Scientific Forecaster Discussion
fxus61 kgyx 251855
Area forecast discussion
National Weather Service Gray ME
255 PM EDT Thu may 25 2017
a broad area of low pressure from the Ohio Valley through the
mid Atlantic coast will slowly lift northeast tonight...reaching
Cape Cod by Friday morning. Low pressure will continue
northeast into the Maritimes through Friday night. Weak high
pressure will build over the area on Saturday and will shift
offshore on Sunday. Weak low pressure over the eastern Great
Lakes will lift north into western Quebec Sunday night and will
drive a cold front toward the region on Monday. The front will
slowly cross the area late Monday night and Tuesday.
Near term /until 6 am Friday morning/...
higher pressure and easterly winds have kept much rain from
intruding into northern New England by retarding the advancement
of precipitation into Maine and northern and central New Hampshire until
the last couple of hours. The flow has intensified along the
coast as the pressure gradient increases/low pressure nears.
Temperatures have been kept down in this marine airmass while
northern sections were able to break out into the 60s.
Cam models have been correct in showing a weakness this
afternoon in precipitation fields over New Hampshire and especially Maine
as energy diverges both towards northern New York state as well as
offshore. We'll see a break in most shower activity more or
less this afternoon and evening...however there will be widely
scattered showers still around...mainly over the mountains.
Around midnight a stronger short wave associated with this
system will pivot into the area and precipitation will increase
both in intensity and areal coverage. This is when we will see
the bulk of the 1-2 inches with this event. We'll see some heavy
downpours for the overnight period into Friday morning.
Winds are picking up as mixing deepens today and expect east-southeast
winds to gust to 25 kt through the night. Continued with
drizzle tonight mainly in between the two systems as the onshore
flow intensifies. Lows will be in the upper 40s to around 50.
Short term /6 am Friday morning through Friday night/...
after the heavier rain expected during the morning
hours...precipitation tapers off to showers by Friday afternoon.
Again the heavier rain will be along the coast with some
enhancement over terrain. The long duration of this event should
preclude any flooding issues but poor drainage areas may see
some brief issues in heavier rainfall that occurs through
tomorrow. Expect temperatures to warm only about 5-10 degrees
from overnight lows tonight to highs Friday. Tomorrow night
clouds will begin to decrease across the region. The upper low
will be engulfed in another circulation south of Greenland while
the surface cyclone fills. Overnight lows Friday night will
drop farther in a drier airmass with lows in the 40s most
locations and perhaps up to 50 degrees in warm spots.
Long term /Saturday through Thursday/...
mean long wave trof position will remain over the Great Lakes, this
will mean a general cool wet pattern can be expect for the
outlook period with a few dry periods between systems.
Starting with Saturday, the system that exits into the Maritimes
allows weak high pres over the area and a drier north to
northwest flow to develop for Saturday into Sunday with cool
temps. By late Sunday into Monday, the next short wave that
rotates around the base of the Great Lakes trof then moves
northeast bringing another period of wet weather with a
developing onshore flow that keeps temps cool. With the mean
upper trof remaining over the Great Lakes through mid week a
continue unstable southwest flow with embedded short waves with
keep unsettled conditions through Wednesday. It appears we may
finally get rid of the onshore flow by midweek so temps may
actually get back to near normal high temps reaching into the
Aviation /19z Thursday through Tuesday/...
short term...IFR/LIFR ceilings developing today and persisting
through tomorrow. East-southeast winds will gust to 25 kts most terminals
through tomorrow. Early on low level wind shear will affect hie and leb tonight.
Drizzle and fog will affect most taf sites outside of hie and
leb tonight before the moderate to heavy rain arrives.
Long term...winds and seas generally light. No flags.
short term...continuing scas through Friday afternoon. At that
point we may need a Small Craft Advisory just for high seas for the outer waters.
Long term...conditions become VFR Sat into sun before returning to
MVFR conditions for Sun night and Monday and possibly through
midweek in scattered showers.
highest astronomical tides of the year on tap for tonight and
Friday night. Have issued a coastal flood advisory for all
coastal zones for around the time of high tide tonight.
Forecast tide will reach 12 feet in Portland and with a storm
surge of .3 to .5 feet will likely see splash-over and flooding
of the usual spots around the time of high tide around 1230 am
ME...coastal flood advisory from 10 PM this evening to 1 am EDT
Friday for mez023>028.
New Hampshire...coastal flood advisory from 10 PM this evening to 1 am EDT
Friday for nhz014.
Marine...Small Craft Advisory until 8 PM EDT Friday for anz150>154.