Area Forecast Discussion
Issued by NWS Portland, ME

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FXUS61 KGYX 210218 AAB

Area Forecast Discussion...UPDATED
National Weather Service Gray ME
1018 PM EDT Sat Jul 20 2019

Hot and humid weather continues into Sunday, but a cold front
will drop down out of Canada during the day on Sunday. This
could trigger some showers and thunderstorms as it does so and
will eventually bring an end to the hot and humid weather.
Cooler and drier air moves in by Monday. Low pressure tracking
near the southern New England coastline Monday night will spread
some rain through the region. The cool and comfortable
temperatures continue through the end of the week but with a
gradual warming trend.


Update..Isolate thunderstorms continue to form to the N and W
and drift into parts of the forecast area before dissipating.
That will continue to be the trend overnight until more
widespread forcing arrives early in the morning.

Around daybreak however things could get interesting in Nrn
zones. Convection allowing models show a complex of storms
spilling into the Wrn ME mtns. There will be ample
instability...possibly surface based...and shear with jet close
by. That could mean some rare organized strong/severe storms in
the morning hours. Lots of uncertainty with that scenario

Previous discussion...It will be a balmy night tonight as the
humid air mass won`t allow the temperature to cool off that
much. Most areas will see lows in the 70s, with upper 70s likely
in southeast New Hampshire. Thunderstorms forming to our west
today could roll into the area overnight. At this time it seems
northern areas will be most favored for this activity, though it
cannot be ruled out elsewhere.


A cold front will be dropping into the area on Sunday. Models
still not agreeing that well on timing of this front considering
how close we are to its arrival. Part of the issue will involve
convection along the front, the outflow of which will push it
forward faster. The best consensus at this time favors the front
moving into northern areas in the morning with showers and
thunderstorms along it. It will then push southward through the
day, perhaps seeing a better push across western Maine. Ahead of
the front the hot and humid air mass remains in place and with a
stronger westerly flow the hot temperatures will be observed
closer to the coast as well. But with cloud cover from
convection around it is possible that temperatures might not
reach the extremes they otherwise could. Will maintain the
current heat headlines as they are, though it is possible that
northern areas could be dropped from the Heat Advisory once
today`s heat ends. Thunderstorms on Sunday could approach severe
levels given the very hot and humid air mass and good mid level
wind flow. Outflow winds will be the biggest concern from the
storms. While heavy downpours are possible, it does not look
like flash flooding will be a threat due to quick storm
movement. These should exit the coast with the cold front in the
evening on Sunday with cooler and drier air being felt already
Sunday night. Low temperatures will primarily be in the 60s but
50s will be common in the north.


Cooler and drier air will enter Maine and New Hampshire Sunday
night, following the passage of a cold front. Dew points will
fall through the 60s during the night with even some 50s dew
points appearing in the mountains. Air temperatures will be
about 15 degrees cooler then over the weekend, mostly in the 70s
to lower 80s for afternoon highs.

Clouds will increase and thicken on Monday as a large scale
trough approaches from the west. This upper level trough will
trigger cyclogenesis in the Mid Atlantic region during the day,
spreading showers or a period of rain to much of southern and
central Maine and New Hampshire.

Models coming into better agreement indicating low pressure
crossing through New England Monday night. The surface low will
track near the coastline and the H8 front. Showers will cross
the region. Sufficient instability aloft may trigger
thunderstorms as well. Plenty of moisture in the atmosphere and
precipitable waters near 2 inches will combine with favorable
dynamics to produce locally heavy rainfall Monday evening and
during a portion of the overnight hours. Over an inch of
rainfall is possible over southern and central areas with
locally higher amounts possible in any persistent heavier

The precipitation continues on and off through the midday hours
on Tuesday before tapering off. An upper level trough will
provide for a chance of a brief shower or two right through much
of the work week. This precipitation will mainly be diurnally
driven and mainly in the north and mountains. A gradual warming
trend can be expected towards the end of the week, albeit not
nearly as warm as this past weekend.


Short Term...VFR conditions expected for the most part. However,
a cold front will be dropping down from the north on Sunday
which will trigger some showers and thunderstorms. These will be
most likely in northern and eastern areas.

Long Term...Areas of MVFR or IFR conditions developing in low
clouds and locally heavy rainfall for all terminals beginning
late Monday in the west and spreading east Monday evening.
Conditions gradually improve to VFR on Tuesday, however a brief
shower may occur. A small chance for showers will continue for
much of the work week. However, this will likely be diurnally
driven and mainly in the north.


Short Term...Southwest flow continues until the cold front
arrives Sunday night. High pressure builds in behind it.

Long Term...A front drops south of the area Sunday night and
stalls south of the area through early next week as low
pressure tracks northeast along it. There will be periods of
heavy rain and fog over the waters during this time.


Hot temperatures continue and may be near record values. The
record highs for July 21st are as follows:

CONCORD: 101 in 1977
PORTLAND: 99 in 1977
AUGUSTA: 94 in 1994


The Sugarloaf NWR transmitter is off the air until further
notice. This will be an extended outage as the tower, which was
severely damaged in a winter storm, is rebuilt.


ME...Heat Advisory until 7 PM EDT Sunday for MEZ018>020-023>028.
NH...Heat Advisory until 7 PM EDT Sunday for NHZ005>011-014-015.
     Excessive Heat Warning until 7 PM EDT Sunday for NHZ012-013.



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