393
FXUS61 KCAR 122259
AFDCAR

Area Forecast Discussion
National Weather Service Caribou ME
659 PM EDT Fri Jul 12 2024

.SYNOPSIS...
A frontal boundary will remain stalled across the region
tonight. A disturbance will cross the region Saturday. High
pressure will cross the region Sunday. A cold front will begin
to approach Tuesday. The front stalls over the region on
Wednesday.
&&

.NEAR TERM /THROUGH SATURDAY/...
Update...
A frontal boundary will remain stalled across Downeast areas
tonight, while an upper level disturbance lifts northeast toward
the southern Gulf of Maine. Isolated/scattered showers will
occur across the region this evening, with an isolated
thunderstorm also possible across central and interior
Downeast areas. These showers/thunderstorms will end later this
evening with the loss of diurnal heating. The stalled frontal
boundary will help focus moisture overnight, where precipitable
water values will approach 2 inches across Downeast areas.
Expect isolated/scattered showers across central and Downeast
areas later tonight. Also expect areas of fog Downeast, patchy
fog elsewhere, tonight. Otherwise, expect partly/mostly cloudy
skies across the forecast area tonight. Low temperatures will
generally range from the lower to mid 60s across the forecast
area. Have updated to adjust for current conditions along with
expected overnight temperatures, clouds and shower chances.

Previous Discussion...
The upper level ridge over the Mid Atlantic and the weak upper
level trof over the Great Lakes will continue to funnel tropical
moisture into the region tonight and Saturday.

For Saturday, showers will start to increase and spread across
the north as the upper level trof starts to move over the state.
This trof will create a frontal boundary at the surface, where
instability can develop in the afternoon. Model guidance shows
the boundary setting up across the Bangor Region and Interior
Downeast where the majority of instability is. Upper air model
sounding show CAPE >1000 J/kg, steep lapse rates, upper level
divergence. Thunderstorms are expected to be pulse storms with
the weaker bulk shear across the area. However, with the higher
lapse rates, moderate DCAPE, and higher PWATS, some
thunderstorms could produce heavy rain and gusty winds.
&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
For Saturday night, the upper trough will quickly move through
the area and convection will end during the evening. There are
some signs of elevated instability persisting through the
evening and have maintained mention of thunderstorms until about
10 pm. Clearing skies develop as the night progresses, but do
not foresee temperatures dropping below the low to mid 60s in
the humid air mass. The moisture will help produce patchy fog
inland and more expansive areas of fog for the Downeast coast.

On Sunday, a dry upper ridge moves through the area. The lack
of clouds and subsidence will help propel temperatures back into
the mid to upper 80s across the area. A deep mixed layer may
even allow a few 90s. Expect little relief even at the coast
with the west-southwest flow. Will probably need to issue a
Beach Hazards Statement due to the cold water temps. Heat
indices will likely remain a few degrees below advisory
criteria. In terms of convection, expect the subsidence and a
cap to inhibit formation of any storms.

High pressure and clear skies remain in place Sunday night, but
so will the humid air mass. Once again, lows will only drop
into the mid 60s for most of the area...a bit warmer than the
previous night.

High temperatures on Monday will again climb into the upper 80s
with a few 90F readings possible. No change in humidity means
another day close to Heat Advisory criteria. The only
differences from Sunday will be a cooler day on the coast due to
a more onshore flow, and the possibility of afternoon
convection. A weak, compact shortwave propagating in a fast
northern stream flow would be the culprit to destabilize the
atmosphere, but there is little agreement in guidance on the
evolution and timing of this feature...possibly because it may
be an MCS that has yet to form. Therefore, confidence is not
high and have generally only assigned 15 to 30 percent PoPs for
Monday afternoon with an eye towards further reductions.
&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
There are signs of a temporary break in the heat later next week
as a fairly strong upper trough digs southward from Canada
towards the northeastern US. However, the price for the cool off
will be continued heat early next week and the potential for
strong thunderstorms Tuesday and Wednesday.

Upper level ridging starts to break down Tuesday, but not before
the most of the area experiences another day in the upper 80s.
It may end up as the warmest day of the week, and the most
likely day for any heat advisories.  Onshore southerly winds
will provide some relief for the Downeast coast. As the vigorous
upper trough digs southward towards the Great Lakes region, a
weakening occlusion will approach the area late day with the
potential for afternoon thunderstorms. The risk will be greatest
in the northern zones. Deep layer shear will increase during the
afternoon and the potential for strong storms is there.

The front tends to hang up over the area Tuesday night into
Wednesday as the upper trough continues to dig southward into
the Great Lakes region. The stalled front seems likely to become
a conduit for strong thunderstorms on Wednesday afternoon.
Impressive deep layer shear and steep low level lapse rates are
two factors that prompt concerns for even more severe
potential than Tuesday.

The front is expected to sweep across the area later Wednesday
and a markedly cooler air mass with dew points back in more
comfortable 50s seems likely. High temps will trend back towards
seasonable readings for Thursday and Friday.
&&

.AVIATION /23Z FRIDAY THROUGH WEDNESDAY/...
NEAR TERM: VFR/MVFR early tonight with isolated to scattered
showers. An isolated evening thunderstorm also possible across
central and interior Downeast areas. Variable conditions with
any fog across northern areas overnight into early Saturday,
otherwise VFR. IFR/LIFR develops Downeast overnight with
isolated to scattered showers along with low clouds and areas
of fog, which persists early Saturday. VFR/MVFR across the
entire region Saturday afternoon with scattered to numerous
showers. Variable conditions with any afternoon thunderstorms.
Variable winds 5 to 10 knots tonight through Saturday.

SHORT TERM:
Saturday night...Chance of IFR to LIFR vis in fog for BHB,
coastal sites and possibly as far north as BGR. Expect generally
VFR further north with light winds.

Sunday...VFR with light SW winds.

Sunday night...Chance of IFR to LIFR vis in fog for BHB and
coastal sites.

Monday...Generally VFR. Slight chance of afternoon
thunderstorms, mostly west of a GNR to HUL line.  Light winds.

Monday night...Slight chance of IFR to LIFR vis in fog for BHB
and coastal sites. Otherwise, VFR with light winds.

Tuesday...VFR outside of scattered afternoon thunderstorms,
mostly north of GNR and HUL.  Light winds.
&&

.MARINE...
NEAR TERM: A Small Craft Advisory for marginal seas remains in
effect for much of the waters, with the exception of the
intracoastal waters, through midnight. Winds/seas then expected
to be below small craft advisory levels overnight through
Saturday. Scattered showers later tonight, with
scattered/numerous showers Saturday. Areas of fog tonight
through Saturday.

SHORT TERM: Fog will be the primary concern until a strong cold
front moves through later Wednesday. Thunderstorms will become
a slight concern Tuesday evening, and a bigger concern later
Wednesday with a strong cold front moving across the waters.
Continued to adjust guidance winds and seas down due to strong
low level stability.
&&

.CAR WATCHES/WARNINGS/ADVISORIES...
ME...None.
MARINE...Small Craft Advisory until midnight EDT tonight for ANZ050-051.

&&

$$


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