Area Forecast Discussion
Issued by NWS Caribou, ME

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FXUS61 KCAR 120443

Area Forecast Discussion
National Weather Service Caribou ME
1243 AM EDT Wed Aug 12 2020

A cold front will approach overnight then slowly cross the
region Wednesday. A secondary cold front will cross the region
Thursday evening. High pressure will build across the region
Friday through this weekend.

A slow moving cold front will approach northern Maine overnight.
Expect scattered showers/thunderstorms across northern and
central areas overnight in advance of the front, with lesser
chances Downeast. Otherwise, expect partly/mostly cloudy skies
overnight. Will also have patchy fog north, with areas of fog
Downeast. Overnight low temperatures will range from the mid to
upper 60s north, to the upper 60s to around 70 interior Downeast
while ranging through the 60s along the Downeast coast. Have
updated the forecast to adjust for current conditions along with
overnight temperatures, clouds and shower/thunderstorm chances.

Previous Discussion...
The fog will again retreat back to the ocean Wednesday. The
front will slide southward during the course of the day. This
means cooler temps and lower humidity in northern Aroostook than
today, but another day of upper 80s to near 90F for Bangor and
Downeast. SBCAPE will again be impressive by afternoon for areas
such as interior Washington and Hancock counties, but shear
will be lacking. Deep instability, PWs, and storm motions point
to more heavy downpours. Also added mention of gusty winds with
the bigger storms Wednesday afternoon. The window of opportunity
will be rather brief in the afternoon as the front sweeps off
the coast by later afternoon.

The cold front will be sliding se heading off the coast Wed
night. Any leftover showers will be moving to the ese and
offshore. Drier and cooler air will follow behind the front
w/overnight temps dropping into the 50s across the northern 1/2
of the CWA, while central and downeast areas see upper 50s to
lower 60s. Some sites in NW Maine, such as Estcourt Station
could see upper 40s. Some fog will linger along the coastal
areas into overnight hrs. Thursday will be a warm day but drier.
An upper trof is shown by the NAM and GFS to swing across the
region during the day. There is some moisture but this looks to
be confined to around the 850mb layer. Forcing is weak.
Therefore, decided to keep the mention of rain out of the
forecast. Clearing Thursday night w/temps once again in the 50s
north and lower 60s south. Another upper trof is expected to
slide across the region as the closed upper low slides across
the Gulf of St. Lawrence. The 12Z ECMWF was very consistent
w/its last few runs in showing some decent mid-level forcing
(vorticity advection) across northern Maine to allow for some
showers. There appears to be a bit more moisture associated
w/this feature to support the shower activity. Slightly cooler
for Friday w/daytime high temps in the lower 80s north and mid
80s south.

The long range guidance shows the upper low to slide off to the
e on Saturday w/yet another spoke of energy dropping se across
the region. A look at the vorticity fields, shows the best
vorticity advection to be across New Brunswick. Both the GFS and
ECMWF show some light shower activity developing across the
region during the day, w/the more concentrated activity along
the eastern side of Maine. Confidence is very low on this setup
given the sfc high to the n ridging down into the region. Plus,
moisture seem confined below 800mbs. Therefore, decided on no
mention of rain w/cooler temps for Saturday. Despite the GFS and
ECMWF trying to bring some scattered shower activity to portions
of the region, decided to stay dry for Sunday as well w/the
high pres at the sfc in place. Near seasonal temps expected.

High pres ridge looks like it will shift to the e early next
week w/a a sw flow aloft. This could allow for the transport of
moisture to be pulled newd. There is a slow moving frontal
boundary that is forecast to push eastward to bring the
increasing chances for some showers and possible tstms. Temps
during this timeframe are expected to be AOA normal.

NEAR TERM: Variable conditions will occur with any showers or
thunderstorms overnight through Wednesday. IFR/LIFR conditions
possible later tonight through early Wednesday with low clouds
and fog. Otherwise, VFR.

SHORT TERM: VFR for all terminals Wednesday night right into
Sunday. The caveat to this will be MVFR/IFR for low clouds and
fog Wednesday night for KBHB. There is a chance for a brief
period of MVFR Friday across the northern terminals w/a brief

Winds will be NNW 5-10 mph Thursday into Friday w/a turn to the
NNE on Saturday.

NEAR TERM: Winds/seas will remain below small craft advisory
levels overnight through Wednesday. Visibilities will be
reduced in areas of fog overnight through Wednesday.

SHORT TERM: No headlines foreseen. Some fog will be around Wed
night lower vsbys to less than 1 NM along w/some showers.
Winds will basically be light and variable through the period
w/seas 2-3 ft.




Near Term...Norcross/MCW
Short Term...Hewitt
Long Term...Hewitt
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