Scientific Forecaster Discussion
fxus61 kgyx 102004
Area forecast discussion
National Weather Service Gray ME
304 PM EST Sat Dec 10 2016
high pressure moves into the area tonight providing a mostly clear
sky, light winds, and very cold temperatures. High pressure will
move east on Sunday with continued cold temperatures over New
England. Low pressure moving through the Great Lakes Sunday night
into Monday will spread snowfall into northern New England as it
shifts toward the Gulf of Maine. There may be some areas along the
coast which mix with rain before precipitation ends Monday
afternoon. High pressure builds in behind the system for Tuesday.
A series of cold fronts Wednesday and Thursday will bring
progressively colder temperatures into the area.
Near term /tonight and Sunday/...
high pressure will nose its way into the area tonight, providing
calm winds and pretty good radiational cooling conditions for most
of the area. Still some uncertainty on whether clouds will
dissipate in the mountains or not. Clouds have hung on tough there
all day with temperatures holding steady. Upstream areas have seen
an abundance of cumulus clouds developing this afternoon, and this
low level moisture may remain locked in the upslope areas through
the evening. But with high pressure moving in, expect advection to
cease and clouds could dissipate. If they do, temperatures could
fall to near zero in the northern valleys, but if the clouds hang
on then temperatures may stay in the teens. Elsewhere, it should
be a fairly good radiational cooling night with most areas falling
into the single digits.
On Sunday high pressure shifts east and temperatures should warm a
few degrees. Still looking at highs below freezing, but a few
degrees warmer than they were today.
Short term /Sunday night through Monday/...
a low will develop across the Great Lakes and move across
northern New England bringing widespread snow from Sunday evening
into Monday. Overrunning precipitation ahead of the warm front
will move into southern New Hampshire late Sunday night and spread
across the entire region by daybreak. The cold high pressure from
the weekend will keep cold air lingering at the surface setting up
cold air damming. Even global scale models show hints of the high
pressure ridge and easterly surface flow along the interior of
Maine signaling the cold air dome. This cold air will be key to
the precipitation type. As the low center moves across the area
the warm sector aloft pushes northwards. The warmest option... the
NAM allows temperatures to reach +3c along the Maine coast.. while
the colder options keep temps below 0c through the entire column.
Have leaned towards the colder solution with just a minor warm air
intrusion and temps aloft reaching around +1c. The warmer solution
is quite aggressive but at the same time the colder solutions have
been trending warmer over the past few runs. A comfortable mid
ground keeps just a bit of mixing along the coast with a brief
region of sleet as the warm air aloft moves in during the day on
Monday. Through the interior the cold air aloft as well as the
surface cold dome keeps ptype all snow. As the low pressure moves
through the area Monday afternoon the precipitation will come to
an abrupt end as the dry slot moves in. A brief period of drizzle
across the south and freezing drizzle in the interior and
mountains is expected before the entire atmosphere dries out.
The cold air dome will also result in a surface coastal front...
expected to remain along I-95 in southern Maine and New Hampshire and
extending northeastward through rkd. Solid 20kt winds on the ocean
side of the front will help to maximize lift over the cold dome
and increase precipitation just inland. Have increased quantitative precipitation forecast
amounts a bit just inland of this line to account for this.
Long term /Tuesday through Friday/...
the coldest air so far this season is expected over northern New
England as temperatures at 850mb bottom out near -30 c over New Hampshire and
ME in the mid week timeframe.
Deterministic and ensemble means are in good agreement concerning
the cutoff low moving into Ontario on Monday night into Tuesday
morning....shifting into Quebec province by Thursday morning. This
particular upper low swings over the northern Great Lakes and
northern New England and towards Greenland by the end of the week.
As mentioned the main story with this system will be the extreme
cold which sets in as early as Wednesday night and trends colder
each day through Friday as reinforcing cold and dry air funnels in
from the north in a couple different waves.
In more detail, temperatures over the mountains will drop to single
digits Wednesday night, decreasing with each successive night
through Friday night until some locations reach as low as -15
degrees f. In the daytime hours northern sections will struggle to
make it above single digits for highs. Farther south...inland and
coastal sections will drop only reach the teens and 20s during
We will most likely need to issue a Wind Chill Advisory behind a
departing baroclinic zone associated with ejecting Atlantic low
pressure Thursday night into Friday morning. Would not be
surprised if other periods met Wind Chill Advisory criteria as
During this time mean cyclonic flow as well as upslope forcing will
bring periods of snow showers...especially for the higher terrain.
With extremely cold and dry air in place most snow will be of the
fluffy variety. The only places we may see rain would be offshore
early on, on the south side of the coastal front.
Ridging aloft arrives for next weekend. Another quick moving
frontal system affects the northeast during this time.
Aviation /19z Saturday through Thursday/...
short term...VFR conditions expected through tonight. Conditions
will rapidly deteriorate to IFR snow from west to east on Sunday
night and remain IFR through Tuesday. Wind shear will impact all
terminals on Monday as a low level jet of around 50kts moves through with
the low center.
Long term...periods of IFR/MVFR in snow showers are likely for hie
and perhaps leb Wednesday. Widespread snow showers are expected
Thursday bringing ceilings and visibilities down to LIFR/IFR.
Surface winds Thursday into Friday morning will gust into the
25-30 kt range.
short term...offshore winds gusting to around 25 knots will continue
into the evening before dissipating. Should see a window from
Sunday into Sunday night of fairly quiet conditions on the waters
before the approaching low tracks near the Gulf of Maine on
Monday. This should bring winds back up to near small craft
criteria levels for the waters.
Long term...Small Craft Advisory for winds may be needed Wednesday
into Thursday as low pressure passes southeast of the waters.
ME...Winter Storm Watch from late Sunday night through Monday
evening for mez012>014-018>028.
New Hampshire...Winter Storm Watch from late Sunday night through Monday
evening for nhz004-006-008>010-014.
Winter Storm Watch from Sunday evening through Monday evening
Marine...Small Craft Advisory until 10 PM EST this evening for anz150-