Area Forecast Discussion
Issued by NWS Portland, ME-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KGYX 161405
Area Forecast Discussion
National Weather Service Gray ME
1005 AM EDT Sun Oct 16 2016
After a dry start...a cold front will approach the region late
today and tonight bringing the chance for a few showers. Monday
should turn out mild and dry before the front to our south returns
north with another round of showers expected Monday night. Even
warmer air will move into southern sections Tuesday...and then all
areas Wednesday with an isolated shower possible. Unsettled
weather is expected for the end of the week with somewhat cooler
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
-- Changed Discussion --1004 AM...minor ESTF update to reflect current satellite trends
as well as the mesonet in near term grids. Also added mention of
the high astronomical tide that is occuring shortly after 11 AM
this morning. Expect we`ll see the tide come within 0.3 of a ft of
reaching flood stage given current tidal trends.
Update...Minor changes to reflect latest
observational trends in temps and dewpoints. Otherwise forecast
remains on track.
Previous discussion...We are seeing valley fog set in across NH
this morning...with cool temps and increased moisture from
yesterday. In addition...return flow is allowing for some stratus
to develop across Midcoast ME. Diurnal heating will help to
scattered both of these out ahead of an approaching front. The
parent s/wv trof across Srn Ontario will shear out to the NE
today. This will take a little bit of the punch out of the front
with time. Hi-res model guidance brings a band of decaying showers
into Nrn and Wrn zones in the late afternoon. The best chance for
measurable rnfl is in the mtns...but S of there confidence is not
high on showers holding together well enough to bring any
widespread precip. SW return flow ahead of the front will bring
above normal temps to the area today however.
-- End Changed Discussion --
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...
Much more mild night in store with the front draped across the
area and cloud cover hanging around. The core of the CAA will
remain N of the forecast area...and the frontal push really stalls
out over the our neck of the woods. With a lack of forcing I do
not expect much in the way of showers overnight. If NW flow can
work into Nrn zones I could see some upslope enhanced lift leading
to more abundant clouds there and maybe a scattered shower.
By Mon what is left of the boundary will lift back N as a warm
front. A mild day is in store with temps climbing into the 70s
across much of the Srn half of the forecast area.
.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
High Impact Weather Potential: Minimal.
Pattern: Plenty of active weather along the west coast as of early
this morning with a second powerful low pressure system coming
ashore late last evening. Landfalling low pressure from two days
previous is racing east across NOAM with surface low now east of
James bay and pushing a cold front towards our region tonight. High
pressure remains in control just south of the New England coast...
but the developing progressive flow suggests a change to the pattern
for our region for the coming week.
Aforementioned Pacific energy spreading through North America
evidence of EPO now moving into positive territory with ongoing
impressive CPAC jet. This teleconnects to mild temperatures over
the eastern United States...and guidance is on board with this idea
through the middle of the week. For the second half of this forecast
period...focus shifts to deepening/southward moving trough over the
Gulf of Alaska leading to downstream flow amplification resulting in
longwave trough development over the central United States by
Thursday with this feature pressing into the eastern states through
Precipitation Potential: Modified maritime airmass over much of the
country with ridging in the southeastern states suggests ample
moisture available for precipitation through the period. The
progressive pattern through Wed/Thu will keep systems moving...with
significant precipitation not expected. However beyond this...as
longwave trough approaches from the west...the pattern is ripe for
deep northward moisture transport and more significant rainfall...
however the details in available forcing at this range are
questionable...so certainly some hope for rain...but confidence
Model Trends/Confidence: Deterministic/ensemble guidance have come
into better agreement over the past 24 hours with rather strong
agreement in the large scale pattern through Friday...with rather
similar handling of developing longwave trough. Despite the
longwave pattern agreement...plenty of details in the llevels to
reduce confidence for the Friday-Saturday timeframe.
Monday Night: Shortwave ridge axis moves east of our longitude...
with developing broad southwesterly flow coaxing front to our south
to return north as a warm front overnight. By Monday evening...
expect convective activity to be ongoing over the eastern Great
Lakes/southern Ontario at the leading edge of moisture/instability
plume and at the nose of a 40-50kt LLJ at H8. This activity will
follow the thickness gradient south and east overnight...gradually
weakening as instability wanes and llevel flow veers. Confidence is
building that rain will impact northern areas and will continue to
trend PoPs upward in this region...with chance PoPs warranted to the
south of this. Can/t rule out a few rumbles of thunder as Showalter
indices fall to around -1 over NH as deep moisture plume arrives.
