791
FXUS61 KGYX 130249
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
1049 PM EDT Fri Jul 12 2024

.SYNOPSIS...
A mid level disturbance will bring a few showers and thunderstorms
to the region tonight and on Saturday with sun breaking through the
clouds by Saturday afternoon.  Drier air works into the region for
Saturday night and Sunday though temperatures will climb.  Humidity
will increase on Monday and Tuesday before a stronger cold front
arrives Wednesday with the potential for some showers and
thunderstorms before cooler and drier conditions arrive to end next
week.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...

1045PM Update...Primary focus with this update was to
incorporate some of the latest 00Z short-range guidance into
PoPs for the rest of tonight. This didn`t result any major
changes, but this did raise PoPs slightly across central and
southern areas as CAMS have been pretty consistent on focusing
in on these areas overnight. Given the abundant moisture in
place and deep warm cloud layer, the main concern remains very
rainfall.

640PM Update...Not much to update at this hour other than
performing a very minor refresh of temps and dewpoints to match
observations. Conditions remain sultry out with not much relief
overnight with temps still expected to remain in the upper 60s
to lower 70s south of the mountains for lows.

Another shower or two may develop along a seabreeze/outflow
boundary interaction over the next hour or so over toward
Skowhegan/Waterville, but otherwise dry conditions will prevail
through the remainder of this evening before another wave brings
increasing chances for showers/storms after midnight,
especially across NH.

Previous...

High Impact Weather Potential: Isolated heavy rain potential
after midnight tonight.

Pattern: A deep plume of mid level moisture is evident on early
afternoon water vapor imagery...squeezed between a shortwave moving
through the Great Lakes region and an upper level low sitting off
the Mid Atlantic coast.  This upper low...as it spreads north is
pushing a stalled frontal boundary back northward allowing a 2" PWAT
airmass to nudge back into southern NH and southwestern ME.  The
offshore upper low will weaken as it moves north tonight...
eventually being pushed east by the Great Lakes shortwave as to
moves just north of New England overnight.  Forecast concerns will
center on any shower/thunderstorm potential along the frontal
boundary that will be draped across the forecast area.

Through this evening: Warm/humid conditions continue this
afternoon with a few showers located just north of surface
front draped near the mountains. These will wane through early
evening. Temperatures will remain rather warm through 8pm...with
values still at or above 80 for much of southern NH and SW ME
with 70s elsewhere.

Tonight: Height falls associated with both the Great Lakes shortwave
and the wave to our south move overhead with WSW flow riding over
the stalled frontal boundary across the region.  PWATs south of the
boundary will be over 2" with MUCAPEs over 500 J/kg.   The mesoscale
guidance indicates that the setup should be sufficient for a few
showers and thunderstorms to develop overnight. CAPE plumes are
skinny so expect the greatest threat they would pose would be heavy
rainfall. Coverage for any shower/storm activity looks to be
isolated-scattered. Will mention the localized flood concern in
the afternoon hazardous weather outlook.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY/...
High Impact Weather Potential: Localized heavy rain threat
through mid morning.

Pattern: Upstream shortwave just north of the area to start the day
will push east...crossing northern Maine towards evening with the
flow aloft turning northwest behind this feature Saturday night.
This shortwave will interact with moisture along the coast to
produce the potential for showers and thunderstorms before a cold
front settles offshore Saturday night drying out conditions.
Forecast focus will be on the shower/storm coverage and any
potential for heavy rainfall along with the impact of the
clouds/precip on temperatures.

Saturday: Overall trend in the mesoscale guidance over the past 24
hours has been to decrease the heavy rainfall threat for Saturday
morning as we actually sit in a bit of a forcing lull by mid
morning as the offshore wave departs...which also acts to shunt
deeper moisture plume east of the region in the morning. A weak
surface low along the stalled frontal boundary over PA/NJ early
Saturday rides ENE during the day which keeps any associated
training convection over southern New England and points south.
The proximity of the northern stream wave should allow for some
scattered convection to develop during the day but the deeper
moisture plume will have pushed east and overall MLCAPEs will be
rather limited as significant cloud cover should persist
through the morning into early afternoon. T8s will be around
+15-16C...which would support mid/upper 80s...and given some
increasing sun for the second half of the day...expect that
we/ll reach these values.

Saturday Night: Surface cold front pushes offshore overnight
allowing somewhat drier air to filter into the region with
clearing skies. This should allow temperatures to fall into the
60s throughout the forecast area which should allow a bit more
relief then the previous few nights.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
A persistent period of hot, hazy and humid weather will
continue until a potentially significant change in the weather
pattern arrives late next week...

