Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Gray ME
534 PM EST Tuesday Dec 1 2015
a storm system will approach from the west tonight. Precipitation
will start out as some light freezing rain away from the coast...especially
in the mountain valleys and near the Canadian border tonight.
Otherwise it will be 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 temperatures.
Near term /until 6 am Wednesday morning/...
630 PM...i've expanded the area of freezing rain advisories and
extended the advisory times as well...since temperatures will be
slow to warm overnight and precipitation is quicker to push north
and east across the forecast area.
frontal lobe of baroclinic Leaf structure has now moved into New
England in advance of a large upper low moving into the Great
Lakes region tonight. First in a wave of warm air advection
showers is moving through New Hampshire and into western Maine. Mixed
precipitation has been occurring all day with this activity as
temperatures struggle to rise above freezing. As warm air advection increases
overnight precipitation will change to all rain with the last
place to change over being the Carrabassett Valley. The good news
is roads were relatively warm before the precipitation started. We
have received reports of accidents however due to the Road
conditions...so going slow or delaying travel is advised. Areas
closer to the coast may contend with fog and drizzle later tonight
as ceilings lower.
For southern and central New Hampshire....
Warm air advection was stalled and thus temperatures remained
below freezing for much of the day across southern and central New Hampshire.
As south winds slowly become established temperatures are coming
up over most of the region save for a few pockets of sub freezing
air. A Freezing Rain Advisory continues for much of New Hampshire **not
including northern Coos...Rockingham...or York counties** through
7 PM for slick roadways and bridges. These areas may see anywhere
from a trace to a tenth of an inch through 7 PM.
For northern Coos as well as northern Oxford...northern
Franklin...and northern Somerset...
A Freezing Rain Advisory begins at 7 PM and continues through 4
am...as these areas hover around freezing before rising above 32
degrees later tonight. These areas may see between a tenth and
two-tenths of an inch of ice.
Short term /6 am Wednesday morning through Wednesday night/...
isentropic lift increases into tomorrow and we will see a day of
steady light rain with temperatures only warming into the 40s.
Categorical probability of precipitation continue into Wednesday night as the upper low
sharpens over the Great Lakes and secondary cyclogenesis occurs.
We should see around 0.75" to an inch of rain Wednesday through
early Thursday morning. The secondary cyclogenesis will help to
pull colder air into the New Hampshire and Maine as it races east Thursday
morning...allowing some snow to begin to fall in the north and as
far south as The Notches.
Long term /Thursday through Tuesday/...
model guidance continues to favor rapid low pressure development Thursday
as upper trough catches up to surface low center across New England. Middle
level low centers are forecast to track across southern New Hampshire and into
southwestern ME...before deepening over downeast or the Gulf of ME. This
will be favorable for strong frontogenesis to the northwest of those low
tracks. At this time...model guidance is in fair agreement that
this places our northern most zones in the best lift. By this time cold
air will have filtered in at the surface...and temperatures aloft will have
crashed quickly towards the coast as middle level lows develop and
pass east. Expecting that precipitation will transition quickly from rainfall to
snowfall north to S early Thursday. Based on middle level low tracks and
resulting forcing...00z model suite seemed too high on quantitative precipitation forecast. 12z
has corrected down some...especially S of the mountains /which is also
along and S of the middle level features/. A blend of
GFS...ECMWF...and wpc quantitative precipitation forecast was used in the forecast...with an
upslope enhancement in the mountains where trapped low level moisture will
be forced over the terrain. In the end a light to moderate snowfall
is appearing more likely...especially the higher in elevation one
GOES...where the cold air arrives earliest. Based on forecast
quantitative precipitation forecast...warning level amounts look unlikely...though isolated 6 inch
reports in the mountains would be possible.
Beyond this middle week system high pressure is forecast to build in.
Ensemble guidance also predicts this to be quite strong ridging
for this time of year. So the trend will be drier through the
weekend...with seasonable temperatures. A multi-model consensus was used
for the forecast with the focus on Thursday weather.
Aviation /00z Wednesday through Sunday/...
short term...conditions will vary from VFR to IFR from east to
west tonight...but all terminals will eventually become LIFR or
IFR in moderate rain or -frza. Drizzle and light rain is more
likely towards morning and into tomorrow afternoon.
Long term...widespread MVFR and areas of IFR will continue across
the forecast area behind one wave of low pressure and during a second
wave. The secondary low pressure will bring a round of snowfall to parts
of northern New Hampshire and western ME...with IFR snow or shsn possible at hie and as
far S as Aug. High pressure builds in for the weekend and
beyond...with VFR conditions expected.
short term...Small Craft Advisory continues for seas through tomorrow evening as
waves increase ahead of low pressure.
Long term...gale force wind gusts are possible Thursday as low pressure
rapidly deepens in the Gulf of ME. High pressure build in for the
weekend...and winds and seas gradually subside.
ME...Freezing Rain Advisory until 10 PM EST this evening for
Freezing Rain Advisory until 4 am EST Wednesday for mez007>009.
New Hampshire...Freezing Rain Advisory until 10 PM EST this evening for
Freezing Rain Advisory until 4 am EST Wednesday for nhz001.
Marine...gale watch from Thursday afternoon through late Thursday night
Small Craft Advisory for hazardous seas from 10 PM this
evening to 7 PM EST Wednesday for anz150-152-154.