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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KCAR 231117
AFDCAR

Area Forecast Discussion
National Weather Service Caribou ME
717 AM EDT Tue Oct 23 2018

.SYNOPSIS...
High pressure will build east this morning. Low pressure will
approach from the west on Tuesday and intensify as it tracks
along the coast Tuesday night into Wednesday.

&&

.NEAR TERM /THROUGH TONIGHT/...
710 AM Update...Hrly temps needed adjustment to match up w/the
latest obs. Tweaked pops to match up w/the radar.

Previous Discussion...
Quiet today and then the action comes into the region tonight.

Cold temps this morning w/many sites across northern and western
Maine seeing upper teens. Satl imagery showed clouds advancing
ene w/the apch of a sfc trof across the central and downeast
region. Regional radar showed some light returns showing up
along this trof. Most of these returns were aloft due to the dry
llvls. Some light snow or sleet possible this morning due to the
low dewpoints. As the the column moistens and temps warm, precip
will transition to light rain. Tried to show this setup through
late morning across the aforementioned areas. Clouds will
continue to overspread the entire CWA this afternoon. Temps will
rise into the upper 30s and lower 40s across the north and west
while central and downeast areas for forecast to hit mid/upper
40s.

Low pres moving across NYS is expected to re-organize off the
southern New England coast and lift along the Maine coast
tonight. The NAM and Canadian GEM are colder w/the blyr temps
and keep the bulk of the QPF further s and e in the form of snow
as far south as Bangor and Calais. The GFS and ECMWF align a
bit closer w/bringing a burst of decent QPF up into northern
areas overnight as the upper low moves along the coast. The GFS
and ECMWF appear to match up better w/the sfc and upper low
while the NAM and GEM look to be a bit dis-jointed w/the
position. Therefore, decided to lean w/a blend of the GFS and
ECMWF for the position of the low moving along the coast and
blyr temps. A nose of milder air is shown by this blend to
to push north to Mars Hill and possibly to Fort Fairfield
through 06Z (2AM). This would allow for rain/snow mix as far n
as the Caribou-Presque Isle region w/rain further south. North
of Caribou, precip looks like it will be all snow. As temps fall
back overnight, precip will go over to snow from Caribou down to
the Greenville and Millinocket region. It looks like there could
be a burst of moderate to heavy snowfall as the upper level
front sets up across the central and northeastern portions of
the area overnight. This feature will aid in strong forcing in
the mid levels. The GFS soundings supported this setup and
decent snow growth. Would not be surprised to see a period of
snowfall rates up to an inch/hr across portions of the Maine
Central Highlands and northern Maine. Another thing to consider
will be the potential for high snow ratios in the snow bursts as
the model guidance appears to be having a hard time showing
the high ratio potential. Attm, decided to play it as a 24 hr
event w/snowfall totals averaging 4-9 inches w/higher amounts
across the higher terrain which could see more than 10 inches.
A shift further south as shown the NAM and GEM could lead to
lower amounts. Therefore, taking this into account, decided to
go w/a Winter Weather Advisory for northern Maine and the Maine
Central Highlands late tonight through Wednesday. This was
collaborated w/GYX.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
A complex winter storm scenario unfolds Wednesday. Cyclogenesis
occurs in the Gulf of Maine Tuesday night and by Wednesday
morning, a vertically stacked low will be over the forecast
area. The important issue is exactly where. The 00Z suite of
guidance generally shifted the entire system further south. Thus
areas towards the Allagash and Saint John Valley now receive
less snowfall than previously expected. The prime snowmaker will
be a deformation band that will propagate north and west
Wednesday morning with potentially heavy snow at times. Most of
the snow will be north of a line from Greenville towards
Millinocket and Houlton and the heaviest accumulations will be
elevation dependent. Thus the highest totals will be in the
Katahdin region and into the upslope high terrain west of Rt 11
in northern Penobscot into Aroostook counties. Boundary layer
issues remain a concern along the eastern border of Aroostook
County and may need to knock down totals a bit there. Snow
ratios will be decent in the band...towards 10 to 1 with good
omega in the dendritic growth zone...but will lower the ratios
once the band weakens in the afternoon. Leaned towards NAM and
raw temp guidance for Wednesday. The trowal will continue to
affect large portions of the forecast area Wednesday evening and
have extended the Winter Weather Advisory to 2am Thursday
morning when the H700 low and trowal should be safely east of
the area. Winds become the next concern in a northwest flow for
Thursday. Gust over 30 mph are expected...and may hit 40 mph at
usually windy locations such as Greenville and Frenchville. Some
snow shower activity may persist towards northern Aroostook
County on Thursday in the cold air advection. Cu and sc fields
will occur across most of the area Thursday with highs in the
30s north and low 40s for Bangor and the coast. Wind chills will
be in the 20s...to go with fresh snow cover in the northern
zones. Winds continue Thursday night with lows in the 20s.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
High pressure builds Friday with lighter winds, but highs will
still only be in the low to mid 30s north and upper 30s to lower
40s in the southern half of the forecast area. Friday night will
be the coldest night of the season to date with strong
radiational cooling and snow cover dropping lows to the low
teens north and teens nearly as far south as Orono and Old Town.
Saturday will start with high pressure in control, but low
pressure will advance up the eastern seaboard later Saturday
into Sunday. A strong, cold easterly flow will be induced
between the low and departing high pressure over Labrador. The
cold air mass will eventually be displaced, but the question is
how quickly and whether snow will fall before the warm air
arrives. Using a blend of the warmer ECMWF and colder GFS, went
for a period of snow late Saturday into Saturday night before
the warmer air and rain arrives for Sunday. The broad area of
low pressure will keep rain in the forecast into Monday with
temperatures moderating into the 40s to low 50s for Sunday and
Monday.

&&

.AVIATION /11Z TUESDAY THROUGH SATURDAY/...
NEAR TERM: VFR into early evening and then conditions will drop
to MVFR to IFR w/snow across northern sites mainly north of
KHUL. KBHB will generally see rain possibly mixed w/some snow
for KBGR.

SHORT TERM: LIFR to VLIFR in snow is expected from GNR to HUL
northward for much of Wednesday into Wednesday evening. Periods
of IFR to LIFR in snow may also occur at BGR and BHB Wednesday
morning. After the snow ends, winds become an issue Wednesday
night into Thursday. Gusts to 35-40 kts are possible. VFR
conditions are forecast Thursday into Saturday.

&&

.MARINE...
NEAR TERM: No headlines expected into tonight. E winds will pick
up overnight to speeds of 15 kts w/gusts to 20 kts over the
outer zones. Wave heights will begin to build later tonight to 4
to 5 ft.

SHORT TERM: Small Craft Advisory conditions are expected
Wednesday afternoon into Friday. There`s a chance of a brief
gale depending on the exact track of low pressure in the Gulf of
Maine on Wednesday. Towards Saturday night into Sunday, there`s
a significant risk of a more prolonged period of gale
conditions.

&&

.CAR WATCHES/WARNINGS/ADVISORIES...
ME...Winter Weather Advisory from midnight tonight to 2 AM EDT
     Thursday for MEZ001>006-010.
MARINE...None.

&&

$$

Near Term...Hewitt
Short Term...MCW
Long Term...MCW
Aviation...Hewitt/MCW
Marine...Hewitt/MCW