Scientific Forecaster Discussion
fxus61 kcar 240143
Area forecast discussion
National Weather Service Caribou ME
943 PM EDT sun Jul 23 2017
high pressure will dominate the weather through Monday. Low
pressure will track south of the region Monday night. High
pressure will build across the region later Tuesday through
Near term /through Monday/...
935 PM update: skies have remained clr ovr our rgn thru the mid
eve hrs, although latest Sat imagery does show the leading edge
of hi/mid cldnss apchg the ME/New Hampshire border from the west...so cldnss
should enter SW/wrn ptns of the rgn late tngt and Erly Mon morn,
which is what the current fcst is advertising. Subsequently,
the only chgs this update were fcst hrly temps/dwpts into the
late ngt based on latest mid eve sfc obs with no sig chgs to
fcst lows posted at 5 am.
Orgnl disc: another unseasonably cool night is expected.
Decoupling will occur with clear skies and light winds. A
shallow inversion will form and will likely be steeper than last
night as the air aloft has warmed. There will also be
increasing high clouds in the southern half of the forecast area
later in the night. With all of that in mind, the forecast
calls for upper 30s to lower 40s in northern zones and upper 40s
to lower 50s south. Record lows are possible north of Houlton.
The cloud cover will gradually increase on Monday as a complex
of two low pressure systems moves eastward from the Midwest.
While the clouds will increase, the trend in pops continues
downward. A wave currently in the Ohio Valley is progged to
become the dominant system and rapidly eject eastward south of
the surface ridge that will remain entrenched over Maine. The
forecast track takes it from the vicinity of Long Island to a
position south of Nova Scotia by Monday evening. Meanwhile, the
more northern surface low in the eastern Great Lakes region will
weaken and fill...while staying well west of the area tomorrow.
Will go with no higher than chance pops by late Monday
afternoon for the southern half of the forecast area...with the
highest risk towards the coast. Since the high remains over the
area, it will be another day with below normal highs and low
humidity. Due to less cloud cover, have raised highs into the
low to mid 70s for most areas. The exceptions will be the
Moosehead Lake region and coast where more cloud cover and the
threat of showers results in highs only reaching the upper 60s.
Onshore easterly winds on the coast will also help reduce
Short term /Monday night through Wednesday/...
surface high pressure will be ridged north and east of the
region Monday night while low pressure tracks to the south. An
upper level trof will approach from the west later Monday night.
The most significant rains will remain south of the region,
across the Gulf of Maine, Monday night. Will have a chance of
rain downeast Monday night. High pressure will impede the
northward extent of the rain, with lesser rain chances
northward across the remainder of the forecast area and possibly
not reaching the Saint John valley. The upper trof will cross
the region Tuesday with a chance of showers, mostly across
central and downeast portions of the forecast area. Shower
chances will then diminish during the afternoon, with decreasing
clouds. High pressure will build across the region Tuesday night
through Wednesday. Skies will be partly cloudy during the
evening, with mostly clear skies overnight. Mostly/partly sunny
skies are expected across northern areas Wednesday, with mostly
sunny skies across the remainder of the forecast area.
Temperatures will be at below normal levels Tuesday. Near
normal, to slightly above normal, level temperatures are
Long term /Wednesday night through Sunday/...
as high pressure slides away to the east and a cold front
approaches from the west, clouds will increase Wed night and
some precip may reach the western border around dawn. Showers
appear increasingly likely across the entire cwa, and perhaps a
few storms, Thu and Thu night. There seems reasonable agreement
on the front nearly stalling along the coast or over the Gulf
of Maine on Friday, allowing some showers to continue over the
southern half of the County Warning Area. However, beyond that, the models
diverge significantly next weekend. The CMC is by far the most
pessimistic, having a slow moving cut-off low slogging up the
New England coast and keeping central and downeast areas in the
rain both Sat and sun. The GFS is the driest, showing a deep
trough with the surface front, but no lingering cut-off, while
the European model (ecmwf) shows hints of a surface low over the weekend, but
keeps it and any precip to the south. Generally kept pops to 20%
or less over the weekend, but did show some areas of 30% pops on
Saturday in case some precip lingers.
Aviation /00z Monday through Friday/...
near term: VFR conditions continue with excellent vis and no
cigs until Monday. The cigs will be above fl050 and mostly south
of gnr and hul.
Short term: generally expect VFR conditions across
northern/central areas Monday night, with occasional MVFR/IFR
conditions possible downeast. Occasional MVFR conditions are
possible downeast early Tuesday. Otherwise, VFR conditions are
expected across the region Tuesday. VFR conditions are expected
across the entire region later Tuesday through Wednesday night.
Variable conditions are possible with any showers or
thunderstorms Thursday, particularly across northern and
near term: no significant weather is expected with light winds
and seas 2 feet or less. Fog is not forecast, but rain is
possible later Monday.
Short term: winds/seas will remain below Small Craft Advisory
levels Monday night through Wednesday. Visibilities will be
reduced in rain Monday night, with a chance of showers Tuesday.