907
FXUS61 KCAR 232027
AFDCAR

Area Forecast Discussion
National Weather Service Caribou ME
327 PM EST Mon Dec 23 2024

.SYNOPSIS...
Low pressure will approach tonight and track along the coast on
Tuesday. High pressure will slowly build down from the
northwest Wednesday through the end of the week and crest over
the area this weekend.

&&

.NEAR TERM /THROUGH TUESDAY/...
Challenging Forecast with Hazardous Travel Impacts Expected
Tonight into Christmas Eve.

This evening will feature high clouds increasing with a very dry
and cold boundary layer. Winds have shifting SW with moisture
advecting ahead of an approaching positively tilted sharp 500mb
trof. Expecting temperatures to fall this evening into the
single digits north with teens south across the CWA. Winds are
generally light and variable if not calm for much of the night.
Late this evening expecting the boundary layer to moisten up
over the Moosehead Region and North Woods with light snow
developing. A weak surface low pressure along the boundary will
track into Southern Maine and up along the Downeast coast into
Tuesday which will aid in the enhancement of precipitation.

What has changed?...Models continue to enhance the strength of
the 500mb trof with stronger area of PVA. The jet stream
increases with upper level divergence enhancing the surface lift
along and north of a developing coastal thermal gradient. In
addition, stronger moisture advection despite this being a
Alberta clipper origin will enhance QPF values compared to what
has been modeled till today`s hi-res CAMs and 12z global suite.

Timing...Light snow develops from 10PM - 2AM tonight from west
to east. Snow will become moderate at times especially in the
Central Highlands to Downeast Coast into the morning hours. Snow
will taper late morning from the North Woods to around Noon
along I-95 and then not until tomorrow evening for the Downeast.

Snowfall...liquid QPF expected to be around 0.1 inch north, 0.2
to 0.3 inch in the Central Highlands and 0.35 to 0.5 inch for
the Downeast Coast. Modeled soundings show decently moist DGZ
with 30-40kt winds which will prevent the snow being very fluffy
but still decently fluffy expected. Opted to go with a 19-20:1
ratio across the north, 18-19:1 ratio in the Central Highlands
and then a 14-16:1 ratio along the Downeast coast. There is some
hi-res CAMs tomorrow afternoon showing weak instability in the
DGZ suggesting some convective enhancements possible. This gives
us storm totals of 2-4 inches for Northern and Northeast
Aroostook County into Northern Somerset, Piscataquis and
Penobscot Counties. Across the Central Highlands including
Moosehead, Baxter to Houlton then down to Bangor and Danforth
area expecting 4-6 inches. For Interior Downeast including Route
6 and 9 expecting generally 5-6 inches with isolated higher
amounts up to 7 inches possible. Coastal Hancock including Route
1 and MDI expecting 4-7 inches then Coastal Washington including
Cutler, Lubec and Eastport expecting 6-9 inches. It is possible
Downeast Maine could see higher amounts with several hi-res
models including 18z HRRR, HREF, NAM, ICON and RAP showing
double digits from Jonesport eastward. This will be a challenge
with how fluffy, warm air intrusion as the low passes by and the
amount of liquid. Opted for now to hoist Winter Weather
Advisories for the Central Highlands including Greater Bangor
area and from Coastal Hancock to Northern Washington and
Southern Aroostook County. Opted to upgrade to a Winter Storm
Warning for Coastal and Central Washington County due to
increased confidence in snowfall totals over the 6 inch
threshold and the potential for higher amounts.

Impacts...Travel! Big holiday travel day is expected with
several roads being impacted including I-95. Conditions will
improve late morning into midday along and NW of I-95. Downeast
expecting impacts to travel all day with slippery roads.
Snowfall will be light and fluffy and with light winds not
expecting any blowing concerns. Tomorrow evening winds may gust
as high as 15mph after the snow ends which could cause some
drifting in open areas.

