Area Forecast Discussion
Issued by NWS Portland, ME

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697
FXUS61 KGYX 301409
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
1009 AM EDT Thu Mar 30 2017

.SYNOPSIS...
High pressure will gradually build in from the northwest today.
Expect a mostly sunny day with temperatures near normal for
this time of year. Low pressure tracking through the Ohio Valley
will track off the southern New England coastline Friday night,
spreading snow through northern New England which will last
through the day on Saturday. There may be some rain near the
coast. High pressure follows quickly on the heels of the
departing low Sunday into Sunday night. The next low pressure
system will track south of our area on Tuesday with possibly another
chance of rain or wintry precipitation.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
1010 AM Update...Just a few minor adjustments to the going
forecast at this hour. Have added more cloud cover to
eastern/northern zones as moist low level cyclonic flow is
bringing bkn strato-cu into that region. Otherwise, increased
wind gusts a bit for today with observed gusts around 25 MPH.
Otherwise, no changes to winter storm headlines at this time -
will be assessing new data over the next several hours and try
to pin down model trends in low track and temperature profiles.

7am update... Minor update for current conditions and to drop
the Small Craft Advisory for the bays as winds have decreased.

Today will be the sun before the storm as weak high pressure
will crest over the region this afternoon with partly sunny
skies and temperatures approaching 50 in the south and upper 40s
north.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/...
Snowstorm Friday night into Saturday for southern NH and
interior western Maine...

Complex scenario is continuing to evolve for Friday night into
Saturday. Low pressure currently over Omaha will move
northeastward over the next 24 hours before deepening and
redeveloping off the coast of New Jersey on Saturday. This will
spread precipitation into western New Hampshire on Friday
morning and eastwards into Maine by Friday evening. Snow will
become heavy at times overnight. The low will move east Saturday
bringing snow to an end.

Track forecast has increased over the past day and confidence is
now high that the low will move nearly dead east from New Jersey
passing south of Long island and out to sea. Despite the track
confidence considerable uncertainly still exists in the amount
and location of the heaviest precipitation and the precipitation
type.

The more easterly track of the low lends of a sharp cut off in
the amount of precipitation occuring within our CWA. And in fact
precipitation amounts vary from 1.5 - 2 inches along the
Massachusetts/New Hampshire border in the CT river valley where
there is the highest confidence on high amounts to a widely
varying low confidence 0.25-1.25 inches near Jackman in the
Northeast. Most of the variability in amounts is due to the
northeastward extent of the heavy precipitation shield and I
have leaned towards the Euro for the extent of precipitation as
a middle ground between the wet NAM and drier GFS.

The uncertainty doesn`t end with amounts; ptype is still a
concern. Temperatures will be hovering near freezing for most of
the event with the wet bulb temperature as the driving factor
between rain and snow. Just to add some fun there are some hints
at a warm nose to the south which would cause sleet to mix in
along the mass border. Overall have leaned cold with the
temperatures and thus more towards snow and expect and mixing to
go rapidly over to snow as the heaviest amounts move in late
Friday evening.

With so many more questions than answers have opted to hold onto
the Winter Storm Watch with this package but have expanded it
into interior western Maine where the temperatures and
precipitation amounts support over 6" of snow.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
A few upslope snow flurries and scattered snow showers will
develop across the highest terrain Sunday night as the system
exits off the east coast. That leaves the forecast area with
dry, high pressure over the region on Monday.

Next system approach from the south Monday night. There is
considerable model to model and run to run differences with the
track of this system with the GFS and GGEM bringing some
precipitation to the region on Tuesday, while the Euro remaining
further to the south. The general track coming out of the
southeastern states is similar to our Friday/Saturday threat,
however with next weeks system, low level temperatures appear to
be a few degrees warmer than this weeks.

High pressure will follow on Wednesday with little in the way of
cold air associated with it. This sets the stage for another
system passing by to our west as our active pattern continues.

&&

.AVIATION /14Z THURSDAY THROUGH MONDAY/...
Short Term... VFR conditions will continue today with a slight
chance of MVFR in the mountains this morning as upslope flow
continues. Friday will see conditions rapidly deteriorate to IFR
in snow from west to east. Coastal terminals may see a mix of
rain but interior will be snow. LIFR possible overnight Friday
night into Saturday in snow. Snow will come to an end on
Saturday returning conditions to MVFR and then VFR.

Long Term...Generally VFR conditions through the period.
However, ceilings and visibilities will potentially drop on
Monday night and Tuesday as a system approaches from the south.

&&

.MARINE...
Short Term... Will hold onto the SCA on the ocean waters today.
High pressure crests over the region before the next storm
brings marginal gale conditions for Saturday night.

Long Term...Mainly conditions below SCA through the period.
However, southeasterly winds will increase Monday night into
Tuesday, with SCA conditions and possibly brief gusts into gale
force.

&&

.TIDES/COASTAL FLOODING...
A very high astronomical tide will occur early Friday morning
with 11.1` expected in Portland at around 06Z. Onshore winds and
seas will just be beginning to develop at this time. Northeast
flow will be more pronounced during the Saturday afternoon high
tide which is lower at 10.3`. Expect about a 0.5 to 1.0 storm
surge at that time which would bring the storm tide to around
11.0 feet or so. With waves only running 5 feet or so at the
time, splash-over nomograms suggest to only expect little or no
impacts along the coastline.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Winter Storm Watch from Friday afternoon through Saturday
     afternoon for MEZ012-018-019.
NH...Winter Storm Watch from Friday morning through Saturday
     afternoon for NHZ003>013-015.
MARINE...Small Craft Advisory until 8 PM EDT this evening for ANZ150-
     152-154.

&&

$$

NEAR TERM...Ekster



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