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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KGYX 050438
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
1238 AM EDT Wed Aug 5 2020

.SYNOPSIS...
Showers and thunderstorms associated with TS Isaias will become
more numerous through this evening, especially across NH. Winds
will pick up later this afternoon as well then the brunt of the
storm with locally heavy rainfall should hit this evening into
the pre- dawn hours Wednesday. The storm exits to the north
early Wednesday with temperatures settling near normal and lower
humidity levels for Thursday and Friday. Temperatures and
humidity will begin to creep up over the weekend, but it will
remain mainly sunny and fair.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
1230am Update...Just a quick AFD-only update here to note that
we have cancelled all of the inland TS warnings and also the
flash flood watch. TS warnings remain up along the coast at
least until the next NHC advisory update.

Update...Made a fairly comprehensive update in preparation for
the 03z NHC update for Isaias. Biggest changes were to speed up
timing of both PoP and winds thru the forecast area as the storm
accelerates. Winds are consistently gusting between 30 and 40
knots and should generally remain there for the next hour or
two. Winds are steadily decreasing to our SW...and that will be
the trend locally as well. The majority of the heavy rain has
also moved out of the forecast area...and so I will be
evaluating taking the flash flood watch down with the next
advisory package as well. Slow but steady improvement is on the
way.

Previous discussion...At 19z a 994 millibar tropical low was
vicinity of the Tri-State Region...with three hour pressure
falls on the order of 10 millibars across that area. Latest
surface analysis remains in good agreement with current track
forecast as the center of Isaias races northward into the Hudson
Valley. Shear continues to increase across our area as we are
in the favored quadrant for strong convection along with
isolated tornadoes. Expect scattered low-topped rotating storms
through early evening with brief spinups and damaging surface
winds gusts with the stronger cells. Per latest HREF, a band of
convection entering southern New England on NWS Doppler Radar
mosaic will pivot northward across the area this evening,
accompanied by strong wind gusts and brief heavy rain.
Accompanying this band will be a plume of precipitable water
approaching two inches. Strong upslope flow into our favored
higher terrain could result in some localized flooding as this
band crosses the higher terrain. Convection will quickly end
from south to north overnight as the decaying tropical system
accelerates into southeast Canada.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM THURSDAY/...
Behind this system...we could see a stray shower across northern
areas Wednesday as a weak cold front crosses the area. Otherwise
a partly to mostly sunny day with highs mainly in the 80s.
Behind the cold front...mainly clear and less humid with some
patchy valley fog possible. Lows will range from the mid 50s to
lower 60s.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
A quiet stretch of weather awaits the long range forecast period for
the end of this work week into the start of the next. By Thursday
morning, an upper level trough will be exiting east across the
Canadian Maritimes...in its wake a mid-level thermal trough crosses
into New England with h850 temps dipping a little below normal, to
about 8-10C. A little low level moisture in westerly flow will lead
to some clouds over the mountains but other than that weather will
be fair with comfortably afternoon highs in the 70s to low-80s and
dew points in the 50s.

Broad surface high pressure builds into New England by Friday which
ought to keep showers along a weak boundary south of the forecast
area, although there will be an uptick in humidity over the southern
part of the forecast area. An upper level shortwave approaches the
coast late Friday which produces some cyclogenesis along the
aforementioned boundary over the waters; while widespread rain isn`t
expected it could fling enough moisture back into New England to
produce widely scattered mountain rain showers during the afternoon
as the trough axis aloft crosses.

A ridge of high pressure crosses Sunday into Monday with more dry
weather; meanwhile a southwest wind sets up over the eastern CONUS,
trending temperatures up through the weekend and into the middle of
next week. High temperatures are expected to warm well into the 80s
and into the low-90s over the interior by Monday. A series of weak
shortwaves bring PoPs back at least over the mountains during the
first half of the coming wAVIATION...
MARINE...
HYDROLOGY...
TIDES/COASTAL FLOODING...eek.

&&

.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
Short Term /through Wednesday Night/...TS Isaias will bring
widespread MVFR/IFR conditions and gusty winds this evening,
with conditions improving from south to north Wednesday morning
to widespread VFR along with decreasing winds. Valley fog
possible Thu AM vcnty of KHIE/KLEB.

Long Term...VFR prevails through the end of the work week and
weekend with high pressure over the area. Low clouds and fog may
impact valley and coastal sites Friday and Saturday mornings...
and possibly at HIE/LEB Sunday morning.

&&

.MARINE...
Short Term /Through Wednesday Night/...Strong south to
southeast winds expected with the passage of TS Isaias tonight
along with building seas. Winds will diminish overnight but seas
above 5 ft are likely to linger for Wednesday.

Long Term...A quiet period of weather is expected for the end of
this week and into the next as weak high pressure settles over
the region and gradually sAVIATION...
MARINE...
HYDROLOGY...
TIDES/COASTAL FLOODING...lides east into the Atlantic. Seas
start to build ahead of an approaching trough by the beginning
to middle of the next work week.

&&

.HYDROLOGY...
Showers and thunderstorms associated with TS Isaias could
produce torrential downpours this evening. Western areas can
expect the highest rainfall totals, especially across the higher
terrain in the mountains where southeasterly upsloping will occur.
One to two inches with as much as three inches of rain is possible
across the favored upslope terrain. Elsewhere...generally less
than an inch is likely. Heavy rain could lead to localized flash
flooding.

&&

.TIDES/COASTAL FLOODING...
A modestly high astronomical tide will occur shortly after
midnight tonight. As the remains of Isaias pass by to our west,
a strong south to southeasterly flow may coincide with this
tide depending on the exact timing with the system. Building
seas and gusty onshore winds may allow for about a foot or so of
storm surge (current model runs appear to have a low bias).
This may lead to localized splash-over across the region tonight.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Tropical Storm Warning for MEZ023>028.
     Coastal Flood Advisory until 2 AM EDT early this morning for
     MEZ023>028.
NH...Tropical Storm Warning for NHZ014.
     Coastal Flood Advisory until 2 AM EDT early this morning for
     NHZ014.
MARINE...Tropical Storm Warning for ANZ150>154.
&&

$$

NEAR TERM...Watson
SHORT TERM...Cannon/Schwibs
LONG TERM...Casey