Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Caribou ME
1235 PM EDT Tuesday Oct 13 2015
a cold front will approach today and cross the area tonight.
Another cold front will cross the region Wednesday. High pressure
will build over the region Thursday. Low pressure will move over
the region Friday.
Near term /through tonight/...
update...added isolated thunderstorms for this afternoon as a
shortwave moves north out of the Gulf of Maine. Instability aloft
with this shortwave and the lfq of an upper jet will help trigger
a few storms. The best shot appears to be for the down east region
this afternoon. Any storms will spread north towards Houlton and
Presque Isle early this evening. Also added isolated thunderstorms
with the cold front passage in northern zones this evening.
Previous discussion... an upper low visible on the water vapor
satellite channel across the central Great Lakes early this
morning will move east and weaken to an open trough as it moves
across southern Quebec tonight. At the surface low pressure crossing James
Bay will track northeast and across northern Quebec. This will
send a cold front into western Maine this evening, and across the
remainder of the County Warning Area tonight. A secondary cold front will be found
to the west of the area by 12z Wednesday morning with significantly
colder air remaining to the west of the area.
Today will be another mild day in the warm sector ahead of the
approaching cold front. Moisture being pulled north ahead of the
front will mean a lot of low clouds across eastern Maine. The
threat of showers will be on the increase today as a weak low
moving north along the coast helps to transport moisture north. At
the same time showers with the approaching cold front will move in
from the west late in the day or during the evening. The best
chance of showers today will be across downeast Maine, and across
the eastern half of the County Warning Area this afternoon. More clouds and
showers are expected this evening as the cold front works across
the region. The best chance of showers with the front will be
across the western and northern zones. As the colder air remains
behind a secondary cold front to our west it will be another mild
night with some late night cooling in the far west.
Short term /Wednesday through Thursday/...
a secondary cold front will cross the state on Wednesday,
bringing gusty west winds and the chance for a few showers during
the afternoon. High temperatures will only in the 50s across much
of far northern Maine as these areas will see frontal passage the
earliest, but just about everywhere else will have time to rise
into the 60-65 degree range.
Drier air will work into the region behind the front, leading to
clearing skies. Winds will decrease as well, though there will be
enough of a gradient to preclude totally calm conditions. Even
still, good radiational cooling will occur, especially in the usual
sheltered cold spots across the northern Maine Woods. Lows will
range from the upper 20s in these areas to the middle 30s across the
rest of northern Maine. Central Maine down to the coast will mainly
be in the upper 30s to lower 40s.
A weak surface boundary will lift northward across eastern Quebec on
Thursday while an upper shortwave pushes through aloft. Moisture
with these features will be limited, but there may be enough lift to
generate a shower or two over the north Maine Woods and lower Saint
John valley. Thursday's highs will be quite cooler than Wednesday,
ranging from the middle 40s in the Saint John valley to the middle 50s
Long term /Thursday night through Monday/...
lots of uncertainty in the extended. Low pressure will approach
from the west Thursday night and cross New England on Friday. The
GFS is faster and deeper with this system than the European model (ecmwf). The GFS
also generates a second low in the wake of the first, prognosticated to
cross from southern Quebec into Maine on Saturday, offshore by
Saturday night. This would keep widespread rain around for both
Friday and Saturday. Meanwhile, the European model (ecmwf) has no second low,
allowing drier conditions to prevail on Saturday. Have gone with
likely probability of precipitation for Friday afternoon given at least some model
agreement, but Saturday only warrants chance probability of precipitation given the model
differences. Thereafter, the overall pattern becomes deep upper
trofiness with high pressure at the surface. A weak wave or two
will rotate around the trough, so have kept some slight chance
probability of precipitation in for Sunday. The upper trough finally begins to push east
by Monday with the high pressure taking hold, so it should be a
dry start to the work week. The one thing that is looking likely
is that much colder air is going to overspread the area by the
weekend. Highs on Saturday, Sunday, and Monday will likely only in
the 40s, and in fact, some locations across northern Maine could
struggle to get out of the 30s during the day.
Aviation /18z Tuesday through Sunday/...
near term: IFR and at times vlifr ceilings are expected today.
Mostly IFR through this evening with improvement to MVFR by Wednesday
morning in the wake of the first cold front.
Short term: MVFR ceilings are likely Wednesday, especially at the
northern terminals, as a cold front crosses the region. Showers
will be possible as well, but these are not expected to reduce
visibility below MVFR. Skies will become mostly clear overnight
Wednesday night, with VFR expected by 06z. This will prevail
through Thursday and Thursday night. Clouds will once again lower
to below 3000 feet on Friday as low pressure swings across the area,
producing widespread rain. MVFR conditions will prevail into
Saturday, with some improvement possible by Saturday afternoon.
update...added thunderstorms for this afternoon and went to
widespread fog through this evening.
Near term: the wind and seas will remain below Small Craft Advisory
levels today. A Small Craft Advisory has been issued for tonight
starting at 02z/10 PM ahead of a cold front as the seas are
expected to build to at or above 5 feet with wind gusts to around 25 knots.
Short term: a Small Craft Advisory is now in effect for
Wednesday. Southwest winds will increase out ahead of an
approaching cold front. While current temperature profiles
indicate only marginal mixing, winds of 35 knots will lie just off
the surface. This means that should more mixing occur...gusts of
25-30kt will be possible. Have capped the forecast at 25 knots for
now, but the threat is enough to warrant the Small Craft Advisory. In addition,
seas of 5 to 6 feet are expected. The winds will become northwest
and subside to 10-15 knots with gusts to 20 knots Wednesday night, but
seas will be slow to respond, remaining around 5 feet into Thursday
morning. As such, the Small Craft Advisory may need to be extended and transitioned
to one for hazardous season only.
Marine...Small Craft Advisory from 10 PM this evening to 8 PM EDT
Wednesday for anz050>052.