Area Forecast Discussion
Issued by NWS Caribou, ME

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FXUS61 KCAR 261535
AFDCAR

Area Forecast Discussion
National Weather Service Caribou ME
1135 AM EDT Tue Mar 26 2024

.SYNOPSIS...
High pressure exits across the Maritimes today. A warm front
crosses the region tonight through Wednesday. Low pressure will
approach Thursday, cross the Gulf of Maine Friday, then exit
across the Maritimes Saturday.
&&

.NEAR TERM /THROUGH TONIGHT/...
Update...
High pressure exiting across the Gulf of Saint Lawrence will
still ridge across the region today. At the same time, an
inverted trof will extend north toward the Gulf of Maine from
low pressure located well to the south. Moisture will expand
north along the inverted trof. However, drier air with
retreating high pressure will slow the advancement of rain
across northern areas this afternoon. Generally expect
precipitation in the form of rain this afternoon. However,
pockets of light freezing rain or patchy freezing drizzle are
possible dependent on how rapidly precipitation expands north.
Otherwise, expect increasing clouds across northern areas this
afternoon with cloudy skies Downeast. High temperatures today
will range from the upper 30s to around 40 north, with mid to
upper 30s Downeast. Have updated to adjust for current
conditions along with expected afternoon temperatures, clouds
and precipitation chances/types.

Previous Discussion...
The inverted trof will push moisture northward into the region
today and into tonight. By tonight, rain will spread across the
entire region. With temps and dew points cooling towards
freezing in the higher terrain, freezing rain will return,
especially in the North Woods. Some areas in central and
southern Aroostook and northern Penobscot could cool enough to
see freezing rain as well, but only a glaze is expected. Due to
the warmer temps, rainfall, snowpack, and calm winds, patchy to
areas of fog are expected across the area throughout the night.
&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
Strong warm advection will occur with 850mb temps
moving towards 10C by Wednesday morning. This will set up a
steep low level inversion that will persist through Thursday
night. The CAD will slowly release its grip on the area by
Wednesday morning. Temperatures will remain above freezing for
the most part Wednesday through Friday.

While there is some uncertainty in how much rain falls Wednesday
and Wednesday night, dense low level moisture should be able to
at least squeeze out light rain and drizzle as the remnants of a
weakening occluded front moves over the area and stalls. Fog
will also become a threat Wednesday through Thursday night as
dew points surge into the 40s over the cold, snow-covered
terrain.

The ridge in the Atlantic will not budge Wednesday into
Wednesday night while the occluded front remains stalled over
the area. The upper flow become more meridional as the upper
ridge gains amplitude east of the area. Increasing baroclincity
develops Wednesday night into Thursday with steadily increasing
PoPs.

Low pressure is expected to be drawn northward along the old
occluded frontal boundary along the Eastern Seaboard Thursday
into Thursday night. This southern stream low will phase with an
upper trough moving out of the Great Lakes region. The amount
of deep moisture from the Gulf of Mexico/Caribbean being pulled
northward spurs concern for significant rainfall. PWs may rise
towards 1.5 inches on the coast by Thursday...a very high
reading for March.  There are still uncertainties on the track
and evolution of the low...which will depend on the blocking
high in the Atlantic, but the trend with the latest guidance has
been to the west. This means more rain. If the ridge is
displaced a bit further east, the heaviest precip will fall in
the Canadian Maritimes. The best chance for heavy rain currently
appears to be Downeast where we conservatively expect over 3
inches of rainfall by the weekend at this point. The warm and
wet week could yield significant river rises by late week if the
westward trend observed in recent guidance solidifies.

Guidance indicates a negatively-tilted trough may develop
Thursday night with a rapidly deepening surface low moving from
the Delmarva coast due northward towards the Gulf of Maine.
Thus, the greatest lift and rainfall will occur late Thursday
and Thursday night. Small stream and urban flooding are a
concern by Thursday night given the combination of snowmelt and
rainfall.
&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
The expectation is that strong lift persists over the area
Friday as the negatively-tilted trough quickly cuts off aloft
and the surface low continues to rapidly deepen as it tracks
towards the Bay of Fundy and the Canadian Maritimes.

As this process occurs, attention turns to snow. The CWA will be
the cold side of the low with accumulating snow possible as
early as Friday and probable by Friday night. Accumulation
amounts and distributions will again depend on the low track.
The max rainfall scenario is also the max snowfall scenario. If
the low tracks further east in the Maritimes, a glancing blow of
snow results Friday night towards the eastern border of the
state.

The expectation that this low does materialize and quickly
becomes a closed low in the Maritimes leads to a forecast for
strong northwest winds on Saturday with some snow shower
activity in the north. Decreasing PoPs and clouds are
anticipated by Saturday afternoon as high pressure slowly builds
eastward into the area. Temperatures will trend back to normal
readings for late March.
&&

.AVIATION /15Z TUESDAY THROUGH SATURDAY/...
NEAR TERM: Across northern areas, expect VFR/MVFR this
afternoon with a chance of rain. Across Downeast areas,
MVFR/IFR this afternoon with increasing rain chances. Local
freezing rain or patchy freezing drizzle possible through early
afternoon. IFR/LIFR regionwide tonight with rain and fog.
Pockets of freezing rain or patchy freezing drizzle also possible
across northern areas. East/northeast winds 10 to 15 knots with
gusts up to 20 knots today, then 5 to 10 knots tonight. Low
level wind shear later this afternoon into tonight.

SHORT TERM:
Wednesday...IFR due to cigs/fog/drizzle. Light south winds.

Wednesday night and Thursday...IFR tempo LIFR due to
cigs/fog/drizzle. Light and variable winds.

Thursday night...IFR due to cigs/rain. Winds becoming NW 5 to 10
kt.

Friday...IFR cigs/vis in rain. NW winds 10 to 15 kt.

Friday night...IFR vis due to snow north of GNR and HUL. MVFR
tempo IFR due to rain/cigs for BGR and BHB. Northwest winds 15
to 25 kt.

Saturday...IFR in morning north of HUL due vis in snow. MVFR in
the afternoon due to cigs. MVFR in the morning for BGR and BHB,
becoming VFR in afternoon. NW winds 15 to 30 kt.
&&

.MARINE...
NEAR TERM: A Small Craft Advisory remains in effect for all the
waters this afternoon through tonight. However, a few wind gusts
could approach gale force this afternoon. Increasing rain
chances today. Rain and patchy fog tonight.

SHORT TERM: Small Craft Advisories have been extended into
Wednesday due to seas. Fog is likely to take hold Wednesday into
Friday morning. Winds may be sufficient for another Small Craft
Advisory by Friday morning. Gales are a threat Friday night into
Saturday as strong northwesterlies develop.
&&

.HYDROLOGY...
Heavy snow in the past week combined with warm and rainy
conditions this week offers a chance of rivers rising towards
action stage or greater by late this week. Of particular
interest will be the Piscataquis River. Uncertainty remains in
how much rain falls later this week with a slow moving low
pressure system moving up the Eastern Seaboard.
&&

.CAR WATCHES/WARNINGS/ADVISORIES...
ME...Winter Weather Advisory from 2 PM this afternoon to 8 AM EDT
     Wednesday for MEZ001-003-004-010.
MARINE...Small Craft Advisory until 8 PM EDT Wednesday for ANZ050>052.

&&

$$


Near Term...Norcross/LaFlash
Short Term...MCW
Long Term...MCW
Aviation...Norcross/MCW
Marine...Norcross/MCW
Hydrology...MCW


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