000
FXUS61 KGYX 220127
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
827 PM EST Fri Feb 21 2020

.SYNOPSIS...
High pressure will remain in control of the weather across
northern New England through the weekend. Temperatures will
begin moderating tonight with above normal temperatures
continuing through the beginning of next week. By the middle
and latter portions of next week, a series of weather systems
will likely bring a period of unsettled weather.

&&

.NEAR TERM /TONIGHT/...
830PM UPDATE...
Updated again to bring low temperatures down a bit more in some
of the cold spots. Berlin and Whitefield already closing in on
the zero degree mark as of 8PM. With no clouds in sight, expect
these great radiators to frost right through their low level
dewpoint and approach 10 below zero. Other areas which have a
good chance of seeing zero degrees again include Fryeburg,
Lewiston, and Plymouth.

6PM UPDATE...
There`s not a cloud in the sky this evening. Regional satellite
shows even upstream this is the case all the way to James Bay.
Low level dewpoints remain quite dry... around zero degrees, and
winds are even lighter at this hour than they were last night at
this time. Thus expect excellent radiational cooling conditions
tonight and northern valleys should fall to around zero.
Dewpoints are a bit higher than last night and we are starting
out a bit warmer as well, so it won`t be quite as cold as last
night. However, it will still be quite chilly. I`ve made
adjustments to the forecast to reflect the idea of even colder
temperatures. Even though some warm/moist advection begins aloft
tonight, this should happen above the low level inversion and
allow ground level to stay calm and cold.

ORIGINAL DISCUSSION...
High pressure was anchored over the south central states today,
with the northeastern extent pushing into New England.
Subsidence provided sunny skies along with light winds. After a
cold start, temperatures have warmed into the low to mid 20s at
most locations across NH and ME, with a few of the warmer spots
in the upper 20s.

Given the very dry air mass /KGYX sounding from 21.12Z shows
precipitable water values of 0.04 inches/ temperatures tonight
will drop quickly under clear skies and light winds...however it
won`t be as cold as it was last night. Most spots will be in the
8 to 15 degree range for lows, as compared to many observations
in the negative single digits last night.

&&

.SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/...
The center of the large high pressure system will shift east
towards the SE CONUS on Saturday. This will allow for more
downsloping westerly flow over northern New England, which will
help bump temps up. In addition the colder air around T9 will be
gradually eroding from the SW. Saturday`s highs will be about
10 degrees warmer than today, and is part of a warming trend
that will continue for several days.

A weak surface trough will shift into the White Mountains from
Canada and move SE during the day Saturday. This will
essentially make for increasing cloudiness for the foothills and
mountains, and perhaps a few flurries along the international
border. Elsewhere there will be little impact. Overnight lows
will be in the teens and lower 20s Saturday night

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
The long term forecast period will start off with a broad area of
high pressure over the southeast US stretching into the western
Atlantic. New England will be on the northwest periphery of
this high with return flow allowing for several days of well
above normal temperatures going into the first half of next
week. Towards the middle of next week a split flow pattern at
500 mb will become more consolidated with a trough developing
over the central US leading to a period of active weather the
middle to second half of next week. There is chance during the
second half next week that an impactful system will develop near
the Mid-Atlantic and track towards New England.

The last several runs of deterministic and ensemble guidance
have shown that a period of active weather is likely toward the
middle to late next week as a deep 500 mb trough develops over
the central US and moves eastward. There has been some
uncertainty in the evolution of this trough leading to
uncertainty in the strength and track of next week`s potential
one to two systems. The 12Z model suite is in fairly good
agreement that the first system will be weak and pass to our
south bringing only a chance of precipitation late Tuesday. A
second system will follow Wednesday night into Friday morning
with a fair amount of uncertainty in p-types. Ensemble solutions
have the track of the second system ranging from well southeast
of the 40/70 benchmark to the Great Lakes. Another factor
complicating p-types is that temperatures early next will be
quite mild for this time of year with highs approaching normal
values for late March as opposed to late February.

The uncertainty in the extent of frozen p-types with the
potential system late next week lies in three waves at the 500
mb level...all of which are currently in the RAOB data sparse
Pacific. The first wave will be a northern stream short wave
moving into British Columbia Saturday. This wave will race
across southern Canada leading to a weak low passing to our NW
Monday night. This low will have a cold front behind it and the
question remains whether this cold front can push far enough
south into our area ahead of our potential system(s). The next
wave of interest is a closed 500 mb low that will also move
onshore Saturday into southern California. This 500 mb low will
slowly move into the Mississippi Valley Monday and open up as it
does so. The third and final wave is currently south of the
Aleutians and will move into the Pacific NW late Sunday night.
This wave will dig down the Rockies Monday and interact with the
opening closed low carving out the long wave trough over the
central US Tuesday. Ensemble sensitivity experiments are putting
emphasis on this third wave and the track of the primary low
moving into our area sometime Wednesday night into Thursday. The
idea is that the harder this third wave digs the more amplified
the long wave trough becomes over the central US. This would
place our area too far to the east for an all snow event with
the primary low tracking to our west.

Bottom line is that there is potential for an impactful system
Wednesday night into Friday.  Current thinking is that this a
scenario where a lot of things have to go "just right" to produce an
all snow event with a snow in the mountains and rain along the coast
a likely outcome. With a fair amount of uncertainty emphasis on
the third wave I would be hesitant to latch onto any trends the
next couple of days until this wave moves into the RAOB data
dense network of North America sometime after 00Z Monday.

&&

.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
Short Term...Widespread VFR conditions will prevail with little
in the way of cloud cover through this TAF cycle. Increasing SW
flow aloft may bring some marginal LLWS conditions to mainly NH
terminals late tonight into Saturday morning.

Long Term...VFR conditions are expected into early next with
period of active weather likely from the middle to end of next
week. A potentially strong low pressure system will likely bring
restrictions around Thursday&&

.MARINE...
Short Term...A weak front crosses the waters tonight and winds
and seas will increase somewhat in response. A SCA has been
issued for the outer waters and Penobscot Bay beginning tonight
and through early Saturday afternoon. Winds be westerly and
light the remainder of Saturday into Sunday.

Long Term...Quiet on the waters into early next week. A period
of active weather is expected to start the middle of next week
with the potential for a strong low pressure system passing over
New England bringing strong winds and elevated seas late
Wednesday into Friday.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...Small Craft Advisory from 9 PM this evening to 1 PM EST
     Saturday for ANZ150>152-154.

&&

$$

NEAR TERM UPDATE...Kimble
SHORT TERM...Hanes
LONG TERM...Schroeter

NWS GYX Office Area Forecast Discussion








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