Area Forecast Discussion
Issued by NWS Caribou, ME

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FXUS61 KCAR 270840
AFDCAR

Area Forecast Discussion
National Weather Service Caribou ME
440 AM EDT Wed Mar 27 2024

.SYNOPSIS...
A warm front crosses the region Wednesday. Multiple low pressure
systems then pass offshore Wednesday night through Friday night.
Low pressure then slow tracks through the Maritimes Saturday
and Sunday.

&&

.NEAR TERM /THROUGH TONIGHT/...
An anomalously strong upper ridge over the open Atlantic Ocean
amplifies as an upper trough digs into the Great Lakes region.
This will draw very warm air northward into the CWA over a very
steep low level inversion. 925mb temps will surge towards Strong
moisture advection northward and saturated low levels will
promote fairly constant drizzle today and tonight as well as
fog. Chances for fog are fairly good this morning and even
better this evening through the night as dew points climb
towards 40F or higher. A Dense Fog Advisory will have to be a
consideration later today and tonight.

As CAD is eroded this morning, there is a chance for pockets of
freezing drizzle in Aroostook County, but in spite of temperatures
around 32F, there has not been much evidence of any impacts.
Temperatures will be rising above the freezing point early this
morning.

In terms of precip amounts today, PW values are increasing above
an inch today, but forcing is weak. A shortwave is propagating
northward across the area today, but there is not much lift and
overall rainfall should not amount to much more than a tenth of
an inch or so.

For tonight, an old occlusion eases into the area from the west
and deepen moisture will advect northward from the Gulf of
Mexico along the boundary. Increasing baroclinicity and lift can
be expected by later tonight with moderate rain developing. Low
temps tonight will drop no more than a few degrees from readings
this afternoon.
&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
A series of shortwaves cross the region Thursday through Friday
night ahead of a full latitude trough that takes on a negative
tilt as it progresses into the eastern Canada and the US, as it
becomes anchored in the general vicinity of James Bay/Southern
Hudson Bay. The result will be a period of generally rainy
weather from Thursday into Friday, with the possible exception
of far NW portions of the forecast area, where the rainfall
could be more spotty in nature and could be possibly mixed with
some snow at times. Precipitation could be heaviest on Friday,
with a 40-50kt low level jet (more focused at 950mb than 850mb)
passes just offshore. For now looking at 3/4-1 inch across far
NW areas, 1-2 inches then down to a Presque Isle to Dover-
Foxcroft line then 2-3.5 inches over the remainder of the area,
with heaviest amounts over Washington and coastal Hancock
counties. Refer to the hydrology section of the AFD for details
on potential impacts, including that of snowmelt.

The main question is how quickly does colder air move in on the
backside of the main low once it begins to deepen Friday
afternoon/night as it tracks from S of Nova Scotia to eastern
Nova Scotia then. For now, it is becoming increasingly likely
that the precipitation could change over to all snow from W to
E late Friday/Friday night. However, what is uncertain is how
quickly this transition will occur and how much precipitation
will be lingering over the area is it does so. For now only
looking for a few inches of snow, however, depending on how the
developing low tracks over the Maritimes, and how far to the
west its precipitation shield is, the answer could range from
little to no snow, to an advisory level snow. If the latter
scenario plays out, the higher snow totals should end up over
the eastern portions of the forecast area, closest to the
low/with the most amount of precipitation on the backside of the
system.

There should be gusty winds with this system with the passage of
the low level jet Friday and the low deepening to the SE Friday
night generally in the 25-40 mph, with some higher gusts across
higher elevations, generally above 2000 ft.

Highs on Thursday should be around 5 degrees above normal, and lows
Thursday night 10-15 degrees above normal. Highs on Friday
should be near normal, but could occur by early afternoon or
sooner. Lows Friday night should be around 5-10 degrees above
normal.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
The closed low gradually fills over the Maritimes Saturday
followed by northern stream shortwave ridging to build in
Saturday night. This should allow for precipitation to taper off
from SW to NE during this time frame. Winds should also
gradually diminish as well.

A northern stream trough passes Sunday followed by northern
stream shortwave ridging Sunday night. The low levels should be
sufficiently dry to preclude any precipitation as the trough
passes. Note slight chance pops are kept over far NE portions of
the area to reflect the low chance that the decaying low over
the maritimes impact lingers longer over the region than the
vast majority of guidance indicates.

Deep layer ridging builds in Monday-Monday night, so it should
be dry.

A northern stream trough approaches from the west on Tuesday,
working to push the ridge offshore. Most models and ensembles are
slower in doing so than previously forecast, so have lowered
pops on Tuesday and slowed the timing of the onset of
precipitation.

Temperatures should be near to slightly above normal from
Saturday night through Tuesday.


&&

.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
NEAR TERM: LIFR to VLIFR is expected today and tonight due to
low cigs, fog and drizzle. Low level wind shear is expected this
morning, and may continue into the afternoon north of HUL.
Southerly winds up to 50 kt will be possible at FL020 this
morning in a corridor from HUL to FVE. VLIFR can be expected at
times this morning and is likely this evening through the
night.

SHORT TERM:
Thursday-Thursday night...IFR or lower likely.

Friday...IFR or lower probable. Low chance for rain mixing with
or changing to snow in the afternoon across the North. NW winds
G15-25KT possible. LLWS possible at southern terminals in the
afternoon.

Friday night-Saturday morning...IFR or lower possible with snow
at Northern terminals and rain possibly mixed with snow at
southern terminals. NW winds G20-30KT possible with LLWS also
possible at southern terminals Friday night.

Saturday afternoon...Becoming VFR southern terminals and MVFR at
northern terminals. NW winds G20-35KT possible.

Saturday night and Sunday...VFR. NW winds G15-25KT possible.

&&

.MARINE...
NEAR TERM: Fog will set in over the water this morning and
persist through tonight. The fog will be locally dense. Long
period southeast swell will slowly diminish today and tonight,
but seas up to 7 or 8 feet necessitate keeping the Small Craft
Advisory in place today into the evening.


SHORT TERM: Fog remains the main issue over the waters Thursday
and Thursday night, with winds generally light into Thursday
evening, then increasing, but remaining below SCA levels late
Thursday night.

SCA conditions develop on all waters Friday, with a low chance
of gales by late afternoon. Gales are probable on all waters
Friday night, and possibly linger into Saturday morning. SCA
conditions then on all waters for the remainder of the day
Saturday. Conditions should improving to sub-small craft levels
by Sunday morning.

&&

.HYDROLOGY...
The heavy snow pack from this weekend is expected to melt
somewhat before heavy rains at the end of the week accelerate
the melting process. The snowpack is not quite ripe for melt
yet, but with heavy rainfall and somewhat saturated soils,
standing water could be an issue before water enters the main
stem rivers. In the north, main stem rivers will mostly be able
to absorb the additional input, but in the south, the
Piscataquis and Mattawamkeag are at risk for reaching minor
flood level late this week/early next week respectively. The
Penobscot will be slightly less impacted, but some points on the
lower reaches could reach action stage. In the far north, the
additional water input may be enough to finally move the ice on
the Saint John.

&&

.CAR WATCHES/WARNINGS/ADVISORIES...
ME...None.
MARINE...Small Craft Advisory until 8 PM EDT this evening for ANZ050-
     051.

&&

$$


Near Term...MCW
Short Term...Maloit
Long Term...Maloit
Aviation...MCW/Maloit
Marine...MCW/Maloit
Hydrology...Maloit


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