Area Forecast Discussion
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FXUS61 KGYX 291611 AAC
Area Forecast Discussion...UPDATED
National Weather Service Gray ME
1111 AM EST Tue Nov 29 2016
An area of low pressure moving through southern New England will
spread wintry precipitation into northern New England this morning
before transitioning to rain for much of the area by this
afternoon. Precipitation ends from west to east this evening, but
another area of low pressure will bring more rain possibly
changing to snow in northern areas Wednesday night into Thursday.
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Have extended parts of the winter weather advisory where
temperatures are reluctant to rise above freezing. Most areas are
seeing freezing rain or drizzle at this time but snow may be
mixing in at times. Removed coastal NH as readings have come up in
this area. Concord...Laconia...and nearby locations as well as
coastal Cumberland County are slowly warming and may be able to
drop advisories before noon.
Another...more robust area of precipitation is moving NE from NY
state and Massachusetts so we are not out of the woods yet.
825 AM Update...
Areas of freezing rain...freezing fog...and rain are moving
through NH and portions of Maine this morning. Temperatures are
warming up gradually every hour although dew points are
low which is a concern. Will be watching closely the next couple
hours and have added Rockingham and Cumberland to the Winter
The first substantial radar echoes have made it into New
Hampshire, though so far only traces of precipitation have been
observed. Several observing sites have reported "UP" or unknown
precipitation, while some have actually reported freezing rain.
Heavier band of precipitation will arrive in New Hampshire within
the hour. Temperatures this morning have been on the rise over
southwest New Hampshire and much of the area in general, though
temperatures remain at or below freezing with dewpoints even lower
suggesting that evaporational cooling could keep temperatures near
freezing a little longer. Near the coast Portsmouth and Portland
have risen to 31 and 30 degrees respectively with precipitation
still a ways off. These areas will likely rise above freezing
before precipitation arrives. As a result will continue current
advisory structure. Have made some adjustments to temperature,
POP, and weather grids based on latest observations and expected
trends. Otherwise no substantial changes to the forecast were
Today will feature a complex precipitation type forecast
resulting from very cold temperatures this morning and cold air
damming across interior western Maine.
A shortwave trough ejecting out of the base of a large Midwestern
upper low will track through New England today. Weak surface low
pressure will track through southern New England, which will help
to keep the low level winds out of the east, piling up cold air
against the higher terrain. Regional radar already shows stronger
echoes moving through New York state and into Massachusetts, but
surface observations reveal that most of this is not reaching the
ground until you get to western New York. This is a result of very
dry air in the mid to low levels of the atmosphere as evidenced
by the 00Z sounding from GYX last night. This dry air could allow
the first bouts of precipitation to start as light snow as it
moves into New Hampshire near sunrise. But strong warm advection
aloft (in the 850 to 700 MB layer) should change precipitation to
rain as it falls. However, surface temperatures in many areas may
remain below freezing creating a period of freezing rain which
could cause icy conditions on roadways.
Across southern New Hampshire, temperatures are already beginning
to warm up a bit from their early morning lows, but dry air at the
surface indicates that temperatures may stay below freezing as
precipitation begins to fall. As a result, the Freezing Rain
Advisory will continue and has been expanded to include the
Manchester and Nashua corridor. It is possible that freezing rain
may arrive even further east into Rockingham County as well, but
there is still a good deal of uncertainty regarding when that will
arrive and what temperatures will be when it does so. Will need to
monitor this and might need to expand the advisory again depending
on how conditions evolve.
Northern New Hampshire may begin as snow and transition to sleet
and freezing rain during the mid morning. It is expected that
south to southeasterly low level winds will allow warm air to mix
down in the Connecticut River Valley today which will allow
temperatures to warm above freezing. However, there is still some
uncertainty on when that will occur. There could be up to a tenth
of an inch of ice accumulation before temperatures warm up.
Across interior western Maine and east central New Hampshire there
should be a pretty decent cold air damming setup today which will
allow low level temperatures to stay in the 20s to low 30s even
into the afternoon. This will provide the opportunity for a longer
period of freezing rain and ice accumulations of a tenth of an
inch or slightly more before temperatures eventually warm.
