Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Gray ME
1142 am EST Friday Dec 13 2013
weak low pressure and a cold front will cross the region today.
High pressure will build in from Canada late tonight and Saturday
morning then retreat to the north and east Saturday afternoon.
Low pressure will redevelop along the middle Atlantic coast Saturday
night before tracking northeast across the Gulf of Maine on
Sunday. High pressure follows this system for Monday and Monday
night. Another low will cross the region Tuesday night and early
Wednesday. A ridge of high pressure follows for Thursday.
Near term /through tonight/...
have updated the grids based on current observations and radar
imagery. Upslope snow showers will continue for several more hours
across the higher terrain. Some heavier snow showers making it all
the way to Southern York County and southern New Hampshire as
well. Wind chill advisories may be required for tonight as well.
No changes to the temperature and wind grids this morning.
updated to lower the chance of snow early this morning then
increase it somewhat for middle to late morning based on latest radar
trends. Otherwise a few tweaks based on latest observed data.
a weak low pressure system will track to the east just north of the forecast
area this morning. This will drag a trailing cold fnt east across the
forecast area this morning then out to sea this afternoon. This fnt
will bring some -shsn to the forecast area...mainly across the north/Montana
zones where light accumulations are possible. With very cold air in
place the snow will be light and fluffy...a 20 or 30 to 1 snow to
water ratio...so 1 to 3 inches are possible even though quantitative precipitation forecast
amounts will be very light...mostly under a tenth of an inch. The
highest summits could pick up even more. There is a chance of a
flurry or two even down toward the coast when the fnt moves through.
This system moves through quickly due to a strong westerly upper level
jet that will help support strong wind gusts during the day...both
ahead of the fnt...a SW wind...and behind the fnt...a west northwest wind.
Temperatures are actually rising in some locations prior to 3 am due to
increasing SW winds and some cloudiness. High temperatures will top out
ahead of the fnt in the north/Montana zones and perhaps after the fnt moves
by in southern and central areas where downslope flow will offset some
of the cold air advection. Looking for highs only 10 to 15 most
north/Montana locations...teens to near 20 in the foothills and in the 20s
elsewhere...warmest near the coast.
Short term /Saturday through Saturday night/...
high pressure builds in tonight allowing winds to drop off. With clear
skies and snow cover...though not real deep...should provide very
good radiational cooling. Temperatures will drop below zero most
everywhere away from the coast with 10 to 20 below zero north/Montana
zones and zero to 10 below elsewhere. Along the coast and extreme
southeast New Hampshire temperatures may fail to drop below zero...but won't miss it by
The high settles over the area Saturday morning with lots of
sunshine to start the day. The high begins to retreat to the north and
east Saturday afternoon as an upper level short wave lifts NE into the
region. Warm air advection begins late in the day as a storm
system gathers itself over the Middle Atlantic States. Thus expect
clouds to increase from S to north during the afternoon with snow
beginning to develop from S to north across southern and central New Hampshire and SW
and coastal ME during the late afternoon hours. Some light
accumulation possible over southern most New Hampshire by the end of the day...
but the main impact from this system will hold off until after 6
Long term /Sunday through Thursday/...
the models are in decent agreement on longwave pattern through early
next week. A persistent upper trough along with an extended period
of below normal temperatures can be expected this period. We begin
the period with phasing of northern and southern stream energy
that gives rise to a rapidly deepening coastal low that will track
just inside the favored 40n/70w benchmark on Sunday. This track
would result in a plowable snow event for the entire forecast
area. Given forecaster confidence a Winter Storm Watch has been
posted for the entire County Warning Area with the new public package this
morning. Some lingering clouds and mountain snow showers Sunday
night into Monday with the upper trough and upslope flow. A ridge
of high pressure then crests across the area for Monday night and
early Tuesday. Another impulse and associated weak surface low
will cross the region late Tuesday through early Wednesday.
Aviation /18z Friday through Wednesday/...
short term /through Saturday/...VFR today except MVFR ceiling and
visibility in -shsn activity in the north/Montana areas...impacting hie and
possibly affecting leb. SW winds shift to west northwest and become very
gusty today due to increasing pressure gradient lining up with strong
westerly flow aloft in association with strong upper level jet. VFR
tonight and Saturday morning as high pressure builds in. High retreats to
the north and east Saturday afternoon as a developing storm system to our
SW begins to spread clouds then -sn northward into the forecast area. This
will lower ceiling/visibility from S to north later in the afternoon...
especially over more southern areas.
Sat night - sun...IFR likely in snow.
NE surface wind gusting to 30 knots along coast.
short term /today through Saturday/...will update to input latest
observed data resulting in a few tweaks to the previous forecast. Cold
fnt moves through today. Strong SW flow ahead of the fnt shifts to
the west northwest. Strong upper level westerly jet will help winds to mix down
creating frequent gale force gusts over the open waters. Even the
bays may see a few gusts to 35 knots. Strong cold air advection over
warmer water will continue the strong gusts into this evening even though
the pressure gradient begins to weaken. Will continue the glw open waters
and an Small Craft Advisory for the bays through 7 PM this evening. Winds and seas drop
off tonight and Saturday as high pressure builds in.
Sat night - Monday...gales likely with gusts near storm possible
outside the bays.
ME...Winter Storm Watch from Saturday evening through Sunday
evening for mez007>009-012>014-018>028.
New Hampshire...Winter Storm Watch from Saturday evening through Sunday
evening for nhz001>010-013-014.
Marine...Small Craft Advisory until 7 PM EST this evening for anz151-
Gale Warning until 7 PM EST this evening for anz150-152-154.