Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Caribou ME
346 PM EDT Friday Sep 19 2014
high pressure will build across the region today and move east of
the area Saturday. A cold front will approach northern New England
Sunday...and cross the area Sunday night. A second cold front
will cross the area Tuesday.&&
Near term /through Saturday/...
guidance has been in good agreement with surface high pressure
continuing to build south and east tonight. This will be
accompanied by a upper level ridge that will eventually flatten out.
There are some high clouds across Quebec this afternoon that will
slowly work their way into the forecast area this evening and overnight. This
leads to tricky low temperature forecast tonight because
raditational cooling would not be maximized given the increasing
cloud cover however dewpoints in the upper teens to lower 20s
would support hard freeze across portions of the region. Also
temperatures will depend upon how quickly the high moves off to the
south and east and return flow kicks in. Decided to lean more with
clouds moving in and increase in return flow given this temperatures
are generally expected to be in the middle to upper 30s with coastal
areas in the in the low 40s. However given the uncertainty of the
forecast evening shift will be closely monitoring and could need
to drop temperatures significantly depending on how this situation
plays out. Saturday guidance continues to agree that high pressure
will continue to retreat south and east with clouds on the
increase through the day. Also breezy conditions can be expected
as gradient sets up across the forecast area. Surface low and frontal
boundary across Quebec will slowly approach the forecast area so have brought
slight to chance probability of precipitation across the far north and northwest portions of the
Short term /Saturday night through Monday/...
Saturday night, moist onshore flow and a decent pressure gradient will
lead to a mild night with lows in the 50s. Cold front will still be
several hundred miles off to our west, so only a chance of showers.
Sunday will be a mild, somewhat muggy day with highs around 70 and a
decent breeze from the south. Front inches closer with a wave
developing along the front in upstate New York and moving
northeast to US. A separate system looks to develop off the New
England coast but is expected to remain southeast of our waters.
Some older model runs did have this system merging with the system
to our southwest, but now appears they will stay separate.
Shower chances increase late Sunday and especially Sunday night
over the northern half of the area and raised probability of precipitation a bit to
account for somewhat better model agreement. There is some elevated
instability and can't rule out an isolated rumble of thunder, but
left out of the forecast for now.
Cold front moves through Monday during the day with showers
tapering off from west to east. The air behind this cold front is
not as cold as the air we have over the area this morning and
Long term /Monday night through Friday/...
cooler airmass moves in Monday/Monday night as the system exits,
but it will not be as cool as the airmass presently over US. A
weak system will move in from the northwest on Tuesday bringing
maybe a few showers and second shot of cool air...about the same
coldness as today's airmass...for Tuesday night into Wednesday.
High pressure moves south of the area Thursday with warmer and
mostly dry westerly flow setting up. Models are in pretty good
agreement for the extended.
Aviation /19z Friday through Wednesday/...
near term: VFR conditions expected through the period.
Short term: as a system approaches from the west and moist onshore
flow increases, we may begin to see some IFR and MVFR ceilings
late Saturday night especially toward the coast. Areas of MVFR for
Sunday with localized IFR near the coast, becoming more widespread
IFR Sunday night as rain moves in. Improving to VFR most areas
near term: no headlines at this time. However later Saturday seas
and winds do increase with southerly flow to near Small Craft Advisory conditions.
Short term: conditions will approach small craft for winds and
seas late Saturday/Saturday night as onshore flow increases ahead
of an approaching system. Conditions will remain near small craft
levels through Monday.