Currently the winter weather advisory ends at 4PM, but cold air
damming situations are notoriously long lived and it is possible
that this might need to be extended in time if temperatures fail
to warm as forecast. Along the Maine coastline an easterly wind
should allow warmer air to move in from the ocean and keep most of
the precipitation as rain.
In the western Maine mountains, temperatures at all levels may
remain cold enough for snow for a majority of the day, allowing
snow to accumulate to 3 to 6 inches. However, warm air aloft
should move in eventually even up to the Canadian border so there
may be a change over to freezing rain in this region as well later
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.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/...
Precipitation should come to an end from west to east tonight as
low pressure moves east. Low level winds shift to the west
allowing the cold air damming to break and warmer temperatures to
arrive especially over the coastal plain and southern parts of the
area. In fact, daily high temperatures may occur in the evening or
even up to around midnight. But eventually as the low moves
further away there should be an opportunity for at least some
cooling with temperatures bottoming out generally in the 30s.
.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
At 500 mb models continue to trend toward a less amplified and
less blocky pattern through the weekend and into early next week.
For the most part the troughs will be fast moving, but this will
not preclude a significant event, given the thermal gradients
this time of year. Temps will bounce around a bit through the
period but generally should be near to above normal.
Starting Wednesday the second of the almost back to back systems
will move in as fairly impressive chunk of energy rotates around
base of trough to our west and begins to form a coastal surface
low. Should see a strong surge of mid-level warm advection
Wednesday afternoon and evening, which will lead to moderate to
maybe heavy rain. And, it will be mainly rain at the start, with
the possible exception of a period of snow in the far NE zones, as
highs climb to into the 40s to around 50 in the south. By
Wednesday evening, should see cold air starting to move down from
the N and may turn the precip back to snow in the far NE. Should
see the rain end across southern NH and SW ME Thursday morning,
with precip winding down from SW-NE during the rest of the day.
Cold air will continue to move in from the N, with snow creeping a
little bit southward and lowering in elevation a bit across the
mountains. There is the possibility that areas from Coburn Gore
and Jackman northward could see six inches or more of snow.
Friday will see a bit of a break, as ridging builds in briefly,
and temperatures will stay above normal but not quite as warm as
previous days. The upper level low finally tracks to our north
and drags a cold front through area Friday night into Saturday.
Temperatures return to normal over the weekend, but other than a
few rain/snow showers it should stay dry. Next chance of
precipitation will be centered around Monday, with the Euro
showing a deepening coastal storm while the GFS advertises a
ridge, so forecast confidence is low for early next week.
.AVIATION /16Z TUESDAY THROUGH SATURDAY/...
Short Term...Should see conditions worsening to IFR this morning
from west to east. Precipitation may start out as light snow
before transitioning to freezing rain and then rain as the
temperature warms. When this transition occurs is a difficult
thing to pinpoint even this late in the game. The longest period
of freezing rain may be at Augusta or Whitefield where freezing
rain could last into the early afternoon. By this evening stronger
winds moving in just above the surface will lead to low level wind
shear at all TAF sites through tonight.
Long Term...Conditions improve to VFR briefly on Wednesday morning,
but flight restrictions return from SW-NE Wednesday afternoon
with IFR or lower expected Wednesday night. Gradual improvement
to VFR on Thursday. Mainly VFR expected Friday and Saturday, with
the exception KHIE, which will likely be stuck at MVFR in upslope
clouds and SHSN.
Short Term...Southeast winds ahead of the developing low tracking
near the coastline will strengthen and likely gust to gale force
over the outer waters this evening into tonight. Winds should
diminish a bit after the low moves by.
Long Term...SCA may be needed Wednesday night into Thursday in SE
flow ahead of low pressure and then in NW flow behind the
-- Changed Discussion --ME...Winter Weather Advisory until 1 PM EST this afternoon for
Winter Weather Advisory until 4 PM EST this afternoon for
Winter Weather Advisory until 10 PM EST this evening for
NH...Winter Weather Advisory until 1 PM EST this afternoon for
Winter Weather Advisory until 4 PM EST this afternoon for
MARINE...Small Craft Advisory until 4 AM EST Wednesday for ANZ151-153.
Gale Warning until 1 AM EST Wednesday for ANZ150-152-154.
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