Area Forecast Discussion
Issued by NWS Caribou, ME

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FXUS61 KCAR 300405

Area Forecast Discussion
National Weather Service Caribou ME
1205 AM EDT Tue May 30 2017

A stationary front will remain over the Maine coast overnight.
An weakening occluded front will cross the region Tuesday
morning. Another frontal boundary is expected to slowly cross
the region late Tuesday night and Wednesday.

12am update...No changes with this update. The front continues
to decay as it enters the forecast area while high pressure
strengthens to the east.

Original Discussion... A weakening occluded front will apch and
cross the Rgn from the W as a s/wv alf from QB shears apart.
This front will wash out whats left of a weakening stationary
front currently near the Downeast Maine coast. Rnfl amts will be
lgt, with the most ovr NW ptns of the Rgn where the shwr band
will be a little more organized before weakening further E.
Patchy fog will be possible late tngt with the llvls of the
atmosphere becoming more moist with any additional lgt rn and
winds becoming lgt.

With shwrs already E of the Rgn by Tue morn, any remaining fog
should lift by mid morn with breaks in the ovc possible by Tue
aftn. Fcst warmer aftn 925 temps suggest warmer hi temps across
Nrn and Cntrl ptns of the Rgn Tue with Downeast areas tempered
by a geostrophically enhanced sea breeze. The next round of
shwrs with the next s/wv rotating SW to NE arnd upper lvl low
pres ovr Ont Prov will just be entering Wrn ptns of the Rgn
later in the aftn.

Widespread showers are expected Tuesday night and Wednesday as
a shortwave rotates around an upper low situated over Ontario.
South flow will keep marine air in place across much of the
region on Wednesday, thereby limiting the potential for
thunderstorms. The exception will be across the North Woods,
where model guidance is indicating 300-800 J/kg of CAPE will be
available by afternoon. Have kept a chance of thunder for these
areas. This CAPE will wane overnight as daytime heating is lost,
and guidance is not very generous with elevated instability, so
don`t expect any thunder much past sunset. Showers will wind
down after midnight Wednesday night, but additional
precipitation will be possible Thursday as a weak cold front
moves through. Moisture will be lacking with this fropa, so any
showers will be scattered and light in nature. Wednesday will be
another cool day across the region owing to marine air and
plentiful cloud cover, but increasing sunshine and west winds
behind the front will allow temperatures to reach into the mid
60s to around 70 on Thursday.

Differences in model solutions making a tough forecast for
Friday. The aforementioned upper low will draw closer Thursday
night and Friday with another, stronger shortwave to lift across
New England. However, the latest GFS now has a nearly
stationary front lying stretched across Downeast Maine, which
would limit most precipitation, particularly thunderstorms, to
inland regions from Bangor south. It also swings the shortwave
through early on Friday. Meanwhile, the ECMWF and Canadian are
6-12 hours slower with the shortwave and also allow surface
instability to develop across the entire interior forecast area.
Noted that while the ECWMF now lags the highest instability
behind the best shear, the GFS has them timed more concurrently.
As such, should its frontal position be incorrect, the
potential is there for strong storms to develop. Given the
uncertainty, have reduced mention of any convection to slight
chance. This uncertainty continues right through the weekend,
with the GFS and ECMWF not agreeing in timing, placement, or
strength of shortwaves rotating around the departing upper low.
Given this, have stayed close to a blend through the extended,
which resulted in slight chance/chance PoPs for much of the

NEAR TERM: Mainly MVFR clgs ovrngt for our TAF sites with
intermittent IFR clgs/vsbys possible late tngt with shwrs
and patchy fog. Conditions will gradually improve to low
VFR by Tues aftn, with the possible xcptn being KFVE.

SHORT TERM: Widespread MVFR conditions will prevail Tuesday
night through Wednesday due to low ceilings, rain, and patchy
fog. IFR will be likely 00z-12z Wed and Thu, particularly at the
southern terminals. Conditions will gradually improve after 12z
Thu as drier air works in behind a passing frontal boundary.
Scattered showers will be possible Thu afternoon, but they
should be light and expect VFR conditions at all terminals after
16z. VFR conditions continue Thu night, then more showers,
along with MVFR ceilings and visibilities, are possible Friday.

NEAR TERM: No Hdlns xpctd thru Tue with wv hts 2 to 3 ft ovr the
outer MZ waters and 1 to 2 ft ovr the intracoastal MZ waters.
We went with about 85 to 90 percent of WW3 wv guidance for fcst
wv hts which is advertising a 5 to 8 sec primary wv pd.

SHORT TERM: Headlines are expected to be needed through Thursday. South
winds will increase Tuesday night into Wednesday and again Wednesday
night and Thursday. These increasing winds will allow seas to build
to around 4 feet, but both winds and waves will remain below Small
Craft Advisory levels. A better chance for possible SCA conditions
arrives Friday and Friday night.


Near Term...Kredensor/VJN/MCW
Short Term...Hastings
Long Term...Hastings
Marine...Kredensor/VJN/MCW/Hastings is the U.S. government's official web portal to all federal, state and local government web resources and services.