Area Forecast Discussion
Issued by NWS Portland, ME-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KGYX 231702 AAD
Area Forecast Discussion...UPDATED
National Weather Service Gray ME
102 PM EDT Fri Sep 23 2016
A strong cold front will gradually drop south across the area
today accompanied by showers and isolated thunderstorms. This will
be our last above normal day as much colder and drier air will
flood into the area tonight behind the cold front. Canadian high
pressure will arrive tonight, remaining in control of our weather
through the weekend and into early next week. We`ll see cool days
and cold nights, with a frost possible for northern areas both
Saturday and Sunday nights.
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
1107 AM Update: Only minor changes this hour to increase PoP
across Nrn NH as the next band of showers drops S. Convection
across Ern NY is still producing intermittent lightning...so I see
no reason to drop thunder for Srn zones.
944 AM Update: Primary changes this hour are to better define PoPs
associated with northern band of shower activity now entering my
far northern zones...with this activity likely to sink south and
weaken with time as mid/upper level forcing depart to the north
and east. Did reduce temperatures over southern sections a tad
based on what will likely be quite limited solar insolation. Am
noting a few lightning strikes over eastern Lake Ontario last
hour...and while the setup does not favor much thunder...do not
yet feel compelled to remove the slight chance mention from the
745 AM Update: Have boosted PoPs within band of showers to
categorical for the next couple of hours as it sinks
south...although rainfall amounts will remain light. Am tracking
another band of showers still north of upstate New York closer to
the cold front at H8 /surface wind shift has pulled south of this
region. This will bring the potential for continued shower
activity over northern areas despite the recent drying trend noted
in this area on GYX radar imagery. No other significant changes at
632 AM...this ESTF update reflects current radar trends as well
as the 10z mesonet.
At 06z...an east-west frontal boundary extended from northern
Maine through southern Quebec. A series of weak 1015 millibar waves
were rippling eastward along this boundary. NWS Doppler radar mosaic
showed a broken band of moderate convection along and to the north
of the frontal boundary. For today...Shortwave impulse situated
along the Quebec-Ontario border on GOES water vapor imagery will
race eastward and drive the surface cold front south across the
forecast area. The heaviest QPF of between one-quarter and one-
half inch will be confined to northern and mountains sections this
morning with amounts trailing off to under one-quarter inch
further south and east. Highs will range from the 60s across the
mountains and international border to the 70s over the southern
half of New Hampshire into extreme southwest Maine.
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...
For tonight...any lingering showers vicinity of the Massachusetts-
New Hampshire border should quickly exit to our south this evening
as drier air arrives behind the cold front. There will be some
lingering upslope clouds across the mountains...otherwise we`ll
become mostly clear tonight. The lingering low clouds in the
mountains and some late night valley fog and stratus should preclude
any significant frost threat over the mountains and international
border area tonight. Lows will range from the upper 30s across the
mountains to near 50 along the New Hampshire seacoast. On
Saturday...breezy and cool with sunshine mixing with instability
clouds by afternoon in the cool cyclonic zone.
.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
In the long term...a large upper low across eastern Canada will
continue to rotate east with time bringing spokes of short wave
energy to New England. With surface high pressure in place, this
will primarily mean several reinforcing shots of cooler and drier
air along with cloud cover. PW values drop to near a quarter inch
Sunday, Monday, and Tuesday mornings. Overnight lows will drop
into the 30s and 40s during this time with highs generally in the
50s and 60s. Expect areas of frost both Sunday morning and Monday
mornings. Will possible need a frost advisory in areas where the
growing season continues.
After Monday the forecast becomes less clear with timing of a
frontal passage differing widely among deterministic models.
Spaghetti plots are in some agreement concerning a warm front
arriving Tuesday while high pressure pushes offshore. Another
sprawling vertically stacked cyclone deepens over the Great Lakes
region and pushes the attendant cold front through New England.
The Euro seems too fast while the GFS seems too slow and is also
generating several surface waves with numerous bullseye
precipitation centers. It has been very hard to come across rain
lately...and since there is so much doubt have kept PoPs in the
long term in the slight chance to chance range at this time.
.AVIATION /18Z FRIDAY THROUGH TUESDAY/...
Short Term /through Saturday Night/...
Summary: A cold front will push south of the region this evening
with high pressure building in it/s wake through Saturday and
remaining over the region through Saturday night.
Restrictions: Band of showers will bring MVFR restrictions northern
terminals...with CON/MHT/PWM/RKD likely seeing brief drops to MVFR.
Conditions improve to VFR as showers depart this evening...with
LIFR/IFR fog likely HIE/LEB...and possible CON/AUG. VFR for Saturday
/ Saturday night with the exception again being overnight fog
Winds: Northwesterly winds 10g16kts this afternoon will diminish to
5-10kts /light and variable in the valleys/ for the overnight before
increasing to 12g20kts from the northwest for the day Saturday.
Northwest winds will diminish to below 10kts again Saturday night.
LLWS: No LLWS expected through Saturday night.
Thunder: Very slight chance of thunder MHT through 21UTC...but
chance not great enough to mention in TAF. No thunder beyond this
through Saturday night.
Long Term...VFR Sunday through Monday. Except chance MVFR/IFR in
patchy valley fog Sunday night at HIE and LEB. MVFR is possible
in Showers Monday night and Tuesday.
Short Term /through Saturday/...winds and seas gradually build
today ahead of the cold front with post frontal wind surge
providing a period of marginal small craft winds and seas outside
the bays tonight. There`ll be a second surge in wind Saturday
afternoon in the deepening cold air with marginal small craft
Long Term...Winds and seas should drop below SCA levels late
MARINE...Small Craft Advisory from 8 PM this evening to 6 AM EDT
Saturday for ANZ150-152-154.