Area Forecast Discussion
Issued by NWS Portland, ME

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690
FXUS61 KGYX 220212
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
1012 PM EDT Fri Jul 21 2017

.SYNOPSIS...
A weak front drops south across the area tonight and Saturday
before stalling over southern New England. Several areas of low
pressure will track through southern New England along this
front late this weekend and into early next week, providing a
chance of rain while keeping temperatures cool.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
1010 PM...Think showers are done for the night, at least until
a few spkls over central NH and the far ern zones wind down in
the next hour or so. Otherwise, skies should clear to just sct
cirrus, if they are not clear already. Expect to see some valley
fog, especially in the mountains, where it should decouple
easier, and temps will drop. ACross the coast and the south,
winds may stay up enough to prevent much decoupling in the non-
sheltered areas, and given current 02Z temps in the upper 70s in
some spots, I have bumped up mins a bit these areas.

615 PM...Bets dynamics and thermodynamics staying N of the CWA,
and as convection drifts SE into the CWA it will weaken. Still
may see an isolated TSRA or two along the intl border and into
central Somerset county through about sunset. Otherwise look
for a mostly clear and warm evening, as westerly flow will be
slow to wind down, and decoupling will likely not happen to
later tonight.

Previously...NWS Doppler Radar mosaic shows scattered
convection has developed over Quebec, northern Maine, and into
New Brunswick as surface heating...a series of weak
boundaries...and an approaching shortwave work in tandem.
Modified raobs show CAPEs of 1000 to 1500 j/kg with a few storms
across our far northern and eastern Maine zones capable of
strong wind gusts and hail through early evening. Otherwise...a
dry night as a surface cold front settles southward into the
region. lows will range from the upper 50s to mid 60s.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
On Saturday...a blend of clouds and sunshine as the cold front
continues to settle south across the area. There could be an
isolated afternoon shower over the southern half of New Hampshire
into adjacent southwest Maine...otherwise a dry and warm summer
day with highs ranging from 75 to 80 along the international
border to the 80s elsewhere. The front will continue to press
south Saturday night...with mostly clear skies from Northern New
Hampshire through Central Maine and partly cloudy skies for the
remainder of the area as high pressure noses in from eastern
Canada. Lows will range from around 50 near the international
border with 50s to near 60 elsewhere.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
On Sunday the large upper low over eastern Canada and northern
Maine will begin moving east as a short wave kicker approaches
in the mid level flow in the vicinity of the northern Great
Lakes. This short wave opens up as it digs south into New
England Monday and Tuesday. Ridging fills in briefly on
Wednesday before another stronger upper low follows a similar
path for the end of the work week. This active pattern looks to
continue keeping precipitation chances in the forecast.

As far as temperatures, the hot air is suppressed southward
with NAEFS showing negative temperature anomalies at 925mb
Monday through Wednesday. Highs only warm into the 60s and 70s
each day due to cloud cover and rain (this is several degrees
below normal for this time of year for PWM and CON). Overnight
lows will generally be in the 50s with a few 60s creeping back
in (right around normal).

At the surface, a chain of weak low pressure centers develop
along a baroclinic zone that will be initially centered to our
south and west Sunday. Precipitation will spread from west to
east Sunday night into the Monday as the system shifts
northeast. This slow moving, vertically stacked system will have
high PWAT air to work with (although it will be higher to the
south) as well as moderately deep warm cloud depths...
especially Monday night into Tuesday. Mean specific humidity
anomalies will be +2-3 standard deviations above normal
according to the NAEFS. Therefore heavy rain and localized
flooding will be a prime concern for the 48 hr period. Current
model timing for Sunday night into Monday`s precipitation
(arriving after dark) would preclude any real severe weather
threats at this time.

Thunderstorms chances increase Monday into Tuesday morning
however as lapse rates increase, reaching around 7 C/km Monday
night preceding the short wave passage. A cold front sweeps
through during this time and should help focus storms. Depending
on how much heating we get there may be marginally severe
storms with damaging wind and hail early on but again antecedent
cloud cover will be an issue.

Wednesday high pressure crosses the area. Another cold front
marches through Thursday night into Friday, but parent forcing
is so far forecasted to be well displaced in Canada.

&&

.AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...
Short Term...VFR with isold MVFR in tsra psb vicinity of
International border through early evening. Lcl IFR conditions
are psb Sat AM  and again Sun AM in valley stratus and fog.

Long Term...Cool and unsettled weather returns with showers and
MVFR ceilings being the norm for the daytime and IFR in fog
and stratus returning into the overnight from Sunday through
Tuesday as moisture pools along frontal boundaries. LLWS may be
a concern Sunday with near calm winds at the surface and an
increasing LLJ near LEB and HIE.

&&

.MARINE...
Short Term /through Saturday night/...Winds and seas are
expected to remain below SCA threshold through the period.

Long Term...Winds and seas remain below SCA criteria through the
end of the weekend and into next week. A frontal boundary
stalled over or near the waters will keep winds light and
stratus and dense fog over the waters.

&&

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

&&

$$
SYNOPSIS...Schwibs
NEAR TERM...Cempa/Schwibs
SHORT TERM...Schwibs
LONG TERM...Hanes
AVIATION...Schwibs
MARINE...Hanes/Schwibs



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