Scientific Forecaster Discussion
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Area forecast discussion...updated
National Weather Service Gray ME
831 PM EST Thu Nov 14 2019
some very light snow will cross parts of the area early this
evening before we dry out. We will be a little warmer Friday but
this will be occurring ahead of a strong cold front. The front
crosses the area with snow showers and squalls along with
sharply falling temperatures. Expect to fall back into the teens
and single digits again Friday night. Below normal temperatures
stick around through the weekend with a warming trend and a
return to active weather next week.
Near term /until 6 am Friday morning/...
830 PM update...
updated to include a few higher pops along an area of increased
moisture convergence/frontogenesis near the coast. This
developing trough is sustaining some scattered light snow
showers primarily across the capital district and towards the
coast from Portland towards downeast. Any accumulations in
western ME will be confined to the mid coast where moisture and
forcing is better. Also adjusted winds and sky cover for this
update. Overnight lows were dropped at a couple sites which had
already reached their forecast lows, including Berlin, New Hampshire.
540 PM update...
have adjusted pops, qpf, and snowfall totals for portions of
Grafton and Carroll counties in New Hampshire where more snow has fallen
via web cams than forecast. These snow showers are lightening
and moving east and will continue to drop light snow as they do
so the next couple of hours. Overnight sky cover will be
diminishing from the southwest as drier air works in. Low
temperatures look good at the moment will keep an eye on them if
skies clear faster or slower than expected.
early this evening we should continue to see very light snow
across much of the nrn half of the forecast area. This is due
mainly to a couple of moist layers within the warm air advection regime. Weak
lift in the layer around 10000 ft is likely producing some ice
crystals which are falling into the shallow low level clouds.
This is leading to light snow but unlikely to see much
accumulation...if any outside of the mtns.
With increasing clouds and light sly flow the temps overnight
will be much warmer than last night...which is not saying much.
Will have to watch the amplification of a weak wave offshore
late tonight...as some guidance is indicating that it will try
and work some moisture back towards the midcoast. I have light
snow accumulations there confined mainly to the immediate coast.
Short term /6 am Friday morning through Friday night/...
the main story Fri will be the strong cold front set to cross
the area late in the day. All signs point towards a sharp
boundary approaching the area from the northwest around 7 PM. There are
plenty of ingredients in place for snow squalls...including
temps near freezing crash below behind the front. Given the set
up a couple snow squall warnings are not out of the question.
For starters I blended in some higher-res guidance to capture
the progression of the boundary in the pop fields. I suspect we
will be able to further refine that motion tonight and with the
early forecast updates Fri. I also used a non-diurnal temp trend
late in the day. S of the front will remain in the 30s...with
temps quickly falling thru the 20s behind it. I also blended in
some raw 2 M temp guidance Fri night...as the cold air advection should keep
the boundary layer fairly well mixed and stave off any
radiational cooling effects.
Long term /Saturday through Thursday/...
overview: surface high pressure builds into New England on
Saturday and settles overhead Saturday night, favoring another
cold night for the middle of November. Sunday sees the high
pressure lift northeast as a broad trough moves into the Great
Lakes region. That trough remains there through Tuesday night,
driving a series of coastal lows up the Atlantic coast that look
to generally be low-impact for our region. After a chilly
start, temperatures will gradually warm each day through the
Impacts: no significant impacts anticipated on land at this time,
but the coastal systems next week will be monitored as any
westward changes in track could lead to impacts.
Details: Saturday morning will begin with our region in the wake
of an Arctic front and surface high pressure building into New
England. Expect a clear and sunny day, even in the mountains
with no precipitation. The high should be nearly overhead
Saturday night, and with clear skies Saturday evening,
temperatures will likely drop quickly after sunset and
conditions will be near ideal for radiational cooling. The only
complicating factor is clouds expected to move in after
midnight, especially in southern portions of the region, may cut
off the cooling thereafter. All that said, blended guidance
that weighted some cooler solutions a little more heavily and
came up with near zero in the mountains to the lower to mid
teens along the coast and in southeast New Hampshire. This will easily be
the coldest night of the long term period.
Sunday sees the surface high move northeast as an upper level low
moves up the Atlantic coast and a broad upper level trough
enters the upper Midwest/western Great Lakes. The trough will be
the primary influence on our weather through the rest of the
period as the upper lows looks to pass to the east of the
benchmark Monday night. Over land, clouds will build along the
ME coast and in southern New Hampshire on early Sunday, gradually spreading
northward into the mountains late Sunday evening. We should
remain dry during the day, but precipitation chances are
introduced Sunday night as the low approaches.
The rest of the forecast is rather low confidence as the pattern
becomes a little more active and unsettled. Monday looks rather
cloudy with a mix of rain and snow showers. The low pulls
northeast on Tuesday, but the upper trough over the Midwest digs
south toward the southeast U.S. And slowly moves east through
Wednesday night. The trough picks up on a southern stream
disturbance and it then races up the Atlantic coast late Tuesday
through Wednesday. Stuck pretty close to the long-term model
consensus pops Monday through the end of the period, which
results in chance pops for most of the region each day. Also
stuck with snow/rain showers or a mix of the two for weather as
there sill be ample time to fine-tune p-types as this part of
the forecast comes into better focus.
Saturday looks to be the coldest day of the period as we
experience a gradual warming trend that ends with temperatures
close to normal in the early-mid part of next week.
Aviation /01z Friday through Tuesday/...
short term...local IFR in the mtns early this evening as -sn
crosses the area. Will have to watch for a period of IFR in -sn
at rkd this evening in a window from 23z to around 5z. Otherwise
conditions are expected to be VFR or trending to VFR overnight.
A strong cold front and sharp wind shift will cross the area
from northwest to southeast early evening Fri. Local IFR or lower conditions
are possible in shsn along the front as well as surface gusts to
25 kt in the vicinity of any shsn.
Long term...with high pressure building in, generally calm winds
and VFR conditions expected at all terminals through Sunday.
MVFR conditions expected at the southern New Hampshire and southwest ME
terminals beginning Sunday night as clouds move in from the
south; these conditions gradually spread to all terminals by
Monday morning. Unsettled Monday through Tuesday night as clouds
dominate and -shsn/-shra bring occasional IFR conditions to all
short term...Small Craft Advisory conditions will develop tonight in SW flow. A
gale watch has been issued for strong northwest wind gusts behind a
strong cold front Fri night.
Long term...gales likely to be in effect for the outer waters
Saturday morning, but winds diminish below 25 kt by Saturday
evening. Winds and seas build again late Sunday through Monday
with seas to 10-11 ft possible on Monday. Conditions begin to
improve on Tuesday and remain below Small Craft Advisory criteria through the
rest of the period.
Marine...Small Craft Advisory until 6 PM EST Friday for anz150>154.
Gale watch from Friday evening through Saturday morning for