075
FXUS61 KGYX 301202
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
802 AM EDT Sun Jun 30 2024

.SYNOPSIS...
Low pressure passing NW of Maine will continue lifting a warm
front through the region this morning. A cold front then
crosses this afternoon bringing scattered strong to severe
thunderstorms. Cooler and drier air arrives tonight followed by
a short wave crossing southern New England bringing slight
chances for showers. High pressure builds in MOnday night
through mid week for fair weather. The next frontal system
crosses New England sometime Wednesday night through Thursday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
635 AM Update...Have mainly trimmed back PoPs for the next
couple of hours as much of the area is devoid of shower
activity and convection over Upstate NY is weakening as it
tracks east. The warm and humid airmass is pushing into the area
with dewpoints already climbing into the low 70s across southern
NH. Otherwise, no significant changes to the forecast thinking
for today with scattered strong to severe storms developing
across northwest zones early this afternoon.

Previously...

Latest water vapor imagery shows a positively tilted trough over
easter North America with an embedded short wave crossing into
Quebec and a secondary embedded wave crossing the northern Great
Lakes. The leading short wave has spawned a surface low over SE
Canada that will track towards the Canadian Maritimes with the
attendant warm front lifting northeast of Maine this morning. The
secondary short wave will dive southeastward sending a mid level
speed max towards the International Border around mid day with
modest height falls occuring later this afternoon and evening. All
the while, a cold front drops southeastward through the area
providing a trigger for convection. The severe threat window starts
around 2 PM as storm cross into northern NH and NW Maine and
persists until 7 PM as storms reach the coast.

A review of the last three runs of the HREF shows that the projected
convective parameter space has remained similar over the past
24 hours. This has resulted in no significant changes in
forecast thinking for the threat of severe storms this afternoon
and evening. The HREF mean MU CAPE builds to 1500-2000 J/kg
amidst a corridor of deep layer shear of 40-50 kts by early
afternoon. Hodographs remain fairly straight with little turning
of winds in the low levels, while CAMs do highlight an area of
enhanced SRH across central and Downeast Maine. Convective mode
looks to be primarily broken line segments making damaging winds
the primary threat. The latest RAP does show 0-3 km shear
approaching 35-40 kts across northern NH into central Maine and
will have to watch the orientation of these shear vectors
against line segments for the potential of QLCS spin ups. Mid
level lapse rates remain unimpressive while the magnitude of
deep layer shear will be sufficient for a supercells that will
be capable of large hail. Another variable to watch will be
cloud cover as skies will be mostly cloudy to start today. The
00Z HREF suggests there will be breaks in the cloud cover over
the interior by mid morning while clouds may persist longer
across southern NH and coastal Maine. Dewpoints are forecast to
climb near 70F so solar heating will play a role in whether
convective coverage can over/under achieve. SPC maintains a
Slight Risk across much of the area driven by 15 percent wind
probabilities followed by 5 percent hail, and a 2 percent
tornado.

Highs today will climb into the mid to upper 80s south of the
mountains and away from the immediate coast. These temperatures
combined with dewpoints near 70F will bring heat indices into the
low to mid 90s while falling short of Heat Advisory criteria. Highs
in the north and along the Mid Coast will be in the 70s.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...
Convection will be pushing offshore this evening with the cold
front while the secondary short wave lags over Upstate NY. This
wave will maintain chances of showers in the mountains through
the first part of tonight. Drier air working into the region
will eventually lead to drying trend across the region by day
break with lows dropping into the 50s north to low 60s across
the south.

The lagging short wave crosses southern New England Monday
bringing chances for showers across central and southern New
Hampshire. Otherwise, there will be a mix of sun and clouds with
temperatures rising into the 70s with comfortable humidity
levels as dewpoints will be in the 50s.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
At 500 MB across NOAM and environs we still a pattern that
gradually favors warmer and more humid conditions, although
nothing that I would call hot through next week. We will near
the boundary of the sub-tropical over the Atlantic and the jet
stream to our N, so we can expect some rounds of SHRA/TSRA, but
no significant widespread events.


Monday night will be the coolest of the stretch with clearing
skies and light winds. Expect lows in the upper 40s in some mtns
pots and generally low to mid 50s elsewhere. Tuesday looks
mainly sunny and dry with low humidity, as high pressure crosses
the region, and highs 80-85, but cooler along the mid-coast.
Flow shifts SW as the sfc high shifts offshore, and the
resultant return flow will bring in more humid conditions.
Wednesday looks mainly dry though, but with partly sunny skies
and highs 80-85 once again.

A weakening cold front moves in from the NW Wed night, and
loses its steam over the CWA, so some SHRA and maybe some TSRA
are possible Wednesday night into early Thursday, but expect
clearing skies and warm and humid conditions on Thursday.

Weak high pressure moves in for Friday, so its be dry, but
still warm and humid. Next weekend remains uncertain as we sit
beneath weakly anticyclonic flow and troughing to our W, which
the means the potential waves and rounds of convection, but it
should stay on the warm and humid side.

&&

.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
Short Term...A cold front crosses the region this afternoon
bringing broken lines of strong to severe thunderstorms.
Confidence is not high enough in coverage to put in the TAF
while the current timing for storms is around 18Z in the
mountains with these storms reaching the coast around 23Z. Drier
air moving into the region Sunday night favors VFR conditions
into Monday.


Long Term...VFR expected Monday night through Wed, with
possible valley fog Monday night. Then more widespread flight
restrictions possible Wed night into early Thu in SHRA/TSRA and
some fog.

&&

.MARINE...
Short Term...SCA conditions due to both winds and waves are
expected to continue through today ahead of an approaching cold
front. Winds shift slowly shift northwesterly and diminish
Sunday night...though residual SCA waves will likely persist
through the first half of the night. Winds and seas will be SCA
thresholds on Monday.

Long Term...Generally light flow is expected through the middle
of the week with winds and seas staying below SCA levels, but it
could pick up some Wed night or Thu.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...Small Craft Advisory until 11 PM EDT this evening for
     ANZ150>154.

&&

$$

NEAR TERM...Schroeter
SHORT TERM...Schroeter
LONG TERM...Cempa