849
FXUS61 KGYX 250321
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
1121 PM EDT Mon Jun 24 2024

.SYNOPSIS...
Showers and thunderstorms will come to an end tonight with the
weather turning drier and warmer for Tuesday and Wednesday.  Low
pressure will bring another round of showers Wednesday night
with somewhat cooler and drier air arriving for the remainder of
the work week.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
11pm Update...Showers have quickly collapsed to the coast and
should be out of here by midnight for most locations. Clearing
behind is also progressing well.

940pm Update...Quite a busy evening in the hydro department.
Precip efficiency and slow storm motion/training was a good
combo to produce areas of minor and flash flooding (a few road
washouts have been reported in Chesterville, ME) this evening.
This activity should be subsiding as elevated instability is
beginning to wash out as low pulls to the east. Skies should
begin to thin after midnight, which could bring lows in the
lower 50s to the mountains. Believe some breeze remains across
much of the coast and interior tonight for temps to stay in the
upper 50s.


Previous Discussion...
500 MB with weak sfc reflection current over the CWA, but
slowly track ESE this afternoon and evening. It has been setting
off some nearly stationary convective cells sine this morning,
but no signs of lightning yet. Given, they are not very large,
they been posing almost no issues, expect for the little cluster
near Jay, ME which has put down 1-2 in the last couple hours.
They are also line up roughly W-E along a sfc boundary from the
cluster in Jay off to the where the Penobscot river meet Pen
Bay. Impacts should be limited but will have to keep an eye
anything that hangs a round the same place too often. Also as
that system shift to the SE expect the chance of showers to
shift a little more SE toward the coast this evening. Winds on
the back side will shift N and pick up a bit toward evening, but
these should be diminishing after midnight as well. All showers
should be done by 04-06Z, with clearing from W-E following. The
usual mtn valley may decouple late, which could lead to some
fog there, with lows ranging from the low to mid 50s in the
mtns, to near 60 in srn NH and on the ME coast.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY/...
High pressure builds in with NW flow Tuesday morning with the
ridge cresting over the CWA in the afternoon. This should allow
for a mainly sunny and warm day with highs mostly 80-85,
although a little in some mountain spots and a little warmer in
the more populated corridor of S NH. I think winds slacken off
enough in the afternoon that a sea breeze develops, but it will
develop late and will be limited to the immediate shoreline.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
High Impact Weather Potential: Threat for widespread severe weather
is low through the long term forecast.  Late Wednesday...if
approaching surface cold front arrives earlier than currently
expected...there would be a severe thunderstorm threat.

--Pattern and Summary--

Unblocked pattern with multiple shortwaves embedded within the
northern stream flow indicates a fairly changeable period of weather
with strong ensemble guidance agreement on precipitation events
Wednesday night and again this weekend.  The timing of these events
will likely determine what...if any severe weather threat they will
pose. Temperatures will be above normal on Wednesday and again ahead
of the weekend frontal system...returning to around or just below
normal behind these systems.  This overall yields a warmer/wetter
than normal period.

--Daily Details--

Tuesday Night - Wednesday: Warm front pushes through the region
Tuesday night with decent LLJ push followed by weak warm advection
through Wednesday as the mid level flow slowly backs ahead of the
next shortwave trough over the Great Lakes.  Could see a few showers
or a rumble of thunder Tuesday night...with dry and warm conditions
to take back over for the day on Wednesday as T8s edge up slightly
from those on Tuesday.  Thus...upper 80s to lower 90s are likely
south of the mountains with more clouds and cooler temperatures
aloft keeping highs near 80 to the north.  Surface dewpoints will
have moved upward into the 60s...so it will feel a bit humid...
though these values should fall short of pushing heat indices much
above the actual air temperatures.

Wednesday Night: Next northern stream shortwave arrives Wednesday
night and while the global deterministic/ensemble guidance from the
EC and GFS are are in solid agreement that this feature will bring a
round of showers and possible thunderstorms as a cold front pushes
through the area /with a wave of low pressure potentially forming on
the front/ the GGEM ensemble as well as today/s 12Z NAM that are
flatter with the front largely coming through dry. While this spread
in the ensemble guidance suggests caution going with nearly
categorical PoPs over southern areas as shown in the NBM...feel that
the pattern overall is one that would support precipitation given
modest mid level wave and PWATs in the warm sector 1.5-1.75".
Thus...will continue forecast messaging of likelies.  Timing does
not favor severe weather potential given a lack of instability...but
the kinematics will be there...so any speeding up of the cold front
could introduce severe thunderstorm potential. The shortwave does
look to move through quickly...which limits the overall hydro
threat.

Thursday through Saturday: High pressure builds into the region
Thursday as low pressure moves into the Canadian maritimes...moving
overhead Friday and then offshore for Saturday. This should provide
for a dry end to the week through at least the first half of
Saturday.  Temperatures fall back towards seasonal norms
Thursday...and even a few degrees cooler for Friday with drier
Canadian air allowing afternoon dewpoints on Friday to fall into the
40s.  Temperatures begin to rebound on Saturday ahead of the next
frontal system.

Saturday Night - Sunday: There is rather good ensemble agreement for
another frontal passage late Saturday/Saturday night.  Current
expected timing wouldn/t be conducive to a significant severe
weather threat...but residual instability and a rather impressive
moisture plume /PWATs push back above 2"/ indicates keeping an eye
on this period in later forecast for potential hydro issues.  Showers
may linger into Sunday with temperatures at or slightly above
seasonal norms.

Monday:  High pressure builds back into the region to end the
forecast period with another push of Canadian air bringing drier and
cooler conditions to end the forecast period.

&&

.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
Short Term...MVFR breaks up shortly after midnight but before
daybreak. Valley fog is possible at possible at both KHIE/KLEB,
although it will depend on how quickly each of those clear out.
Vfr is expected on Tuesday.

Long Term...VFR Tuesday night and Wednesday. A cold front
passing through the region Wednesday night will bring the
greatest threat for restrictions in showers and possible
thunderstorms. During this period...MVFR/IFR restrictions are
possible...with fog also possible by Thursday morning. VFR
daytime Thursday-Saturday

&&

.MARINE...
Short Term...SCA remains up for the open waters E of Casco Bay
mainly for seas, but could be some N winds gust to near 25 kt
briefly late tonight. Otherwise winds/seas will fall SCA levels
on Tuesday.

Long Term...Marginal SCA conditions in southerly winds on
Wednesday and Wednesday night ahead of an approaching cold
front. The next threat for SCAs does not arrive until late
Saturday.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...Small Craft Advisory until 5 AM EDT Tuesday for ANZ150-152.

&&

$$


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