Scientific Forecaster Discussion
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Area forecast discussion
National Weather Service Gray ME
359 am EST Sat Jan 20 2018
a weak ridge of high pressure will build into the region today
with warmer temperatures than yesterday. A milder flow and
above normal temperatures follow for the upcoming weekend. A
storm system moving into the Great Lakes will bring wintry
precipitation Monday into Tuesday with temperatures warming. A
cold front Tuesday night brings colder air back into the region.
Canadian high pressure will gradually build towards the region
towards the latter half of the work week.
Near term /until 6 PM this evening/...
warm air aloft early this morning will be replaced by the first
in a series of cold fronts that will cross the region. Despite
cold air advection, downsloping and increasing sunshine will
allow for temperatures to climb into the 40s for most areas
today. Portland will reach around 48 degrees which is well short
of the record high of 55 degrees set in 2006. In the northern
mountains, expect mid to upper 30s for highs.
Scattered snow showers will occur over the upslope regions of
the mountains through this afternoon.
Short term /6 PM this evening through 6 PM Sunday/...
a secondary push of cold air associated with another weak cold
front will push through the region tonight. This will continue
the scattered snow showers in the mountains with mainly clear
skies in the south. The clearing conditions may allow for
readings to drop more quickly in a few of the more sheltered
Interior Valley locations.
This front will weaken and dissipate somewhat over southern
portions of the forecast area on Sunday. This front will set up
the boundary for the next system approaching from the southwest
in the extended portion of the forecast. Some overunning aloft
will allow for additional cloudiness and yet another chance for
snow showers in the far northern mountains. It will still be
above normal in terms of temperatures for this time of the year.
Expect highs in the 30s north to the lower 40s south.
Long term /Sunday night through Friday/...
a cold front will drop down into the northern part of the area
Sunday night and slide through the rest of the area on Monday
with a light northeast wind behind it as axis of Canadian high
pressure slides into northern Maine. Meanwhile, a large upper
level low pressure system will be moving into the Great Lakes.
Warm advection ahead of this system will bring some light snow
Monday night. Generally 1 to 3 inches expected across the entire
The wound up surface low moves into Ontario and Quebec and
occludes on Tuesday, with secondary low pressure forming along
the remnant cold front which will be trying to push northward as
a warm front. Unfortunately it won't make a lot of progress
inland across eastern New Hampshire and western Maine as
easterly low level winds promote cold air damming. Thus the warm
air will ride right over the top of the colder surface air just
as the next round of precipitation arrives with the main
synoptic system. Thus we should expect snow changing to sleet
and freezing rain for much of the area. Thankfully the light
snow preceding the freezing rain should limit the impact of the
icing, though up to a quarter inch of ice is possible in the
typical ice prone areas from Fryeburg to Augusta. The warm front
may make it into southern New Hampshire and push onshore at the
Maine coastline, allowing temperatures to warm well above
freezing, reducing the duration of freezing rain here.
Temperatures behind the warm/coastal front will warm into the
upper 40s to low 50s, but do not expect interior areas to
benefit from this until after the cold/occluded front moves
through Tuesday afternoon/evening.
Models have come into better agreement on the track and
especially the timing of this wave, though the details of the
cold air damming are notoriously difficult for models to pick up
on especially in the longer range of the forecast. All models,
however, do show the kinks in the surface isobars and northeast
winds in the interior, the best indicator that damming will be
present. The track of the newly emerging surface low runs just
inland of the coast, suggesting that coastal areas will indeed
see warming behind the coastal/warm front. However, would not be
surprised if this track shifts just a bit to the right as we
get closer in time and models start getting a better handle on
the low level cold air, so we cannot rule out the icing for the
Cold front pushes eastward across the area Tuesday night, but
the cold air will primarily be moving in aloft, with
temperatures at the surface not falling too much considering the
better mixing behind the front relative to ahead of it.
Secondary front drops in from the north on Wednesday bringing
better cold air and some snow showers. This cold lasts through
Thursday and Friday with highs below freezing and lows in the
single digits and teens.
Aviation /09z Saturday through Wednesday/...
short term...low level wind shear in most areas this morning in developing warm
air advection pattern.
Mainly VFR conditions across the region, however
northernmost regions such as hie and hie will likely have a
period of MVFR conditions in lower stratus and -shsn. Gusty SW
winds will develop today.
Long term...should see increasing clouds and lowering ceilings
Monday into Monday night with snow arriving from southwest to
northeast. Expect widespread IFR conditions with a wintry mix of
precipitation on Tuesday for most areas. Low level wind sheer
will be likely to the north of a warm/coastal front. A cold
front Tuesday night brings drier conditions and should see
ceilings improve to VFR at least by Wednesday except for
northern mountain areas.
short term...winds and seas will increase with a period of
scas, especially out over the outer waters. Winds may approach
gales, but we will only see 2-3 hours of them over the far outer
waters. Therefore, continuing with scas.
Long term...expect increasing southerly flow over the waters
ahead of a cold front on Tuesday. Winds will likely reach gale
force with a possibility for some storm force gusts in the
eastern waters. Winds shift to the west behind the cold front
Tuesday night with wind speeds possibly reaching gale force
many rivers continue to be affected by ice. With the upcoming
precipitation, it is possible that additional flow in these
rivers could cause renewed ice jam flooding Tuesday into
Marine...Small Craft Advisory until 6 PM EST this evening for anz151-
Small Craft Advisory until 6 am EST Sunday for anz150-152-154.