Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Caribou ME
246 PM EDT Friday Aug 29 2014
high pressure will slide to the south tonight and Saturday. A
trough of low pressure and associated cold front will cross the area
Sunday into Sunday night. This front lift back to the north
through the area as a warm front Monday into Tuesday.
Near term /through Saturday/...
high pressure building in will result in a continuing sunny afternoon
with comfortable temperatures.
The high will crest over the area this evening before sliding off
to the east overnight. Clear skies this evening will give way to
increasing high clouds overnight. Lows will generally be in the
low to middle 40s except a little warmer along the coast.
Saturday will feature filtered sunshine under increasing middle and
high clouds. At this point showers associated with a cold front
look to remain off to the north and west so removed the chance of
showers over the north from the forecast through the afternoon.
S/SW winds will bring in warmer temperatures with highs generally
in the low to middle 70s except a bit cooler along the coast.
Short term /Saturday night through Monday/...
skies will either be mcldy or becoming cloudy Sat night across northern portions
of the forecast area...with showers becoming more likely across northwest portions of the forecast area
by daybreak sun as a cold front from qb prov approaches from the west. Jet
streak energy hi aloft...limited surface heating and precipitable waters of 1.50 to 2.00 inches
later during the day sun will facilitate a band of organized showers...
with forecast sbcapes approaching 500 j/kg in the afternoon and Erly evening hours
suggesting a potential of thunderstorms. Given the high precipitable waters ...we will
mention heavy rainfall enhanced wording with thunderstorms. Moderately strong deep
layer shear accompanies the Sun afternoon/Erly evening forecast soundings...but
with limited convective available potential energy shown at this time...we believe it would be difficult for
thunderstorms to become dynamically organized for wind/hail enhanced wording
at this time...but cannot be ruled out completely.
A more definable middle level S/WV-sfc low from the Great Lakes could
result in another band of heavier showers and possible thunderstorms over msly
downeast areas Sun night as both systems track over the downeast coast
late Sun night. With both areas of enhanced rainfall sun into Sun night...most
of the forecast area will generally receive between 0.50 to 1.00 inch of rainfall...
with local 1 to 2 inch cnvctv rainfall bullseyes possible. Tmg of
showers and 6hrly qpfs from sun through Monday were based on a blend
between the faster 12z opnl GFS and the other opnl 12z models
which were a little slower.
With a broad frontal bl stalling near the downeast coast late Sun
night...and little cool/dry advcn behind this front...at least patchy
fog can be expeceted across the forecast area late Sun night into Monday morning. Otherwise
remnant upper troffing over the forecast area will bring partly to mcldy skies Monday
with possible showers and afternoon thunderstorms...with forecast soundings Monday afternoon
showing up to 500 to 1000 j/kg of SBCAPE over SW portions of the forecast area. Overnight
temperatures will be above normal both ngts due to cloud cover...SW winds and
very moist low level air. Dytm hi temperatures will be at to perhaps a few degree f
Long term /Monday night through Friday/...
unsettled weather is setting up for the extended period of the
forecast. An upper level low over Hudson Bay...its surface low
over James Bay...with a front extending south through the central
Great Lakes into southern ill...a weak slow moving frontal boundary
along the coast of Maine at the start of the period. By Tuesday
morning...the low over James Bay tracks north towards the upper low
as the low start to become cold core. The associated front moves
east into the western Quebec...south through the eastern Great Lakes. The
frontal system along the Maine coast moves into the central Gulf
of Maine. Tuesday evening...the continues to mature...the front moves
into western Maine...a new low shows along the frontal boundary over
the eastern Great Lakes. By Wednesday morning the new low moves east into western
Maine. By Wednesday evening the low will move east of the area. The upper
level flow across the region will be meridional through early
Friday...with the jet stream just north of the area. This will allow
for rapidly movement of shower activity to move through the area.
Late Thursday a new upper level trough moves south out of northern
Canada...bringing a cold front through the area Sat evening and by
the end of the period will be into the central Gulf of Maine.
Loaded the superblend...used the superblend diurnal for hour temperatures.
Added 15 percent to winds for gusts over land...25 percent for
gusts over coastal waters. Loaded nawave 4 for seas in the coastal
Aviation /18z Friday through Wednesday/...
near term: VFR through Saturday.
Short to long term: initially...all taf sites will begin VFR...
with MVFR clgs and visibilities associated with low cldnss and visibilities
with organized showers and possible thunderstorms working northwest to southeast across
the region beginning Sun afternoon and continuing across downeast areas by
sun evening. All sites should then lower to IFR to LIFR in low St
cldnss...showers and patchy gog overnight Sun night. After Monday fog...all
taf sites should improve MVFR to low VFR by Monday afternoon with scattered
showers and afternoon thunderstorms bringing briefly lower conditions. Conditions
should remain the same Monday night and then improve to VFR on Tuesday.
MVFR conditions are possible across all taf sites Tuesday night with the
passage of showers with VFR returning for Wednesday through Friday.
near term: winds and seas have diminished at this time below Small Craft Advisory
levels. Conditions will be tranquil on the seas through tonight
with winds increasing once again through Saturday out of the
south. Conditions are expected to remain below Small Craft Advisory levels through
Saturday afternoon however.
Short to long term: initially no hdlns for Sat night...then
increasing southwesterly wind fetch to 10 to 20 knots may bring short period WV
heights to near Small Craft Advisory criteria for sun and Sun night. Both winds and waves
should subside by Monday to sig below Small Craft Advisory criteria and remain so through
middle week. Very moist tropopause air will increase the potential of
marine fog beginning by sun and continuing through most of Monday...with Sun
night into Monday morning being the foggiest period.