Area Forecast Discussion
Issued by NWS Caribou, ME

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FXUS61 KCAR 281032

Area Forecast Discussion
National Weather Service Caribou ME
632 AM EDT Sun May 28 2017

A cold front will move into the area Sunday and stall. The
front will return northward Monday as a warm front. An occluded
front will cross the region later Monday night.


630 AM Update...Needed to adjust the cloud cover to bring some
llvl clouds into northern and eastern sections per the latest
visible satl imagery. Some fog has developed as well but will
burn off w/in the next hr. Low clouds a result of a sse flow.
These low clouds will dissipate after 12Z(8 AM) w/the help of
the sun. Also backed up the timing of showers until late this
afternoon as the latest sounding data from the RAP indicates
llvls staying dry most of the day and forcing weak.

Daycrew will need to keep an eye on the convective potential
across the far w and n later this afternoon and evening. There
is some CAPE as stated below, but the latest run of the RAP
continues to point to the shear being weak(<20 kts). Attm,
stayedthe course and kept the thunder out of the forecast for
this update.

Previous Discussion...
The main challenge will be placement of shower activity and convective

Some patchy fog expected this morning will burn off quickly by
7 AM. Temps did drop into the mid and upper 30s in some of the
low lying areas this morning. Temps are forecast to warm into
the 60s and lower 70s this afternoon before clouds move in from
the wnw. A stated above, a cold front is expected to drop across
the northern and western areas this afternoon. There is some
mid level forcing would be enough to trigger some shower
activity. The short range guidance advertises things to
destabilize some especially the NAM and RAP. Both indicate CAPE
potential of 300-400 joules w/lapse rates steepening
some(6.0-6.5 c/km). Some lacking factors are shear is weak and
temps might not quite hit the convective temp. The area that
could realize this would be the western areas of Aroostook and
Somerset County but this would be isolated. Moisture also looks
to be limited at first, but the column is expected to moisten by
late afternoon. Attm, decided to not to add any thunder to the
forecast as confidence is low. Will re-visit this w/the morning

The front is forecast to stall across northern Maine tonight
w/showers around. Kept 30-40% going across the northern and
westerns sections. Given the light sse wind and temp/dewpoint
spread being less than 3, decided to add patchy fog for the
overnight period. Overnight temps are expected to be in the mid
and upper 40s.


A few showers will be possible Monday morning as the warm front
exits northern zones northward into Canada. Otherwise, the day
looks fairly dry until later when an occluded front approaches
from the west. The predominant feature on Monday will be a
southerly to southeasterly flow of moist marine air northward
such that cloudy conditions will prevail with highs only
reaching the upper 50s to near 60F. The occluded front has
weakening dynamics with no surface-based or elevated
instability. Rainfall amounts will reach a quarter inch at most
and that`s most likely on the western fringes of the forecast
area since the front will decay as it crosses the area. The
occluded front slowly exits eastward on Tuesday
morning...leaving the southerly flow intact and resulting in
another cool and cloudy day. Highs will be just slightly warmer
into the lower 60s. Another shortwave will rotate around a broad
closed upper low in Ontario. This shortwave and associated
surface trough will reach the area later Tuesday into Tuesday
night. With a bit more cooling aloft, this trough may have some
instability aloft and a few thunderstorms, but current
indications are so modest, that it`s best to hold off including
any mention of thunder in the forecast for now.


A large closed upper low over northern Ontario will be a
persistent feature with shortwaves rotating around the low into
Maine every day in the longer range. This means seasonally cool
temperatures and afternoon/evening showers.  Temperatures will
finally warm back towards 70F on Wednesday as winds become more
southwesterly...producing some sunny breaks. This will likely
generate surface-based instability as yet another surface trough
and upper level shortwave rotates around the Ontario upper low
and arrives Wednesday afternoon. As a result, have included a
chance of thunderstorms for the afternoon and evening. This
front will bring in slightly cooler and drier air for Thursday,
but scattered shower activity will remain a risk with the
possibility of another shortwave rotating around the Ontario
low. A more vigorous shortwave will arrive later Friday or
Friday night for a potentially heavier round of showers.


NEAR TERM: Generally VFR w/a brief period of MVFR this morning
due to radiation fog. The fog will burn off by 730 AM. Conditions
are expected to drop down to MVFR and possibly IFR for KBGR and
KBHB after midnight w/some fog and low cigs.

SHORT TERM: Monday will start with IFR cigs towards BGR and BHB
and MVFR cigs further north. All sites will become VFR Monday
afternoon, but return to IFR by later Monday night into Tuesday
morning. Conditions will slowly rise to MVFR Tuesday afternoon,
but again return to IFR Tuesday night into Wednesday morning.
VFR is expected by Wednesday afternoon...outside of
thunderstorms and the VFR will continue into Thursday.


NEAR TERM: No headlines anticipated through this term. Winds and
seas are forecast to be around 10 kts w/seas 2 to 3 ft mainly
for outer zones.

SHORT TERM: Some patchy fog is possible Monday morning. The fog
will return later Monday night, but will really set in Tuesday
night into Thursday morning. Two to three foot swell is expected
during the period. Adjusted model winds down due to stable
conditions over the cold waters.





Near Term...Hewitt
Short Term...MCW
Long Term...MCW
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