752
FXUS61 KCAR 050809
AFDCAR

Area Forecast Discussion
National Weather Service Caribou ME
409 AM EDT Sat Apr 5 2025

.SYNOPSIS...
Low pressure approaches from the west today into tonight, then
crosses the area on Sunday. Weak high pressure builds Sunday
night and Monday. Low pressure approaches from the west Monday
night, crosses Maine on Tuesday, then exits into the Maritimes
Tuesday night. High pressure builds into the region on
Wednesday and slides south of Nova Scotia on Thursday.

&&

.NEAR TERM /THROUGH TONIGHT/...
High clouds will thicken and lower today ahead of an
approaching occlusion. While most of the day may be dry, precip
will arrive quickly late in the day from west to east. Although
highs will be near 40F, evaporative cooling will quickly reduce
boundary layer temps and expect rain to mix with snow and
change to snow rapidly during the late afternoon and evening.
CAD sets up later today into tonight, allowing only very slow
warming at the surface while temperatures warm aloft. Critical
thicknesses are quite marginal for snow. A warm nose aloft will
ensure precip changes to sleet and freezing rain Saturday night
from south to north. The last hold out will be northern
Aroostook County where accumulating snow is most likely. All
told, one to three inches are expected in the North Woods and
northern Aroostook. Less than an inch will fall elsewhere. The
mixed precip has prompted Winter Weather Advisories.
Accumulating freezing rain is most likely in the North Woods
from the Moosehead Lake northward, but have added eastern
Aroostook County to the advisory with this update. Freezing rain
is most likely to accumulate less than a tenth of an inch. The
only exception may be in the Moosehead and Katahdin regions.

While forcing is generally weak, moisture advection is strong
with PWs increasing towards an inch or more for southern
portions of the area. This is the moisture from the storms in
the lower Mississippi Valley. A northern stream upper trough
will phase with this southern stream moisture later tonight
into very early Sunday morning. Most guidance shows steadier
precip during this period as a triple point low forms near the
coast on the occlusion. Total QPF for the event remains over a
half inch for most of the area.

Kept mention of sleet in the forecast for areas where surface
temps rise above freezing through much of the night. A
subfreezing layer is expected to persist from just above the
surface towards 850mb.  By later in the night, the southerly
flow increases with mixed precip changing to all rain in
southern portions of the forecast area such as the Bangor area.
The warmer and moister air will likely generate fog. The thicker
fog arrives towards the coast later in the night as surface
winds diminish.
&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
Northern stream trof passing well north of Maine on Sunday as a
weak surface system tracks into the Maritimes. A secondary cold
front will cross the area later in the afternoon. Steady precip
ends behind the departing occluded front and weak surface system
and tapers to showers. Intially in the morning could still be a
freezing rain/sleet mix across the north but most locations are
already plain rain. The secondary cold front will shift winds to
the NW and cold air advection kicks in. High temperatures will
top out in the mid 40s across the north, upper 40s for the
Central Highlands and low 50s from Bangor to the Downeast Coast.
Intially rain showers across the north in the afternoon will
gradually change to snow showers as the column aloft cools below
0C but not expecting much accumulation. W-NW winds in the
afternoon gusting 15-25mph at times.

Sunday night expecting high pressure to settle down over the
state as a weak cold front works SE into Quebec. A weak storm
system will be tracking well south of Cape Cod with moisture
advecting northward off the Gulf of Maine. Expecting a partly
cloudy night north with mostly cloudy skies south. Temperatures
falling back into the upper teens to low 20s north with upper
20s to near 30F for the Bangor Region, Central Highlands and
Downeast Coast. Looking at a few snow showers from the Bangor
region to the coast as the boundary layer moistens up but not
expecting much accumulations.

