Area Forecast Discussion
Issued by NWS Portland, ME-- Remove Highlighting --
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FXUS61 KGYX 211349
Area Forecast Discussion
National Weather Service Gray ME
949 AM EDT SUN AUG 21 2016
High pressure anchored well offshore will circulate warm and
increasingly humid air into the region today. A strong cold front
will move through the region tonight with a period of rain
expected across the region. Behind this...much cooler and drier
air will arrive for Monday and Tuesday as high pressure builds
into the region. As this high shifts offshore by midweek...expect
temperatures and humidity to gradually increase.
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
-- Changed Discussion --950 am update: Only minor tweaks to reflect current sky cover
conditions and temps otherwise no changes at this time.
8am update: Quick update for the morning sky cover forecast based
on using latest visible satellite imagery. Stratus and areas of
fog only along midcoast Maine and sunny elsewhere over far
southern and coastal areas of Maine and southeast New Hampshire.
Rest of forecast looks good so no other changes needed at this
627 AM...minor ESTF update
to reflect current satellite trends and to ingest the 10z mesonet
into near term grids.
Due to onshore winds and building seas, there is a moderate risk
of rip currents along the coast of Maine and New Hampshire today.
At 06z...a 1024 millibar high was centered south of Newfoundland.
A 991 millibar low was centered over northern Ontario Province
with a trailing cold front through the eastern Great Lakes. GOES
infrared imagery showed broken clouds and patchy fog developing
across the region in the persistent onshore flow courtesy of the
Newfoundland surface high. For today...clouds along with coastal
stratus and fog should lift and breakup for at least several hours
this morning before the more significant cloud shield with the
approaching cold front arrives this afternoon. Highs today should
be mainly in the 70s...with a few 80 degree readings mainly over
southern New Hampshire and the Connecticut valley. A band of showers...and
possibly some embedded thunder...arrive in the Connecticut valley towards
dusk ahead of the cold front with scattered showers possible
-- End Changed Discussion --
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...
The cold front will sweep east across the forecast area tonight
accompanied by a band of showers with locally heavy downpours. By
morning...its cleared the coast with any lingering morning showers
confined to our far eastern Maine zones as well as the mountains.
QPF will range from as much as one and a quarter inches in the
mountains to between one-half and three quarters of an inch elsewhere.
Lows tonight will range from the 50s in the mountains to the lower
and mid 60s elsewhere. On Monday...lingering morning clouds and
widely scattered showers for the mountains...otherwise a mostly
sunny day in the downslope flow. Highs will range from the 60s in
the mountains to the 70s elsewhere.
.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
High Impact Weather Potential in the Extended Forecast: Minimal.
High pressure settled over the Appalachians Monday night will
continue to allow for cold air advection over Northern New England
Monday night. Much drier air settles into the region with dew
points dropping into the 40s across the majority of Maine and New
Hampshire. Despite gradient, winds may decouple in sheltered
inland valleys by late at night. This will lead to the chillest
readings in quite some time with overnight lows in the 40s inland
with lower 50s along the coast as H8 temperatures drop to about
This sets the stage for a September like day on Tuesday with
partly sunny conditions and dry 70s over the region for highs.
Still plenty of cold air aloft and cyclonic curvature along with
relatively steep lapse rates to allow for CU to develop during the
Warm air advection aloft will allow for an inversion Tuesday
night. This will likely lead to more patchy fog. This developing
west to southwesterly flow will lead to a rebound in temperatures
by Wednesday as a surface ridge of high pressure exits off the New
England coastline. Daily highs in the 80s will become more
By Thursday, warm conditions will persist with a slow, gradual
increase in dew points and humidity values continuing. This will
continue on Friday, however a developing trough of low pressure
associated with a cold front near the coast may allow for cooling
conditions right along the waters edge during the day. With the
heat and humidity in place, scattered showers and a few
thunderstorms are possible during the day. However, there is not a
well established moisture connection from the Atlantic or the Gulf
of Mexico so rainfall amounts are not expected to overly heavy.
In essence, the dry trend continues in the most part for the
extended. There will be more dry conditions behind this front.
Although readings will cool down below this front, a southwest
flow aloft will still keep temperatures near or above normal for
this time of the year.
.AVIATION /14Z SUNDAY THROUGH THURSDAY/...
Short Term /through Monday/...VFR conditions will be variable to
IFR/LIFR in developing areas of coastal stratus and fog as well as
some interior late night valley fog. Valley fog burns off by 14z
today...but coastal low clouds may remain. By tonight showers
associated with a cold front will produce widespread MVFR/IFR
conditions. Conditions improve to vfr Monday morning with a NW
surface wind gusting up to 20 kt.
Long Term...VFR conditions look to dominate flying conditions
through Thursday...with restrictions limited to overnight fog
potential each night HIE/LEB and possibly CON.
Short Term /through Monday/...light south to southeast flow will
increase later today and early tonight ahead of a strong cold
front any may briefly approach small craft in gusts outside of the
bays. Seas will also build but should remain just below 5 ft. Northwest
winds follow the cold front for late tonight and Monday with winds
and seas expected to remain below small craft threshold.
The increasingly southerly flow and building seas will result in
a MODERATE RISK of RIP CURRENTS along area beaches today.
Long Term...Winds and waves to remain below sca levels with
northwesterly winds turning southwesterly for Wednesday and
Thursday. Southwesterly winds may reach SCA levels on Thursday
night and Friday.