-- Discussion containing changed information from previous version are highlighted. --
793
FXUS61 KGYX 162246
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
646 PM EDT Mon Sep 16 2024

.SYNOPSIS...
High pressure will remain entrenched east of the region through
midweek before some moisture over the southeastern states
builds north increasing the chance for showers south of the
mountains Wednesday and Thursday with cooler temperatures.
Canadian high pressure builds in from the north to end the week
and through the weekend with seasonable temperatures and dry
weather expected.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
-- Changed Discussion --
620pm Update...Temperatures beginning to decrease this evening
with very little to modify existing forecast. Blended in some
MAV guidance for our falling temps tonight, with lows still
expected to fall into the lower 50s to mid/upper 40s interior.

Previous Discussion...
High Impact Weather Potential: Locally dense fog tonight.

Pattern: Stagnant pattern in place with blocking setup along the
east coast as H5 ridge axis resides over the northeastern United
States...while a cutoff at H5 partially associated with Potential
Tropical Cyclone 8 off the southeast coast.  This pattern will
remain in place through the near and short term portion of the
forecast resulting in warm...dry...and overall quiet conditions. The
most impactful portion of the forecast over the past few days has
been overnight fog...and that will remain our focus for tonight.

Through this evening: Temperatures a bit warmer than yesterday
at this time...but overall a very quiet evening with clear
skies...and temperatures beginning to fall pretty quickly given
the dry airmass in pace. 8pm temperatures will still be
mild...generally in the 60s throughout the area.

Tonight: Very similar setup to last night with two minor changes.
The first will be some cirrus arriving well after midnight from
southwest to northeast as some high-level moisture associated with
PTC8 off the Carolina coast streams north and east.  This should
have little to no effect on another very good radiational cooling
night as winds decouple.  The second change is a slightly warmer
airmass overhead and therefore for most areas...have a similar
pattern for low temperatures...but with values a few degrees warmer
than last night...generally in the lower 50s...with a few cool spots
just below 50.  Areas of valley fog are again expected as these lows
will be below afternoon crossover temperatures.
-- End Changed Discussion --

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
High Impact Weather Potential: Locally dense fog Tuesday night.

Pattern: Aforementioned blocking pattern will remain in place
through the short term forecast period...the energy diving into
western North America spells some potential for eventual changes in
the long term forecast and beyond.  Therefore...as the surface and
mid level ridge axis remains overhead through the period...the focus
will be on daytime highs...which remain well above normal for the
middle of September...as well as overnight fog potential.

Tuesday: While the surface and mid level patterns will not have
changed substantially...upper level moisture associated with PTC8
near the southeast coast will continue to stream north and east
during the day...which will provide for a good amount of cirrus.
Otherwise...the forecast will remain the same...with another
warm/dry day expected along with light winds given the high just
east of the area.

T9s reach 20C across the area...ticking up slightly from
Monday...which will likely result in the warmest high temperatures
of the week.  +20C yields over 80F with no superadiabatic
assistance...so expect that we`ll be able to see lower to mid 80s
throughout the forecast area.  Guidance has been biased low
throughout this abnormally warm stretch of weather...so will follow
closer to the warmer MAV...but still push highs above this.  The
weak gradient will allow for a robust seabreeze to develop...keeping
highs lower toward the coast. Inland...winds will remain rather
light.

Tuesday Night: High clouds will continue overhead...but good
radiational cooling conditions are expected again with lows likely
reaching values just above where they were Monday night...with lower-
mid 50s expected.  Dewpoints will have increased over the previous
24 hours...so expect a similar occurrence of fog overnight with the
valleys again favored for a period of fog...some of it locally
dense.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Deep layer ridging over the Northeast starts to break down on
Wednesday leading to a downward trend in temperatures the second
half of the week. All the while, moisture from a low pressure
system moving over the Carolinas will lift northward bringing
more in the way of clouds and low chances for rain Wednesday
night into Friday. The best chances for rain will be across
southern New Hampshire while total precipitation on whole will
likely average below normal for the long term period. A cold
front moving southwest through Maine will shunt this moisture
southward Friday followed by high pressure building in from the
north over the weekend.

Wednesday will be another warm day with clouds increasing south to
north. Any rainfall associated with a the system moving north
through the Mid Atlantic looks to hold off until Wednesday night.
Deterministic and ensemble guidance continue to suggest that
the bulk of rainfall associated with this system will remain
south of the area with NBM PoPs topping out around 40 percent
along the NH/MA border Wednesday night. PoPs decrease to the
north dropping below 15 percent north of the mountains.

Weak troughing will linger along the East Coast Thursday into
Friday, while the majority of model solutions keep any
appreciable rainfall south and east of the area. Therefore, the
current precipitation deficit for the month of September looks
to increase through the end of the week. Highs on Thursday will
mainly be in the mid to upper 70s lowering to the low 70s on
Friday. A cold front dropping southwest through the area Friday
will usher in a cooler and drier air mass over the weekend. High
pressure building in behind the front will bring fair weather
with highs in the 60s and lows in the 40s over the weekend.

&&

.AVIATION /22Z MONDAY THROUGH SATURDAY/...
Short Term...

Summary: High pressure will remain centered just east of the
region through Tuesday night with quiet weather conditions
outside of morning valley fog.

Restrictions: VFR through the period outside of morning fog at
HIE/LEB/RKD and CON.  Confidence is least at CON...but will include
it for a short time...with a very similar setup to last night.
Otherwise...some high clouds /25kft/ expected on Tuesday...otherwise
little in the way of lower-level cloudiness expected.

Winds: Southwest winds around 5kts with seabreezes near 10kts both
this afternoon and again Tuesday afternoon with overnight winds
calm/light-variable.

LLWS:  No LLWS is expected through Tuesday Night.

Lightning: No lightning is expected through Tuesday Night.

Long Term...VFR likely prevails during the day time Wednesday
through Saturday. Night time valley fog will bring the potential
for IFR/LIFR most nights at KLEB and KHIE. Onshore flow and
increasing clouds from a system passing south of New England
will also bring the potential for cigs around MVFR thresholds
Wednesday night and Thursday night.

&&

.MARINE...
Short Term...Winds and waves remain below SCA levels through
Tuesday night.

Long Term...Winds and seas remain below SCA thresholds Wednesday
and Thursday. Southerly flow Wednesday shifts NE Thursday as low
pressure approaches and stays south of New England. Low
pressure passing south of the Gulf of Maine will bring seas
building to 5 ft by Friday with continued NE flow with gusts
around 20 kts. Seas remain elevated around 5 feet into the
weekend with NE winds subsiding from their peak on Friday.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...None.

&&

$$


NEAR TERM...Arnott/Cornwell
SHORT TERM...Arnott
LONG TERM...Schroeter