Temperatures generally mild given clouds/precip although position of
warm front across the region spells a good contrast...with mid 50s
likely south...but only lower-mid 40s north.
Tuesday: Strong Low pressure north of the northern Great Lakes
Tuesday morning moves north and east through the day...pulling
aforementioned warm front north...with the warm sector spreading
through at least NH before getting hung up in the climatologically
favored location along the NH/ME border. East of this location
expect low clouds to hold on at least into early afternoon...with
skies scattering out to the south and west of this. T9s rocket to
+20-21C over southern NH by afternoon...while remaining stuck around
+12C over western Maine. Certainly bust potential on temperatures
based on exact frontal location...but highs near 80 are possible
southern NH...but stuck in the 50s to around 60 for much of Maine.
Best threat of a shower will be near the international border with
departing warm front early and approaching cold front late...but
expect much of the day will be dry.
Tuesday Night-Wednesday: Aforementioned cold front drops through the
region...but with little dynamic support...expect another decaying
line of showers to cross the region with a quiet day for Wednesday
as cold front settles through the region. No more than
chance/scattered PoPs for Tuesday night with the front...with dry
conditions likely Wednesday as deeper moisture is temporarily pushed
south of the region. As mentioned by the previous forecaster...CAA
behind cold front is weak...and thus another mild day is in store.
In fact...for our Maine locations...we/ll see highs a good 5-10F
warmer than on Tuesday with T9s +13 to +17C from north to south.
Wednesday Night - Thursday Night: There is increasing agreement
that the front to our south will again return north during this
period with deeper moisture also making a return given backing
mid/upper level flow ahead of strengthening trough to our west. We/ll
likely be stuck in low clouds and possibly fog through much of the
period...with increasing chance for showers /period of rain?/ as
southwesterly flow aloft deepens and forcing over the advancing
front increases. Lows 40s/50s and highs in the 50s/60s.
Friday - Saturday: The forecast looks to end on a continued
unsettled note with good agreement that upstream longwave trough
will remain west of our longitude through Saturday. Given this
orientation expect building +PWAT anomalies along the east coast as
upstream longwave trough taps both GOM and western Atlantic. Plenty
of disagreement on the surface details...with potential low pressure
development ahead of the trough as well as a westward-moving cutoff
over the western Atlantic...that may get pulled into the deep
southerly flow. No doubt will continue shower mention through the
end of the forecast period with temperatures above climo given
entrenched southerly flow...but tempered by what will likely be a
few rounds of showers/rain. Certainly some hope during this period
for heavier rainfall amounts...but way too early to start thinking
about specific timing/location.
.AVIATION /14Z SUNDAY THROUGH THURSDAY/...
Short Term...Areas of valley fog are developing with cool temps
again early this morning. Local LIFR will be possible...mainly
across NH interior terminals. Farther E...areas of MVFR CIGS are
possible with developing onshore flow helping to force some
stratus. Daytime heating will help to lift both the stratus and
fog this morning...as a front approaches from the W. Not confident
enough in widespread SHRA with the front to put in any prevailing
groups in the TAFs. Best chance will be the far N around
HIE...though with the front decaying with time even that is not a
high confidence forecast. High pressure and VFR conditions nose
back in for Mon.
Long Term...Deteriorating flying conditions Monday night with a
band of showers /isolated thunder over NH?/. MVFR/IFR restrictions
may continue over ME terminals through much of Tue before
improvement to VFR. Showers may bring additional restrictions
Tuesday night HIE/LEB...otherwise VFR Tuesday night-Wednesday.
Showers return Wednesday night-Thursday with MVFR/IFR restrictions
Short Term...SCA remains in effect outside of the bays for
increasing SW flow later today. A few wind gusts to 25 kt and seas
building to 5 ft during the afternoon and evening. Winds and seas
will gradually diminish into early Mon.
Long Term...Southwesterly flow strengthens ahead of an
approaching cold front Late Tue/Tue night with SCAs likely into
early Wed. Winds/waves below SCA conditions late Wed through Thu.
-- Changed Discussion --We`re currently in the period of high astronomical tides. The high
tide that occurs shortly after 11 AM this morning is currently
running between 0.2 and 0.4 ft mllw above projections because of
the increasing south-southwest flow. The high tide should come
within 0.25 ft mllw of reaching flood stage for both seacoast NH
as well as southwest coastal Maine.
-- End Changed Discussion --
-- Changed Discussion --ME...None.
MARINE...Small Craft Advisory until 6 AM EDT Monday for ANZ150-152-154.
-- End Changed Discussion --