Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Gray ME
1227 PM EST Monday Nov 30 2015
high pressure will build over the region today and slowly move
offshore late tonight and Tuesday allowing a storm system to
approach from the west late Tuesday. Precipitation may start out
as some light freezing rain in the mountain valleys especially
near the Canadian border Tuesday night into early Wednesday.
Otherwise it will be mainly rain for most of the area. Colder air
begins arriving Wednesday night and may change precipitation over
to light snow before ending. High pressure then builds over the
region for the end of the week and into the weekend with pleasant
weather and moderating temperatures.
Near term /until 6 PM this evening/...
have updated grids based on current observational trends and
latest mesoscale model run. Cumulus field in the Gulf of Maine
continues to move embedded in the mean low level flow. Wind
direction should switch to the southeast by midday. This may bring
a few light flurries or scattered showers to the New Hampshire seacoast and
possibly over portions of York County today.
Otherwise...little in the way of changes to the grids. Some icing
is still expected over northern interior areas Tuesday night.
high pressure builds across the area today with very
dry air allowing sunny skies. Temperatures will be cool and below
seasonal levels. Used a blend of models for temperatures.
Short term /6 PM this evening through Tuesday night/...
high pressure begins centered over the area tonight...it will
slowly move offshore later tonight and Tuesday. With clear skies
and calm winds under the dome of high pressure tonight radiational
cooling will once again occur so temperatures will be quite cold.
On Tuesday models show the leading edge of the warm advection
clouds spilling across the upper ridge axis over the area and
spreading into southern areas by middle morning and further north and
east in the afternoon. There is a chance precipitation over
southern and western New Hampshire may begin late in the afternoon. Over
those areas temperatures aloft and boundary layer temperatures
both will be too warm so only rain would be expected. Due to the
cold start and the increase in clouds temperatures will be cool
but closer to seasonal levels.
Long term /Wednesday through Sunday/...
a prolonged period of southwesterly upper level flow is expected
within the warm sector of a slow moving upper level trough
tracking through the Great Lakes. Several rounds of light
precipitation are expected with generally weak waves of low
pressure tracking through the southwest flow. The entire area
should be solidly in the low/middle level warm sector Tuesday night
and Wednesday but surface temperatures will be a bit more tricky.
For Tuesday night... cool and dry air will be in place at the
surface when the warm advection precipitation begins arriving.
This is not a situation which screams cold air damming... as the
surface high pressure center will be well offshore. However...
temperatures will start off near or below freezing in
northeastern parts of the forecast area. With up to 60 hours of
subfreezing temperatures prior to the onset of precipitation in
the mountainous area of northwest Maine... it is expected that
ground temperatures will be cold even if air temperatures warm to
near freezing. Therefore a period of light icing is expected in
this area. Temperatures may be slow to warm on Wednesday as clouds
prevent any significant solar heating and warm advection pattern
promotes a surface temperature inversion. Valley locations will be
particularly vulnerable to continued light icing into the day
Wednesday. Total precipitation amounts will be fairly light so ice
accumulation will also be fairly light though accumulations of
around a tenth of an inch are possible.
Worth noting is that some models do track a slightly stronger
surface low a little closer to the coast Tuesday night with a
northerly wind flow over the coastal plain. If this were to
occur... then colder temperatures would be possible further south
with a period of light icing possible even as far south as
Lewiston and Augusta. But the greatest threat area is expected to
be in Somerset County and areas near the Canadian border.
Another wave will track northeast through the area Wednesday night
as the main upper low begins arriving from the west. Models vary
on the strength and placement of the surface low but generally
expect another round of light rain. Rain may change to snow before
ending as colder air begins arriving first aloft and then at the
surface late Wednesday night and into Thursday when the upper
low moves overhead. Best chance of any accumulation would be in
The upper low moves east Thursday night with cool surface high
pressure building in from the west and likely lingering into at
least early next week. Temperatures will be right around seasonal
normal levels or perhaps a few degrees above normal.
Aviation /18z Monday through Saturday/...
short term...VFR through Tuesday.
Long term... increasing clouds and showers will likely provide a
period of IFR or LIFR conditions Tuesday night through Thursday.
Precipitation may change to snow before ending on Thursday. High
pressure brings VFR conditions again for Friday.
short term...high pressure builds over the waters today and
tonight then moves east Tuesday. Winds and seas to be light
through Tuesday. No flags.
Long term... weak low pressure tracks near the Gulf of Maine
Tuesday night into Wednesday with another area of low pressure
tracking through Wednesday night into Thursday. Winds will shift
to the northwest behind the low on Thursday and could strengthen
enough to warrant a Small Craft Advisory into Thursday night.