Area Forecast Discussion
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FXUS61 KGYX 221728 AAD
Area Forecast Discussion...UPDATED
National Weather Service Gray ME
128 PM EDT Thu Sep 22 2016
High pressure centered over Vermont will gradually drift offshore
by late today. A cold front over the Saint Lawrence valley will
gradually sink southward into the mountains and foothills later
today accompanied by a few clouds and widely scattered showers.
Low pressure will track east along this front tonight accompanied
by more widespread shower activity. The low will exit the coast
early Friday and help drive the front and showers to the south of
the area by evening. Dry conditions and the coolest air of the
season are expected over the weekend, and through much of next
week, as a large Canadian high pressure system builds south across
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
1217 PM Update: Very minor changes this hour primarily to match
hourly temperatures and fully clear sky cover over southern NH
and southwestern ME.
940 AM Update: Modified temperatures today to better define
afternoon seabreeze...but with little change to expected high
temperatures. Also adjusted sky cover for current band of
altocumulus as a ribbon of mid level moisture /seen in GYX 12Z
RAOB/ pushes east. Mostly sunny skies will be the rule outside of
this area with deeper moisture not arriving until evening over the
622 AM...Minor ESTF update to reflect the 10z mesonet in near
At 06z...a 1024 millibar high was centered over southern Vermont.
A cold front extended from the rooftop of Maine into the Saint
Lawrence valley. GOES infrared imagery showed mainly clear skies
across the forecast area. The light winds and clear skies were
allowing patchy stratus and fog to form across interior valley
locations. For today...the surface high will slide east and
offshore. The cold front will gradually sink southward into our
mountains and foothills by evening. It`ll be accompanied by
increasing clouds and a low chance for a late day shower near the
international border. Highs today will range from lower and mid
80s over the southern half of New Hampshire and adjacent southwest
Maine to the 70s elsewhere.
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/...
Low pressure will race east along the slow-moving cold front
tonight with the most widespread showers found from the northern
third of New Hampshire eastward through the western Maine mountains
and foothills. lows will be in the 50s to around 60. The low exits
the coast Friday morning and will serve to drive the front to the
south of the area by evening. Showers with the frontal boundary
will end from north to south during the day as drier air begins to
spread in from the north with some late day sunshine for northern
areas. Highs will range from the 70s over southern New Hampshire
and adjacent southwest Maine to the 60s elsewhere.
.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
The focus of the extended still is on the cool shot expected for
the weekend that will gradually moderate as we head into next
There remains strong model agreement on both strength and location
of ridging...up thru Nunavut. The greater than 3 standard
deviation anomaly in the Nrn reaches of Canada will have the
tendency to lead to lower than normal heights both W and E of the
ridge axis. One such anomaly looks to at least brush New England
over the weekend. The real core of the cool air does not look like
it will head for the heart of the region...but model forecasts
still bring H8 temps below zero for Nrn zones. The CAA
accompanying this will bring breezy conditions Sat and Sun...with
a chill in the air despite some sun. The pressure gradient Sat
night may preclude frost by keeping the boundary layer somewhat
mixed. A better chance looks to be Sun night...as surface high
tries to nose into New England. If we can decouple...low temps in
the low to mid 30s look possible for Nrn zones.
The forecast becomes more uncertain beyond the weekend when it
comes to how quickly ridging breaks down. The 22.00z ECMWF is a
little more progressive and breaks down the ridge in only a couple
of days. The GFS on the other hand lingers ridging over the
Northeast thru the middle of next week.
.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
-- Changed Discussion --Short Term /Through Friday Night/...
Summary: A cold front will slowly settle through the region tonight
and on Friday bringing deteriorating flying conditions. High
pressure and drier air will arrive from the north Friday night with
Restrictions: VFR at the moment all sites. As the front arrives
from the north tonight...expect deteriorating conditions
/some IFR fog possible LEB ahead of the front overnight/...with
shras possible HIE/AUG/LEB/RKD by daybreak Friday...spreading south
during the day. This will likely bring a period of MVFR
restrictions as early as late tonight HIE...spreading to LEB/AUG
through early Friday. Confidence decreases further south...where
restrictions may be more brief as shower activity weakens.
Improvement to VFR is likely all sites Friday night...with
additional restrictions possible HIE/LEB in fog development.
Winds: Southerly winds less than 10kts today /with sea breezes
developing at all coastal sites/. Winds will go light/variable
tonight before gradually shifting northwesterly and increasing to
12g18kts for the day on Friday before decreasing to less than 10kts
from the northwest Friday night.
LLWS: West/southwesterly winds ahead of the front will strengthen
tonight...with 1-2kft winds increasing to around 30kts overnight
with a period of LLWS. No LLWS beyond this.
Thunder: Very slight chance of a thunderstorm Friday afternoon over
far southern NH /MHT/...otherwise no thunder is expected.
Long Term...VFR to prevail thru the weekend and into early next
week. High pressure will be building in over the weekend...which
may bring breezy conditions but dry S of the mtns. Will have to
watch for some upslope clouds bringing MVFR CIGs to HIE Sat and
Sun before the high center arrives. Sun night could see clear and
calm promoting fog in the river valleys...so local IFR or lower is
possible...especially at LEB...HIE...CON...and MHT.
-- End Changed Discussion --
Short Term /through Friday/...Quiet on the waters with winds and
seas remaining below SCA criteria today. Winds and seas will increase
tonight and Friday as a cold front gradually sinks south across
the region...but should remain below small craft threshold.
Long Term...As front slips S across the waters Fri night into
Sat...winds and seas may briefly approach SCA
thresholds...especially outside of the bays. Then steady offshore
flow should build seas to around 5 ft on the outer waters into
early next week.
NEAR TERM UPDATE...Arnott