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393
FXUS61 KGYX 230027
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
827 PM EDT Sat Jun 22 2024

.SYNOPSIS...
A stationary front lifts northward as a warm front tonight, with
waves of low pressure riding along the front. Oriented in the
warm sector tomorrow, there is a slight to enhanced risk of
severe thunderstorms across the area tomorrow, with the risk of
tornadoes and damaging winds being the primary concerns. A cold
front will then cross Sunday night and Monday with additional
unsettled weather before high pressure builds in by Tuesday,
bringing drier conditions. Temperatures moderate through the
middle of the week, with another cold front bringing showers and
storms late Wednesday. High pressure then builds in late in the
week, bringing drier and cooler conditions.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
-- Changed Discussion --
820 PM...Another night with some uncertainty in the models, but
there is a better chance for showers across the N again for
much of the night, with a lesser to the S, until closer to
daybreak when the warm frontal showers move through with perhaps
some thunder. So have kept POPs until after midnight.

Previously...A stationary front draped west to east from the
Great Lakes through New England will provide a focus for clouds,
showers, and perhaps some embedded thunder through tonight.
Currently, much of the forecast area is experiencing a stable
boundary layer with cool northeast flow on the north side of
boundary. Current radar trends are for convection to track
southeast through western New England while convective cells
stay just south of New Hampshire.

Subtle height falls tonight will allow for elevated instability to
build while waves of low pressure lift northeastward out of the
Great Lakes region. These waves of low pressure will act to lift the
stationary front northward as a warm tonight into Sunday morning.
The 12Z CAM suite suggests that there will at least be scattered
showers across the area tonight with embedded thunder while there is
decent spread in coverage and resultant rainfall. PWATs will be high
through tonight on the order of 1.8 inches along with warm cloud
depths pushing 12kFT, so there will be the threat of heavy rainfall
with elevated instability. The more robust CAM solutions suggest
that coverage will be scattered enough to limit the over flood
threat while isolated instances of flooding cannot be ruled out.
Otherwise, with plenty of low level moisture there will be fog
potential tonight with lows ranging from the low 60s across SW
New Hampshire to the mid 50s across northeastern zones.
-- End Changed Discussion --

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY/...
Confidence is increasing for a relatively active severe weather day
in northern New England on Sunday. The Storm Prediction Center has
issued an Enhanced Risk (level 3 out of 5) across southern and
central NH to the Maine border and a Slight Risk (level 2 out of 5)
across much of the remaining forecast zones. The Enhanced Risk is
driven by 10 percent tornado probabilities and 30 percent wind
probabilities. For some local area climatology context... the SPC
has only issued three 10 percent tornado Day 1 outlooks since 2010
and this is the first 10 percent tornado outlook for a Day 2
convective outlook. By no means is this a slam dunk for widespread
severe weather impacts as there are some failure modes that could
reduce the severe threat.

Forecast details: A warm front will be pressing SW to NE through the
area Sunday morning and is progged to lift north and east of
Franklin County by mid day. A cold front will then sweep across the
area Sunday night. The northward extent of the warm front can
sometimes be failure mode as it may not push as far north as
modeled, while as the previous AFD mentioned, a strong LLJ should
aid in this front`s progress. This will put much of southern
and central New Hampshire and SW Maine within the warm sector.
How well this warm sector destabilizes is also in question as
most CAMs keep skies mostly cloudy. Nevertheless, despite the
potential for mostly cloudy skies, CAMs suggest ML CAPE will
build to 1500-2000 J/kg by mid day within the warm sector. This
buoyant airmass will be juxtaposed with deep layer shear of
40-50 kts, which will be enough to support supercell structures
and storms capable of all hazards.

For the last couple of model cycles CAMs have suggested there could
be multiple rounds of convection with the first round initiating
within a pre-frontal trough across southern and central New
Hampshire between 18Z-21Z. These initial storms will have the best
chance for becoming discrete supercells and with curved hodographs,
0-3 km CAPE >100 J/kg, and STP values around 3, these storms will
encounter an environment favorable for tornadoes. Mid level
lapse rates are not overly impressive, but given the potential
for strong rotating updrafts severe hail will also be threat.
CAMs generally suggest these initial storms will sustain
themselves as the track east bringing the all hazard severe
threat into western Maine.

