Area Forecast Discussion
Issued by NWS Portland, ME

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000
FXUS61 KGYX 300205
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
1005 PM EDT Thu Oct 29 2020

.SYNOPSIS...
The remnants of Zeta will bring light rain to the southern half
of the area and a rain snow mix further north through early
evening. As the center of this system passes to our south
tonight, colder air will be drawn into the area changing precipitation
to snow from north to south. Across southern New Hampshire and
parts of southwestern Maine, the first snow accumulation of the
season is likely. Amounts will generally be on the light side,
but the first snowfall can often take people by surprise. Cold
weather lasts through at least Saturday before high pressure
shifts east and allows temperatures to slowly rebound. Another
cold shot arrives early next week.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
10 PM Update...First wave of precipitation is moving off to the
east at this time and is mostly in the form of rain. The next
wave of light precipitation across upstate NY will move across
southern zones overnight into Friday morning. Northeasterly
winds continue to increase as the remnants of Zeta pass off
well to the south of Nantucket combined with high pressure
moving in from the north. Gusts may approach 25 to 30 mph over
the landmass overnight as the gradient continues to tighten. As
drier air moves in from the northeast, cooling will take place
and gradually change precipitation over to light snow for most
areas, but very little is expected to accumulate. Forecasted max
accums are over southernmost NH where an inch or two may fall,
perhaps up to 3 or 4 inches across the higher terrain above 1500
ft.

630 PM Update...Little change to the going forecast at this
time. Rain is falling across the forecast area at this time
except for higher elevations of the Whites. The column will
gradually cool overnight allowing for a change to snow before
ending. Lowered expected snow accums just a little bit for most
zones, mainly due to the lack of strong UVVs expected here on
out. Highest accums are still expected to be in the Monadnocks
of New Hampshire.

Previously...


***First accumulating snow of the season expected south of the
 mountains***

At 18z a wavy frontal boundary extended from south of the Gulf
of Maine through the DELMARVA and southeast CONUS. NWS Doppler
Radar mosaic showed a blossoming precipitation shield spreading
northward into the forecast area in advance of low pressure and
the remnants of Zeta. This area of precipitation will gradually
overspread much of the area by early evening as the remnants of
Zeta track along the baroclinic zone to our south. It`ll be
mainly rain to start with snow...or a mix with snow confined to the
higher terrain. Evaporational cooling and colder air advecting
into the area from the north with cause precipitation to transition
to snow from north to south and from the higher terrain to
valley locations. I adjusted snow amounts a bit based on the
latest guidance and expanded the advisory to Sullivan county.
Highest snow amounts will be found across southwest New
Hampshire where amounts of up to 4 inches are possible for
elevations above 1000 ft. There will be a sharp south to north
gradient of QPF across the area along with the timing of the
changeover to snow to contend with. Lows tonight will range from
the mid 20s to lower 30s.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
Friday will be a cold and breezy day as the system exits into
the maritimes. Lingering precipitation south and east of the
mountains and foothills will end during the morning followed by
clearing skies during the afternoon. It`ll be an unseasonably
cold day with highs in the mid 30s to around 40. Clear skies and
diminishing winds tomorrow night and high pressure builds into
the area. It`ll be a cold night for late October with lows in
the teens across the mountains with mid teens to lower 20s for
the remainder of the forecast area.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
Progressive 500mb flow will continue during the extended period,
with general weak ridging transitioning to a sharp 500mb trough
by the beginning of next week before trending back to zonal /
broad ridging by the end of the work week. Temperature roller
coaster is in store through this period with cool weather on
Saturday moderating a bit by Sunday before an anomously cold
airmass moves into New England by Monday and lingers through
Wednesday. Temperatures are then expected to moderate to above
or even well above average by Friday. Overall precipitation
looks to run below normal with a chance for rain late Sunday
into Sunday night, with shower activity in the mountains on
Monday.

High pressure will be in control on Saturday with no impactful
weather expected on Halloween night. Surface ridging quickly
moves to the east with return southerly flow during the day on
Sunday as a highly amplitude trough digs into the Ohio River
Valley. Chances for rain increase by Sunday afternoon to end the
weekend with showers expected into Sunday night as a strong
surface cold front moves through the region. Much colder on
Monday with a blustery day on tap as wind chill values will
struggle to stay above the freezing mark. Snow showers will most
likely be concentrated to the NW upslope areas of the mountains
but winds will be gusty on NW flow all the way to the coast.
Will have to watch for the possibility of some light snow Monday
night into Tuesday morning as vort max swings through the
region. Cold weather will continue into Tuesday before zonal
flow and moderating temperatures reaches the area by mid-week.
Quiet weather expected Thursday into Friday with surface ridging
and a general SW to W flow. High temperatures could be well
above normal by Friday as model mean is showing 850mb Temps of
+10C.

&&

.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
Short Term /Through Friday Night/...MVFR in -RA and mtn -SN
lowering to IFR in -SN throughout from north to south btw 03 and
08z. Conditions improving to VFR throughout by 16z Fri. Northerly
wind developing with gusts to 25 kt late tonight into Friday
before diminishing late Friday.

Long Term...VFR conditions this Saturday with high pressure and
clear skies in full control. Conditions could trend down hill by
Sunday afternoon as a marine layer could possible impact coastal
TAF sites as strong onshore southerly flow develops. IFR
conditions could be possible Sunday night with rain showers
ahead of a cold front.

&&

.MARINE...
Short Term /Through Friday Night/...NE flow will increase in
response to low pressure moving S of New England. Marginal gales
are likely across the outer waters...with SCA conditions for the
bays with gusts of 25 to 30 kt. Winds will diminish Friday
afternoon but with lingering SCA conditions for the open waters.

Long Term...High pressure will be centered over the coastal
waters on Saturday with conditions remaining below SCA.
Southerly flow increases by Sunday afternoon ahead of an
approaching cold front with SCA conditions possible. Cold front
quickly pushes through by Monday morning with strong offshore
winds and at least SCA conditions for the outer coastal waters,
Gale conditions can`t be rule at this time.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...Winter Weather Advisory until 10 AM EDT Friday for NHZ007-011-
     015.
MARINE...Small Craft Advisory until 2 PM EDT Friday for ANZ151-153.
     Gale Warning until 2 PM EDT Friday for ANZ150-152-154.

&&

$$

NEAR TERM...Ekster
SHORT TERM...Schwibs
LONG TERM...Dumont


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