Area Forecast Discussion
Issued by NWS Portland, ME

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FXUS61 KGYX 171813
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
113 PM EST Wed Jan 17 2018

.SYNOPSIS...
Developing low pressure off the mid Atlantic coast will
intensify as it moves rapidly northeast through the Gulf of
Maine today. High pressure builds eastward into the region late
in the week and into the weekend with a return southwest flow
bringing warmer temperatures by the weekend.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
110 PM Update...All warnings and advisories remain in place.
Snow is falling at varying intensities across the region, with
some breaks from time to time. The sun is even out in spots in
the far northern portion of the CWA. Another 1 to 3 inches can
be expected, mainly on the coastal plain. However, a band of
snow currently across eastern NY will likely swing across NH
this afternoon in association with the main short wave trough.
This could result in a resurgent period of moderate snow later
this afternoon. Otherwise, will have to watch for the potential
for freezing drizzle late this afternoon and early evening if
the low levels do not dry out that much. Will examine this
possibility over the next couple of hours before explicitly
forecasting it.

9 AM Update...Have made a few minor adjustments to PoP timing
and weather for the afternoon hours based on latest trends in
regional radar/sat data as well as latest mesoscale model
information. Right now, the snow is light, with a break in
steady accumulating snow currently ongoing across western and
northernmost zones. The next weak wave is approaching from the
south and should allow the radar to fill in with returns once
again over the next few hours. So far we have received reports
of anywhere between 2 and 5 inches of snow, so current
headlines will remain unchanged through the afternoon.

previously...

550 AM...at 10z a 1021 millibar low was centered south of Long
Island. This low continues to gradually strengthen with three
hour pressure falls of between 3 and 4 millibars centered south
of Cape Cod. For this ESTF update...only minor adjustments to
near term grids to reflect the current mesonet in near term
grids.

Prev disc...
At 07z...a 1023 millibar low was offshore of the DELMARVA with 3
hour pressure falls approaching three millibars noted south of
Cape Cod. GOES water vapor imagery showed a shortwave impulse
over the eastern Great Lakes. For today...the impulse will race
east across the northeast CONUS and quickly offshore by evening.
This energy will allow the offshore low to strengthen
moderately as it races east-northeast across the Gulf of Maine
this afternoon. UVM with shortwave and convergence with coastal
front will aid in precipitation development across the area
today. The models have backed off a bit on QPF...but snow ratios
should still allow us to approach the 6 inch threshold across
southern New Hampshire and along the Maine coastal plain with
this system. THe snow will quickly wind down from west to east
during the afternoon as the low and upper support quickly exit
the forecast area. There is a possibility that right along the
mid coast the coastal front could briefly cause the snow to mix
with or change to rain early this afternoon. Otherwise this
should be a straight snow event for the forecast area. The
current advisory and warning areas remain the same with this
package...although snow amounts were trimmed back a bit in many
areas.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/...
Some lingering upslope clouds and mountains now showers
early...otherwise clearing tonight as the upper trough and
surface low move well offshore. On Thursday...weak ridging
provides a mainly sunny day. A cold front will sag southward
towards the international border during the afternoon with a few
clouds and perhaps a few mountain flurries. It`ll be a
seasonable day with highs ranging from the mid 20s to the lower
30s across the region.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
A weak ridge of Canadian high pressure will build over the
region Thursday night. This airmass will not be overly cold with
only seasonably cool overnight lows mainly in the teens across
the forecast area. Some clouds will move into northern New
England as well, preventing significant radiational cooling. A
few snow showers will be scattered about in northern areas as a
fast moving short wave trough approaches the region.

A warming trend will begin on Friday as a southwesterly flow
develops across the Eastern United States. There will be a few
snow showers within the warm air advection pattern. The
atmosphere will remain relatively moisture starved however. This
will limit the snow showers to the northern higher terrain.

Another thaw on tap with mild temperatures expected over the
weekend. Southern areas should reach into the 40s for daytime
highs as a cold front remains locked just north of Maine and
New Hampshire.

The cold front will eventually sweep through the region by
Sunday night. This will allow cool Canadian air into the region
for the beginning of next week. In the meantime, model guidance
suggests possibly some mixed precipitation as low pressure moves
north from the Mid Atlantic region. The 00Z Euro offers the
coldest solution for this next event.

&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
Short Term /through Thursday/...MVFR with areas of IFR in snow.
Aft 20z...conditions gradually improving to VFR throughout with
sct MVFR in mtn -shsn.

Long Term...Mainly VFR conditions across the region. Widespread
ceilings and visibilities lowering in a mix of precipitation
early next week as low pressure heads towards New England.

&&

.MARINE...
Short Term /through Thursday/...We`ll continue with marginal SCA
seas through tonight for a combination of swell...and for wind
generated waves from our passing coastal low.

Long Term...Expect SCAs with a developing southwesterly flow on
Saturday with possible gales along the outer waters. Gales are
possible early next week with low pressure approaching from the
south.

&&

.HYDROLOGY...
All rivers have now fallen below flood stage, but ice jams have
frozen into place in some areas. Rivers will still need to be
monitored as these jams could move without notice.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Winter Weather Advisory until 7 PM EST this evening for
     MEZ012>014.
     Winter Storm Warning until 7 PM EST this evening for
     MEZ018>028.
NH...Winter Weather Advisory until 4 PM EST this afternoon for
     NHZ003>007.
     Winter Storm Warning until 4 PM EST this afternoon for
     NHZ008>015.
MARINE...Small Craft Advisory for hazardous seas until 7 AM EST
     Thursday for ANZ150-152-154.

&&

$$

NEAR TERM...Ekster



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