Scientific Forecaster Discussion
fxus61 kcar 252214
Area forecast discussion
National Weather Service Caribou ME
614 PM EDT Mon Sep 25 2017
warm high pressure remains over the region today and tonight.
A backdoor cold front from eastern Quebec will cross northern
Maine early Tuesday afternoon, reaching the downeast coast by
late evening...then stalling. This front will return north in
the form of a warm front Wednesday. Meanwhile, a stronger cold
front from central Canada will cross the region later Wednesday
Near term /through Tuesday/...
6:15 PM update...another unseasonably mild and muggy night
across the County Warning Area. In fact, the lows tonight will be above average
for mid-late July. Dew points are mostly in the mid 60s to
around 70f early this evening, which is just about unheard of
this time of year. One lone shower developed in southern
Piscataquis County late in the afternoon, but it has since
rapidly dissipated. It will be clear to p/cloudy tonight with
some patchy stratus possible late tonight along the immediate
coast. Other than some very minor tweaks to the forecast
elements based on the 6 PM observations and the latest satellite
trends no updates are planned at this time.
Previous discussion... tonight will be a very warm and humid
mid Summer ngt in late sept, spcly ovr hier trrn lctns as the
core of the unseasonably warm air mass rotates ovr the rgn. Most
areas will stay clr to mclr, with only downeast coastal areas
being brushed with oceanic St and patchy fog late ngt into Erly
Otherwise the 12z dtmnstc 12z GFS, ECMWF, and cangem models
agree pretty closely that a fast movg zonal S/WV from north cntrl
can will move into ern qb and Labrador by Tue morn will begin to
squash this historic upper ridge/high that has resided ovr the
ern great lks and the northeast U.S., Including New England.
This will allow a backdoor cold frontal passage beginning midday
across the extreme north and reaching the downeast coast by late
evening. This will be dry cold frontal passage, only accompanied
by mid cld band, with mid lvl lapse rates to stable to allow for
much in the way cnvctn. The earlier arrival of the cold front
across the north with some cldnss will commute the rapid rise of
temps from reaching highs ovr this ptn of the rgn as warm as
this current aftn as sfc winds become north to NE. Further S ovr
low trrn cntrl and interior downeast areas however, temps will
have one more uninterrupted run at highs of upper 80s to lower
90s with west-southwest sfc winds before the front arrives late in the aftn
and Erly eve respectfully.
Short term /Tuesday night through Thursday/...
the muggy weather will continue Tuesday night and Wednesday as
the weak warm front lifts back north into Quebec/New Brunswick.
However, relief will be in sight in the form of a cold front
which will approach from the west late Wednesday and cross the
state Wednesday night into Thursday morning. There could be a
few showers around Tuesday night and Wednesday morning owing to
increasing moisture, but the bulk of any rain will fall later
Wednesday through Wednesday night just ahead of and along the
front. The highest precipitation totals will fall across
northern Maine where up to a half inch is possible, though much
of the region will see a quarter inch or less. Models are
indicating sb CAPES of 500-900 j/kg will be possible across the
North Woods Wednesday afternoon, so have continued with the
chance for thunderstorms in this area. Wednesday's highs will
mainly be in the lower to mid 70s, while lows will be in the mid
50s to around 60.
The front will push offshore by early Thursday afternoon, bringing
any lingering rain showers to an end and ushering in a drier and
much more seasonable airmass. Highs will be in the mid 60s to lower
70s, warmest for interior downeast, but a brisk northwest wind will
make it feel a bit cooler.
Long term /Thursday night through Monday/...
much cooler and drier weather on the way for the end of this
week into early next week. Another rainless stretch is looking
likely as a ridge will build across the region, though a few
showers are possible on Saturday as an upper trough swings
through. It will definitely feel more fall- like, especially
Friday and Saturday when highs will only be in the upper 50s to
lower 50s. Patchy frost will be possible in northern areas over
the weekend, mainly in those usual cold valleys.
Aviation /22z Monday through Saturday/...
near term: VFR conditions xpctd across all of our taf sites tngt
thru Tue, with a possible exception of low MVFR/IFR clgs and
reduced vsbys with oceanic St and patchy fog brushing the
downeast coast late tngt into Erly Tue morn and briefly
Short term: IFR/LIFR conditions are likely at the southern
terminals 00z-12z Wednesday due to fog and low ceilings, while
prevailing MVFR with occasional IFR is expected across the
north. A cold front will bring showers and possible thunderstorms
Wednesday and Wednesday night, especially at the northern
sites. Prevailing MVFR conditions are expected Wednesday and
Wednesday, with IFR possible in any precipitation. Fog and low
stratus will return to the southern terminals after 00z Thu, but
it will dissipate 09-12z Thu once the front moves through. All
sites are expected to be VFR by 18z Thu and remain so through
Friday, although patchy River Valley fog will be possible early
near term: with ww3 WV guidance indicating higher swell radiating
from distant Maria not xpctd to arrive much before Tue eve, we
held off on any Small Craft Advisory for seas for our outer mzs for now. Saying
this, it will be possible for occasional hi sets of swell to
result in an hr or two of WV hts arnd 6 ft over our outer buoys
between now and Tue eve, and certainly later shifts can update
to an Small Craft Advisory if deemed necessary. WV pds will cont to be a very
long 12 to 16 sec.
Otherwise, oceanic St and fog will be returning later this eve
and contg thru Tue as high dwpt air becomes in contact with cold
Gulf of ME waters.
Short term: a Small Craft Advisory for hazardous seas will be needed
for mid to late week as long period swell from Maria keeps seas at 4-
7 feet. Winds will increase to 15-20 kt Wednesday night and Thursday
with a cold frontal passage, but they are expected to remain below
Climate...record highs were tied or broken across northern and
eastern Maine this afternoon. At Caribou, the high of 88f
broke the previous record of 83f set in 2007. It was also the
warmest temperature ever observed so late in the season. At
Bangor, the high of 88f tied the record high last set in 1930.
For a complete list of record high temperatures please see the
news stories on the top section of our web Page at