-- Discussion containing changed information from previous version are highlighted. --
058
FXUS61 KGYX 220232
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
1032 PM EDT Fri Jun 21 2024

.SYNOPSIS...
A cold front will stall over Southern New England tonight
through Sunday as waves of low pressure ride along it. This
will result in near seasonable temperatures and rounds of
scattered showers and thunderstorms. Another front will then
cross on Monday with additional unsettled weather before high
pressure builds towards the middle of next week bringing warmer
weather.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
-- Changed Discussion --
1030 PM...Based on latest meso models and current radar lowered
POPS for much of the CWA through about 09-10Z, but kept the chc
POPS going along the boundary in the N, although these will
likely remain light showers overnight. Also did the usual
tweaking of T/Td based on current obs as well. Temps and Tds
generally lower than forecast, although there will be little in
the way of temp movement overnight except N of the boundary in
the Jackman-Rangeley area.

725 PM...Notable changes were mainly to POPS to keep things
drier across all all bu the N zones through this evening, except
far SW NW where showers have the highest chc of occuring this
evening. There is still a slight chance across much of the
area, but nothing significant for the rest of the CWA. I did
pull thunder out of the forecast for much of tonight
reintroducing toward daybreak as the weak low moves into srn New
England, but anything that does occur would be elevated until
after some warming occurs in the far S. Otherwise
temps/winds/sky adjusted to better line up with current obs.

The back door cold front continues to make progress
southwestward this afternoon, and is currently making its way
into southwest New Hampshire. Scattered showers continue to
develop along and behind the front, with clearing limited to
northeastern areas of the CWA. Temps have warmed into the mid
80s ahead of the front, allowing for some scattered
thunderstorms this afternoon, particularly in Cheshire county. A
strong storm can`t be ruled out either there, but most of the
strong to severe threat looks to remain to the south and west.

The front stalls to our southwest tonight, with rounds of
showers and storms moving along and to the north of the front.
The high res guidance continue to waiver on where the main
threat for the heaviest rainfall will be. The two main areas of
focus look to be across far southern NH near the Mass border,
with a second area through the higher terrain of New Hampshire
and into western Maine. There is some concern for the risk of
localized flash flooding tonight in these two areas, but it will
be highly dependent on whether or not convection begins to
train over the same areas overnight. As mentioned, the high res
guidance solutions continue to vary, but there is concern from
the general set up of a stalled front on the periphery of a
ridge.
-- End Changed Discussion --

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY/...
The risk for isolated flash flood concerns continue into
tomorrow as the front begins to slowly move northward as a warm
front again. Rounds of showers and storms continue through the
area around the periphery of the ridge. The flood threat again
would come from heavy showers and storms training over the same
areas over time. The whole day won`t be a washout, with breaks
of sun still likely through the day. There is also the risk for
some stronger storms across southwestern NH, which will be
located near the warm front by the afternoon hours.

There continues to be discrepancies in the high res guidance
tomorrow as well. The 3km NAM and HRRR keep much of the area
socked in with drizzle, showers, and highs in the low 60s. Other
guidance is not as dreary, with temps making it into the 70s
with more breaks of sun. This forecast rides the middle ground,
but acknowledges that some areas are likely to be cooler, and
others warmer, but tries to avoid a 10-15 degree bust for any
one spot.

The warm front makes slow progress through the forecast area
tomorrow night, continuing the concerns for localized flooding,
especially in areas that see most of the rainfall tonight and
tomorrow. The speed of the front will determine how much more
rainfall we see, but the current thinking is through the bulk of
it would be pushed north of the border by daybreak on Sunday as
another MCS rides along the ridge. However, any slowing of the
front would bring a greater heavy rainfall risk into our area,
so we`ll need to monitor this progress closely over the next
day.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
Overview: Relatively progressive flow across the northern CONUS
with a broad 500mb trough across the region that will bring
shortwave trough passage and periods of storms through the week.
Potential for more prolonged ridging towards the end of next
week. This will bring periods of active weather with
thunderstorms and temperature swings from near normal to above
normal.

Impacts:  Localized heavy rain is possible Sunday across Northern NH
and the Western Maine mountains.  In addition, severe weather could
be possible across southern areas on Sunday dependent on how much
clearing occurs.  Another round of possible strong thunderstorms is
possible towards mid-week.

Forecast Details:  Sunday the stationary boundary becomes a warm
front and surges north of the area bringing the region back into the
warm sector, especially southern areas.  Where the boundary sets up
and stalls will be a possible focus area for localized heavy rain as
strong moisture convergence is expected along the boundary and
forcing increases as a surface low develops along the boundary.
Threat for severe weather will increase as a robust mid-level
shortwave and associated cold front pushes through the area sometime
late Sunday.  The big question is how robust the marine layer will
be in place and if it cane burn off in time. Monday the shortwave
trough swings through with the potential for much cooler weather and
showers, but this depends on the timing of the trough.  Some
guidance is slowing the progression of the mid-level low which could
allow rain shower activity to linger into Monday evening. Tuesday
looks to have the highest potential for being the driest day of the
week as a shortwave ridge moves over the area with a rebound in the
temperatures back into the 80s. Wednesday could be warm once again
as a return to southwest flow is still expected ahead of the next
approaching trough from the Great Lakes. A period of storms is
possible in the Wednesday night into Thursday timeframe as the next
cold front swings through the area. Timing on this front still has
timing spread of 12 hours or so in the model guidance. Potential for
much cooler weather and Canadian high pressure by Friday next
week.

&&

.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
Short Term...Scattered showers bring brief restrictions to New
Hampshire terminals into this evening, with mainly MVFR to VFR
ceilings elsewhere. Ceilings then lower to MVFR and IFR
overnight, with showers at times. Showers continue at times
tomorrow, with ceilings likely improving to MVFR tomorrow
morning. There are low PROBs for thunderstorms across southern
and western NH terminals during the afternoon. Ceilings lower
again tomorrow night to IFR in most spots, with showers and a
low PROB for a thunderstorm overnight.

Long Term...Showers and thunderstorms could bring temporary MVFR to
IFR conditions on Sunday with the highest threat across the
airfields of New Hampshire. Showers and storms could be possible
into Monday morning before drier weather returns Monday night
through at least Wednesday morning with VFR conditions
anticipated.

&&

.MARINE...
Short Term...Northeasterly flow continues behind a cold front
through tomorrow, with conditions remaining below SCA levels.
Patchy dense fog is possible tomorrow night as a warm front
lifts across the waters.

Long Term...Southerly winds increase over the waters on Sunday ahead of
an approaching cold front. Seas and winds could reach SCA level by
Sunday afternoon and last through the Monday morning. Cold front
swing through on Monday with a return to offshore through Tuesday
before winds increase along with seas once again by Wednesday from
the south again as another cold front approaches the region.

&&

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

&&

$$

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