Area Forecast Discussion
Issued by NWS Portland, ME

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FXUS61 KGYX 241941

Area Forecast Discussion
National Weather Service Gray ME
341 PM EDT Mon Jun 24 2019

A warm front will cross the area Tuesday, followed by a cold
front Tuesday night, which will produce a period of showers,
with a chance of thunderstorms. A cold front will push southeast
through the area Thursday bringing showers and thunderstorms.
High pressure builds in briefly for Friday, but a large upper
level low will position itself near the CWA over the weekend,
providing unsettled conditions.


The weak sfc ridge over the area this afternoon shifts to the
east overnight. This will allow for WAA to begin aloft, and
will see cirrus increase this evening, with some mid layer
clouds moving into the wrn zones before daybreak. Should be
enough clear skies early for some rad cooling, especially in the
east. Lows will range from mid-upper 40s in the mtns to the
upper 50s in srn NH, where some low level sfc moisture may work
in. It should stay dry thru the night, and have held chc POPs in
SW zones until 10-12Z.


Sfc air mass remains very dry in the morning, with the
exception of srn NH and CT valley, which will see sfc moisture
begin to rise. So, outside of these areas, I think most if not
all of the of the CWA remains dry well into the morning, if not
early afternoon. Decent 850 MB trough develops ahead of the
system, with a bit of jet associated, so expect initial shot of
WAA to produce a line of convection which, may be energetic
enough to produce some elevated TSRA as it moves thru NH and
into wrn ME. Think that central and nrn ME will be too stable
overall for any convection to last that far NE. Look for
showers or some patchy DZ to continue behind the initial line.

It will be cool as the SE flow picks up a bit ahead of the
occlusion, and highs will generally be in the 60s, with a few
spots in the east and the south possibly reaching 70. A lot of
these warmer temps will be in the morning, as evap cooling with
the rain, and the increasing onshore flow will work to cool
things down once the rain starts.

The main line of showers should clear NH by 22-00Z, and move out
ME zones by around midnight or so, although some showers will
linger in NH in the evening, and ME thru most of the overnight.
Once the showers end, expect clouds to ling until after sunrise.
Lows will mostly be in the mid-upper 50s, with srn NH holding
in the low 60s.


Upper air pattern across North America features three troughs
across the northern half of the continent while the subtropical
ridge is a bit suppressed across the southern tier. As we go
forward in time, the easternmost trough lifts northeast toward
Greenland while the westernmost one heads toward the Pacific
Northwest. The central one heads through the Great Lakes and
toward Hudson Bay. The subtropical ridge gradually builds and
eventually noses northward in the weakness between the central
and western troughs, ultimately shoving the central trough from
Hudson Bay southeast toward our area later this weekend.

Surface low pressure forms over the Gulf of Maine as the frontal
boundary moves through early Wednesday morning. While the
boundary shifts east and lifts north, the surface low lingers
over the Gulf of Maine which will set up an easterly onshore
flow for northern New England developing through the day. Thus
expect high temperatures in the low to mid 70s for much of Maine
and coastal New Hampshire while central and western New
Hampshire, protected from the maritime influence by ranges of
hills and mountains, will warm into the 80s. This greater
warming may lead to some instability in the afternoon with a
chance of showers and thunderstorms mainly for western New
Hampshire. This activity will be aided in part by another trough
axis rotating around the Hudson Bay low which may allow activity
to spread east through the overnight.

Upper trough axis is primarily to our northeast on Thursday,
however some scattered showers and thunderstorms will be
possible for most of the area as daytime heating kicks in and
temperatures warm into the low to mid 80s across New Hampshire
and upper 70s to low 80s for western Maine. The trough finally
fully blows through Thursday night setting up an offshore flow
regime for Friday. This will allow the coastal plain of Maine
to get in on the warmth that much of New Hampshire had been
experiencing in for the previous few days. Low to mid 80s will
be common area wide with only a small chance of afternoon
showers and thunderstorms mainly in the north.

Next trough axis shifts through the region Friday night into
Saturday, though models are unsure whether to favor
precipitation on the northern or southern end of this trough.
The surface features are a bit messy and unclear, but with a
warm and slightly humid air mass in place as the trough arrives
we could see some thunderstorms.

The core of the Hudson Bay low shifts southeast into our area on
Sunday. The result will be cooler temperatures and all daytime
heating going toward the generation of instability for showers
with a few rumbles of thunder. Thus expect widespread showers
during the day on Sunday. In fact, this scenario is one where
small hail would be fairly common with the convective activity
as temperatures aloft within the core of the upper low will be
quite low.


Short Term...VFR thru tonight, then MVFR-IFR, in SHRA/BR and low
cigs moves in from SW-NE during Tuesday, and will linger
through much of Tuesday. Some TSRA are possible, especially Tue

Long Term...Generally expect improving conditions on Wednesday,
but a developing easterly flow could keep some lower ceilings in
across the coast of Maine. Could see some shower or thunderstorm
activity on Thursday and Thursday night as a trough crosses the
region. Winds will shift offshore behind the front and clear
things out to VFR for the whole area on Friday. More showers and
thunderstorms will be possible on Saturday, though, with another
trough moving in.

Short Term...There`s a small chance that SE winds approach 25 kt
gusts, and seas get near 5 ft for a few hours Tue aft or eve.

Long Term...Weak low pressure lingers over the Gulf of Maine
Wednesday with a light easterly flow expected. A cold front
moves through Thursday night and shifts winds to the west as
high pressure crests to our south on Friday.





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