Area Forecast Discussion
Issued by NWS Caribou, ME

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FXUS61 KCAR 170549

Area Forecast Discussion
National Weather Service Caribou ME
1249 AM EST Sun Nov 17 2019

High pressure crests over the area tonight and builds east on
Sunday. Low pressure moving north along the eastern seaboard
will track east of the region Monday night and Tuesday. An
upper level trough crosses the area on Wednesday before high
pressure builds in on Thursday.

1245m update...Bumped up lows for the remainder of tonight.
Decreased lows for Sunday night as clear skies and light winds
persist much of night. The end of the night is tricky in terms
of the arrival of precip towards the coast. The immediate coast
will rise above freezing with the onshore winds, but not too far
inland, there`s a risk of freezing rain early Monday morning.

Previous Discussion...
Sfc hipres currently located over far sern Quebec, along the Ontario
border. High conts to build twd the CWA this aftn and wl likely set
up ovr the area by 12z Sun. Expect nw winds wl continue to gust
until sunset bfr decreasing and eventually decoupling ovrngt. Clear
skies wl dominate ovrngt leading to excellent radn`l cooling conds.
Tonight may be the coldest night of the year thus far. Min temps
back on Thursday reached -10F ovr portions of the North Woods while
expecting mins tonight to dip to near -12 to -13F, if the mid-deck
of thin clouds can hold off until close to 12z. Either way expect
more record-setting cold temps by morning. Hv gone well blo guidance
for tonight as well as below bias-corrected guidance.

High wl slowly build east and into the Maritimes on Sunday with
return flow beginning to kick in after 18z. Expect that temps
tomorrow wl be warmer than tda although still some 12-15 degrees blo
normals for this time of year.

H5 ridging builds ovr the FA drg the day tomorrow ahead of cntrl upr
lvl trof mvg twd the Great Lks toward the end of the pd. At the same
time the srn stream wv wl be heading north along the coast but more
about this in the short term section.

Strong high pressure continues its trek east Sunday night with
return flow advecting warmer, moist air into New England. This
warming trend continues into Monday as SW flow between a digging
trough in the Great Lakes and amplifying downstream ridge
holds. Low pressure slowly intensifying off the east coast is
forecast to move north into this flow. At that time, would
expect low to carry on into open Atlantic, however, timely
tilting of the trough out west will provide a more northerly
component. This will be key for final placement of the lows
position into the Nova Scotia vicinity Monday night. Most
guidance shows this solution, but there continues to be a spread
for the low center. GEFS mean has a slight eastward shift,
tracking along the eastern coast of NS, but plenty of members
still show an outcome on the southern shore. The EPS is also
varied, although a slower and slightly westward shift is noted
over prev progs. How influential the tilt becomes will also rest
on jets at the base of the trough aloft and just coming on
shore out west Monday afternoon.

Needless to say, placement of the low will be important for
surface temperatures as well as temperatures in the mid-levels
for precip type. With the mature low tracking towards Nova
Scotia, much of Maine will be exposed to the shield of precip to
the NW in the comma head. As bulk of precip tracks into the
region, NE winds at the surface will keep low level cool air in
place. In the north and west this means sfc temps right around
freezing. Downeast, in closer proximity to the low, would be
exposed to more of the WAA. This warm air is very apparent on
the NAM, with 850mb temps as much as +10 to 12C through to a HUL
to BGR line. GFS and ECMWF solutions are more reserved, with +2
to 5C across the FA. The NAM solution would lead to an initial
round of freezing rain from interior Downeast to the north
before changing to rain in the deeper warm layer. EC and GFS
solutions would complete this transition only across Downeast,
with a mix of sleet/freezing rain across north before changing
to snow on back side Tuesday morning. Will side with the EC and
GFS given consistency and overall agreement for these temps.
This means a freezing rain/snow event in the north and freezing
rain to rain towards Downeast. Since the NAM also shows a
similar termination for liquid/freezing changeover, also feel
more confident on transition area.

Integrated water vapor transport into the Gulf of Maine Monday
afternoon is notable via NAEFS. The moisture content of at or
above 1 PWAT combined with tight pressure grad between
exiting high and incoming low is currently forecast to produce
about three quarters to an inch of QPF through Tuesday. Although
the system is progressive, will see some moderate precip rates
for freezing rain and rain. Once winds shift NW on the back
side, expect a quick changeover to snow in the north where the
Crown of Maine could see a quick couple inches. Snow showers
will progress as far south as central eastern Maine overnight
before warmer temps return north Tuesday as precip tapers off to

Theme behind exiting low will be cool and dry. Except for a few
snow showers over higher terrain in the stiff flow, the next
chance for widespread precip falls on Friday. Pattern looks to
be a typical overunning event, with low pressure tracking
through Michigan and the Great Lakes. Precip would break out
over New England Thursday night/Friday morning, beginning as
snow and snow showers. Southerly flow near the coast would
transition much of Downeast to rain. On the backside, cooler air
would again transition this to snow into the early part of the
weekend. Many variations on this disturbance, and not much can
be said likely at this time, however a large system looks to
impact the Northeast and New England late this week.

The week is forecast to be comparatively warmer than this past,
with temperatures closer to normal, but still a couple degrees

NEAR TERM: VFR next 24 hours under high pressure with light

Sunday Night: VFR with light winds.

Monday through Mon Night: IFR sigs with rain and mixed precip beginning
at Downeast TAF sites in the AM, moving north in afternoon.
Northern sites will transition to all snow Mon night. NE winds
shifting N. Gusts to 25 kts possible.

Tuesday and Tues night: IFR with snow in the north and rain
Downeast. Winds from NW becoming light.

Wednesday and Wed night: All sites MVFR with snow showers
possible, light NW winds.

Thursday: MVFR in snow showers, light NW winds.

NEAR TERM: Seas will continue to diminish through the day on
Sunday. Winds will remain below SCA levels into Sunday evening.

SHORT TERM: Winds and seas will build Monday morning through
the afternoon, with a Gale Watch posted for the day. Long period
swell of 8 to 12 sec is expected to continue through the
period. Winds will be around gale force with rain Monday morning
and afternoon. Seas react accordingly building 10 to 13 feet in
outer coastal areas. Intracoastal will range from 2 to 8 feet.
Waves slowly diminish Tuesday afternoon as winds shift offshore
Monday night. Even so, SCA conditions may continue through most
of Tues night.

Some minor overwash and erosion will be possible at low
lying/vulnerable areas during and around high tides beginning
Mon afternoon. How many high tide cycles pose a threat will
depend when and how strong the wind shift is as storm departs.
This can play a large role on TWL/surge departure.

An Arctic airmass will be in place tonight. In this anomalously
cold air mass, expect that temperature records may be set or

Nov 17th forecast lows   Record lows
Caribou: 3      4, 1943
Bangor: 6   8, 1933
Houlton: -1    7, 1968
Millinocket: 8   11, 1967

MARINE...Gale Watch from Monday morning through Monday evening for

Near Term...Farrar/Foisy
Short Term...Cornwell
Long Term...Cornwell
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