Area Forecast Discussion
Issued by NWS Caribou, ME

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FXUS61 KCAR 080208

Area Forecast Discussion
National Weather Service Caribou ME
908 PM EST Thu Dec 7 2023

High pressure will cross the area overnight into Friday. A warm
front will approach Friday night then cross the region
Saturday. Intensifying low pressure tracking across Maine will
draw a cold front across the region Sunday night into Monday.
High pressure builds Monday night into Tuesday.


9:08 PM Update: Satellite pictures and observations confirm
that more low clouds have dropped south into northern Aroostook
County along with flurries. Some of the lower clouds have made
it all the way south into parts of eastern Washington County.
The cloud forecast for the remainder of the night remains a
challenge with very low forecaster confidence. Given the overall
persistence of the clouds since last night will side toward it
remaining partly to mostly cloudy across the north while it
should remain clear from Bangor south to the Hancock County
coast. Where the sky is clear, temperatures have dropped to zero
to 5 above, but where the sky is cloudy temps are mostly in the
teens. Given the difficulty in trying to predict what will
happen with the areas of stratus overnight, it makes the
temperature forecast a real challenge. If an area can clear out
for just a couple of hours before daybreak temps could quickly
plummet. For now, will adjust temps to reflect the current
observations as of 9 PM, but am reluctant to make too many
changes to the overnight lows. In some areas an argument could
be made to raise them across the north, but if the clouds move
out later tonight it would end up being a mistake.

Previous discussion:
A mid level trof exiting to the east will continue to hold
shortwave energy over the northeast. For this evening, isolated
snow showers will continue for eastern parts for the St John
Valley, Central Aroostook, and Southern Aroostook. Vorticity
models show the vort max sagging south tonight, mainly into the
Central Highlands. However, the NW flow in the upper levels will
bring drier air into the region, helping to reduce moisture and
cloud cover. The early cloud cover in the north will help keep
temps above zero, except in the North Woods where winds will be
lighter allowing for more cooling. For the south, clear skies
will drop temps into the single digits.

For Friday, upper level ridging will start to move in behind the
trof. RH models show the clouds in the north completely clearing
by later in the morning, but high-res QPF models show some
isolated showers in NB. Cannot rule out the possibility of a
morning snow shower in this area. By the afternoon, expect sunny
skies with temps in the 20s across the region.


Radiational cooling with a very shallow inversion is the
forecast challenge for Friday night. Have leaned towards the
lower guidance given the usual troubles of models with shallow
winter radiation inversions. Readings below zero can be expected
across much of Aroostook County while teens are forecast for
Bangor and Downeast.

Warm advection and increasing cloudiness will the story for the
weekend. Expect sunshine on Saturday morning to give way to
clouds overspreading from the southwest. The concern for later
Saturday afternoon into Sunday morning will be freezing
drizzle...most notably in upslope locations such as Piscataquis
County and northern Penobscot County. Strong low level moisture
advection and warming temperatures over existing snow pack will
likely result in fog formation Saturday night into Sunday
morning for much of the area.

Any frozen precip exits the area Sunday morning. Low clouds will
remain entrenched over the area all day, but warm advection will
lift temperatures towards the mid 40s to around 50F on the
coast. Fog could linger well into the morning, but increasing
south winds later in the day reduce coverage mostly to high
terrain and upslope areas. Light rain and drizzle can be
expected Sunday, but the heavier precip will remain west until
Sunday night.


Temperatures warm steadily all of Sunday night and the high
temperature for Monday could occur before daybreak. Winds will
steadily ramp up through the night. The strongest winds will be
after midnight Sunday night through Monday morning. Have favored
NBM winds for this forecast that offers 60 mph or higher gusts
on the coast and nearly 50 mph at Bangor. Based on the forecast
pressure gradient and low level jet strength, local rules of
thumb strongly suggest wind headlines will be needed and power
outages can be anticipated. The only caveat is the low track
trending further east as advertised by the hemispheric GEMS.
Across all of the models, the forecast low track has been
trending slowly east in recent days.

Two other concerns with the Monday event will be precipitation
and coastal flooding. In general, current projections are for
one to two inches of rainfall. Deep Atlantic moisture with PWs
over 1.2 inches are anticipated. WPC has placed the area in a
marginal risk in the ERO. The good news is that the system is
progressive and not expected to linger over the area for a long
time. The heaviest precip will fall in higher terrain in
locations such as Piscataquis County where snow depth is highest
and response to heavy precip/snowmelt is more rapid. As a
result, will have to watch flood potential as the event becomes
more in focus this weekend.

The high tide for Monday morning will be near 9am LST. It is not
a particularly high astro tide, but high enough to warrant
concern. Max storm surge could coincide with the high tide. A
storm surge of 2 feet is certainly a possibility. In addition, wave
runup could deliver rocks on exposed roads on Mount Desert
Island and the Schoodic Peninsula.

Cold air advection arrives Monday afternoon. Rain will change to
snow with an inch or two conceivable in Aroostook County and
degradation to travel conditions as temps plummet below the
freezing mark. Winds will continue to be the story Monday night
with gusts above 30 mph most of the day across the entire area.

Temperatures decrease towards seasonable readings for the
remainder of the week. A series of moisture-starved northern
stream clippers will move across the area for the remainder of
the week. None look particularly promising for replenishing
snow cover in a significant way.


NEAR TERM: Aroostook Terminals...MVFR cigs continue with local
IFR at KFVE. The lower clouds should begin to dissipate toward
morning, but confidence remains low regarding the timing and
extent of the clearing. VFR conditions are expected Friday,
although can`t rule out MVFR persisting in the morning. NW
winds 5-10 kts.

Downeast Terminals...VFR conditions overnight and Friday. NW
winds around 5 kts.

Friday night into Saturday...Mostly VFR until Saturday afternoon
when MVFR cigs overspread the area from west to east. Light

Saturday night and Sunday...IFR to LIFR cigs with IFR vis in
fog Saturday night into early Sunday morning. Freezing drizzle
is possible Saturday night into early Sunday morning. South
winds steadily increasing towards 10 to 20 kt by later Sunday
afternoon.  LLWS possible by Sunday evening.

Sunday night...IFR to LIFR cigs, IFR to LIFR vis in fog and
drizzle, LLWS expected. South winds increasing all night with
gusts to 50 kt possible by late night.

Monday...Mostly IFR to LIFR cigs. IFR vis in locally heavy rain.
LLWS continues. South winds gusting to 50 kt in the morning,
becoming westerly 20 to 30 kt in the afternoon.

Monday night and Tuesday...MVFR cigs north of GNR and HUL,
otherwise VFR. Tempo IFR in snow showers north of GNR and HUL.
West winds 15 to 30 kt.


NEAR TERM: Winds and seas will remain below SCA conditions
tonight and Friday. Seas 1-2 ft.

SHORT TERM: The primary concern will be the potential for storm
force winds and seas approaching 20 ft later Sunday night into
Monday. Have bumped up winds and seas with this update. There is
still a chance the stronger winds will track east of the waters,
but the higher probabilities lie with the stronger winds.





Near Term...CB/LaFlash
Short Term...MCW
Long Term...MCW
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