Area Forecast Discussion
Issued by NWS Portland, ME-- Highlight Changed Discussion --
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FXUS61 KGYX 181707
Area Forecast Discussion
National Weather Service Gray ME
107 PM EDT Tue Apr 18 2017
High pressure will pass to our north through Wednesday. The
circulation around this high will bring a cool onshore flow to
the area. Weak low pressure passes to our north on Wednesday
and will bring some showers to the region. Another low will
bring steadier precipitation late Thursday into Friday. The
precipitation could fall as some snow in the mountains. High
pressure builds in for the weekend.
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
-- Changed Discussion --1 PM Update...Very little in the way of adjustments at this
hour. The going forecast remains in good shape.
930 AM Update...Just a few minor adjustments to cloud cover for
the rest of the morning into the early afternoon hours. Several
large holes in the lower bkn/ovc exist across the CWA so tried
to better pin these down in the grids and some places are
completely sunny, and others cloudy. Otherwise, still expecting
front to drop in from the northeast today which will shift the
winds to east this afternoon.
Northerly flow across the area continues to drain in colder
air. Temperatures have fallen through the 40s this morning and
into the 30s. An area of snow has been noted over eastern and
central Maine which is occurring behind yet another front
pushing in from the east. It is possible that some of this
precipitation could make it into the Kennebec Valley, and yes it
could fall as some snowflakes. But overall this should be quite
light and not amount to much more than a flurry or sprinkle.
Much cooler air in place aloft today means we will start off
much cooler. Being nearly a month on the warm side of the
equinox means the April sun will do quite a bit to warm things
up this afternoon over western New England where temperatures
will rebound into the 50s to near 60. But across eastern New
England the cold advection continues until winds begin to turn
around to the east. This easterly flow will bring cool, maritime
air into the area, keeping temperatures in the 40s. Clouds
associated with the maritime air may also move in, but dry
conditions in the lowest levels should make it difficult for any
precipitation to form.
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.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/...
Cool onshore flow continues tonight, but we will not see a good
push of higher dewpoints moving in off the water. As a result,
we should be able to cool into the 30s or even 20s. Areas that
remain free of low clouds will have the best chance of dropping
below freezing. This will be across interior Maine and New
Flow becomes more southeasterly on Wednesday as a frontal system
approaches from the west. Gradually this will bring in some more
moist air and a better chance of low clouds and even possibly
drizzle. Temperatures stay in the 40s again across Maine but may
make the low to mid 50s in New Hampshire. Any more substantial
convective showers associated with the approaching front and mid
level wave will not arrive until later in the afternoon or
.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
The 500 mb pattern continues to hold onto large scale omega
blocking across the western half of the northern hemisphere,
which will keep things active across New England as smaller
scale waves moves through in the mid-late week period. This
pattern has kept the coldest air locked up in Arctic Canada,
and sending waves of the moderately colder air down into the
CONUS. However there are signs of the blocking breaking down
toward the end of the forecast, which may open the way for the
cold core of air to start to spread equatorward next week.
Either way, it looks like it will be hard to find any warm
spells in the next week to ten days with temps generally running
normal or below.
Wednesday night will bring some showers to the region as
weakening low tracking across Quebec, bringing a quick warm
front cold front combo. Models continue to trend northward with
best forcing and QPF may not amount to more than one or two
tenths of an inch at best, mostly associated with weak WAA Wed
night. May see somewhat of a break on Thu in precip, if not
clouds, although even some breaks of sun may be possible on Thu
as well, as wind develops a bit of westerly component and we
see a break in the onshore flow, with temps warming to near
normal in the upper 40s north to near 60 in southern NH.
This will be short lived as another wave approaches from the
west Thu night and crosses the region on Fri. This system is
compact, but shows a little negative tilt, so a steadier precip
is expected Thu night into Fri as this system moves through, and
could produce a half to three quarters inch of QPF. Models are
trending a bit warmer with this system, and it looks like
mostly rain for all but the higher terrain in the mountains,
where it could mix with or change to snow at times, with some
accums possible. Otherwise warm, and somewhat moist boundary
layer should keep things mainly rain. Best chance for snow
outside of the mountains would be Fri night, but this will be as
system is exiting, and again will likely be in the form of some
flakes mixing in with no accums expected.
Saturday looks mainly dry, with some SHRA possible in the mtns,
but Sunday into Monday starting to become lower confidence as
srn stream closed system allows for a wavy zonal flow in the nrn
stream across New England. The Euro would keep us mainly dry
with variable clouds and temps running on the cool side of
normal, holding back any system associated with the srn stream
low until Tuesday. Will continue to lean toward a dry Sunday,
with chance pops early next week.
.AVIATION /17Z TUESDAY THROUGH SATURDAY/...
Short Term...Mostly VFR conditions expected today, but a
maritime air mass moving in from the east could bring some MVFR
ceilings with time. The chance of these lower clouds arriving
will increase tonight into Wednesday.
Long Term...MVFR-IFR Wed night, with worst conditions on the
coast. Some improvement to MVFR, or even VFR possible Thu, then
a return to IFR or lower Thu night into Fri, with improvement to
VFR possible Saturday, although could see some gusty NW winds
Short Term...Relatively light winds and low seas expected today
and tonight as high pressure slides by to the north. However, a
period of stronger easterly flow is expected this afternoon in
the wake of a cold front which could lead to a few gusts up to
25 kt. A developing southeast flow on Wednesday will strengthen
to as high as 25 KT and allow waves to build up to around 5 FT
Long Term...Should see winds/seas diminish Wed night and stay
below SCA into Thu night, but SCA will likely be needed Fri into
Cool air in place across Maine and eastern New Hampshire will
keep relative humidity values higher than recent days. But west
of the mountains we will see relative humidity drop below 35
percent again today with light winds expected. The cool, moist
onshore flow overspreads the entire area tonight into Wednesday.
There will be a chance of showers Wednesday night with more
widespread rain expected Thursday night into Friday.
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 today or