Scientific Forecaster Discussion
fxus61 kcar 161643
Area forecast discussion
National Weather Service Caribou ME
1243 PM EDT Mon Sep 16 2019
Canadian high pressure will build across the region today into
Near term /through tonight/...
1240 PM update: based on high resolution cam models, we did
increase pops across the forecast area in the Erly eve tm frame when Max
shwr cvrg was shown as the upper trof axis crosses the rgn,
spcly ovr the NE hlf of the forecast area. Shwr cvrg will then ramp down
fairly promptly late tngt. Otherwise, just minor chgs to fcst
hi temps for lctns where latest sfc obs showed temps near or
slightly abv prev fcst hi temps.
Orgnl disc: a cold upper level trough will dig southward over
maritime Canada while a powerful upper ridge builds in the
midwestern US. In general, this pattern will pull cold air
southward from northern Quebec into the forecast area, along
with plentiful 925/850mb moisture in a northerly flow. The net
result will be cool and generally cloudy conditions through
tonight. Highs will struggle to 60f in northern Aroostook
County, but the coast will reach the mid to upper 60s with some
morning sunshine before clouds increase. A surface trough and
minor shortwave propagating southward towards the base of the
broader upper trough will help set off isolated to scattered
showers this afternoon into the evening. Instability is very
modest, up to 100 j/kg in a layer up to maybe 700mb. Precip
amounts up to a hundredth of an inch are most likely towards the
Saint John River Valley this afternoon. Otherwise, no more than
a trace is expected further south. 850mb temperatures behind
the trough will drop off towards 0c by later tonight in northern
Aroostook County. The expectation of continuing low level
cloudiness and steady northerly winds resulted in a Monday night
low temp forecast of low to mid 40s north and upper 40s in the
southern half of the forecast area. Any extended clearing or
reduction in winds could result in lows dipping into the 30s.
Short term /Tuesday through Wednesday night/...
an upper level trof will exit across the Maritimes Tuesday,
while surface high pressure builds toward the region. A
disturbance moving through the trof could bring a slight chance
of showers to eastern portions of the forecast area Tuesday.
Otherwise, partly cloudy skies are expected Tuesday. High
pressure then builds across the region Tuesday night through
Wednesday night. Expect partly cloudy/mostly clear skies Tuesday
night, with mostly clear skies Wednesday through Wednesday
night. High pressure will bring favorable conditions for
radiational cooling both Tuesday and Wednesday nights. Frost and
freezing temperatures are expected across much of northern
Maine Tuesday night. Frost will again be a concern Wednesday
night, with the risk also extending to the normally colder
portions of downeast Maine. Temperatures will be at below normal
Long term /Thursday through Sunday/...
high pressure will remain across the region Thursday through
Saturday, then begin to move east Sunday with a cold front
approaching late. Expect mostly clear skies Thursday into
Sunday. Clouds will then begin to increase late Sunday in
advance of the cold front, with a chance of showers late Sunday
night. Expect near normal, to slightly above normal, level
temperatures Thursday. Above normal level temperatures are
expected Friday through Sunday.
Aviation /18z Monday through Saturday/...
near term: VFR for bgr, bhb, Old Town, Machias and other sites
towards the coast. North of a gnr to hul line, expect prevailing
MVFR cigs today. MVFR cigs will still be possible tonight for
these northern terminals.
Tuesday...MVFR ceilings possible early. Otherwise, VFR.
Wednesday through Friday...generally VFR conditions are
expected across the region. However, variable conditions are
possible with any valley fog during the late night and early
near term: westerly winds with some gusts to 15 kt will shift to
northwesterly winds tonight with gusts up to 15 kts continuing.
Seas will continue around 2 ft or less.
Short term: winds/seas are expected to remain below Small Craft
Advisory levels Tuesday through Wednesday night.