Area Forecast Discussion
Issued by NWS Portland, ME

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FXUS61 KGYX 090328
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
1028 PM EST Thu Dec 8 2016

.SYNOPSIS...
Another cold front will cross the region overnight. Mountain snow
showers will continue through Friday...with several inches of snow
possible north of the notches. The coldest air of the season will
move in behind the front...with highs struggling to break freezing
even at the coast. High pressure will build in for the weekend
continuing cold temperatures. A low will approach the region on
Monday with snow spreading across the region and rain mixing in
along the coast through Tuesday.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
1025 PM...Just a few minor tweaks based on current obs and
latest mesoscale models. Secondary cold front still on track to
cross the CWA in the 06-12Z range, with upslope snows increasing
in intensity in the mountains between and 06-08Z.

740 PM...First cold front now exiting the CWA moving offshore off
coastal ME attm. Secondary cold front will cross the region after
midnight, and will usher in the colder air. In between there is a
little bit of a lull in the SHSN in the mountains, although a few
scattered showers and flurries are possible this evening. The
better accumulating snow here will begin closer to midnight as the
the front moves through and the cold upslope flow kicks in.
Overnight low will drop off some this evening, but will wait for
the push of cold air, and will range from the low 20s in the north
to the upper 20s in srn NH and on the coast.

Previously...The first cold front is crossing the mtns at this
time...forcing a broken band of snow showers thru the forecast
area. Based on area webcams and a small handful of automated
observations...visibility has dropped to 1/4 mile at times in
these squalls. Temps are also falling below freezing behind the
front...especially in the mtns and foothills. So some refreezing
of minor snow accumulations will likely occur on roadways. I have
issued a couple SPSs to handle this threat into the early evening.
After the passage of the front...temps will gradually decrease
overnight in a well mixed environment. Upslope snow showers will
tend to stick closer to the high terrain...as Froude numbers go
back towards critical after the initial surge of CAA. Then the
secondary Arctic front approaches the forecast area around
midnight. Once again deeper mixing will allow some snow showers to
cross the ridge line and track towards the coast. Snow squall
parameters do appear favorable for some of these to also be heavy
at times. The focus of the heaviest precip however will remain
closer to the highest terrain.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/...
Cold NW flow will continue on Fri. Closed mid and upper level lows
will remain over the Canadian Maritimes...with strongly cyclonic
flow directed over the high terrain. With a lingering pool of low
level moisture upstream in Canada...upslope snow showers should be
favorable for moderate accumulations over parts of Nrn NH and
adjacent Wrn ME. It is not out of the question that a winter wx
advisory may be needed for a few zones.

Farther S...high temps will struggle towards freezing with strong
CAA thru the day. Wind gusts will top out around 25 to 30 kts at
times...making it feel even colder. CAA continues into the
overnight...so mixing will limit the overall cooling off of temps.

&&

.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
A relatively zonal flow will persist through the start of next
week...with a series of weak waves moving through. By Tuesday a
long wave trough develops over Hudson bay and cold air shifts
southward into the central CONUS. This will allow for a storm
system to move up the ohio valley and into Northern New England.

The weekend begins with cold high pressure building into the
region. Mountain Snow showers will come to an end of Saturday with
clearing skies. Winds will decrease through the region as the
pressure gradient decreases. Overnight temperatures will drop to
near zero through the mountains... with isolated valleys below
zero. A few clouds remaining in upslope regions would be enough to
prevent widespread below zero temperatures.

On Sunday clouds will start to move in from the west in advance
of a developing system moving up the ohio river valley for Monday.
The trend over the past few days has been to push back the timing
of the storm... with precipitation not moving into our
southwestern areas until very early Monday morning. Expect
precipitation to begin as snow region wide and spread across the
region through the day on Monday. By Monday night the
possibilities expand with the changing storm track. GFS tracks
further inland which has the effect of allowing warm air aloft to
infiltrate through southern maine. With the high pressure for
Saturday and Sunday the cold temperatures are likely to remain
dammed at the surface, so warm air aloft would put a period of
mixed precipitation into southern Maine coastal plain. While a
mixed scenario is one possibility, it is not the only one.
Increasing strength of cold air aloft could also drive the storm
track slightly further south keeping any above freezing
temperatures off shore in teh Gulf of Maine. At this point have
leaned towards a colder solution, in part because of the strength
of existing cold air mass.

The track of the storm will also have an impact on the winds,
with a south track resulting in a more classic nor`easter type set
up with gusts too around 30along the coast. A inland and warmer
scenario keeps the center of the storm over us and results in
lower wind speeds. Have hedged to the stronger winds in keeping
with the colder solution.

The active pattern continues through next week with another
chance for precipitation on Wednesday.

&&

.AVIATION /04Z FRIDAY THROUGH TUESDAY/...
Short Term...First cold front is crossing the mtns at this hour
with a band of snow showers along it. Very brief IFR or lower
conditions are possible with this front...mostly likely to hold
together thru AUG...possibly RKD. NW flow develops behind the
front...keeping areas downwind of the mtns VFR tonight. HIE will
remain MVFR in upslope clouds...and occasional MVFR CIGs may work
into LEB overnight. HIE may also see rounds of SHSN that drop
VSBYs to IFR or lower at times...especially with Arctic frontal
passage around midnight tonight. Strong NW flow continues
Fri...with surface gusts around 25 kts. Upslope SHSN continue at
HIE thru the day.

Long Term...
Sunday night MVFR clouds moving in west to east. Expect IFR snow
to develop late monday. Tuesday may see a period of mixed precip
along the coast.

&&

.MARINE...
Short Term...I have upgraded the outer waters to gale warning for
Fri...and made the bays SCAs beginning this afternoon. First cold
front will cross the waters this evening...with winds increasing
to SCA thresholds. The secondary Arctic front crosses the area
tonight. Gale force wind gusts will begin behind this front.
Strongest wind gusts will linger into Fri evening before gradually
diminishing.

Long Term...
Storm developing Monday into Tuesday will result in wind and waves
increasing to near Gale.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...Small Craft Advisory until 11 PM EST Friday for ANZ151-153.
     Gale Warning from 10 AM to 11 PM EST Friday for ANZ150-152-154.

&&

$$
SYNOPSIS...Curtis
NEAR TERM...Cempa/Legro
SHORT TERM...Legro
LONG TERM...Curtis/Legro
AVIATION...Curtis/Legro
MARINE...Curtis/Legro



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