Area Forecast Discussion
Issued by NWS Caribou, ME

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201
FXUS61 KCAR 232340
AFDCAR

Area Forecast Discussion
National Weather Service Caribou ME
640 PM EST Thu Feb 23 2017

.SYNOPSIS...
Low pressure will move through Quebec today bringing a cold
front through the region tonight. High pressure will return on
Friday. A warm front will cross the region Friday night.

&&

.NEAR TERM /THROUGH FRIDAY/...
645 pm update...
Cdfnt extndg fm sfc low acrs the St. Lawrence Rvr down thru sern
Quebec with area of convection currently crossing the far north.
Temps are still in the 40s with isold lightning strikes acrs the
Allagash in area of mid-lvl instability. Ongoing fcst has this well
in hand with isold thunder acrs the north for the next couple
of hrs and see no reason to chg with this update.

Areas of fog has already mvd in off the ocean and affecting
Bangor and areas to the east and expect this wl continue to work
its way north slowly ahd of cdfnt. Dwpt depressions wl drop with
widespread fog acrs most of the CWA aft midnight tonight. No
chgs needed at this time.

Prev discussion blo...
Low pressure is expected to pass to the north of the State
Tonight. This system will produce light rain across the north
this evening as it passes. There is also a chance of isolated
thunder in western and northern areas. Later tonight skies will
partially clear and with low level moisture in place and higher
dew points across southern areas expect areas of fog to develop.
Weak high pressure will move across the region early Friday then
off to the east. Another low pressure system will approach from
the southwest late Friday. This system is expect to spread rain
into the area during the day Friday. Snow and or mixed
precipitation is possible in the far north late Friday as a
layer of warmer colder air moves in at lower levels.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
A weak cold front will sag south across northern areas Friday
evening. Cold air in the low levels will funnel in behind the
front Friday night. Meanwhile. low pressure across the Great
Lakes region will track northeast overnight Friday and draw the
front back north as a warm front. This will result in a period
of light overrunning precipitation Friday evening into Saturday
morning. Based on critical thicknesses, the precipitation
should be mainly in the form of sleet and freezing rain north of
a Greenville to Houlton line, with just plain rain south of
there. As the warm front lifts north of the state later Friday
night and Saturday morning, expect any lingering precipitation
to be in the form of rain showers. Any ice accumulation across
far northern areas will be light, generally less than a tenth
of an inch. A freezing rain advisory will likely be needed for
Friday night through early Saturday morning for northern areas.

Otherwise, Saturday will be a mainly cloudy with the chance for
a few showers or drizzle, as the best forcing remains to our
west during the daylight hours Saturday. It will be a mild day
Saturday as southerly winds usher in much milder temperatures
in advance of an approaching cold front from the west. Expect
temperatures across the forecast area to range from the upper
30s to near 40 degrees across the St. John Valley to the mid to
upper 40s across downeast areas.

Rain chances will increase by Saturday evening as a cold front
approaches from the west, with all areas expected to see some
measurable rain Saturday night in advance of the approaching
front. Expect areas of fog Saturday night. The combination of an
extended period of above freezing temperatures, along with the
anticipated rainfall, may result in some ice movement on areas
rivers and streams across central and portions of interior
downeast Maine. Thus, after coordination with neighboring WFO
GYX, a flood watch has been issued for this area. (Please see
hydrology section below). The cold front will cross the region
late Saturday night with rain ending after midnight. The rain
could end as a brief period of snow across the north and west
after midnight Saturday but little in the way of accumulation is
expected.

It will turn cooler on Sunday as a secondary cold front crosses
the region. Along with the cooler temperatures will be the
chance of a few snow showers, mainly across the north, with
partly cloudy skies across downeast areas.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
A cold front approaching from the west Sun night will move
across the state during the day Monday. Some snow showers are
possible with the front, mainly from the Central Highlands
northward, and our snow squall parameter is putting out values
suggestive of possible snow squalls as the front passes through.
Indeed, looking at BUFKIT GFS soundings reveals forecast lapse
rates over 8C/km up to 800mb, and some sites show minimal CAPE,
as well.

Beyond Monday, models appear to have diverged some in their
solutions, with the GFS showing a compact Low passing across
southern New Eng and across the Gulf of maine, giving precip to
the southern CWA, while the ECMWF and CMC both show a ridge of
high pressure. Active weather pattern likely for mid-week, with
one or two low pressure systems likely to impact the CWA. Models
have fairly divergent solutions at this time, so tough to tease
out details at this time. 12z Wed to 12z Thu appear to have the
highest chance of being impacted, so did boost POPs in that
period, and are in good agreement with GYX grids.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
NEAR TERM: Cdfnt wl move across northern terminals with MVFR
possible at PQI, CAR and FVE in light rain. HUL will be the
question regarding any rain falling but expect they will see IFR
vsby restrictions after 05z. Expect three northern terminals
will become VFR after 09z, remaining VFR until closer to end of
TAF valid time as mixed precipitation moves in from the south.

BGR and BHB will likely be IFR and possibly LIFR after 04z in
extensive low-level moisture. BGR may improve to MVFR after 15z
with BHB remaining IFR through end of TAF valid time.

LLWS can be expected first few hours this evening with 23040 at
FL020.

SHORT TERM: IFR/MVFR conditions are expected Friday night through
Saturday. -FZRA is expected to affect the northern
terminals(KFVE,KCAR,KPQI,KHUL) Friday night through early
Saturday. Widespread IFR conditions are expected Saturday night
in rain and areas of fog. Conditions will improve to VFR behind
the cold front.

&&

.MARINE...
NEAR TERM: Have used the GFS for sustained winds. For waves:
Currently a southerly fetch is developing across the Gulf of
Maine and has become the primary wave system. There is also a
secondary southeasterly longer period swell system present based
on wave spectra from 44027. Expect wave heights to build to
around 7 feet this evening then subside Friday as winds
diminish. A longer period secondary southeasterly swell system
(1-2 feet/12 seconds) will develop Friday Morning. Will use the
Near Shore Wave Model to populate wave grids.

SHORT TERM: Wind/seas are expected to remain below small craft
advisory levels Friday night. Winds/seas will then begin to
increase to small craft advisory levels late Saturday and
Saturday night. Winds/seas will be at small craft advisory
levels on Sunday.

&&

.HYDROLOGY...
After collaboration with GYX and intra office collaboration,
have issued a flood watch for ice jams for central areas, as
well as interior downeast Maine, from Saturday morning into
Sunday evening. The combination of above freezing temperatures
and a period of rain later Saturday into Saturday night, will
result in the potential for ice movement and ice jams. Rainfall
amounts are expected to generally range from one-half to three-
quarters of an inch across the area. However, the mild
temperatures will increase snow melt/run off on area waterways,
resulting in possible ice movement and ice jams. However,
mainstem rivers are expected to remain below bankfull, outside
of any potential ice jam development.

&&

.CAR WATCHES/WARNINGS/ADVISORIES...
ME...Flood Watch from Saturday morning through Sunday evening for
     MEZ010-011-015>017-031-032.
MARINE...Small Craft Advisory until 2 AM EST Friday for ANZ050-051.

&&

$$

Near Term...Farrar/Mignone
Short Term...Duda
Long Term...Kredensor
Aviation...Farrar/Mignone/Duda
Marine...Farrar/Mignone/Duda
Hydrology...



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