Severe Thunderstorm Warning 110, NWS Gray, ME

Area Forecast Discussion
National Weather Service Gray ME
1050 AM EDT Sun Aug 23 2020

.SYNOPSIS...
Above normal temperatures will continue as a frontal boundary
meanders north and south across the area. The front will also
bring chances for showers and thunderstorms into next week,
although the prospect of widespread beneficial rainfall remains
low. Some thunderstorms this afternoon and evening could contain
strong gusty winds and hail.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
1035 AM...Notable adjustments come to POPs for today as I
adjust based on timing of the current cluster of convection
crossing S of the intl border attm. This should move through and
shift S a bit thru about 18Z or so. About the time this dies
off and exits east should start seeing instability convection
developing over srn and central NH, where boundaries were left
over from Saturday's storm. Once again these storms have decent
mid-lvl shear to work with and could produce some rotating
updrafts, but it will probably be limited to a few at best.
Also, added hazard of today will be some potential for heavy
rain and back building producing a small chance for for flash
flooding.

Otherwise it looks to be a warn and humid day across much of
the area, with highs 85-90 in central and srn NH.

735 AM...Minor update to drop the dense fog advisory for the mid
coast and capital district of Maine.

Prev disc...
405 AM...Minor ESTF update to add dense fog advisory to mid
coast Maine where I expect low visibilities to be most
widespread and persistent.

Prev Disc...
At 06z...a wavy frontal boundary extended from the Gulf of Maine
through central New England to the Ottawa Valley. GOES infrared
imagery showed a few high and mid clouds across the area...
otherwise light winds and mainly clear skies were allowing
areas of stratus and fog to develop across the forecast area.
NWS Doppler Radar mosaic showed an area of convection along and
north of the baroclinic zone over southeast Ontario associated
with warm air advection and a weak impulse. Extrapolation and
available short range guidance has this activity entering far
northern New Hampshire by 13z. For today...the boundary will
work its way back north across the area. Daytime heating will
yield CAPES AOA 1500 j/kg across much of the region. Convection
will become more widespread by afternoon with modified soundings
suggesting multicell and a few line segments with damaging wind
gusts the primary threat. However...closer to the boundary
there should be sufficient shear for a few supercells and the
possibility of a brief spinup. Highs today will range from the
upper 70s and lower 80s in the mountains through central and mid
coast Maine where more widespread clouds and convection will
limit heating. Elsewhere...mid 80s to around 90 will be the
rule.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...
Convection should quickly fizzle again this evening with loss of
heating. Overnight...we'll see mainly clear skies and light
winds contribute to areas of stratus and fog developing. Lows
ranging from 50s in the mountains to lower and mid 60s
elsewhere. On Monday....the boundary remains draped across the
area with the prospect of another round of showers and
thunderstorms and the potential for a few strong to severe
storms with wind again the primary threat. High temperatures
will be similar to Sunday.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
The upper level pattern will consist of a broad ridge stretching
from California to the Midwest and the southeastern states. More
meridional flow over Canada will continue to thread energy
through a mean trough over eastern Canada which dips down into
the northeastern states. A closed low will travel southeast
within the trough and eventually stall over the Gulf of Saint
Lawrence.

On Tuesday we will be in a warm sector with the associated
surface low well to our north. There will be antecedent cloud
cover due to moderate theta-e advection. An increasing LLJ will
support stratus and fog from Portland to the Mid Coast and north
to include the lower Kennebec Valley during the morning hours.
A cold front will move through during the morning and early
afternoon before pushing offshore. The timing of the FROPA as
well as the expected cloud cover will tamp down the possibility
of storms. That said, partly sunny skies should develop over
parts of southern NH and southwest ME, and this is where
stronger storms could develop, with damaging winds being the
main concern. All storms will have the capability of localized
heavy rainfall and gusty winds.

Highs will vary Tuesday from north to south, with readings in the
lower 70s north to mid/upper 80s south in the stronger WAA.
Tuesday night will be cooler with drier air allowing
temperatures to drop into the upper 40s north to mid/upper 50s
south. This is where lows will linger for several days. Highs
will also be cooler and in the mid 60s north to upper 70s south
through the Saturday.

PWATs get down to about a third of an inch over the mountains
Wednesday morning. PWATs will be slightly higher for Gray, where
the minimum for that date is 0.45". With high pressure building
in, residual clouds over the mountains and gusty NW winds will
be what will keep us from tanking. Thursday morning will also be
chilly but moisture will be starting to return at that point.

After Tuesday's cold front we will stay mostly dry until late
Thursday as short wave energy crosses the area and a warm front
nears from the south. IVT shows a tropical connection as
moisture from the tropical cyclones affecting Louisiana snakes
its way around the Bermuda high and towards New England. At this
time it looks like most of the precip will be to our south, but
we should see scattered showers at least over portions of NH.
Another WAA regime and FROPA set up looks to bring us a rainy
weekend.

&&

.AVIATION /15Z SUNDAY THROUGH THURSDAY/...
Short Term /Through Monday/...Areas of MVFR and lcl IFR in cigs
and fog...improving to VFR aft 12z with sct MVFR and brief IFR
developing in -SHRA/TSRA. Aft 00z Mon...Areas of MVFR and lcl
IFR in cigs and fog once again...improving to VFR aft 12z Mon
with sct MVFR and brief IFR developing in -SHRA/TSRA.

Long Term...MVFR and local IFR conditions are likely Tuesday in
-TSRA as a cold front moves across the area. Improvement to VFR
 should occur after 18Z Tuesday. VFR expected Wednesday and most
 of Thursday before a chance of showers return to southern
 sections. Gusty NW winds develop behind the frontal passage
 Tuesday and continue into Wednesday. There may be a period of
 LLWS early Wednesday morning with a 40-50 kt LLJ just above.
 Local IFR will also be possible in dense valley and ground fog
 early Tuesday morning.

&&

.MARINE...
Short Term /Through Monday/...Winds/seas stay below SCA levels.
Vsby restrictions at times in fog, haze and scattered showers
and thunderstorms.

Long Term...Winds may approach 25 kts for the outer waters late
Tuesday/early Wednesday with a frontal passage. Waves may
approach 5 ft over the outer waters next weekend.

&&

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

&&

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

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