756
FXUS61 KGYX 132136
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
536 PM EDT Thu Jun 13 2024

.SYNOPSIS...
A cold front will cross the region on Friday...bringing
scattered showers and thunderstorms to the region. Cooler and
drier air will build in for the weekend. Next week...a large
ridge of high pressure will build towards the Northeastern
United States with warming temperatures. An extended period of
significant heat is expected to develop by Tuesday and continue
through the remainder of the week with most locations seeing
high temperatures into the 90s.

&&

.NEAR TERM /THROUGH FRIDAY/...
540 PM Update... A quick update was made to PoPs across Coos
county to account for some shower activity that is arriving from
VT. Otherwise, just loaded in the latest observations at this
time.

Previously...
High clouds gradually increase overnight tonight as a cold
front approaches. The clouds and southerly flow help to keep
lows mainly in the 60s overnight. Some showers from this
afternoon`s convection begin to push into northern areas after
midnight, and will slowly diminish in coverage as they move
toward the coastline through the daylight hours tomorrow
morning. A few thunderstorms are also possible overnight toward
the Canadian border, but these are also expected to weaken as
they move southeastward.

&&

.SHORT TERM /FRIDAY NIGHT/...
The front gradually moves through the area during the daytime
tomorrow. Morning showers give way to a mix of sun and clouds,
allowing temps to warm into the upper 70s to low 80s south of
the mountains with increasing dew points. Southeastern NH stands
the best chance to warm into the mid 80s with a bit more
sunshine. Across the mountains, more showers and a few
thunderstorm begin to develop again by the early afternoon.
These then progress southeastward through the day with the
front.

The best chance for some strong to severe storms continues to
be across southeastern and southern New Hampshire, where the
greatest heating and shear look to combine. Some isolated strong
to severe storms are also likely elsewhere across the coastal
plain during the mid afternoon, but it looks like the front will
be clearing the coastline too early in the afternoon to cause
more of a concern. Some heavy rainfall is also possible,
especially across southeastern New Hampshire where a couple
rounds of storms are possible, and could cause some localized
issues that will need to be monitored.

Showers and a few thunderstorms gradually diminish along the
coastline through the evening and into the overnight hours as
the front moves offshore. A developing area of low pressure
passing offshore helps to slow the front a bit and keeping the
showers near the coast through the overnight, so only gradual
clearing is expected by daybreak on Saturday. Cooler and drier
air begins to make its way into northern areas tomorrow night,
with lows dropping to near 50 degrees.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
     Multi Day Heat Expected Next Week...

High Impact Weather Potential: Multiple days of heat indices in
excess of 95 to 100F beginning Tuesday likely continuing through the
end of the week.  The potential exists for heat indices in excess of
105F especially over southern NH and SW ME.

--Pattern and Summary--

The long term period opens with a mobile longwave trough overhead
which will move east of the region by Sunday.  Beyond this...a
significant pattern change is in the works...with longwave troughing
digging down the west coast of North America which will help push
western US ridging to the east.  The result will be a building ridge
across the eastern half of the United States on Tuesday with this
ridge locking in place over the northeast for the middle and latter
portions of the week.  This ridge looks to be rather impressive for
any time of the summer...not to mention mid June...with H5 return
intervals approaching or exceeding 30 years by Wednesday and
Thursday and nearing the top end of the GYX sounding climatology.
Thus...the primary forecast concern for the long term will center on
temperatures rather than precipitation as the proximity of the ridge
next week will likely preclude much in the way of rainfall while
temperatures will potentially near record highs centered around the
first day of astronomical summer.

--Daily Details--

Saturday - Sunday: One last stretch of dry and seasonable weather is
expected to open the period this weekend as offshore cold front
pushes east on Saturday with Canadian high pressure building
overhead for Sunday.  The ensemble guidance envelope includes some
members that have a few showers along the coast as the frontal
boundary slows over the Gulf of Maine...but expect the day to
feature morning clearing...seasonable temperatures /highs in the
upper 60s in the mountains to the upper 70s across southern NH/ and
dramatically lower dewpoints than on Friday.  This sets up a good
radiational cooling night Saturday night with 40s common across the
area.  Expect some of the northern valleys will dip again into the
upper /and perhaps middle/ 30s.  Sunny weather expected for Father`s
Day with T8s in the upper single digits suggesting highs in the 70s
to around 80 from north to south.

Monday: High pressure settles south of Maritime Canada with deep
layer ridging building towards the region from the west will allow
return flow to strengthen...with temperatures building to star the
week.  Monday looks seasonably mild with nearby high pressure /weak
gradient/ indicating a robust sea breeze with highs along the coast
in the 70s...and temperatures reaching the lower to middle 80s
inland.

Tuesday - Thursday: T8s push into the upper teens by Tuesday with
some potential to push above 20C by Thursday...which represents a 1
in 10 year to 1 in 30 year event for this time in June.  Fully
mixed...+20C suggests mid 90s which is well-captured by the NBM for
Wednesday/Thursday.  This is right in the vicinity of daily records
for this period /for example...CON for Tuesday, Wednesday, and
Thursday is 98F/.  A slightly more southerly trajectory to the
gradient should allow the immediate coast to stay cooler on Tuesday
/ 70s to lower 80s / with a seabreeze but by Wednesday and Thursday
the gradient turns more westerly with the heat pushing to the coast.
Dewpoints begin the period in the lower 60s on Tuesday...and then
into the mid/upper 60s by Wednesday-Thursday with some ensemble
members going higher than this. While a few ensemble members have a
convective complex trying to push into our area at some point in the
extended...this has little ensemble support and conceptually doesn/t
fit given our proximity to the center of the ridge.  Thus...will
maintain a dry forecast through the period.

&&

.AVIATION /22Z THURSDAY THROUGH TUESDAY/...
Short Term...VFR prevails through the overnight, with some MVFR
ceilings and scattered showers reaching LEB and HIE during the
early daylight hours. Periods of MVFR and showers continue at
LEB and HIE much of the day, while the remaining terminals see
brief restrictions with showers and a few thunderstorms in the
mid to late afternoon. Showers linger across coastal terminals
into the evening, and then VFR returns Friday night. Some valley
fog may bring restrictions late tomorrow night.

Long Term...Any lingering showers should depart the region
early Saturday...with VFR conditions and northwesterly winds
10kts before winds diminish Saturday night with light winds/VFR
conditions Sunday through Tuesday.

&&

.MARINE...
Short Term...South-southwesterly winds freshen ahead of an
approaching cold front tonight, with marginal SCA conditions
developing after midnight. SCA conditions continue tomorrow,
then the front crosses the waters tomorrow evening with showers
and thunderstorms. High pressure begins to build across the
waters by late tomorrow night.

Long Term...High pressure builds over the waters this weekend
before settling south of the waters early next week. Given this
setup, winds/waves are expected to remain below SCA levels
through the long term period.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...Small Craft Advisory from 1 AM to 8 PM EDT Friday for ANZ150-
     152-154.

&&

$$

NEAR TERM...Tubbs
SHORT TERM...Clair
LONG TERM...Arnott
AVIATION...Arnott/Clair
MARINE...Arnott/Clair