Scientific Forecaster Discussion
fxus61 kgyx 180220
Area forecast discussion
National Weather Service Gray ME
920 PM EST sun Dec 17 2017
a weak area of low pressure will cross the region Monday
bringing some light snow to the region. Another low and
associated cold front will cross the area Tuesday with
scattered rain or snow showers. Colder weather returns for
Wednesday and Thursday as high pressure builds southeast into
the region. Another system will spread precipitation into the
area Friday night and Saturday.
Near term /until 6 am Monday morning/...
920 PM update...just a few minor adjustments to temperatures
for the next several hours based on latest trends in
observational data. Otherwise, forecast is on track with high
clouds moving into the region from the south and southwest.
6 PM update...little change to the going forecast. Have mainly
adjusted temperatures downward across mainly northern zones
where radiational cooling will occur longer ahead of the
advancing high cloud cover. Otherwise, forecast remains on track
with increasing high clouds as we progress through the evening.
Cirrus starting to roll in across the southern and western
zones, and this will progress slowly north and east overnight as
weak warm air advection begins aloft in advance of a shallow 500 mb wave
approaching from the west. Temps should drop off quickly this
evening in many spots, and lows will likely be reached by
midnight, with temps pretty steady after that. Mins will range
from around zero in the N, to 10-15 above along the coast and in
srn New Hampshire. Will like see some light snow start to break out in srn
New Hampshire and the CT valley toward daybreak, but most of the area will
be precip free overnight.
Short term /6 am Monday morning through Monday night/...
the snow will overspread the rest of the County Warning Area during the first
part of the morning with snow arriving everywhere before noon.
For the most part the snow will be light, as it is mostly being
driven by a broad area of weak warm air advection in the mid levels. Although
it will snow through most of the daylight hours, ending mid
afternoon in srn NH, and by early evening on the mid-coast, many
spots will come in with only around an inch. The exceptions
will be the mid-coast, as some stronger thermal circulations
develop around a developing low along the ME coast, but even
here, snow amounts are unlikely to be much over 2 inches. Also,
the mtns could see up to 2 inches as well. Highs Monday will
likely be late in the day, mostly in the 20-25 range inland
areas of ME and the nrn half of NH, and 25-30 near the ME coast
and in srn New Hampshire.
The snow should end in all but the mtns Monday evening. Shsn
could continue in the mtns overnight with some additional light
accums. Otherwise, look for clouds to linger, and temps to only
drop off a few degrees, as lack of flow keep inversion in place.
Expect lows in the mid-upper teens in the north to the mid 20s
in the south.
Long term /Tuesday through Sunday/...
as one weak system departs the area early Tuesday morning
another approaches from the west. Ahead of this second system,
temperature will warm above freezing across southern areas
Tuesday allowing for a mixture of precipitation across the
region. Precipitation should be fairly light with the greatest
threat for minor accumulations of snow in the mountains.
Mountain snow showers will continue into Wednesday as another
weak trough crosses the region and colder air starts to move
into the region from the northwest.
High pressure will build across the region for Thursday and
Thursday night bringing a return of cold temperatures. As the
high moves offshore Friday, warm advection on the back side of
the high will bring clouds into the region. At this time, it
looks like there will be enough dry air in the low layers of the
atmosphere to prevent any precipitation from reaching the
ground as a warm front moves north aloft.
The latest model runs are significantly different than those
from yesterday. Models are now tracking low pressure northeast
Friday and Friday night across the Great Lakes. This will allow
for significant warming across the region Friday night and
Saturday with moisture from the southeastern states moving
northeast along the frontal boundary associated with this low.
With warming temps, much of the precipitation Friday night and
Saturday would fall as rain in southern areas with precipitation
in the mountains possibly changing to rain, as well. Since this
is still almost a week away, there is plenty of uncertainty
involved in the eventual track of the storm and any impacts.
Aviation /02z Monday through Friday/...
short term...VFR through tonight. Terminals drop to MVFR in
light snow Mon morning, and will probably see IFR Mon afternoon
into Mon night with low cigs continuing despite the snow ending
around sunset Monday.
Long term...MVFR conditions possible in rain and snow showers
Tuesday and in snow showers in the mountains on Wednesday. VFR
conditions expected Thursday and Friday.
short term...waters remain quite tranquil through Mon night.
Long term...scas likely Tuesday afternoon through Wednesday.
Winds and seas below Small Craft Advisory criteria for Thursday and Friday.