216
FXUS61 KGYX 171707
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
107 PM EDT Wed Jul 17 2024

.SYNOPSIS...
Another day of heat, humidity, and storms today, but change in
pattern will bring relief through late week. A cold front passes
this afternoon and evening, bringing drier and somewhat cooler
conditions for the end of the week into the weekend. High
pressure builds in from the west with mostly dry conditions
forecast.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
1 PM...Quick update for the SVR watch until 8 PM. Storms popping
to our W a little earlier than expected, but otherwise forecast
looks good.

11 AM...Mostly just tweaked the timing of POPs this afternoon to
bring convection around and after 19Z, and along with this this
slowed the increase of sky cover through the afternoon afternoon
as well, especially further S and closer to the coast. Maxt Ts
were unchanged and today should be the last of the scorchers
for awhile.

7am Update...Not many changes here this morning, most areas
start sunny which will aid in meeting Heat Adv criteria once
again today as well as adding some instability for storms this
afternoon. Bumped up wording to include damaging winds in the
SPC SLGT Risk area for this afternoon.

Previous Discussion...
Another hot and humid start to the day, but dry. This should be
the last of our stretch of widespread temps reaching the 90s
before cold front arrives later. Trend beginning this afternoon
will be increasing shower and strong to severe storm coverage,
some containing gusty to damaging winds...and all the potential
for very heavy downpours.

Despite a late afternoon/evening MCS passing through Tuesday,
the hot and humid airmass remains overhead. Temperatures should
again quickly rise into the 80s and lower 90s through the late
morning and early afternoon. Remaining humidity will make it
feel like mid to upper 90s for most interior locations from NH
into south central ME. A bit more onshore flow may save the
immediate coast from these temps.

An approaching cold front this afternoon will be the first step
to replacing this airmass, but it won`t happen without
consequence. Scattered thunderstorms should be developing along
the VT/NH and ME/QC border by early afternoon. For now, CAMs
resolve these in multicell clusters roughly oriented along a
line as the front moves east. Storm motion is such that cloud
layer vectors are quick and from the SW, resulting in potential
training along an axis across the interior into mid afternoon.
So the greatest chance for precip through much of the afternoon
will lie inland from the coast. This should change come the
evening as this activity is forced NE. Into these hours, expect
the multicellular aspect to shift more stratiform or perhaps a
smaller scale bowing segment punching northeast that brings
thunder chances to the coast as well as the waters.

With wind damage fresh on our minds from storms Tuesday, this
will again be a threat this afternoon. The building temps should
steepen low level lapse rates, increasing dewpoint depression
and building a prominent inverted V signature in area
soundings. This is built below a fairly moist sounding with
ample DCAPE approaching 1000 j/kg. ThetaE vs. pressure
difference between the surface and upper levels is around 20-25,
which is another good indicator for storm containing gusty to
damaging winds. High freezing level and somewhat limited CAPE
should stem severe hail, but can`t rule out smaller sizes in the
stronger storms. Expect an interior corridor of these storms
with strong winds to be focused from the ME capitol region, down
through the ME/NH Lakes region and then southern NH.

This was hinted at above, but training storm motion in this very
humid and warm environment will also lead to storms containing
torrential rainfall. Repetitive storms moving over the same
locations will lead to a flash flood threat. A greater chance of
this looks to be from SW NH through to the Kennebec Valley of
ME. Again, this looks like where a corridor of storms slows
before continuing east later in the evening. HREF ens max brings
some values of 2 inches in 3 hours across southern NH and the
Kennebec Valley, and has been fairly consistent showing this
signal. This is closer to flash flood guidance for the ME
locations (particularly wet over the past week), but southern NH
also received up to 1.5 inch Tues evening with passing storms.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/...
Storm intensity should be waning later in the evening with loss
of daytime heating and passing front. Heavy rain threat should
wrap up around midnight as long as no remaining clusters of slow
moving storms linger. Otherwise skies begin to thin from west to
east.

A few lingering showers will be possible across central ME
Thursday, but instability is largely kept capped with drier air
and warm temps aloft relative to sfc. Less humid air will be in
the region, but it will still be warm. A start to relief
regardless.

&&

.LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
More comfortable lows are on the way for Thursday night thanks
to the drier air, mostly clear skies, and light winds behind the
cold front. Most should see lows in the 50s with upper 40s even
possible across the northern valleys.

A period of pretty quiet weather is expected from Friday
through the weekend with high pressure largely in control along
with a dry airmass. There will be a chance of showers late
Saturday as a weak cold front crosses through, but this looks
mainly confined to northern areas, and moisture does not look
particularly favorable with this system at the moment. While
temperatures will be "cooler" than what we have been
experiencing lately, highs in the 80s are still forecast each
day, possibly close to 90 degrees for southern areas on Saturday
ahead of the frontal boundary. The silver lining is that
dewpoints will be lower to make the warm temps more manageable,
and temperatures will be able to cool off more at night. We`ll
probably have some valley fog at night/early morning, too.

Mostly dry conditions look to start out Monday of next week,
but after that global models are in pretty decent agreement
showing a broad low pressure approaching the OH Valley/Great
Lakes region. Out ahead of this system, moisture will be on the
upswing, and a warm front lifting northward toward New England
will increase chances for precipitation toward the end of the
forecast period (late Tuesday or even slightly beyond into
Wednesday). This is supported by the GFS/ECMWF ensembles, and
the NBM showing increasing PoPs on Tuesday looks good.

&&

.AVIATION /17Z WEDNESDAY THROUGH SUNDAY/...
Short Term...Spots of MVFR ceilings early, becoming VFR today.
Rounds of showers and storms will be possible for the interior
terminals, some containing vis reducing rainfall as well as
strong winds. Showers linger through midnight, with a cold front
passing and expected wind shift. A trend back towards MVFR or
even IFR is possible late tonight, with VFR Thursday.

Long Term...Mainly VFR Friday through the weekend with the
exception of nighttime/early morning valley fog. A weak front
approaching from the north late Saturday could bring a few
showers to northern areas, but this would be primarily for HIE.

&&

.MARINE...
Short Term...A cold front approaches the region today, passing
late tonight into Thursday morning. This could bring a round of
storms to the waters later, which fog may preempt. These storms
may contain gusty winds.

Long Term...Winds switch to NW to N into Thursday night, but
these will become onshore by Friday afternoon as the seabreeze
develops. Another weak front crosses late Saturday and could
result in another brief wind shift to the NW. High pressure then
settles over the waters Sunday into Monday before low pressure
brings increasing precip chances by Tuesday.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Heat Advisory until 6 PM EDT this evening for MEZ012-018>024-
     033.
NH...Heat Advisory until 6 PM EDT this evening for NHZ004-006-
     008>010-012>015.
MARINE...None.

&&

$$


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