Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Gray ME
856 PM EDT Tue Sep 27 2016
a cold front will move well offshore this evening. A strengthening
northeast flow behind this frontal system will produce more clouds
and patchy drizzle and fog overnight into the day on Wednesday.
High pressure will gradually build into the region from the north
late Wednesday and Wednesday night. The high will remain parked to
our north while low pressure over the Midwest drifts slowly north
and east. Moisture from this system will gradually spread into the
region Thursday and Friday. The best chance of rain will be this
weekend when a large upper level low pressure system over the
Great Lakes lifts to the north, spreading rain into New England.
Near term /through Wednesday/...
update...elevated showers are forming over the top of low level NE
flow. Warm air advection over the shallow cooler air will continue thru the
night...gradually developing farther and farther SW as the deeper
marine air moves in that direction. The low level stratus is also
on the move swwd. The main areas evident on infrared satellite are
pushing into the Penobscot Bay region at this hour...though some
low cloud appears to be developing well west of this area in the
vicinity of pwm. This should all fill in rather quickly as the
clear air continues to cool quickly towards the dewpoint. As that
stratus thickens...some patchy drizzle is possible with the weak
warm air advection and lift on top of the inversion.
Previous discussion...at 18z...a cold front was situated just
offshore with a 1011 millibar low situated along it. Another weak
boundary extended from the rooftop of Maine through the Saint
Lawrence valley. Skies have broken out between these two features
with partly sunny skies across the forecast area. National Weather Service Doppler
radar mosaic showed scattered convection with this boundary over
southeast Quebec. For tonight...the weak boundary over Quebec will
settle south across the area with clouds and widely scattered
showers. As the flow becomes more onshore overnight...we'll see
lower clouds and patchy drizzle and fog develop. Lows will range
from the upper 40s to lower 50s.
Short term /Wednesday night/...
on Wednesday...we'll see slow improvement from northeast to
southwest as high pressure centered near the Gaspe Peninsula
gradually spreads drier air into the area. It should remain
mostly cloudy over much of southern and western New Hampshire and
extreme southwest Maine while the rest of the area sees partial
clearing. It'll be cooler then today in a strengthening northeast
breeze with highs only in the mid 50s to lower 60s. Clouds begin
to spread back north on Wednesday night as the system over the
Midwest attempts to move into northern New England.
Long term /Thursday through Tuesday/...
Thursday morning begins with a large scale closed upper level low
firmly entrenched over the nations mid-section. Southerly flow
aloft over New England will keep temperatures at least near normal
despite variable cloudiness and intermittent precipitation. The
closed low looks like it will remain over the Ohio River valley
through Friday and at least into Saturday before starting to
migrate to the north and east. The low will begin to weaken a bit
on Sunday and Sunday night before becoming an open wave late
Monday night. The entire extended period will be dominated by this
upper level low. While it may not produce a tremendous amount of
rain... it will create mostly cloudy skies and rain showers
throughout the period.
Aviation /01z Wednesday through Sunday/...
short term/through Wednesday night/...VFR will lower to MVFR
tonight with LCL IFR psb in drizzle and fog. Conditions improve to
MVFR throughout aft 13z Wed, bcmg VFR by 17z over northern New Hampshire
eastward into much of ME.
Long term...a slow moving closed upper level low will generate
some flight restrictions at times over the weekend. Expect cloudy
skies in the long term with scattered rain showers. Will likely
see some MVFR/IFR cigs and vsbys associated with the showers.
short term /through Wednesday night/...strengthening northeast
flow will bring Small Craft Advisory conditions outside the bays tonight and
continuing through Wednesday. It's likely the Small Craft Advisory will need to be
Long term...will likely need a Small Craft Advisory for most of
the weekend as a slow moving system will generate onshore flow.
Seas are expected to remain above advisory criteria into at least
Marine...Small Craft Advisory from 2 am to 8 PM EDT Wednesday for