Additional storms are forecast to form along and ahead of a
cold front that will continue the severe threat across the area
into Sunday evening. These storms look to take on the form of
multi cell clusters and broken line segments that will bring
more of a damaging wind threat. Storm motion will be quite swift
working against the flash flooding threat, while the threat for
repeat rounds of convection will bring the potential for
localized flash flooding. High temperatures are forecast to
range from the mid 80s across southern NH to the upper 60s
across far eastern zones.

The severe threat will be on the downward trend around sunset,
with thunderstorms waning around 10 pm. It will remain humid
over the area Sunday night with additional chances for showers
through the overnight. Lows will range from the low 60s north to
upper 60s south.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
Overview...

A cold front clears the coast Monday morning, with high
pressure building in through Tuesday. The high shifts off the
east coast by Wednesday. A cold front likely crosses the area
late Wednesday, with high pressure moving in behind the front
for late in the week.

Details...

Lingering showers are likely across the higher terrain on
Monday as the upper level low swings through behind the front. A
gradual drying trend is expected across the area through
daytime. Seasonable temps are expected with highs ranging from
the low 70s to low 80s from north to south. The high building in
behind the front crests the area on Tuesday and brings a return
to an increasingly warm and humid airmass.

Tuesday looks mostly dry with dew points still mainly in the
50s, but temperatures rebound into the 80s in most spots, to
near 90 across southern areas. Wednesday turns more humid with
southwesterly flow, and temps warming into the mid 80s to low
90s in most spots. A cold front approaches during the day on
Wednesday, with scattered showers and storms likely late in the
day and into Wednesday night. The front may take into Thursday
morning to fully clear the area, with high pressure building in
by late in the day Thursday.

This area of high pressure builds in from Canada, bringing much
drier and sunnier conditions to the area. Temperatures also
look quite seasonable with the high, with daytime highs in the
upper 70s to mid 80s Thursday and Friday, and lows mainly in the
50s at night. Temperatures and humidity likely begin to
increase again by next weekend and the high moves offshore and
brings a return to the southwesterly flow.

&&

.AVIATION /01Z SUNDAY THROUGH THURSDAY/...
Short Term...Low cigs, SHRA and fog will likely bring widespread
IFR/LIFR tonight. Low cigs and reduced vsby will likely impact
KAUG, KRKD for much of the day Sunday. Elsewhere, cigs should
lift through the morning before a cold front brings multiple
rounds of TSRA Sunday afternoon and evening. These storms will
bring the threat of severe weather and flight restrictions are
likely at times. IFR to LIFR is likely Sunday night in lowering
cigs and fog as drier air does not arrive until Monday.


Long Term...Lingering showers are possible Monday morning, but
then VFR conditions prevail from Monday afternoon into
Wednesday. Nighttime valley fog will be possible, especially at
LEB and HIE. Showers and storms are then likely late Wednesday
and Wednesday night, with brief restrictions at times. VFR
returns on Thursday and prevails into the weekend.

&&

.MARINE...
Short Term...Easterly flow persists through tonight ahead of a
warm front lifting through the waters. Southerly flow increases
Sunday with winds and seas bringing SCA conditions by Sunday
afternoon. A cold front crosses Sunday night and strong to
severe thunderstorms will form ahead of this front and will
track into the waters Sunday afternoon and evening.
Thunderstorms diminish Sunday night while elevated seas maintain
SCA conditions into Monday morning.

Long Term...Lingering seas greater then 5ft are possible into
Monday as a cold front clears the waters, with high pressure
building in for Tuesday. The high shifts east by Wednesday, with
SCA conditions possible in increasing southwesterly flow ahead
of an approaching cold front. The front crosses the waters
Wednesday and into Thursday, high pressure building in behind
the front for late in the week.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...Small Craft Advisory from 5 PM Sunday to 8 PM EDT Monday for
     ANZ150-152-154.

&&

$$

SYNOPSIS...
NEAR TERM...Cempa/Schroeter
SHORT TERM...Schroeter
LONG TERM...Clair
AVIATION...
MARINE...