and last into Wed and Thu.

&&

.HYDROLOGY...
We are expecting 1-2 inches of rain with locally higher amounts from
Tuesday into early Thursday. With snowmelt and the additional
rainfall, river rises will be possible with the chance of some
localized minor flooding.

&&

.TIDES/COASTAL FLOODING...
We are entering a period of high astronomical tides which will
coincide in part with the weak storm system moving up the coast.
There are two primary tides we are monitoring for minor coastal
flooding, Tuesday evening and Wednesday evening, though high
water conditions may continue during the high tides into the
weekend.

For Tuesday night the astronomical tide at Portland is 11 FT.
Winds over the waters will be out of the east at about 20 KT
with nearshore waves building to 5 or 8 FT. This would lead to
about a 1 FT surge along coastal New Hampshire and southwest
Maine and create the potential for minor coastal flooding,
splash over, and beach erosion.

The tide Wednesday night is 11.5 FT at Portland. At this time
winds will be out of the southeast at about 15 to 20 KT which
will not promote a strong surge on its own but will likely keep
a residual surge in the Gulf of Maine of up to 1 FT with waves
of 5 to 9 FT. Minor coastal flooding, splash over, and beach
erosion is possible with this tide as well.

The next two tidal cycles will see tides of 11.7 FT at Portland
Thursday night and Friday night, but atmospheric conditions
contributing to storm surge will be on the decrease and we are
not expecting significant issues with these tides.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...Small Craft Advisory from 7 PM Tuesday to 6 PM EDT Wednesday
     for ANZ151-153.
     Small Craft Advisory from 2 PM Tuesday to 6 PM EDT Wednesday
     for ANZ150-152-154.

&&

$$
NEAR TERM...Cannon
SHORT TERM...Cannon
LONG TERM...Marine



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