Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Gray ME
638 PM EST Monday Nov 30 2015
high pressure will 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 a period of snow Thursday before
ending as another area of low pressure intensifies over eastern
Maine. High pressure then builds over the region for the end of
the week and into the weekend with pleasant weather and moderating
Near term /until 6 am Tuesday morning/...
stratus deck remains and moisture continues to move in from the
SW. Models show this trend continuing overnight with a finger of
moisture along and just off the coast. Another area of stratus
over Canada is moving into northern sections of New Hampshire and western
Maine. As pointed out in a previous discussion... this makes the
overnight low forecast challenging. It appears we will have some
areas cooling while others remain more stable under cloud cover.
Well after midnight when many areas might see low temperatures
under normal radiational cooling conditions warm air advection
will actually make temperatures increase... at least over New Hampshire.
Tried to show this trend in the nocturnal curve for temperatures
and dew points overnight. Also adjusted cloud cover as don't think
the deck(s) are going to go away in some spots.
Previous discussion... complex cloud and therefore min
temperature forecast for tonight across western Maine and New
Hampshire. Boundary layer winds have switched to the
south...allowing low level moisture to pour in off the Atlantic
Ocean. A 3500 foot cloud deck will continue to slowly migrate
north this evening...possibly becoming trapped under the inversion
This low level cloud deck will make for challenging overnight mins
for tonight. Areas to the north which are clear will radiate very
quickly...with temperatures dropping fast through the teens. The
coast of Maine and southern New Hampshire should remain quite a
bit warmer with less radiational cooling limited to after
Have not seen any precipitation despite echoes on latest 88d imagery.
However...would not be surprised if a couple flurry reports come
Short term /6 am Tuesday morning through Tuesday night/...
clouds advance and thicken from west to east on Tuesday. Areas of
rain with patchy freezing rain will break out later in the day
over central/northern New Hampshire before spreading east. Thermal
profiles suggest a deep warm layer aloft with temperatures just
below freezing at the surface over the mountains and well into the
interior. Will continue forecasting the threat of freezing rain as
a weak area of low pressure crosses through the Gulf of Maine
Tuesday night. With marginally cool temperatures...we mainly
expect only up to a tenth inch of ice with this system.
However...we will continue to monitor as confidence levels remain
low for ptype and amounts of liquid equivalent.
GFS/Euro solution appear to be the most reasonable in terms of
quantitative precipitation forecast. 12z NAM appears to wet for this scenario.
Long term /Wednesday through Monday/...
focus of the extended is on the first couple of periods through
Thursday...after the initial wave passes to the NE. A secondary wave
will develop along the front and ride northeastward into New England. After
a brief break in precipitation...or drop in intensity...another batch of
precipitation moves in Wednesday evening. Mild air will still be in place
aloft...so expect mainly cold rainfall. Upper low pressure will move
towards New England by early Thursday. As it does so...heights and
temperatures will crash quickly behind the secondary wave. In the northern
zones a change over to snowfall is possible.
Recent model trends...including gefs...have been towards a
stronger secondary low pressure in or near the Gulf of ME. As the 500 mb
low catches up to the surface low...rapid development takes place over
eastern ME. Currently...the 30.12z European model (ecmwf) is the strongest with this
evolution...throwing significant quantitative precipitation forecast back into parts of west central
ME. With sub-freezing temperatures surface and aloft in place...the trend has
been towards a plowable snowfall for at least the mountains of ME.
However...at this range it is still entirely possible that
development occurs too far east to bring enough precipitation for
appreciable accumulations in our forecast area.
Beyond Thursday...high pressure builds in and will more or less control the
weather for the remainder of the extended. A couple of weak frontal
passages are suggested in the guidance...over the weekend and
early next week...but little weather is expected outside of mountain snow
Aviation /00z Tuesday through Saturday/...
short term...a few areas of MVFR expected over southwest Maine as
well as southern/central New Hampshire as cumulus fields continue to
move inland from the Gulf of Maine. Areas of IFR developing in
rain south Tuesday night with freezing rain well to the north.
Long term...widespread MVFR conditions are expected Wednesday as
secondary wave of low pressure moves northeastward along the East Coast. Areas
of IFR will be possible in the heavier precipitation. Early Thursday
intensification of low pressure may bring a change to snow as far S as
Aug...which would extend IFR conditions. Upslope shsn will also
develop around hie and linger into Thursday night.
short term...conditions will remain below Small Craft Advisory levels.
However...low level cumulus fields will remain over the waters with
perhaps sprinkles or flurries tonight and Tuesday. Rain arrives
Long term...with low pressure forecast to develop in the Gulf of ME
Thursday...winds and seas will build to Small Craft Advisory thresholds. There is a low
probability for gales...dependent on strength and track of low
pressure. Small Craft Advisory conditions will linger into the weekend before high pressure
allows winds and seas to diminish.
November 2015 is in the top 10 for warmest ever.
Portland will most likely come in at the 4th or 5th warmest ever.