483
FXUS61 KCAR 050455
AFDCAR

Area Forecast Discussion
National Weather Service Caribou ME
1255 AM EDT Fri Jul 5 2024

.SYNOPSIS...
A weak cold front will stall across the area overnight. The
front then slowly lifts back north Friday into Saturday as a
warm front. Another weak cold front will begin to cross the
region Sunday and move east of the region Monday. A surface
trough is expected to cross the area Tuesday.
&&

.NEAR TERM /THROUGH TODAY/...
Update...
A weak cold front, currently crossing northern Aroostook county,
will stall across central portions of the forecast area late.
An isolated shower could accompany the front across northern
areas. Isolated showers are then possible across central and
Downeast areas later tonight. Patchy fog is possible across
northern areas overnight, with areas of fog Downeast. Otherwise,
expect partly/mostly cloudy skies across the forecast area
overnight. Low temperatures will range from around 60 to the
lower 60s north, to the upper 50s to around 60 interior
Downeast and mid to upper 50s along the Downeast coast. Have
updated to adjust for current conditions along with expected
overnight temperatures, clouds, shower chances and fog coverage.

Previous Discussion...
A low pressure system to the north in Canada will swing a cold
front through the region tonight and Friday. By Friday, a low
pressure system intensifying over the Great Lakes will start to
lift a warm front across the region. During the morning, the
warm front will be over the Gulf of Maine, with showers and
patchy fog over coastal Downeast. By the afternoon, CAMS models
show the warm front moving into the Central Highlands. Some
guidance shows the warm front progressing slightly faster with
showers reaching into the North Woods by the afternoon.
Nevertheless, rain showers will cover the majority of the center
of the region. In addition, afternoon heating and frontal lift
will produce convection along the line of instability. High res
models show an unorganized area of 900-1200 J/kg of CAPE
stretching from Greenville to Houlton, which is to be expected
along the higher terrain. Weaker, but still high, CAPE north of
this line will also produce thunderstorms as well. Recent upper
air model soundings show a more impressive directional bulk
shear, though the speed at the surface and mixing layer are
lower than previous events. Cannot rule out possible strong
pulse thunderstorms with the instability. However, as the storms
cross over the higher terrain, they will be entering a more
stable environment with the S flow marine layer, weaken the
storms.
&&

.SHORT TERM /TONIGHT THROUGH SUNDAY/...
The warm front will continue to progress slowly northward
Friday night. Afternoon convection along the boundary will
gradually diminish in the evening. Otherwise, fog and low clouds
will spread northward under a frontal inversion. That will help
limit lows to the mid 60s for most of the area. The cool spot
will be the Downeast coast with an onshore flow producing lows
in the 50s.

The warm front continues to slowly push northward on Saturday
with rain likely. The low level frontal inversion is expected to
hold on much of the day, keeping highs in the low to mid
70s...even as 850mb temps surge towards 18C in the afternoon.
Surface-based instability is most likely to stay west of the
area due to the inversion. The exception might be the far
western portions of the North Woods. Given PWs around 2 inches
and strong deep layer shear, any surface-based convection could
be troublesome. In spite of the impressive precipitable water,
forcing looks weak and not expecting widespread QPF much above a
half inch. Locally higher amounts are possible with
thunderstorms. Did add mention of thunderstorms Saturday
afternoon and evening due to elevated CAPE and the chance that
the inversion breaks inland.

Weak low pressure slowly tracks across the area Saturday night.
Low level moisture advection along the low track increases the
risk of another round of fog and low clouds. Elevated
instability maintains a risk of thunderstorms through the
evening. Once again, lows will only drop to the mid 60s for much
of the CWA.

For Sunday, the low exits the area and ridging builds. In the
absence of any cold advection in the wake of the low,
temperatures will climb well into the 80s across much of
northern and eastern Maine. Humid conditions continue with dew
points in the mid to upper 60s. In terms of thunderstorms,
rising heights and warming aloft seem likely to overcome the
surface-based heating. Kept a slight chance of thunderstorms in
the forecast for the afternoon.
&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
The powerful subtropical ridge in the Atlantic will continue to
dominate early next week, keeping fronts from crossing the area
with cooler Canadian air masses. This mean temps and humidity
well above normal, but falling short of records. Both Monday and
Tuesday will bring highs in the mid to upper 80s. Onshore winds
will keep it a bit cooler along the coast.

The risk of afternoon thunderstorms increases Tuesday per the
04/12Z GFS while the 04/12Z ECMWF suggests a higher risk on
Wednesday. While operational models show strong dynamics for
Wednesday, the case for severe storms remains in doubt due both
to timing and potential for low level clouds limiting heating.
Did drop off Wednesday high temps back into the 70s based on
more cloud cover.

The cold front Wednesday night offers a good chance to bring
temporary relief to the heat and humidity for late next week.
&&

.AVIATION /05Z FRIDAY THROUGH TUESDAY/...
NEAR TERM: Variable conditions across the region overnight into
early Friday with any low clouds or fog, most extensive
Downeast. IFR/LIFR, possible VLIFR, with any fog. Otherwise,
generally VFR/MVFR with isolated to scattered showers overnight.
Variable conditions with any thunderstorms Friday which could
produce locally heavy rain. Variable winds 5 to 10 knots
overnight into Friday.

SHORT TERM:
Friday night...Thunderstorms are possible in the
evening...mostly north of GNR and HUL. Otherwise, fog is likely
to set in for all sites later in the night with IFR to LIFR vis.

Saturday...Fog and IFR cigs may be persistent into the
afternoon for coastal sites and as far north as Bangor. Other
sites will be VFR by afternoon. Afternoon thunderstorms are
possible for all sites.

Saturday night...Fog and IFR cigs will most likely move north
from the coast to affect all sites again. Thunderstorms are
possible in the evening.

Sunday...IFR cigs will gradually lift to MVFR in the morning and
all sites will gradually become VFR in the afternoon. There is a
slight chance of thunderstorms in the afternoon for inland
locations.

Sunday night...Expect generally VFR except possibly on the coast
to include BHB.

Monday into Tuesday...Mostly VFR except the threat of nighttime
fog and low clouds for coastal sites such as BHB.
&&

.MARINE...
NEAR TERM: Winds/seas below small craft advisory levels
overnight through Friday. Fog developing overnight and
persisting Friday. Isolated/scattered showers later tonight
into Friday.

SHORT TERM: Stable conditions persist through the period with
little chance of any advisories. Adjusted winds downward this
weekend due to stability. Fog is a more likely threat in this
warm and humid regime. Everyday well into next week should
feature some degree of fog or haze.
&&

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

&&

$$


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