Temperatures...Highs will be in the upper teens to low 20s
across the north. Mid 20s for the Central Highlands and upper
20s to around 30F for the Downeast coast. It may touch 32-34F
for the immediate shoreline and islands as the low pressure
passes but will drop back below freezing once it passes to the
east.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
As the storm exits Tuesday evening into Wednesday, expect some low
clouds to remain in northerly low level flow. The cold air mass
in place before storm remains entrenched over the area with lows
dropping back into the single digits and teens for Tuesday
night and highs in the 20s Wednesday. Some readings near the
freezing mark may be expected for coastal Downeast.

High pressure at the surface and aloft will remain in control
over area weather through the remainder of the period. A
blocking pattern emerges by late week. Temperatures aloft warm
through the period, but cold air remains trapped under a
steepening inversion. The challenge in the forecast will be
whether stratocumulus persists through the period under the
inversion. Such a development will have a huge impact on low
temperature forecasts. Clearing at night will foster strong
radiational cooling given the fresh snow cover, light winds and
time of year. Lows could drop below zero. On the other hand,
cloud cover could keep lows in the 20s. NBM percentiles reflect
the uncertainty. For now, have taken an optimistic position on
cloud cover after Wednesday and leaned towards a consensus of
guidance on lows.
&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
Although the column warms through the period under the
anomalously strong upper ridge, the coldest nights of the week
may be Thursday night and Friday night with widespread single
digits...and possibly sub zero readings in northern zones. Given
these lows and the time of year, high temperatures will make
little progress with the inversion. Most of the area stays in
the 20s both days other than the Downeast coast where lower 30s
are forecast.

The high slowly breaks down during the weekend into early next
week and a frontal system is expected to approach from the west.
The question will be whether the high breaks down in this
forecast period or hangs on into next year. While the air mass
modifies during the weekend, CAD sets up and any initial precip
later Sunday into Sunday night stands a decent chance of being
freezing rain or sleet even through we have specified snow in
the forecast for now.

Besides timing, the other variables of interest early next week
will be the amount of precipitation and warming. Using a blend
of guidance, we transitioned P-type to rain on Monday with highs
pushing into the mid to upper 30s and staying in the 30s into
Monday night.  PoPs were capped below 50 percent Sunday night
through Monday night due to the timing uncertainties.
&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
NEAR TERM: VFR this evening. Becoming MVFR overnight with IFR
possible especially at southern terms due to vsby. -SN will
develop overnight and spread eastward. IFR/MVFR will become VFR
late tomorrow from SW to NE. Tonight winds light and variable
turning N 5-10kt tomorrow afternoon.

SHORT TERM:
Tuesday night and Wednesday...Predominately MVFR cigs with light
N winds.

Wednesday night into Saturday...Generally VFR with light N
winds. MVFR cigs may hang into Wednesday night, but the trend
should be improving for late week...albeit slowly.

&&

.MARINE...
NEAR TERM: Small Craft Advisory for the Coastal Waters from
Midnight tonight till 1PM Tuesday. SW wind gusts up to 30kt are
likely during this time. Seas will be building 3-6ft. Intra-
Coastal waters seas generally 2-4ft with a few gusts up to 25kt
during the day tomorrow.

SHORT TERM: A brief SCA may be needed Tuesday night into
Wednesday with northerly winds gusting to 25 kt. High pressure
builds Wednesday night through the rest of the week with winds
and seas remaining below advisory criteria.

&&

.CAR WATCHES/WARNINGS/ADVISORIES...
ME...Winter Weather Advisory from 10 PM this evening to 1 PM EST
     Tuesday for MEZ005-006-010-011-015-031.
     Winter Weather Advisory from 1 AM to 1 PM EST Tuesday for
     MEZ016-029-032.
     Winter Storm Warning from 1 AM to 7 PM EST Tuesday for MEZ017-
     030.
MARINE...Small Craft Advisory from midnight tonight to 1 PM EST Tuesday
 for ANZ050-051.

&&

$$


Near Term...Sinko
Short Term...MCW
Long Term...MCW
Aviation...Sinko/MCW
Marine...Sinko/MCW