Area Forecast Discussion
Issued by NWS Caribou, ME

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FXUS61 KCAR 022141

Area Forecast Discussion
National Weather Service Caribou ME
541 PM EDT Tue Jun 2 2020

Low pressure tracks from southeastern Quebec to southwestern
Maine by Wednesday evening, then to the southeastern Canadian
Maritimes by Thursday morning. Weak high pressure builds over
the area Thursday and Thursday night. A cold front approaches
from the northwest Friday, then slowly pushes south through the
state Friday night and early Saturday. Canadian high pressure
then builds in for the remainder of the weekend.


545 PM Update: Outside of some minor adjustments to fcst cld cvr
this eve based on latest sat imagery trends, fcst hrly temps/dwpts
were updated into the ovrngt hrs based on obsvd aftn hi temps
and trends seen from latest avbl sfc obs. Otherwise, the rest of
the near term fcst elements essentially remain the same from
last update.

Prev Disc: Northern stream shortwave ridging exits to the
southeast early this evening, followed by a northern stream
shortwave tracking from SW Quebec to the Gulf of Maine tonight.
This coupled with increasing isentropic lift on the I-295 and
I-300 isentropic surfaces and some frontogenesis at 850 hPa
should bring some rain to most of Northern and Eastern Maine
from late this evening into Wednesday morning. For now it
appears that forcing should be far enough S that the Crown of
Maine should stay mainly, if not entirely dry. High resolution
models show all suggest that the isentropic lift/frontogenesis
should be maximized in a NW to SE oriented band from N Somerset
(clipping parts of adjacent Aroostook) county down into Downeast
Maine (with Acadia region on the W end of the best forcing).
Have increased pops to likely overnight in this area.

Otherwise the region remains at the base of a cutoff low
centered over NE Quebec and so shortwaves rotating around the
base of the trough should produce isolated to scattered showers
for the remainder of the day on Wednesday outside of the Crown
of Maine (which should rain dry).

Lows tonight should range from the upper 30s to upper 40s, with
50 possible around Bangor. There should be sufficient cloud
cover to preclude frost overnight. This is around 5 degrees
below normal across the North and near normal elsewhere. Highs
on Wednesday should generally range from the mid 50s to mid 60s,
which is around 5 degrees below normal.


A cold upper low in Labrador will slowly retrograde into
northern Quebec through the period...leaving the area in
cyclonic flow. An upper level shortwave and associated surface
trough rotate through the area Wednesday evening, but am not
expecting much in the way of precipitation. Will go with slight
chance PoPs Downeast in the evening, but dry afterwards. Expect
some fog along the coast with the move humid air mass ahead of
the trough axis, but drier air works into the area later in the
night. Lows will be in the low to mid 40s in northern zones, but
close to 50F for Bangor and the coast. The drier air and warmer
air will be in place Thursday with highs rising into the 70s
with the exception of the immediate coast. A fairly deep mixing
layer led to lowering dew points below guidance and increasing
wind gusts such that some 30 mph gusts are possible from the
west. Thursday night looks dry under the influence of weak high
pressure. The warming trend continues Friday ahead of a cold
front that will sag southward from Quebec late Friday. Humidity
will also increase. Nonetheless, a fairly deep mixed layer
still produces dew points below guidance and generates another
day of gusty west winds. For northern zones...mostly northern
Aroostook County...late afternoon brings the threat of
thunderstorms with strong wind gusts as the cold front
approaches along with a weak shortwave. CAPE looks fairly low,
but DCAPE looks robust and an inverted V structure is
anticipated with very strong shear.


Lots of uncertainty for the weekend. The cold front and the
initial shortwave brings the risk of showers and thunderstorms
into Friday evening. The front basically stalls during the night
while another more potent northern stream shortwave arrives from
the Great Lakes region. This shortwave will certainly energize
the front for Saturday with the threat of more thunderstorm
activity ahead of the front. Once again, shear is strong and
this digging shortwave could bring some decent cooling aloft.
At the moment, there`s not a lot of CAPE showing, but that could
change. Winds are the primary concern right now and the
potential for heavy rainfall training along the slow moving
frontal boundary. The position of the frontal boundary with
respect to afternoon heating will be key. The amplifying upper
trough may keep showers and clouds in the forecast for Saturday
night into Sunday, but should move out for early week as another
cool and dry Canadian high builds for the first half of next


VFR, except for MVFR possible KHUL by early Wednesday
afternoon and MVFR likely with IFR possible at KBHB/KBGR from
around 11Z Wednesday on.

NW wings G15-20KT into early evening, then winds become light
and variable for the remainder of tonight. Winds then remain
light and variable or become out of the S-SW at less than 10kt
Tuesday morning.

Wednesday afternoon/night...VFR except possible fog/IFR at BHB,
Machias and Eastport.

Thursday into Friday afternoon...VFR but westerly afternoon
winds gusting over 30 mph at times.

Friday evening into Saturday...Thunderstorms possible with a
slow moving cold front. Likely IFR cigs later Friday night into
Saturday morning.

Saturday night into Sunday...MVFR cigs expected.


NEAR TERM: A moderate pressure gradient should allow for gusts
up to 20 kt this evening, then it becomes light overnight and
remains so through Wednesday. So winds should be 10 kt or less
overnight and Wednesday. Seas should remain below SCA levels as
well tonight and Wednesday.

SHORT TERM: Fog is expected Wednesday night and again Friday
night into Saturday evening. Long period south swell may exceed
advisory criteria at times Thursday afternoon into Saturday.
Stability over the cold waters led to a reduction in wind gusts
through the forecast period.


The dry streak at Bangor continues today, marking the 17th day
without more than a trace of precipitation. This is the longest
streak since late Sept-early Oct 2017 and is the longest streak
in late May into early June since 1950. Rain is likely in
Bangor late tonight into Wednesday. For now it appears the rain
should hold off until after midnight, but the streak should come
to an end.





Near Term...VJN
Short Term...MCW
Long Term...MCW
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