Monday - Monday Night there is some noticeable differences in
the models on what will happen with precipitation... An
approaching 500mb trof will rapidly dig deep into the Great
Lakes positively tilted. Over Maine the jet will orient itself
up the Eastern Seaboard with moisture advecting northeastward on
increasing SW flow aloft. This will favor surface convergence
as upper level divergence increases. Temperatures warm into the
upper 30s north with mid 40s south but the dew points will be
much lower given dry boundary layer conditions. Opted to
significantly cut back POPs from the NBM output because looks
like more clouds than any precip. Cannot rule out some showers
(rain or snow) along the Downeast coast to Bangor region. Monday
night temperatures dip back into the 20s over the entire area
as the trof approaches.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
Tuesday becomes very interesting with wide differences in
operational models and ensembles over the last several runs. The
southern and northern stream of the jet stream get really close
off the Northeast coast and potential for phasing is likely but
timing and location differ. Sharp 500mb trof continues to dive
SE with a vertically stacked system in the base of the trof as
waves of low pressure track up along the southern stream near
the Gulf Stream. Previous operational runs had a phasing of
storm systems and eventual coastal low developing while latest
operational runs backed off that idea to an extent with ensemble
members still showing the possibility. Another scenario is the
phase to occur late in far Eastern Maine or Coastal New
Brunswick creating a deformation zone to the NW that could
result in a period of snow with cold air drawn down from Quebec
and rain in the southern 1/2 of the CWA changing to snow with
colder air. At this point this seems more favorable and is
depicted in the NBM but this is an important point in the
forecast we will need to refine over the coming 1-2 days. There
is a potential for impactful weather Tuesday AM into Tuesday
Night across Eastern & Northern Maine.

Beyond into late week continued blocking in the North Atlantic
is expected with -NAO conditions as the PNA remains negative
neutral to slightly negative. This will turn the 500mb trof out
into the North Atlantic and overall turns more zonal. Wednesday
into Thursday mainly dry conditions with cold Wed AM lows and
Wed PM highs. Winds shift SW on Thursday and slightly warmer
temperatures with 40s returning. Friday looks to be the next
system as another trof develops to our west and likely will
feature a surface system ahead of the trof.


&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
NEAR TERM: VFR. Chance of IFR vis late today in snow and sleet.
SE winds 5 to 10 kt. For tonight, IFR tempo LIFR in
snow/sleet/freezing rain and IFR cigs. LIFR vis in fog possible
later in the night for BGR and BHB. South winds 10 to 15 kt.
LLWS likely, especially later in the night.

SHORT TERM: Sunday...IFR or lower in the morning becoming VFR
from SW to NE into the afternoon. South winds 5 to 10 kt in the
morning. LLWS possible Sunday morning, NW winds G15-25KT
possible in the afternoon.

Sunday night-Monday night...VFR. Cannot rule out VCSH for
southern terms Monday. NW-N winds G15-20KT possible Sunday
evening. Winds light and variable on Monday into Monday night.

Tuesday-Tuesday night...IFR or lower possible with snow North
and rain/snow changing to snow at southern terminals. LLWS
possible Tuesday, E-SE winds shifting W-NW G15-25KT possible
Tuesday night.

Wednesday...VFR, except for low chance of MVFR or lower early at
northeastern terminals in any lingering snow. W winds G15-25KT
possible.

&&

.MARINE...
NEAR TERM: Have issued a new Small Craft Advisory for tonight
with SE winds gusting to over 30 kt and seas building towards 7
to 8 feet later tonight. Cannot rule out a few gusts to 35 kt
tonight, but not inclined to go with a gale at this point.


SHORT TERM: Small Craft Advisory conditions will weaken and
subside by late afternoon Sun. Winds/seas below SCA conditions
from Sun evening through early Tue morning. SCA conditions
likely Tue mid morning through Wed afternoon for winds and seas.
Cannot rule out a brief period of W-NW gusts to 35kt Tue night
into Wed morning. Winds/seas go back below SCA conditions for
late week.

&&

.CAR WATCHES/WARNINGS/ADVISORIES...
ME...Winter Weather Advisory from 5 PM this afternoon to 6 AM EDT
     Sunday for MEZ001>006-010.
MARINE...Small Craft Advisory from 8 PM this evening to 2 PM EDT Sunday
     for ANZ050>052.

&&

$$


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