-- Discussion containing changed information from previous version are highlighted. --
138
FXUS61 KGYX 210226
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
1026 PM EDT Mon May 20 2024

.SYNOPSIS...
High pressure along the East Coast will bring a warming trend
through mid week. Disturbances tracking across southeast Canada
will bring chances for showers and thunderstorms Tuesday and
Wednesday. A cold front approaches Wednesday night and crosses
Thursday for more widespread showers and storms. Cooler and
drier air moves in behind the front with mostly dry conditions
going into the weekend as high pressure builds in from Canada.

&&

.NEAR TERM /UNTIL 7 AM TUESDAY MORNING/...
-- Changed Discussion --
1030 PM Update... Another round of minor adjustments were made
to the near term portion of the forecast but the overall
forecast thinking remains on track. Low ceilings continue across
the islands and some of this will likely move across portions
of the coast during the overnight hours.

Previously...
745 PM Update... Webcams across portions of coastal York and
Cumberland counties show that a marine low-level stratus bank
has moved onshore, resulting in visibility restrictions.
Satellite trajectories indicate this will persist through at
least this evening and therefore added fog into the forecast for
these locations. Further to the north, there is an area of
thunderstorms moving southeastward over southern Quebec or about
40 miles from the Canadian Border. Lightning has recently been
decreasing with warming cloud tops but will continue to monitor
to see if some of this activity makes it to Somerset county.
Otherwise, but minor tweaks were made to the inherited
forecast.

Previously...
Impacts:
*No significant weather impacts expected

Northern zones that cleared out early this morning warmed up
into the upper 70s today and therefore now have developed a nice
cumulus field. It is not out of the realm of possibility for
one of these to produce a very brief and very light shower this
afternoon as the 500 mb ridge begins to breakdown and flow
becomes more zonal, but it is a low chance. Elsewhere remains
mostly clear, and away from the coast it is expected to stay
that way. This will allow temperatures to drop into the low to
mid 50s across most of the area. The coast, which never made out
of the marine layer, just barely warmed in to the 60s so they
will likely fall a bit cooler to around 50. A temperature
inversion will setup overnight trapping that cool marine air at
the surface making low clouds a possibility again tonight along
the coast. In fact visible satellite and surface observations
already show them advancing.
-- End Changed Discussion --

&&

.SHORT TERM /7 AM TUESDAY MORNING THROUGH WEDNESDAY/...
Impacts:
* Thunderstorms cross the area Tuesday afternoon into the
  evening. A few may be strong with heavy rain and gusty winds.

Westerly flow aloft will advect warm mid level air into the
region and looks to increase 850 mb temperatures to around 15C
by the afternoon. Under mostly clear skies this should warm most
of the area into the low to mid 80s. Similarly to today, the
coast will stay cooler as onshore flow continues and the
Midcoast will likely end up the coolest spot as flow is directly
onshore there. This will amount to temperatures probably only
reaching the low 60s.

Tomorrow afternoon looks to have a good chance of thunderstorms
in New Hampshire and Western Maine, as the remnants of an MCS
look to approach the area. Surface southwesterly flow inland
will drive dewpoints into the low 60s and with excellent heating
lapse rates will be steepening. Latest CAMs show around
30-35kts of effective shear as well as around 1000-1500 J/kg of
CAPE. All these ingredients combined would support thunderstorm
development ahead of the remnant MCS, with some being on the
stronger side. At the very least these will contain heavy rain
as PWAT values are in the 1-1.25 range. Based on the shear and
lapse rates these will also likely contain gusty winds so this
wording has been added to the forecast. Small hail also can`t be
ruled out, but this is lower confidence and has not been
included at this time. How far east these storms are able to
march will depend on the extent of the marine layer in place.
The caveat there is that storms that do run into the marine
layer boundary may see a brief strengthening due to the
increased helicity. The bulk of the MCS remnants look to stay
well north of our area, but CAMs do show a few cells getting
into our area late in the night. The environment looks to stay
supportive of thunderstorms and will be more likely in the areas
that don`t get a storm earlier in the afternoon.

Otherwise, skies look to be mostly clear overnight, but with
elevated dewpoints low temperatures likely only cool into the
upper 50s or low 60s. This will set the stage for what is
expected to be the warmest day on Wednesday.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
Deep layer ridging along the East Coast will bring very warm
conditions to start to long term period on Wednesday. Disturbances
rounding the top of the ridge will bring chances for showers and
convection Wednesday and Wednesday night, mainly across the north.
High falls and the passage of a cold front will bring more
widespread showers and thunderstorms Thursday. There will be a
gradual cooling trend into the weekend with mostly dry conditions as
high as high pressure over eastern Canada extends into New England.

The two sources of potential impactful weather will be the very warm
conditions Wednesday and Thursday and the chance for strong
thunderstorms Thursday.

Wednesday looks to be the warmest day in this stretch of above
normal temperatures with high pressure stretching from the Southeast
to offshore of New England. Southwest winds along T8s climbing to
+17C will bring highs into the upper 80s to low 90s across the
interior. There will be some onshore wind component that will bring
a marine influence on temperatures near the coast while even here
highs will be near 80 degrees. Favorable mixing will keep
dewpoints in the upper 50s where it will be warmest and
therefore the humidity will not be high enough to bring heat
indices higher than the air temperature. Disturbances moving
atop a mid level ridge will trigger some showers and
thunderstorms mainly across the mountains and north Wednesday
into Wednesday night.

Thursday will be warm again with increasing humidity. A cold front
will cross the area from the west, with some timing differences
amongst the 12Z model suite as to when the front will cross.
Some model solutions have the front sweeping across the area
prior to peak heating around mid day, which will limit the
severe potential. A later frontal passage will allow for better
CAPE juxtaposed with sufficient shear for strong to severe
storms, so will have to monitor the timing of this front over
the next few forecast cycles.

The cold front will be offshore by Friday morning with high
pressure building in from the north through the weekend. This
will bring cooler and drier air into the region for what looks
like pleasant conditions for the holiday weekend.

&&

.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
Short Term...Low clouds and possibly patchy fog may cause
localized restrictions tonight, mainly at coastal terminals. VFR
will be the prevailing conditions tomorrow, but thunderstorm
development is expected in the afternoon so expect some brief
restrictions at inland terminals as these come through. Low
clouds may encroach on RKD Tuesday night, but otherwise
conditions should be VFR outside of stray storms. In general
winds remain light through Tuesday.

Long Term...Mainly VFR Wednesday into Wednesday night while some
TSRA could impact KHIE. A cold front crosses Thursday bringing
TSRA that will likely bring periods of restrictions. Drier air
arrives Thursday night allowing for VFR to prevail into
Saturday.

&&

.MARINE...
Short Term...SCA conditions are not expected through Tuesday as
high pressure remains over the waters.

Long Term...Winds and seas remain below SCA thresholds Wednesday
into the weekend. A cold front will cross the waters Thursday
that will bring chances for thunderstorms over the waters.

&&

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

&&

$$


NEAR TERM...Tubbs