Area Forecast Discussion
Issued by NWS Caribou, ME-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KCAR 251030
Area Forecast Discussion
National Weather Service Caribou ME
630 AM EDT Tue Oct 25 2016
Low pressure northeast of the area will slowly move east toward the
open Atlantic through Wednesday. Canadian high pressure will then
cross the region Thursday. Low Pressure from the midwest will
approach Thursday night...cross the Downeast coast by late Friday...
then exit across the Maritimes Saturday.
.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --615 AM Update: Only very minor chgs to fcst hrly temps and dwpts
thru the remainder of the morn based on latest erly morn obsvd
sfc temp/dwpt trends. Otherwise, latest radar imagery conts to
show bands of lgt sn shwrs/flurries rotating NW to SE across
Nrn ME from Ern QB. No chgs necessary for PoPs and cld cvr attm.
Orgnl Disc: An area of sn shwrs is slowly movg ESE out of NE ME
into N Cntrl NB prov very erly this morn with a mid lvl vort max.
Most near term models indicate isold to sct sn shwr cvrg for msly
Nrn ptns of the FA for the remainder of the morn before another
mid lvl vort max swinging Swrd from Ern QB potentially brings more
numerous rn/sn shwrs this aftn across the NE, where we increase
PoPs to the likely range. Fcst hrly sim radar ref from latest hrly
HRRR model runs back this scenario.
Despite sig abv fzg temps xpctd this aftn, heavier shwrs could
result in enough cooling for lgt brief accumulation. Otherwise,
sct shwrs will become all sn this eve as sfc-BL temps cool closer
to fzg. Based on projected aftn 925-850mb temps being about a deg
C less than ystdy aftn, fcst aftn hi temps across the FA should
be at least 2 deg F than ystdy, and perhaps even a little cooler
if cld cvr prevents much in the way of any brief sunshine. This
same difference in 925-850 mb temps will likely result in ovrngt
lows of a couple deg F cooler than this current erly AM.
Winds will be brisk again tdy as they turn from the NW, but not
quite as strong as ystdy, with winds diminishing to less than 10
-- End Changed Discussion --
.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
A cold upper trough remains in place on Wednesday with snow
showers continuing. An inverted trough will extend over the state
from a low well east of Nova Scotia. An unstable layer up towards
H700 will be in place to enable the snow showers. Boundary layer
temps lead to a northward movement of the rain/snow line during
the day, but the air aloft is sufficiently cold to maintain snow
showers all day in northern zones. Will have to keep a close eye
on whether the inverted trough becomes more focused on a
particular region as such a development could produce heavier snow
showers. The upper trough finally pulls out Wednesday night with
snow showers ending. Cold high pressure builds from northern
Quebec and should set up conditions for the coldest night of the
season. Have gone with widespread readings in the teens for
northern zones and mostly mid 20s for Bangor and the Down East
region. The high will generate sunshine for Thursday with highs
just short of 40F in the Saint John Valley and mid 40s for Bangor
and Ellsworth. Clouds increase late Thursday in advance of the
season`s first winter storm. Low pressure will track from the
Western Great Lakes region and redevelop by late night in the Gulf
of Maine. An upper level trough associated with the low will
develop a negative tilt and the surface low will deepen by late
Friday night. As always with early season winter storms, boundary
layer temperatures and elevation will be key issues. As this
point, it appears that a pretty strong onshore ESE flow will
ensure boundary layer warmth for Bangor and all of the Down East
region. The troubles could start as far south as a line from
Dexter towards southern Aroostook County. It`s conceivable that
2-3 inches of snow could fall towards Dover-Foxcroft, Greenville
and Millinocket by daybreak Friday.
.LONG TERM /FRIDAY THROUGH MONDAY/...
The upper low will cut off over Maine and the surface low will
continue to deepen Friday as it moves across the Gulf of Maine
towards the Bay of Fundy. The surface track will minimize warm air
advection northward. The upper low will promote instability aloft
and bring good potential for heavier precip rates. This means that
boundary layer issues often associated with these early season
storms could be negated and snow could remain the dominant P-type.
As a result, have made significant adjustments to the previous
forecast in keeping snow in northern zones all day. Elevation will
remain a big factor and the heaviest snows would likely be in the
Katahdin region and higher terrain in Piscataquis County. Warning
level snows are possible. Used ECMWF surface temps in the grids as
other guidance looked too warm. The snow will gradually wind down
Friday night as the upper low moves east of the state and the
heavier precip rates end. This means a transition back towards
rain with temperatures in the mid to upper 30s. There will be no
real cold air advection behind this low.
Generally warmer temperatures and cloudy conditions will follow
Saturday into Monday. Temperatures will be in the 30s at night and
in the upper 40s to near 50F during the day...which will melt the
snow. There is another shortwave that will cross the area but
timing is very uncertain with solutions ranging from Saturday
night to Monday. The one certainty is that this system will be
.AVIATION /07Z TUESDAY THROUGH SATURDAY/...
NEAR TERM: Msly MVFR clgs and vsbys with intermittent sn and rn
shwrs tdy and msly sn shwrs tngt can be xpctd across Nrn TAF sites
with brief IFR clgs/vsbys possible with heavier sn shwrs.
Otherwise low VFR clgs for Downeast sites, with brief MVFR clgs
SHORT TERM: MVFR cigs with tempo IFR conditions in snow showers
will prevail Wednesday morning. Conditions will lift to VFR in the
afternoon and persist until Thursday night when the trend will be
towards IFR cigs for all sites...and LIFR/VLIFR vis in snow north
of a line from GNR to HUL. This will continue all of Friday and
into Friday night. LLWS is possible. Conditions will improve
Saturday to a prevailing condition of MVFR cigs.
NEAR TERM: Will cont the SCA ovr our outer MZs tdy and tngt msly
due to winds, but also marginal wv hts with cont`d llvl cold advcn
NW winds. Primary wv pds will be msly in the 5 to 6 sec range,
typical of short fetch off-shore wind directions. Kept close to
WW3 wv guidance for fcst wv hts for this ptn of the fcst.
SHORT TERM: SCA conditions may still exist early Wednesday
morning, but winds and seas will quickly diminish during the
morning. The next big event will be the potential for the season`s
second gale event beginning Thursday night and going into Friday
night. SCA conditions will follow the gale and last into Saturday
MARINE...Small Craft Advisory until 4 AM EDT Wednesday for ANZ050-051.