Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Caribou ME
349 am EDT Monday Aug 31 2015
a cold front will cross the region later today. Canadian high
pressure will build across the region Tuesday...then move
southeast Tuesday night as a warm front moves northeast of the
region by Wednesday...bringing warmer and more humid conditions.
Another Canadian cold front will approach late Wednesday...and
cross the region Wednesday night bringing cooler and drier
conditions for the late week.
Near term /through tonight/...
a cold front will move south out of Canada today while a fast-
moving upper trough swings across Quebec into New Brunswick. These
two features will bring scattered showers to mainly northern Maine
this morning into early afternoon. Drier air will quickly spread
into the state behind the front, so expect the showers will come
to a rapid end during the afternoon. Sb convective available potential energy will be meager; most
of the models are indicating 200 j/kg or less. The nam's the usual
high outlier with 400-700 j/kg. Have therefore reduced the mention
of thunder for this afternoon to isolated. Southwest flow out
ahead of the front will usher in very warm air; highs will range
from from the upper 70s across the Saint John valley to the middle
80s in interior downeast. It'll feel a little muggier today too
with dewpoints rising into the 60s.
For tonight...as mentioned above, showers will come to a quick end
during the middle-late afternoon hours, giving way to clearing skies by
evening. The drier air behind the front combined with clear skies
and light winds will allow temperatures to drop into the 50s, with
the sheltered valleys of the north Maine Woods possibly dipping into
Short term /Tuesday through Wednesday night/...
the l/WV pattern over na into the late week will feature a
building hi amplitude ridge over the eastern Great Lakes as an upper
trough builds southward over the West Coast. This places northern/eastern ME in the NE
quadrant of this ridge...meaning that although temperatures will likely
average above normal for this period...the region will be subject to cold
frontal passages that will result in a few near average temperatures days
as S/waves cresting the ridge in central can north of the Great Lakes drop
esewrd into can Maritimes. Ahead of each shortwave will be a nominal
chance of showers and thunderstorms.
Tuesday looks to be an ideal sunny...dry day with light winds as surface
dewpoints drop into the lower to middle 40s over northern and east central portions of
the forecast area. Hi temperatures will be slightly above average. After comfortable evening
conditions...warmer and more humid air will begin to move into the
forecast area from the west-southwest as a warm front traverses across the forecast area late Tuesday
night into Erly Wednesday morning.
Then a shortwave from central can arrives into northern portions of the forecast area by Wednesday
afternoon...bringing likely the best potential of showers and thunderstorms this
week to msly the northern half of the forecast area Wednesday afternoon into Erly evening...especially
considering surface dewpoints rising well into the 60s by Wednesday afternoon...
resulting in projected maximum sbcapes of 900 to 1300 j/kg. With weak
to MDT surface-6km bulk shear...moderately high fzls...and a burst of moderately
hi precipitable waters of 1.30 to 1.60 inches...a few strong thunderstorms with strong
gusty winds...small hail and heavy downpours will be
possible...but a little to soon to mention these possible enhanced
elements in forecast wording at this time. We went with a narrow band of maximum
low likely probability of precipitation across the far north and north central portions of the forecast area during
the middle to late afternoon hours on Wednesday...using a blend between the faster
dtmnstc 00z GFS and somewhat slower European model (ecmwf) for tmg.
Otherwise...whats left of showers and thunderstorms should diminish over
central and interior downeast portions of the forecast area Wednesday evening with the loss
of heating as the initial weak cold front sags southward into the forecast area Wednesday
night. Skies should then become mclr late Wednesday night.
Long term /Thursday through Sunday/...
a secondary cold front will surge southward over the forecast area beginning Thursday
morning across the north...reaching downeast areas Thursday afternoon. For most
lctns...this front will be dry...but and isolated shower or thunderstorm cannot
be ruled out over western downeast areas middle to late Thursday afternoon. Behind
this secondary cold front...surface dewpoints will drop again into the
middle to upper 40s over the forecast area. Aftr uncertainty over the last couple
of days...both the GFS and European model (ecmwf) seem to agree that this cooler
and drier air will last over the forecast area through Friday...with hi temperatures still
at or above average for this tm of season under msly skies and light winds.
Sat appears to be a transitional day back to warmer and somewhat
more humid conditions as surface winds shift back to the west-southwest...but
still under sunny skies as the center of the middle/upper level ridge
moves east over central new eng. The rest of the Labor Day weekend looks
to be fair and warm to very warm with hi temperatures potentially well
into the 80s (xcpt cooler along the immediate coast and HI Mountain trrn)
as the middle/upper ridge holds over new eng...with a little more
uncertainty on Labor Day as a moderately strong cold front from central
can begins to approach the region...but for now we hold off on
mentioning any probability of precipitation to the region on Labor Day.
Aviation /07z Monday through Friday/...
near term: VFR conditions will prevail. Local IFR visibility is
possible early this morning in patchy fog. A cold front will move
across the region today, bringing scattered showers and isolated
thunderstorms to mainly the northern terminals. Brief MVFR
conditions are possible in any precipitation.
Short to long term: mainly VFR for the taf sites through these portions
of the forecast...xcpt possibly a brief period or two of MVFR clgs/visibilities
with any thunderstorm or heavier shower Wednesday afternoon into Erly evening...especially across
northern taf sites.
near term: southwest winds will increase across the waters this
afternoon as a cold front approaches from the north. The front will
move offshore this evening, turning winds to the northwest. Wind
gusts around 15 knots will be possible while seas will top out around 3
feet. Therefore no headlines are anticipated.
Short to long term: no hdlns anticipated through these portions of the
forecast...with WV heights over outer mz waters generally 2 to 3 feet and along
the immediate coast 1 to 2 feet. Went with about 90 percent of ww3
WV heat guidance for the outer mzs and about 60 to 70 percent for
near shore waters.