Area Forecast Discussion
Issued by NWS Portland, ME-- Highlight Changed Discussion --
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FXUS61 KGYX 201039
Area Forecast Discussion
National Weather Service Gray ME
639 AM EDT TUE SEP 20 2016
A weak frontal boundary continued to push offshore through the
Gulf of Maine this morning. A cold front over the Great Lakes will
sweep eastward and cross our area late today and tonight. This
front could touch off a brief shower across the higher terrain
with its passage. High pressure and drier air returns tonight
through Thursday. Another cold front will approach toward the end
of the work week.
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
-- Changed Discussion --638 AM...minor ESTF update to ingest the current mesonet into
near term grids.
At 06z...a weak frontal boundary was situated just offshore and
moving slowly eastward. A cold front was over the upper Great
Lakes with a warm front extending eastward through Quebec province
and northern Maine. Widespread low clouds and fog were found
across the forecast area with little change in conditions expected
through sunrise. NWS doppler radar mosaic showed a band of offshore
showers associated with the weak departing frontal boundary.
Another area of showers was noted along the Quebec-Ontario border
ahead of the approaching cold front. For today...low clouds and
fog should burn off by later this morning with sunshine and warm
temperatures expected ahead of the approaching cold front. It`ll
be another humid day with any late day showers confined to the
higher terrain and international border area ahead of the cold
front. Highs today will be in the lower and mid 80s...expect for
the Maine midcoast given the onshore trajectory.
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.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/...
The cold front will slide offshore overnight. Clearing skies and
light winds should once again allow low clouds and fog to
perform...mainly across the interior valleys. Lows will be in the
50s...except for some lower 60s over southeast New Hampshire.
Mostly sunny and mild on Wednesday as high pressure continues to
build across the area. Highs will be mainly in the 70s...with a
few 80 degree readings over southeast New Hampshire.
.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
After a warm and pleasant start to the extended...the story thru
the middle of next week looks to be at least a temporary
reshuffling of the pattern. Both the 20.00z GFS and ECMWF...along
with the 20.00z GEFS and 19.12z ECMWF EPS agree on the overall
evolution. A greater than 3 standard deviation ridge is forecast
to build into far Nrn Canada...W of Hudson Bay. This strong
ridging will dislodge the polar air...and with high heights in the
middle of the continent we will tend towards lower heights over
the Northeast. It is a favorable pattern to send the chill our
direction. There may be some modification in model guidance in the
coming days...but at things stand now we could be flirting with H8
temps near 0C by Sat night. That will mean a couple things. One is
that we may have another round of frost or even freeze warnings if
we can high pressure to arrive in time. Another is that with mid
level temps that cool and upslope clouds lingering under that cold
pool...it would not be that much of a stretch to see some flakes
mix it at highest elevations. The cold shot does not look like it
will last long however...as the air mass begins recovering as
early as Sun.
.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
Short Term /through Wednesday/...widespread IFR/LIFR through 12z
improving to vfr throughout with lcl mvfr psbl over the mtns btw
19 and 23z in -shra. Aft 04z Wed...areas of MVFR and lcl IFR dvlpg
in valley stratus and fog. Bcmg VFR throughout aft 12z Wed.
Long Term...The period begins with widespread VFR conditions with
weak high pressure over the region. Thu night and Fri this will
give way to a series of s/wv trofs that will bring periods of MVFR
conditions in SHRA or -RA. The timing of the trofs will likely
vary a bit in the coming days...but it looks like two distinct
waves that could bring MVFR or lower conditions to all terminals.
For the weekend we should see VFR return to all terminals except
in the higher terrain where upslope clouds and SHRA will likely
linger with the passing upper trof. So HIE and LEB may see
occasional MVFR thru Sat/Sun.
Short Term /through Wednesday/...Quiet through Wednesday as winds
and seas remain below small craft criteria.
Long Term...Winds and seas generally look to stay below SCA
thresholds thru early next week. As a cold front approaches the
waters late this week...seas outside the bays may approach 5 ft
ME...Dense Fog Advisory until 9 AM EDT this morning for MEZ023>028.
NH...Dense Fog Advisory until 9 AM EDT this morning for NHZ014.