Area Forecast Discussion
Issued by NWS Portland, ME

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FXUS61 KGYX 300328

Area Forecast Discussion
National Weather Service Gray ME
1128 PM EDT Thu Sep 29 2016

High pressure will continue to build into the region from the
north through Friday. Low pressure over the midwest drifts slowly
north and east through the weekend. This low will eventually bring
the chance of showers to the region Friday night through at least
Monday. High pressure will again build in from the north by the
middle of next week.


1130PM UPDATE...
Have made some minor adjustments to overnight low temperature
forecast and increased cloud cover a bit. Although most automated
sites are reporting clear conditions, satellite reveals an
expansive cirrus canopy. This should hold temperatures in check a
bit, but has not prevented some of the favored cooling spots from
cooling a little faster than expected. Regional radar shows some
showers spreading northward through the lower Hudson valley and
into far southern New England. This will have trouble making it up
this way overnight, but could impact southern New Hampshire by

Have updated the forecast to adjust temperature trends based on
latest observations. Have also zeroed out the precipitation
chances for the evening. Some clouds moving in from the south but
should not see precipitation until possibly tomorrow morning.

Dry air in the lower levels of the atmosphere will continue to
drive mainly clear skies into the forecast area through this
evening. However, the flow will gradually veer in the upper levels
of the atmosphere around the periphery of the cutoff Ohio Valley
low pressure system, bringing cirrus to the region. Initially,
clouds will advance into southern New Hampshire late tonight.
There may remain a few low clouds caught underneath the inversion
as well.

In areas that remain clear, patchy fog is expected across the
inland valleys, especially over northern areas. Chilly 30s are
expected in the north and mountain areas for overnight lows with
radiational cooling under clear skies and light winds.


Moderate risk for rip currents for area beaches Friday.

Moisture will continue to slowly rebound northward on Friday with
a low chance pop for showers over southernmost areas. This will be
in response to a nearly stationary area of surface low pressure
along the Mid Atlantic coastline. There will be a sharp division
between cloudy and clear areas as well as a sharp cutoff to any
light precipitation.

Pops increase Friday night as low pressure moves northbound to a
position south of Long Island New York. This track will lend
itself to possibly slightly heavier precipitation along the coast
and portions of southern New Hampshire in the extended portion of
the forecast as the upper level low pressure system remains
relatively stationary. Most mesoscale models today are now
projecting some precip is possible as far north as central areas.
However, have kept precip mainly over southern areas as a dry
atmosphere will initially be in place across the interior.


There is a lot of forecast uncertainty in the extended...revolving
around the lifting of Midwestern cut off low pressure. Both the
29.12z GFS and ECMWF slowly lift the low into the Great Lakes thru
the weekend. As it does so...onshore flow will increase and
diffluence aloft will be more conducive to support showers.
Surface high pressure to the N will try and fight precip a bit
as it continues to supply dry air. This puts the forecast area
between the dry air to the N and showers to the S...and that
battleground is the cause for the uncertainty. Highest PoP will be
across southern zones and near the coast...while northern zones
look to stay dry the longest.

Beyond early next week model guidance diverges in handling of how
the upper low finally lifts out and how the pattern evolves behind
it. The GFS favors higher heights building across New
England...while the ECMWF favors lower heights. This will have big
implications on how progressive the next trof can be as it crosses
the northern tier.


Short Term...Through Friday night, VFR conditions over central
and mountain areas with mainly MVFR conditions over southernmost
areas. Some overnight and early morning valley fog til 13z will
allow for local IFR conditions.

Long Term...As the upper low pressure lifts across the Northeast
MVFR conditions will likely work back into the forecast area in
the form of stratus. SHRA will be more likely at southern NH
terminals MHT...PSM...and CON thru the weekend. At night...cooling
may bring occasional IFR CIGs to southern NH and coastal
terminals. It will be hard to find stretches thru early next week
where MVFR or lower can be ruled out completely.


Short Term...Persistent Northeast flow will continue SCA conditions
outside the bays through Friday. However, seas maxed out this
morning and have subsided slightly.

Long Term...NE flow will continue as upper low pressure lifts
towards the Northeast. As the gradient increases into the weekend
and NE flow picks up...seas will build back over 5 ft on the outer
waters. Winds look to increase to near 25 kts on the outer waters
as well.


MARINE...Small Craft Advisory until 6 PM EDT Friday for ANZ150-152.
     Small Craft Advisory until 6 AM EDT Saturday for ANZ154.



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