Area Forecast Discussion
Issued by NWS Portland, ME

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000
FXUS61 KGYX 230725
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
325 AM EDT Sat Mar 23 2024

.SYNOPSIS...
A significant early spring storm will move across the region
today into tonight...bringing heavy snows...snow and mixed
precipitation across southern New Hampshire and coastal Maine
with a changeover to rain for the seacoast of New Hampshire and
Maine. Icing is likely on the coastal plain and also across
southern NH. This system will push east of the region on Sunday
with improving conditions and seasonable temperatures.
Temperatures moderate early next week with conditions remaining
dry.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Snow, mainly light, continues to overspread the forecast area
from west to east as of 07z. Some sleet pellets are likely
mixing in near the MA border.

Snow amounts with this package have not changed much. Max
amounts in excess of a foot are still forecasted in the
mountains and portions of the foothills. South of there, winter
storm warning amounts (6+ inches) are expected in most of the
warning area on the coastal plain and much of NH except the far
south and southeast.

What has changed in the guidance is that the air expected to
flow over the low level cold air mass has warmed and lowered
some in the models, at least on the coastal plain this
afternoon and evening all while the SFC temps remain cold.
Therefore, in collaboration with surrounding offices, WPC, and
newest guidance we have increased ice amounts some across the
higher elevations of southern NH and the coastal plain of ME (in
a fairly narrow swath). This will be after a slug of several
inches of snow and a period of sleet.

Did not forecast areas of greater than a half inch of ice at
this time. Capped just below. There are mitigating factors
against higher amounts such as, the bulk of the rain will be heavy
with rather large drops which both detract from ice accretion
(more runoff). Also, there will be several inches of snow
beforehand that will give the rain something to soak into. Some
solar radiation with high sun angle this time of year may sneak
in as well. Sleet contamination is expected to mitigate icing
also. With that said we cannot rule out small areas of 0.5"
accretions in the Monadnocks in the NH, and also on the coastal
plain of Maine with some power outages. Will have to carefully
watch temperatures on the immediate coast as they may go above
freezing for a few hours today.

No changes in warning and advisory configuration and timing as
of this time.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SUNDAY/...
The precipitation ends quickly from west to east this evening.
One thing we will have to watch for is increasing winds tonight
with snow and ice on trees and lines which will likely freeze if
it doesn`t fall off first. This could cause some outages.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Overview: Drier air will make its presence felt for Sunday and
into early next week with high pressure centered to the north.
Overnight temperatures will fall below normal. Second half of
the week trends more unsettled with a round or rounds of
precipitation into next weekend. Temperature trends lean above
normal.

Details: Building high pressure entering southern Quebec will
assist in rapidly flushing precip and lower clouds out for
Sunday morning. It is under this high pressure that Sunday
through Mon night is expected to be dry, with mostly
sunny/clear skies. The exception will be some low level moisture
that may allow some cumulus development Sunday and Monday
afternoons.

The lighter winds and mostly clear skies Sunday night should
promote good radiational cooling conditions, particularly across
the north. Its here where valley locations will be especially
calm, and fresh snowpack should allow temps to fall to the
single digits late. Blended MOS guidance in for the evening,
believing that temps should fall off pretty quick towards
sundown. There is more uncertainty on winds towards the coast
overnight, with the NAM suggesting a mixed layer just off the
surface. This could keep temps from falling off too much.

There is even less moisture to play with come Monday afternoon,
and would expect a day of full sun here. It will remain cool as
daytime mixing generates some gusts, but steep inversion at top
of the mixing height should keep even drier air from reaching
the surface.

Some uncertainty approaching Tuesday and midweek, on how quickly
low level moisture advects back into the CWA. There will be a
couple players here, namely a consolidating area of low pressure
off the Mid-Atlantic coast. The low remains fairly stationary,
but areas of moisture do get wicked northward by overrunning
systems west of northern New England. Should some of this low
level moisture be pulled west into the area, drizzle or freezing
drizzle may result Tues night into Wed morning. It will largely
depend on how deep the moist layer is, as well as sfc temps.

From here, guidance diverges from agreement. General consensus
shows a large, occluded low pressure tailing north into James
bay, with elongated cold front nearing the region late week.
This extended front may slow as it nears, which could be a focal
point for additional pressure systems to enter into the region
into late week/next weekend.


&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
Short Term...Conditions deteriorating to IFR as snow continues
to develop early on this morning. Snow will transition to a mix
and then rain MHT-PSM-RKD with a mix continuing at LEB- AUG-
PWM and likely a mostly snow event for HIE. Freezing rain will
be likely at PWM for a time later today. LIFR/IFR CIGS will
persist everywhere this afternoon and evening. Improvement to
VFR overnight as drier air pushes in from the west with winds
gusting around 25 kt. A period of LLWS possible this afternoon
early evening.

Long Term...VFR conditions arrive Sunday-Monday. There will be
the chance for some afternoon cumulus development, but dry air
should promote mostly sunny skies. NNW gusts Sunday morning peak
around 30 kt, before falling through the day. Gusts remain
around 20 kts along the coast through much of the period,
becoming NE Monday.

&&

.MARINE...
Short Term...Gale warnings have been issued for all waters
except for Casco Bay. The Gale off Midcoast ME will start much
earlier and they will get in the strong southerly inflow into
the low pressure system. Everyone else starts tonight and goes
through Sunday morning.

Long Term...Winds along the coastal waters will remain above
20kt for much of the period, with SCA conditions likely. The
outer waters may also see occasional gusts to gale force through
Tuesday. NW winds Sunday shift NE Monday. Wave heights may
remain steady around 7 to 10 ft through the weekend and early
next week as disturbances out to sea continue to propagate
swell, combined with NE wind wave.

&&

.HYDROLOGY...
Flood watch remains in place across southeasternmost zones as a
period of heavy rain this afternoon may cause urban and small
stream flooding.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Winter Storm Warning until 6 AM EDT Sunday for MEZ007>009-
     012>014-018>022-033.
     Winter Weather Advisory until 2 PM EDT this afternoon for
     MEZ023.
     Flood Watch from noon EDT today through this evening for
     MEZ023.
     Winter Storm Warning until 6 AM EDT Sunday for MEZ024>028.
NH...Winter Storm Warning until 6 AM EDT Sunday for NHZ001>006.
     Winter Weather Advisory until 2 PM EDT this afternoon for
     NHZ012>014.
     Flood Watch from noon EDT today through this evening for
     NHZ012>014.
     Winter Storm Warning until 5 AM EDT Sunday for NHZ007>011-015.
MARINE...Gale Warning from 3 PM this afternoon to noon EDT Sunday for
     ANZ150.
     Gale Warning from midnight tonight to noon EDT Sunday for
     ANZ151-152-154.

&&

$$


NEAR TERM...Ekster
SHORT TERM...Ekster
LONG TERM...Cornwell


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