Area Forecast Discussion
Issued by NWS Portland, ME-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KGYX 182239
Area Forecast Discussion
National Weather Service Gray ME
639 PM EDT Tue Apr 18 2017
High pressure will crest over the coastal plain tonight. The
circulation around this high will bring a cool onshore flow to
the area. Weak low pressure passes to our north Wednesday night
and will bring some showers to the region, especially across
the north. Another low will bring steadier precipitation
Thursday night into Friday. The precipitation could fall as some
snow in the highest elevations. The low may hang around
allowing for an unsettled weekend.
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
Surface high pressure will continue to build southwestward
across the region this evening. The leading edge of the SFC high
in the form of a back door cold front/seabreeze can be seen on
radar on the coastal plain at this time and will work inland
going forward early this evening. This will turn the winds to
east and cool off the temps. A few showers are occurring on and
near the mid coast this afternoon and these may continue through
the evening hours, but be quite light.
Getting low temperatures right will be a challenge. Normally
with 1030+ high pressure cresting overhead lows would bottom out
pretty cold. However, moisture trapped beneath subsidence
inversion should allow stratocu to hang on overnight, at least
in patches. This will hamper temp drops in places, so went the
middle of the road with respect to the guidance lows. However,
areas that stay clear and calm will likely get into the 20s
without much trouble.
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
-- Changed Discussion --635 pm Update: Quick ESTF update to input latest obs data.
Quiet evening with some of the clouds over southern Maine slowly
eroding away. Previous forecast looks good. Minor tweaks to
temps and sky grids based on latest data.
The SFC high moves off the the east on Wednesday setting up more
of a southeasterly flow, but still off the water for many.
Therefore we are expecting another cool-ish day. Clouds increase
as the day wears on, with showers entering northern and western
sections of the forecast area during the afternoon hours as a
short wave trough approaches from the west. These will move
across the rest of the region Wednesday night. However, QPF
amounts are expected to be pretty light...generally a tenth of
an inch or less. Some wet snow will be possible at the highest
elevations of the western ME mountains Wednesday evening.
-- End Changed Discussion --
.LONG TERM /THURSDAY THROUGH TUESDAY/...
The models are in decent agreement on the longwave pattern
through early next week. Temperatures will average below normal
with a semi permanent vortex over Hudson Bay and as series of
impulses rotating around it delivering fresh rounds of cold air
to the region. will We begin the period with a frontal system
extending from northern New England through the Great Lakes. A
digging shortwave impulse over the northern plains states will
slide eastward into New England before exiting the coastline on
Saturday. At the surface...an associated surface low will travel
eastward along the quasi- stationary frontal boundary before
exiting the coast Friday night. Showers and patchy drizzle on
Thursday will transition to a steadier rain Thursday night as
overrunning increases in advance of the approaching surface wave.
The rain should taper off from west to east Friday evening as the
low and frontal boundary slide offshore. We`ll see lingering
clouds and a few rain or snow showers across northern and
mountains sections Friday night into Saturday with cold air
aloft...upslope flow...and lingering troffiness. Shortwave
ridging will offer a bit of a respite Saturday night into Sunday
with a weak surface ridge traversing the area. A northern
stream impulse will drive a cold front across the area Sunday
night into Monday marked by clouds and a few showers along with
a fresh shot of cold air to begin the new work week.
.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
Short Term...Mostly VFR cigs are expected tonight, but a period
of MVFR is possible after midnight, especially at southern NH
terminals. A cold front with showers will move through Wednesday
night, and this will likely bring cigs down into the IFR range
later Wednesday night.
Thu...Areas of MVFR in -shra.
Thu night - Fri...IFR with areas of LIFR in RA and FG.
Sfc wind gusts to 25 kt.
Sat...Areas of MVFR in -shra with mtn -shra/-shsn.
Sfc wind gusts to 25 kt.
Short Term...A few gusts of up to 25 kt will be possible this
evening as high pressure builds in but will not be widespread
of frequent enough to warrant a SCA. However, a SCA has been
issued for all waters for Wednesday afternoon and night as
strong winds and higher seas are expected in advance of a cold
Thu...Small Craft conditions are possible.
Fri - Sat...Small Craft conditions are possible...will gales
outside the bays.
Cool, moist onshore flow overspreads the entire area tonight
into Wednesday. There will be a chance of showers Wednesday
afternoon and night more widespread rain expected Thursday
night into the weekend.
Flood warnings continue for the Kennebec, Androscoggin, and
Connecticut rivers, but colder air should allow snow melt to
wane and rivers levels to recede below flood stage tonight.
MARINE...Small Craft Advisory from 3 PM Wednesday to 6 AM EDT Thursday