We begin the long range portion of the forecast on Sunday with
operational models and ensemble solutions suggesting a large and
significant upper level ridge remaining off the seaboard. This will
leave the region with hazy, hot and humid conditions over the
region. Temperatures will likely reach 90 degrees across the
interior and along the coast from approximately Portland and points
south along the shoreline. This may be the start of the first heat
wave for portions of the coast, and a continuation of persistent
heat waves across the interior. This will also be the first day of
the return of hot conditions after one day of clouds and slightly
less warm conditions from the start of the weekend.

Hot temperatures return to the interior once again on Sunday, in
areas where heat indices have been skyrocketing over the last couple
weeks. After the short reprieve, this will be a renewed period of
heat wave conditions for much of the region.

While seabreezes will likely cool off the shoreline slightly during
the afternoon, this warm spell will be noted by more of a westerly
flow aloft, potentially allowing temperatures to reach 90 degrees in
the Forest City as well as much of the southwest coast of Maine and
Seacoast of New Hampshire before any onshore winds develop. Surface
dew points will be slightly lower than this past week, but
nevertheless, hot and humid conditions will lead to a prolonged
period of stressful conditions for outdoor activities and areas
without proper air conditioning.

By Monday, heights aloft will gradually be lowering without any
defined short wave in place. This will allow for a primarily
afternoon, diurnally driven scattered shower and with sufficient
instability, perhaps a thunderstorm or two. Temperatures will be
outright hot with lower to mid 90s expected in all portions of the
forecast area. The only exceptions will be the higher terrain in the
mountains and the Midcoast area of Maine where onshore winds will
allow readings to remain in the 80s. It will be humid with dew
points continuing in the upper 60s, which is actually a very mild
improvement from the lower to mid 70s dew points recorded much of
this week.

Tuesday will be similar to Monday in terms of the chances for
precipitation and hot and humid temperatures across the region.
Tuesday may be day 3 of 90 degrees or higher in a row in
Portland which would be potentially its first heat wave of the
summer, while the interior continues its heat. This all comes
with sunshine, good mixing and H8 temperatures near +18C.

During the muggy period, expect periods of patchy fog. This will be
most likely during the overnight periods along the interior valleys
and also potentially near the coastline.

More heat on Wednesday with perhaps more scattered showers and
storms. Temperatures have the potential to hit 90 or above many
areas. However, model ensembles suggest a significant pattern
change at this juncture as an upper level trough builds towards
the region. Canadian high pressure may build into the region for
the later portion of the weak, bringing cooler and much drier
air to the forecast area.

&&

.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
Short Term...

Short Term /18Z Today through Saturday Night/...

Summary: A stalled frontal boundary across the area will bring a few
showers...thunderstorms and deteriorating conditions overnight with
a few additional showers and storms for the day Saturday before
drier air brings improving conditions Saturday night.

Restrictions: Generally VFR attm and this should prevail through
midnight.  After midnight...there is the potential for some low
clouds and fog along with isolated-scattered showers/thunderstorms
south of the mountains.  These will continue into the early morning
hours Saturday with improvement to VFR for the day. An isolated
thunderstorm is possible AUG-RKD Saturday afternoon with
additional isolated restrictions. VFR Saturday night.

Winds: South and Southwest winds 08G15kts will diminish to 5kts or
less tonight before becoming southwest 5-10kts for the day on
Saturday.  Winds shift to the northwest around 5kts Saturday night.

LLWS: No LLWS expected through Saturday night.

Lightning: Isolated thunderstorms possible after midnight tonight
through the morning hours Saturday with a low potential for an
additional thunderstorm Saturday afternoon from AUG to RKD.

Long Term...Mainly VFR conditions through much of the period.
There will be a chance for IFR conditions in any scattered
showers or thunderstorms mainly during the afternoon periods.
The exception will be Sunday when conditions will be dry all
areas. Patchy fog will continue, mainly at night and mainly over
the interior valleys and perhaps the coastline.

&&

.MARINE...
Short Term...Residual seas and marginal winds necessitate SCAs
for the outer waters from Cape Elizabeth north through tonight.
Winds/wave should remain below SCA levels Saturday and Saturday
night.

Long Term...South to southwest winds will continue through the
weekend and into much of next week. Winds and seas should remain
just below SCA thresholds each day with sea breeze circulations
increasing the gradient and resultant wind fields during the
afternoon periods. Patchy fog expected mainly during the
nighttime and overnight periods.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...Small Craft Advisory until 6 AM EDT Saturday for ANZ150-152.

&&

$$


NEAR TERM...Arnott/Combs
SHORT TERM...Arnott
LONG TERM...Cannon