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000
FXUS61 KGYX 151106
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
706 AM EDT Tue Jun 15 2021

.SYNOPSIS...
Low pressure with showers and a few storms crosses the region
today, then exits to the northeast tonight. High pressure
builds into the region for the middle of the week with
seasonable temperatures and dry northwesterly flow. Temperatures
start to increase by the end of the week. A cold front crosses
Saturday with showers and thunderstorms.

&&

.NEAR TERM /TODAY/...
705 AM Update...
Refreshed PoP according to latest radar analysis... mainly to
tighten the gradient between a zone of convergence near the
coast and isolated shower activity elsewhere. A few pockets of
dense fog remain this morning, but are generally improving,
especially toward the west where dry air is filtering in behind
a subtle surface front. Also worked the HRRR, which best captures
the precipitation coverage this morning, into the temperature
forecast... to allow for a little stronger warming west and a
little cooler temperatures east... but only a couple degrees
difference ultimately. Rest of the forecast is well on track.

Previously...
Rain showers and a few thunderstorms are the story for today as
two areas of low pressure cross New England. Looking aloft, a
vorticity maxima rounds the base of deep troughing over eastern
NOAM, which will spur coastal cyclogenesis south of New
England... along a cold front extending south from Quebec,
associated with the long wave trough aloft. This makes for
somewhat of a complex surface scenario today with cloudy and
humid conditions along the coast and over most of Maine ahead of
this front and warmer, drier conditions behind the front over
much of New Hampshire. Thus PoPs are highest within about 50
miles of the coast early in the day... but will bloom elsewhere
during the afternoon as height falls and steepening lapse rates
aloft allow showers to develop.

As for convective chances... again, a complex scenario today.
Better dynamics exist with the southern wave, but stable onshore
flow undercuts instability east of Portland... especially as low
pressure hugs the coast this afternoon and evening. Meanwhile
the cold pool dipping down from Canada with the poleward
longwave trough steepens lapse rates enough for a general slight
chance elsewhere as 500-1000 J/kg of MLCAPE develop. The surface
pressure trough pushes down from Quebec this afternoon and
evening, providing a focus for convection while taking advantage
of daytime mixing... enough for scattered thunderstorms across
the north, but without much kinematic support.

For temperatures... expect temperatures to be subdued, not to
exceed 70 degrees ahead of the front with more clouds and
humidity. Over New Hampshire however I expect at least 70 degree
readings with mid-70s over the southern interior depending on
breaks in clouds.

&&

.SHORT TERM /TONIGHT THROUGH WEDNESDAY/...
Dry air pouring in aloft will allow showers and storms to wane
with the diurnal trend tonight, diminishing as the system as a
whole shifts east and exits toward the maritimes. Dew points and
temperatures will also come down nicely overnight with low
temperatures in the 40s toward the north and 50s toward the
south. Opted a little warmed than consensus... since strong
mixing doesn`t look to be a factor until the pre-dawn.

For tomorrow, mostly sunny skies prevail with a fresh northwest
wind on the order of 5-10 kts. Given sun, mixing, and
downsloping, again chose the warm side of guidance with highs in
the upper-60s (north) to as warm as the mid/upper-70s for
southern zones. The offshore breeze even allows coastal
locations to warm into the 70s for the first time in several
days.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Upper level pattern for midweek will feature a trough over eastern
Quebec and Labrador which keeps a relatively cooler airmass over
northern New England along with northwesterly flow. The result is
dry conditions, with seasonable temperatures. Highs will be in the
mid 70s to upper 60s. Have kept close to the model consensus
for these few days without much disagreement. Only noteworthy
change was to account for the seabreeze along the midcoast,
keeping temps down slightly for that area.

By Friday night the overall flow pattern has opened up which will
usher in some short waves.  Increasing model agreement over the past
few runs for the next wave to approach the region Friday night and
move through on Saturday. Expect showers and thunderstorms with
this, although do not expect much in terms of widespread heavy
precipitation. Forecast soundings continue to show CAPE across the
area of around 500 j/Kg, which while modest in general is
respectable for global models at this time scale and thus indicative
of solid thunderstorm potential. The southern and western part of
the CWA has the best upper level support as a 80kts jet streak
co-located with the front approaches from Quebec. Will need to
monitor the surface conditions through the week as the northward
extent of the low level moisture in the warm sector will largely
determine the extent of the thunderstorm threat. Southerly flow,
which becomes onshore as you move east through Maine will likely
keep SW Maine and NH as the main threat areas.  Additionally will be
the timing of the front, with a mid-day passage maximizing
thunderstorm potential.

Sunday and Monday shower chances decrease as we see a brief high
pressure builds in ahead of the next wave bringing additional
showers on Tuesday. For next week will need to keep an eye on
both the northern stream bringing another front across the Great
lakes as well as the Gulf of Mexico which could enhance the
moisture into the front.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
Short Term...IFR/LIFR with fog, low ceilings, and occasional
showers rule this morning for eastern and southern terminals
while MVFR and VFR hang on toward the north and west. The
system responsible will very gradually shift east through today,
allowing low ceilings to lift and scatter from west to east
through about mid-day. Some uncertainty exists with KPWM and
KRKD... with potential for fog and low ceilings to hang on for
several hours longer. With this exception, VFR is expected to
prevail and winds will switch to the west... then northwest...
tonight into tomorrow.

Long Term... High pressure and VFR conditions through the end
of the week with afternoon seabreezes. Friday increasing
southerly flow ahead of a front could bring some advection fog
to the midcoast. The front crosses the region on Saturday with
scattered showers and thunderstorms.

&&

.MARINE...
Short Term...Low pressure crosses the waters today with showers
and perhaps a stray thunderstorm with weak onshore flow. The
system exits northeast to the Canadian maritimes tonight with
winds turning offshore through Wednesday. Winds will stay below
SCA thresholds, however incoming swells from Tropical Storm Bill
may bring seas to near 5 ft off the Midcoast of Maine.

Long Term... Quiet over the waters through the end of the week.
Southerly flow picks up on Friday with a cold front crossing
Saturday bringing showers and possibly thunderstorms.

&&

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

&&

$$

NEAR TERM...Casey
SHORT TERM...Casey
LONG TERM...Curtis