Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Caribou ME
627 am EDT Tuesday Sep 16 2014
a weak wave of low pressure will cross the region today. Weak high
pressure will then build across the region tonight. A cold front will
cross northern Maine Wednesday and then stall over central Maine
by Wednesday evening. Weak low pressure from southern Quebec will
track along the front late Wednesday night...followed by strong
Canadian high pressure building across the region later Thursday into
Near term /through tonight/...
530 am update: no changes to probability of precipitation and cloud cover this update...with both
radar and hrly mesoscale model output consistent with the idea of light
showers traversing across the region from qb prov through the morning into
Erly afternoon hours. Otherwise...the trend of slowly rising temperatures was
incorporated into forecast hrly temperatures prior to sunrise...with forecast
hrly temperatures through the remainder of the morning and afternoon modified
to...attm...unchgd forecast hi temperatures.
Orgnl disc: showers with a weak middle level shortwave will traverse across
the forecast area today from the west-southwest...with most of the activity east of the
region by middle afternoon...and even breaks in the cldnss late this afternoon.
Total rainfall amounts will msly range from 0.08 to 0.15 inches...
enough to go with maximum probability of precipitation between 70 and 90 percent. Temperatures...
which initially will be slow to rise due to cloud cover and showers may
have better recovery with limited sunshine this afternoon...but still a
few degree below seasonal norms.
Otherwise...with at least partial clearing and light winds tonight as a
weak ridge of high pressure from the Ohio Valley settles over the region...
the prospects for patchy late night fog exists due to remnant ground
moisture from tdy's showers. Overnight lows will be close to seasonal
Short term /Wednesday through Thursday/...
a weak cold front with little or no precipitation will move into
northern zones Wednesday and stall. There will be a good deal of
cloud cover in northern zones that will hold temperatures in the
50s while Bangor and down east will see more sunshine and warm to
the middle 60s. The clouds will thicken late as an Alberta clipper
low pressure moves along the front and brings some steady rain
into The Crown of Maine Wednesday night. As the low exits Thursday
morning...it will drag a cold front through the area and bring the
coldest air mass of the season to date. Precipitation on mountains
such as katahdin will change to snow. Highs on Thursday will only
be near 50f in The Crown of Maine while lower 60s are forecast for
Bangor and Ellsworth. Brisk northwest winds gusting over 20 miles per hour
are expected in the afternoon. The cold air mass will set the
stage for a hard freeze in northern zones and a frost in the
southern half of the forecast area. The biggest question will be
how fast winds will decrease and allow radiational cooling. For
now...will go with upper 20s to lower 30s for most of the area.
The Allagash will be the cold spot with lower 20s and perhaps a
few readings into the upper teens. The down East Coast will be on
the other extreme with readings in the middle to upper 30s.
Long term /Thursday night through Monday/...
Friday will remain chilly under a large high pressure system.
Highs will be in the low to middle 50s. More frost is possible Friday
night...but strong warm advection and an increasing southerly flow
should reduce the risk. Temperatures will recover to much warmer
levels over the weekend with lower 60s on Saturday and upper 60s
to lower 70s on Sunday. While temperature trends over the weekend
look pretty solid...there remains some question on clouds and
precipitation towards northern Aroostook County as a frontal
boundary will be draped across Quebec...just north of Maine during much
of the weekend. As a result...will maintain chance probability of precipitation for
showers much of the weekend in the far north. The front will
finally push into the area Sunday night into Monday and exit the
region late Monday.
Aviation /10z Tuesday through Saturday/...
near term: initially VFR Erly this morning...then msly MVFR middle morning
through Erly afternoon mainly for northern taf sites in low clgs and visibilities with
showers...while downeast sites lower to low VFR by midday. All sites
should return back to VFR late today into this evening...with patchy
fog late tonight bringing MVFR and perhaps even IFR visibilities to a few taf
sites late tonight.
Short term: generally VFR Wednesday. MVFR tempo IFR Wednesday
night into early Thursday morning. MVFR for much of
Thursday...especially the morning. Becoming VFR Thursday night
near term: no hdlns anticipated. Long period swell from Edouard...well
out in the open Atlantic begins arriving today...with slowly building WV
heights to 3 to 4 feet by late tonight. Went with about 90-95 percent of ww3
WV heat guidance values given the swell nature of the waves.
Short term: long period swell from Edouard may reach 5 feet by Wednesday
night. Otherwise...northwest winds will likely meet Small Craft Advisory criteria later
Thursday with gusts to 25 kts.