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fxus61 kgyx 121519 

Area forecast discussion
National Weather Service Gray ME
1019 am EST Tue Nov 12 2019

low pressure will exit into the Canadian Maritimes this
afternoon. Behind this system, gusty winds will allow much
very cold air to enter the region tonight and Wednesday. High
pressure will crest over New England Wednesday night, with dry
conditions and very cold air over the region. Dry conditions
will linger into Thursday, with a moderating trend ahead of an
Arctic front on Friday. This strong front will cross the region
Friday evening, followed by a dry, but chilly weekend.


Near term /until 6 PM this evening/...
1005 am...have dropped the advisory for the srn tier of New Hampshire
counties, as temps here are pushing into the mid 30s at this
point. Cold front will move through over the next several
hours, and rain is changing to snow as the front moves through,
and the colder air aloft moves in. Nice fine line boundary
between rain and snow showing up on kgyx radar cirrocumulus product.
Models continue to show the precip weakening as it moves east
across the S part of the cwa, so only addl light accums are
possible here, but a few inches could fall in the mountains.
Will be interesting to see how much mixing can occur right as
the front moves thru, and how high temps can get, just briefly,
especially in the downslope areas. Maxes in these are
conservative, since this period will be short lived and are in
the mid to upper 30s. The nrn areas will likely only top at or
below freezing.

7am update... precipitation filing in as the cold front
approaches. Kgyx sounding shows classic fzdz with drier air
aloft and cold air holding tight at the surface. Warm air aloft
has reached north of the White Mountains with kbml now reporting
freezing rain. Expect this to be about the peak of the warm air intrusion
as Vermont has already gone over to snow behind the front. Have
adjusted to add more mix further north. Temperatures across
Maine remain below freezing but southern New Hampshire is
starting to mix out and the Winter Weather Advisory may be able
to expire there by around 9am.

Cold air damming firmly in place as a second wave of
precipitation, this one associated with the cold front,
approaches the area. Low pressure is currently over eastern PA
with height falls of 5mb/3hr over Calais pushing the system up
the coast of Maine. Aloft, most of our area remains in the
classic warm sector with the warm frontal cloud shield located
along the Canadian border and cold front draped down approaching
the Champlain and Hudson valleys. While the warmth has entered
aloft the surface is a different story. Northeasterly flow
is across Maine and extends out into the coastal waters. The
coastal front is located east of the 44007 buoy well out into
the Gulf of Maine and reaching shore south of Boston, Massachusetts. Kgyx
00z sounding showed a fairly deep cold layer,extending up to
850mb, and the kmwn observation of 28f in the last hour
continues to support that.

Cold at the surface and warm aloft sets US up for a classic
freezing rain scenario. In this case the one part missing is the
rain as there is not really any widespread precipitation across
the cold pool at the moment. There is however, plenty of low
level moisture and thus freezing drizzle becomes the ptype of
choice this morning. With that in mind, have expanded the Winter
Weather Advisory to all of southern New Hampshire. While the
cold pool is not as robust as it is across southern Maine we do
see some reports of below freezing temperatures, especially in
the higher elevations of Hillsborough and Cheshire counties and
suspect that elevated surface and colder locations are seeing
freezing drizzle. With the heavier precipitation arriving right
in time for morning travel and dewpoints below freezing expect
the freezing drizzle to transition to a mix of sleet and snow as
the front moves in. While there won't be much accumulations
across southern NH, any amount is enough to be slippery and so
the advisory has been expanded.

The cold front will cross the area later this morning bringing
with it another burst of precipitation. With the cold air expect
this to be mainly in the form of snow, although a brief mix of
sleet at onset is possible further south. Temperatures may
briefly warm to the upper 30s as the front moves through and is
finally able to mix out the cold air but that warmth will be
very short lived as the Arctic air on the backside of the front
comes quickly into the region.


Short term /6 PM this evening through 6 PM Wednesday/...
cold air advection is the theme overnight with temperatures
steadily dropping. The breezy northwesterly flow and cloud cover
will keep the environment well mixed but well mixed cold air
mass will still put temperatures down into the single digits in
the north and teens south. Wednesday the cold air just keeps
coming with temperatures remaining well below freezing across
the region. High pressure will begin to build into the region
allowing for the winds to diminish making way for an even colder
night on Wednesday.


Long term /Wednesday night through Monday/...
high pressure crests over the region Wednesday night with 800 mb
temperatures running in the -12c to -14c range. With clear
skies, light winds and a fresh snowpack in some areas,
temperatures will bottom out rather quickly leading to the
coldest night of the season. Have chosen this night as a target
of opportunity to forecast below most available guidance. Will
forecast near record breaking overnight low temperatures in some
locations with readings dropping down to near zero in the north
to the lower to mid teens in the south. Only fly in the ointment
will be for approaching mid and high level cloudiness from the
west which could potentially shut down the radiational cooling
late at night.

Warm air advection around the periphery of the departing high
pressure system and a weak disturbance aloft will allow for some
cloudiness and possibly some mountain snow showers on Thursday.

We can expect a moderating trend on Friday ahead of an
approaching Arctic front. Daytime temperatures will peak out in
the 35 to 45 degree range in most areas.

Late Friday afternoon and Friday evening, an Arctic front will
cross the region. There will be scattered snow showers and
possibly a snow squall which will mainly be confined to the
mountains and foothills.

Dry and chilly conditions will follow for the weekend.


Aviation /15z Tuesday through Saturday/...
short term...widespread IFR conditions across the region as low
level moisture remains trapped by a surface cold pool. Expect
period of freezing drizzle across the region this morning for
all but the southernmost terminals. A cold front will cross the
region today with temperatures dropping rapidly behind it. As
the temperatures drop, the ceilings improve as we move into
northwesterly flow. VFR returns for Wednesday with much colder

Long term...mainly VFR conditions through the period. However,
the mountains may have a few scattered snow showers and MVFR
conditions at times through the period.


short term...nely flow under cold air damming along the coast
will reverse course midday as a cold front crosses the coastal
waters. Behind the front look for strengthening cold air
advection with winds gusting to gale force. Gale warnings remain
in effect for the outer waters. Winds will begin to diminish on
Wednesday as high pressure starts to build in.

Long term...winds will finally be diminishing over the waters
Wednesday night. Southwesterly winds will be on the increase
Friday ahead of a strong front. Behind this front, wind gusts
may approach gale force by Saturday morning.


Tides/coastal flooding...
tides are running about 1ft above normal, however they are
predicted to remain below flood stage.


records for Portland
November 12 low 16f in 1976
November 13: low 11f in 1941, coldest high: 33f in 1990

Records for augusta:
November 12: low 20f in 1981
November 13: low 13f 1986, coldest high 32f in 1990

Records for concord:
November 12: low 7f 1976
November 13: low 5f in 1976, coldest high 30f in 1894


Gyx watches/warnings/advisories...
ME...Winter Weather Advisory until 7 PM EST this evening for
Winter Storm Warning until 7 PM EST this evening for
New Hampshire...Winter Weather Advisory until 7 PM EST this evening for
Winter Storm Warning until 7 PM EST this evening for nhz001.
Marine...Small Craft Advisory until 6 PM EST Wednesday for anz151-153.
Gale Warning until noon EST Wednesday for anz150-152-154.


near term...cempa/Curtis
short term...
long term...Cannon

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