Area Forecast Discussion
Issued by NWS Portland, ME-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KGYX 200118
Area Forecast Discussion
National Weather Service Gray ME
918 PM EDT Wed Apr 19 2017
Weak low pressure will track across Quebec tonight pulling a
cold front across the region. The front will stall across
southern New England on Thursday as a weak area of high pressure
builds by to our north. Low pressure will move out of southern
Ontario Thursday night and spread precipitation across the
region through Friday. Weak high pressure will build in for
late Saturday into Sunday while low pressure passes to our
south. High pressure builds in early next week.
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
-- Changed Discussion --9 pm Update: Precipitation widespread across the
area...categorical pops cover this well. Heavier showers are mixing
down colder air from aloft allowing surface temps to be colder
than forecast, thus made temp adjustments based on mesonet data.
Also with colder temps expanded areas of mixed ptype for the
next few hours since some currently being observed mainly in the
mountains. By midnight temps should slowly warm a few degrees
as some waa occurs on the southerly flow in the lower levels.
455 pm Update: Quick update to increase pops the rest of the
afternoon and evening across the area. Solid area of showers
currently moving through NH and into western Maine. No other
At 18z...a freshening southeast flow around a 1038 millibar
high over the maritimes and an advancing frontal system over the
eastern Great Lakes. It was a seasonably cool day with onshore
flow and clouds limiting highs to the 40s and lower 50s across
the region. Shortwave impulse evident on GOES water vapor loop
over the upper Great Lakes will race east along with associated
1012 millibar surface low vicinity of the Ottawa valley. NWS
Doppler Radar mosaic showed an area of showers in advance of
this disturbance entering western New England at moment with
activity to cross the area tonight. The column is cold enough to
support some snow and sleet tonight across the higher terrain
near the international border where a few inches of accumulation
will be possible.
-- End Changed Discussion --
.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
The front will be draped along the coast Thursday morning and
move to our east and south during the day before stalling. High
pressure will try to briefly nose into the area from the north
and west during the day. However...along the coastal plain weak
flow will likely result in an onshore flow with lingering moisture
and low clouds for much of the day. Highs will be mainly in the
50s...with some lower 60s over southern interior New Hampshire
as well as the lower Connecticut Valley. Mostly cloudy Thursday
night in onshore flow with light overrunning precipitation
developing overnight from west to east along with the potential
for some light drizzle early along the coast in onshore flow.
The column may be cold enough in the mountains and near the
International Border for some wet snow or sleet across the
.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Much of the long term period looks cool and unsettled as
Canadian high pressure continues to nose into the region at the
SFC. A short wave trough will approach from the west Thursday
night and allow for a light rain event as WAA occurs above the
cool, stable boundary layer. The column may be cold enough for a
few inches of wet snow in the western ME mountains at the
highest elevations. The clouds and showers will be slow to move
out on Saturday as another short wave trough moves in from the
A southern stream system may affect southern zones with some
showers Sunday, but right now it looks as though the bulk of the
action will remain to our south. Strong Canadian high pressure
will return for early next week with fair weather but still cool
.AVIATION /01Z THURSDAY THROUGH MONDAY/...
Short Term /Through Thursday Night/...MVFR with lcl IFR tonight
in -shra and fog with -shra/-shsn in the mtns. Areas of MVFR
cigs lingering on Thu...with MVFR and LCL IFR Thu night in
cigs...fog and developing -RA.
Long Term...IFR conditions are expected Friday in low clouds and
light rain. IFR to MVFR conditions continue to be expected
Friday night into Saturday before improving Sunday and Monday.
Short Term /Through Thursday Night/...Expect Small Craft winds
and seas tonight in advance of the cold front with lingering SCA
seas possible outside the bays on Thu. Winds and seas will increase
once again Thu night and may reach Small Craft by early Friday.
Long Term...Small craft conditions are possible Friday as low
pressure passes to our west.
Cool and moist onshore flow will persist through the end of the
week. There will be showers tonight with more widespread rain
expected Thursday night into Friday.
MARINE...Small Craft Advisory until 6 AM EDT Thursday for ANZ150>154.