-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KCAR 201616
AFDCAR

Area Forecast Discussion
National Weather Service Caribou ME
1216 PM EDT Sat Apr 20 2024

.SYNOPSIS...
An occluded front crosses the region Saturday, then exits
across the Maritimes Sunday. A strong cold front crosses the
region Sunday night into Monday. High pressure then builds
across the region later Monday into Tuesday. Low pressure
approaches Wednesday.

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
12:15PM Update...Sharp edge of the drier air working into the
North Woods with skies clearing along the Quebec border. Can see
cu forming in Quebec in response to the rapidly cooling air
aloft associated with the 500mb shortwave. Steady precip from
the occluded front will continue to slide east this afternoon
into New Brunswick. There remains some modeled soundings
continue to show the airmass trying to become unstable with the
cooling air aloft. However, by the time it reaches our CWA
expecting the loss of daytime heating (the little bit we get) to
wane and just expecting showers and no thunderstorm activity to
survive. However, thunderstorms are possible back west of our
CWA but unlikely to survive at this point into our CWA. Will
continue to monitor trends but cannot rule out in graupel
falling in any showers that do exist with the cooling air aloft
bringing the freezing levels significantly lower than this
morning. No other major changes...

Previous discussion...
The occluded front has moved into the area this morning and has
stalled. An upper level shortwave swinging out of the Great
Lakes region towards Maine is creating a very dynamic situation
ahead of the frontal boundary this morning. H7 temp gradients
are tightening with strong mid level UVVs developing. The
enhanced lift is just now starting to produce an expanding area
of precipitation in southern New England that will advect
northeastward along the stalled frontal boundary towards
Downeast in the coming hours.

Moisture advection south of the boundary will push PWs towards
an inch on the Downeast coast. Low level moisture advection will
generate some fog towards the coast today with dew points
surging into the low to mid 40s. Moderate rainfall will move
across southern Penobscot County and across Hancock and
Washington counties through the morning into the early
afternoon. Overall rainfall totals will reach over a half inch
in those areas today, but amounts will fall off dramatically
north of the I-95 corridor. The North Woods and the Saint John
Valley will receive little to no rain today and experience
warmer high temps in the lower 50s versus mid to upper 40s
Downeast.

The frontal boundary will also feature a particularly sharp dew
point gradient such that afternoon dew points in the North Woods
may be near 20F versus the mid 40s on the coast. The boundary
will sag southward this afternoon as the steadier rain departs
Downeast.

A vort max at the base of the upper level trough arrives this
evening and promises to produce some instability along the front
this evening. Mid-level lapse rates will exceed 7C/km. This
instability will be mostly from the Bangor area and eastward
across the Downeast region. Time of day will work against any
thunderstorms, but some guidance is advertising a few hundred
J/kg of SBCAPE this evening. Will maintain chance PoPs for
showers through the evening. Cannot rule out graupel given the
low freezing levels.

Clearing is anticipated for tonight. Colder air will gradually
advect southeastward behind the front tonight. Lows will drop
into the 30s by Sunday morning.
-- End Changed Discussion --

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
A strong cold front located over the Great Lakes will begin to
approach the region on Sunday. Thought the front should not
reach the area by Sunday, energy and moisture ahead of the
system could produce convection across the north by the
afternoon. Increasing W flow is expected to keep temps in the
40s for the North Woods, but elsewhere could see 50s. By Sunday
night, the cold front is expected to move through the region,
exiting over the waters late. Any light rain showers in the
north should switch over to snow showers with the frontal
passage. This arctic cold front shows in the 925-850mb model
temps with a drastic temp gradient moving through after
midnight. Expect W winds to become breezy late and temps in the
north to decrease to the 20s. The south should see clearing
skies and temps in the upper 30s.

By Monday, the cold front exiting over the waters and the
approaching high pressure will tighten pressure gradients making
for a breezy morning, especially in the north. This coupled with
the cold temps will drop wind chills to the teens with a slight
increase into the 20s by late morning. The high temp for the day
should be in the mid to upper 30s in the north and 40s in the
south. The winds should decrease by the afternoon with high
pressure moving into. By Monday night, expect clear skies with
decreasing winds and temps cooling to below freezing.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
High pressure on Tuesday should help return flow usher in a
warm airmass into the area, bringing temps back into a more
seasonable 50s with increasing clouds. The next system is
expected to move into the region Tuesday night into Wednesday.
Extended guidance shows this system as a intensifying low
pressure system moving across Canada and into the Great Lakes.
However, the Euro and Canadian show the system developing into
an occlusion by Tuesday night with an intensifying triple point
moving across New England by Wednesday. The GFS shows a strong
low center rotating through the state by Wednesday and
continuing through Thursday. Per the previous discussion, the
predictability is not high with this sort of setup, and many
things could happen. We will very likely get some precipitation
some time late Tuesday night to Thursday, with progressively
colder air and perhaps a changeover to accumulating snow toward
Wednesday night or Thursday. Whether we change to accumulating
snow depends on the position of the upper low and how long it
hangs out over our area.

&&

.AVIATION /16Z SATURDAY THROUGH WEDNESDAY/...
NEAR TERM: Terminals north of HUL and GNR will likely remain VFR
through the period. Further south, cigs will become IFR in rain
today. LIFR is possible today at BHB. South winds 10 to 20 kt
will become southwest later today.

SHORT TERM: Sunday...Mainly VFR, though brief MVFR in scattered
showers from MLT and GNR north. W wind 10-15 kts with gusts
around 20 kts.

Sunday Night...VFR until after 6z in the north, when a cold
front moves in from the NW. This could bring brief MVFR/IFR to
areas from PQI north. Winds will be SW 5-10 kts, shifting to the
NW 10-20 kts with gusts to 30 kts late and in the north behind
the cold front.

Monday...Generally VFR, except local MVFR early mainly N of HUL.
W/NW winds 10-20 kts with gusts 20-30 kts.

Monday Night...VFR with light winds.

Tuesday...VFR with S wind 10-15 kts.

Tuesday Night and Wednesday...Low confidence, but potential for
MVFR/IFR late Tuesday night into Wednesday with rain. Generally
S wind 10-20 kts.

&&

.MARINE...
NEAR TERM: Very moist air and moderate rainfall all day will
produce fog today into this evening. The stability will keep
winds generally at 10 to 15 kt from the south with just a few
gusts reaching 20 kt. Seas will be around 3 to 4 feet. Winds
will become westerly tonight around 10 kt.


SHORT TERM: Next chance of small craft comes Sunday night and
Monday. Then a likelihood of small craft late Tuesday into
Wednesday.

&&

.CAR WATCHES/WARNINGS/ADVISORIES...
ME...None.
MARINE...None.

&&

$$


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