Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Gray ME
704 PM EST Wednesday Nov 25 2015
a broad upper level ridge builds over New England tonight and
tomorrow. Much warmer air will pour into the region and above
average temperatures are expected for Thanksgiving and through
Friday. Surface high pressure will hold offshore through
Friday and our next chance of rain will not come until late
Friday afternoon and night as a cold front pushes through the
region. Fair and colder weather will return in the wake of the
front Saturday into early next week. The next chance of
precipitation does not appear to come until midweek and appears it
will fall as rain with low pressure likely passing to our north
Near term /until 6 am Thursday morning/...
7 PM...quick update for T/TD/sky/wind based on current observation. Mins
likely to occur in the next few hours...before temperatures start to
slowly rise...more noticeable along the coast than inland. Clouds
still remain an issue in Thursday morning...with mesoscale models leaning
toward stratus developing /in the 4-5k feet range/...especially
along the coast...while nam12 and Gem /two of the better sky cover
models/ not as robust with this development...and while models are
on track with development over southern New England already...see no
signs of clouds near the mid-coast...where they should be
developing at this time...so holding on off hitting the clouds too hard
through sunrise...although should more across southern New Hampshire as they work
they up from the S.
Previously...high pressure moves offshore tonight. Should see
some decent radiational cooling for the first few hours tonight
before warm advection kicks in and temperatures begin to rise.
Short term /6 am Thursday morning through Thursday night/...
with warm advection ongoing expect temperatures to be much warmer
on Thursday... in the 40s and 50s. Could be some cloud cover
especially in the morning associated with the warm advection. But
it should be a warm and dry Thanksgiving day.
Temperatures do not fall much Thursday night due to the continued
southwest flow... warm advection... and increased cloud cover
ahead of the approaching front.
Long term /Friday through Wednesday/...
Rex block looks to remain in place for the start of the forecast
period with closed low and deep trough over the western Continental U.S. And
broad ridging over the East Coast. 500 mb heights on Friday will
be 2 to 3 Standard deviations above normal for this time of year
and a very warm day with temperatures 10+ degrees above normal is likely.
A weak northern stream wave will approach Friday night with an
associated surface cold front pushing though the region. Models
are currently in fairly good agreement with this feature as far as
timing and quantitative precipitation forecast amounts. With the lack of any moisture and with
forcing weakening as the front pushes southward it appears like
the bulk of the quantitative precipitation forecast will be across our northern forecast area
where a model consensus shows low categorical pop on Friday night.
Pop decreases as you head southward with scattered showers likely
decreasing in coverage south of the mountains. Any shower activity
should push offshore on Saturday morning with the front...but
early Saturday morning there will be a chance for some snow
showers behind the front across northern zones.
High pressure builds in behind the front and will provide fair
but cool weather through the weekend. Our next chance for
precipitation will come towards the middle of next week.
However...at this time the suite of model guidance diverge quite a
bit with this next system.
Upper low over the western Continental U.S. Exits to the east and surface low
pressure develops over the central US. The Euro is much quicker
and further south with this system than the GFS and has widespread
rainfall developing across New England on Tuesday night while the
GFS is more during the day Wednesday and Wednesday night. For now
due to the lack of consistency and spread between the models I
decided to go with a blend of the guidance for days 6 and 7.
Aviation /00z Thursday through Monday/...
short term...could see some increasing cloud cover by morning as
warm advection kicks in but generally expecting things to stay VFR
through Thursday night.
Long term...possible MVFR conditions will be possible Friday night
with the passing of a cold front. Thereafter high pressure builds
in overhead and VFR conditions should persist.
short term...as high pressure moves offshore a southwest gradient
will set up between the offshore high and the approaching frontal
trough. Expect some wind gusts above 25 knots and wave heights
approaching 5 feet with the highest waves being in the eastern
waters where the southwest fetch will be longest.
Long term...small craft conditions will remain through at least
Saturday morning. Then high pressure moves in and the pressure
gradient will weaken. Winds should drop below 25 knots by Saturday
morning but may take a little time for seas to die down as
well...so an Small Craft Advisory may be needed through Saturday afternoon. After
that it looks like no flags will be necessary until the middle of
astronomical tides will be near the peak for the month over the
next few days. On Friday the high tide in Portland around 1130 am
is 11.5 feet. At this time though it is not looking likely that we
will see any flooding as winds will be from the southwest and
parallel with the coast...limiting the surge potential along most
coastal areas. However...along the Maine midcoast the southwest
winds have a slight onshore component...but any impacts in these
areas should still be very minor.
Marine...Small Craft Advisory from 7 am Thursday to 7 am EST Saturday