-- Discussion containing changed information from previous version are highlighted. --
378
FXUS61 KCAR 270428
AFDCAR

Area Forecast Discussion
National Weather Service Caribou ME
1228 AM EDT Thu Jun 27 2024

.SYNOPSIS...
A cold front will cross the region overnight through Thursday
while low pressure moves along the front. High pressure will
cross the region Friday. A cold front will approach later
Saturday, then cross the region Sunday. High pressure will build
toward the region Monday.

&&

.NEAR TERM /THROUGH TODAY/...
-- Changed Discussion --
1220 am update: Rain is overspreading the area along the stalled
cold frontal boundary. Removed mention of thunder for most
locations tonight...expect near the coast. The front does not
cleanly make across the forecast area tonight and there is the
risk of another round of thunderstorms this afternoon for the
Downeast region. Deep layer shear remains very impressive, but
instability appears to be in short supply.

An upper trough crossing northern zones late afternoon into the
evening will bring enough mid-level cooling for a separate area
of isolated thunderstorms...mostly in northern Aroostook
County. These northern thunderstorms will feature a very low
freezing level that merits consideration of small hail.

Previous discussion:
A cold front will begin to cross the region tonight. A
disturbance approaching from the west will help support the
development of surface low pressure along the front. The front
will slow across the region overnight into Thursday while the
surface low moves along the front. The cold front will then
slowly settle south across the forecast area later Thursday in
the wake of the low. Isolated/scattered showers, possibly an
isolated thunderstorm, will occur early tonight. Rain will then
develop overnight with the surface low and approaching upper
level disturbance. Rain will persist early Thursday. Isolated
thunderstorms are also possible with the rain overnight into
Thursday morning. Patchy fog is also expected overnight into
Thursday morning. Precipitation will then taper to showers in
the wake of the exiting low Thursday afternoon. An upper level
trof approaches later Thursday with cooling temperatures aloft
supporting steepening lapse rates. Increased instability with
the steepening lapse rates, along with the cold front, will
also support the possibility of isolated thunderstorms Thursday
afternoon along with the showers. The heaviest rains are
expected across Downeast areas overnight into Thursday morning.
Rainfall totals overnight through Thursday are generally
expected to range from up to around an inch Downeast, with a
half to three quarters of an inch across northern areas.
However, locally heavier totals are possible. Low temperatures
tonight will range from the upper 50s to around 60 across the
forecast area. High temperatures Thursday will range from the
upper 60s to around 70 north, to around 70 to the lower 70s
Downeast.
-- End Changed Discussion --

&&

.SHORT TERM /TONIGHT THROUGH SATURDAY/...
Thursday night, the main upper level trough behind the cold
front will drop south, bringing cooler temperatures across the
region. 850 hPa temperatures will drop to an unseasonably cool 2
to 4 degrees Celsius, and surface temperatures will also drop
accordingly. A batch of post-frontal showers is possible late
Thursday night ahead of the upper level trough, but these are
expected to mostly be confined to the northern portion of the
forecast area, where the greatest instability remains. On
Friday, ridging will move in, bringing quiet weather and a
slight warming for the temperatures aloft. This will keep the
lows Friday night from falling quite as low as Thursday night,
but overnight temperatures will still be unseasonably cool.

On Saturday, a warm front will approach, bringing southwest flow
and increasing humidity. Some showers may pop up ahead of the
front, but the bulk of the precip is not expected until Saturday
night. The main atmospheric change expected on Saturday will be
a moistening of the air column, with PWATS increasing to above
an inch during the day.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
Saturday night, the warm front will cross the area, raising
mid-level temperatures significantly and continuing to increase
PWATs. On Sunday, this will transition to a more showery regime
as the cold front approaches. Timing of frontal passage is
unclear due to differences between the models, but this should
happen late Sunday evening. The complexity in this system is
with the potential for thunderstorms and heavy rainfall. On
Saturday night, it appears that a few elevated thunderstorms are
possible, but with the overall warming of the mid-layers behind
the warm front they do not look widespread. On Sunday,
thunderstorms could be both more widespread and more severe.
CAPE values will be on the increase in the warm, moist air mass
ahead of the front, combined with an increase in bulk shear as
well with the pre-frontal jet. The potential for heavy rainfall
also exists both Saturday and Sunday, with Sunday looking
slightly better ahead of the warm front. This system overall
does not have a long residence time, so widespread rainfall
amounts appear to be on the order of 0.5 to 0.75 inches across
the forecast area. However, with a deep warm cloud layer and the
potential for training, localized heavy precip cannot be ruled
out. These details will have to be resolved further as we get
closer in time and the event moves into the range of the CAMs.

The rest of the forecast looks pretty quiet as ridging moves
overhead early next week, with no notable temperature anomalies.

&&

.AVIATION /04Z THURSDAY THROUGH MONDAY/...
NEAR TERM: VFR late this evening with isolated showers,
lowering to IFR/LIFR, overnight with developing rain with
isolated thunderstorms also possible. Rain possibly heavy at
times late tonight Downeast. IFR/LIFR with rain and isolated
thunderstorms Thursday morning. VFR/MVFR, occasional LIFR, with
showers and isolated thunderstorms Thursday afternoon. Patchy
fog overnight into Thursday morning. Southwest/west winds 10 to
15 knots early tonight, becoming variable 5 to 10 knots
overnight. Variable winds 5 to 10 knots Thursday.

SHORT TERM:

Thursday night through Saturday...VFR. Northwest
winds on Friday at 5 to 10 will become southerly on Saturday at
10 to 15 kt.

Saturday night into early Sunday morning...IFR cigs and tempo
IFR vis in rain. Isolated embedded thunderstorms. LLWS likely.
South winds 10 to 20 kt.

Sunday...IFR becoming MVFR tempo VFR. Afternoon thunderstorms likely.
Southwest winds 10 to 15 kt becoming NW late afternoon.

Sunday night and Monday...Conditions rapidly improving to VFR.
NW winds 10 to 15 kts.* Add discussion here.

&&

.MARINE...
NEAR TERM: Winds/seas generally below small craft advisory
levels tonight through Thursday. However, seas are running just
over 5 ft at the Jonesport buoy in a south swell and have issued
a small craft advisory until 6 am EDT Thursday morning.
Rain developing along with isolated thunderstorms overnight
which will persist into Thursday morning. Showers along with
isolated thunderstorms Thursday afternoon. Patchy fog overnight
and Thursday.

SHORT TERM: Winds increasing to high end SCA Saturday through
Sunday. Seas building to 6 feet by Sunday, subsiding by early
Monday. Potential for fog Thursday night and again Saturday
night into Sunday.

&&

.CAR WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
ME...None.
MARINE...Small Craft Advisory until 6 AM EDT early this morning for
     ANZ050.
-- End Changed Discussion --

&&

$$


Near Term...CB/MCW/Norcross
Short Term...LF
Long Term...LF
Aviation...CB/MCW/Norcross/LF
Marine...CB/MCW/Norcross/LF