Area Forecast Discussion
Issued by NWS Portland, ME-- Highlight Changed Discussion --
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FXUS61 KGYX 291705
Area Forecast Discussion
National Weather Service Gray ME
105 PM EDT Wed Mar 29 2017
Behind a departing low pressure system, a northwesterly flow
will introduce cooler and drier air into the region today. High
pressure will build into the region for Thursday. Low pressure
will then approach the region for late Friday into Saturday
with snow and mixed precipitation likely for the region.
Canadian high pressure will then build into the region on
.NEAR TERM /TODAY/...
-- Changed Discussion --NOON UPDATE...
Band of light rain along a convergent zone has shifted slightly
east of its earlier semi-permanent location. Expect it to
dissipate soon as it has lost its terrain enhancement. More
light snow showers moving in from the north will be affecting
the mountains of New Hampshire and western Maine soon. Have made
adjustments to hourly precipitation chances, but otherwise no
significant changes were needed.
945 AM UPDATE...
A few minor adjustments, mainly to PoPs and temperatures for
today. Mostly dry weather is expected outside of nwly upslope
regions in the mountains. However, for the next hour, a very
narrow convergence band of rain showers across Franklin,
Androscoggin, and Cumberland Counties should persist for a
little bit, then dissipate. Otherwise, we raised snow amounts a
little bit for Fri night- Sat, but a full perusal of the 12z
data is needed to assess trends with the upcoming storm.
730 AM UPDATE...
Minor update to current conditions. Fog has lifted along all
but the immediate coast.
5 AM UPDATE...
Just an adjustment to the rain as the showers are now almost
off shore. Fog is beginning to dissipate along the Vermont
border as the low moves out.
As of 3am, very damp and foggy conditions across Maine and New
Hampshire. Temperatures are in the mid 30s across the region
with dewpoints similar. With most of the region still covered in
snow this relatively warmer air has resulted in patches of dense
fog. This fog will dissipate in the early morning with the
morning sun and developing drier flow.
A low center moving northeast through the Gulf of Maine today
will bring showers to coastal Maine and New Hampshire through
mid morning. As the rain departs northwesterly flow will develop
brining drier conditions. Clouds will slowly clear in the south.
In the mountains a few upslope showers will develop.
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.SHORT TERM /TONIGHT AND THURSDAY/...
High pressure will build in for tonight and Thursday. High
temperatures will return to the mid 40s south to upper 30s north
with mostly sunny skies and light winds.
.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Still some uncertainty with upcoming storm system at the end of
this week in terms of snowfall projections.
Canadian high pressure will remain entrenched over the forecast
area on Thursday. It will gradually retreat to the north and
east on Friday as low pressure exits the Ohio Valley.
00Z operational model suite and ensemble members are in better
agreement tonight bringing low pressure to the New Jersey
coastline Friday night where it will undergo only some modest
intensification. Nevertheless, prolonged period of northeast
flow and warm air advection pattern aloft may very well allow
for steady precipitation Friday into Saturday. Model QPF does
vary however with the Euro being the wettest at this time.
Boundary layer temperatures may be an issue over southern areas
are they often are in the late March and early April time
frame. Used ptpye from wet bulb for the initial portion of the
forecast. As the system departs on its easterly track late
Saturday, a plowable snowfall is possible, mainly over interior
locations away from the shoreline.
Canadian high pressure will then reassert itself on Sunday as
more cold air and near or slightly below normal temperatures
advect into the region. This sets the stage for another possible
repeat with low pressure passing by to our south during the
middle of next week. Temperatures initially look a little warmer
for this second event.
.AVIATION /14Z WEDNESDAY THROUGH SUNDAY/...
Short Term...Generally MVFR through New Hampshire and towards
the northwest of Maine. The low bringing all this moisture will
move off shore today and expect conditions to improve to MVFR
region wide by mid morning. Conditions will continue to improve
into Thursday with just a chance for MVFR ceilings in snow
showers near the international border.
Long Term...IFR conditions developing Friday with area of LIFR
over southern areas possible. These conditions will continue
into Saturday as low pressure passes by to our south. Conditions
improve to VFR on Sunday.
Short Term... Generally calm waters currently. Expect winds to
pick up this afternoon under northwesterly flow as the current
low departs. A Small Craft Advisory has been issued beginning
late this afternoon and extending through the overnight hours.
There isn`t really an upper level jet to mix down any strong
winds but cold advection should be enough to reach SCA even in
Long Term...SCA conditions may occur Friday night into Saturday
as low pressure passes by to our south. SCA conditions possible
once again midweek, next week as yet another area of low
pressure passes by to our south.
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 running 5 feet or so at the time,
splash-over nomograms suggest to only expect little in the way
of issues along the coastline.
MARINE...Small Craft Advisory from 5 PM this afternoon to 8 PM EDT
Thursday for ANZ150>154.