Area Forecast Discussion
Issued by NWS Caribou, ME-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KCAR 232350
Area Forecast Discussion
National Weather Service Caribou ME
650 PM EST Mon Jan 23 2017
Low pressure will intensify along the mid Atlantic coast tonight
and move northeast toward the Gulf of Maine Tuesday...then across
the Canadian Maritimes on Wednesday.
.NEAR TERM /THROUGH TUESDAY/...
-- Changed Discussion --650 PM Update...
Adjusted the clouds to bring high clouds into northern areas per
the latest IR Satl imagery. Temps were dropping off some w/the
latest obs showing readings in the upper teens across portions of
northern and western areas. High cloudiness attm is rather thin
allowing for a further drop in temps until clouds thicken up
overnight. 21Z Sfc analysis showed high pres in eastern Canada
wedging down across the region allowing for drier air into the
llvls. This drier air will hold on through the overnight hrs. No
other changes needed attm
990mb sfc low sitting off the VA/NC coast as of 19z shud begin to
head up twd the NY Bight this evng in area of greatest pressure
falls. Hipres along the Quebec- Newfoundland border wl build east
tonight, continually supplying cold air. Clr skies wl allow temps
to drop quickly tonight acrs the north bfr clds mv back in fm the
southwest twd daybreak.
Complicated fcst for Tuesday as coastal low mvs north along the
eastern seaboard tomorrow. Wintry pcpn wl mv into coastal zones aft
midnight tonight with warm nose already present btwn 850-800mb. The
nwrd progression of this warm nose makes all the difference in the
world regarding ptypes. 12Z GFS rmns the coldest with temps aloft
while NAM rmns the warmest. Latest Euro is now the compromise and
has trended twd the NAM for areas along the Maine/NB border. Given
the juxtaposition of the sfc high to the north with erly flow at the
sfc, thinking is that blyr wl lkly be below freezing thru Wed mrng.
Question bcms what flow aloft arnd H8 does. 12z NAM indicates srly
55-60kt H8 LLJ on Tue straight off the Atlantic, whereas GFS and EC
indicate a more erly jet, thus not as much of a warm nose. For wx
grids hv blended the 12z NAM and 00z EC therefore expecting mostly a
sleet storm for the bulk of the precip duration.
Thorough investigation of NAM/GFS BUFKIT sndgs for the area hinge on
how warm the warm nose becomes and how thick the warm and cold lyrs
are and which model has the best handle on atmos. A difference of a
few hundred feet as well as 1C will make all the difference in the
world in regard to ptype. Have opted to issue a Winter Storm Warning
for areas north of a Dover-Foxcroft to Oxbow line for several inches
of snow, a few inches of sleet as well as a glaze of ice.
For areas further to the south, specifically along an Ellsworth to
Princeton line, think that sleet wl eventually change over to a
possibly prolonged time of freezing rain. Cannot rule out up to
one- half inch of ice especially in the Grand Lakes to Vanceboro
region, though aforementioned uncertainties could lead to more
sleet and less ice. Therefore hv issued a Winter Storm Warning for
Interior Downeast and the Bangor area due to a combo of sleet and
Along the coast, hv gone with a Winter Weather Advisory for minor
sleet accums along with a glaze of ice tomorrow morning. Warm air
shud surge along the coast and allow these areas to rise abv
freezing shortly after noon, ending the threat. Easterly winds wl
gust to between 40 and 45kts as pressure gradient tightens btwn sfc
low to the south and hipres to the north.
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.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
For Tuesday night, a significant sleet and freezing rain event
will continue. A vertically stacked low will slowly progress
northward towards the Gulf of Maine by later in the night. The low
will draw a rich flow of Atlantic moisture northward into the
forecast area through the night into Wednesday morning. PWATs are
several standard deviations above normal and there`s some
instability aloft. The moisture will not move through the area
quickly due to a blocking high in Labrador. There`s not much cold
air aloft and a southerly flow aloft is expected to bring
temperatures in a layer above H850 well above freezing.
Therefore, snow is not an issue...except perhaps in extreme NW
Aroostook County., However, in a narrow wedge under H850, a cold
easterly flow will prevail north of the low. The cold air under
H850 means rain will refreeze as sleet or freezing rain for most
of the area. The big challenges in the forecast were where to
place the 32F line at the surface through the night and the
strength of the elevated warm layer. The 23/12Z NAM suggested a
more southerly flow aloft and greater warming aloft versus the
colder GFS. In the end, the NAM was blended with the ECMWF to
produce a swatch of freezing rain from southern Penobscot County
towards north-central Washington County and southern Aroostook
County. This area has the potential to receive anywhere from a
half to three-quarters of an inch of freezing rain. Along the
coast, precipitation will be rain and winds will die down in the
evening. For the northern zones, the cold layer looks just deep
enough for sleet through the night and sleet may be measured in
inches. If temperatures aloft are just a bit warmer, significant
freezing rain accumulations will have to be pushed northward.
For Wednesday, the storm will be over for most of the area except
lingering mixed precip in NE Aroostook County for the morning.
After the precipitation moves out, the frontal inversion will
erode and temperatures will rise above freezing. Winds be
generally light...which is good news in light of any ice
accumulations. A lot of cloud cover will remain Wednesday into
Wednesday night as low level moisture remains. There`s no
significant cold air advection behind this system as lows on
Wednesday night will drop just below freezing...which could cause
some slick spots. The colder air arrives after a clipper system on
Thursday. This system will produce light precip amounts with up to
an inch of snow in the northern half of the forecast area.
Meanwhile, with temperatures in the mid to upper 30s, Bangor and
the Down East region will have rain shower activity.
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
The long term pattern features a return towards more seasonable
temperatures, but no particularly cold air masses. With a broad
upper trough over the NE US, it will be generally dry and free of
any significant storms. Weaker clipper systems may rotate from the
Great Lakes, but exact timing of resulting snow shower activity
cannot be readily discerned at this point.
.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
NEAR TERM: VFR tonight becoming IFR after 10z at BHB and BGR in
mixed precipitation. HUL may see IFR between 15z and 18z in -SNPL
though confidence was not high and have just included mixed precip
in tempo group.
SHORT TERM: Hazardous aviation conditions are expected Tuesday
night with LLWS and freezing rain/sleet. This will also be
accompanied by low IFR cigs. The low IFR cigs will continue north
of HUL into Thursday...and gradually improve to a prevailing MVFR
condition Thursday night into Friday. Snow showers could reduce
vis for sites north of GNR and MLT on Thursday afternoon.
NEAR TERM: SCA conditions continue this evening before increasing
to gales for the intracoastal area after 10z and storms on the
outer waters. By Tue afternoon expect headlines wl need to be
replaced with another SCA after this time. Expect seas to be
increase aoa 15ft on Tue.
SHORT TERM: After the storm ends, a small craft advisory will be
needed into Wednesday afternoon. After a small respite, the next
small craft advisory seems destined to run from later Thursday
morning into Saturday night.
A storm surge of up to 1.5 feet is expected along with large
waves. The astronomical high tide will occur shortly after 8 am
Tuesday morning, however the largest waves are not expected to
arrive until later in the morning. As a result only minor splash
over is expected. Astronomical tides are also relatively low, so
coastal flooding is not expected.
ME...Winter Storm Warning from 7 AM Tuesday to 1 PM EST Wednesday
Winter Weather Advisory from 1 AM to 1 PM EST Tuesday for
Wind Advisory from 4 AM to 7 PM EST Tuesday for MEZ029-030.
MARINE...Gale Warning from 5 AM to 1 PM EST Tuesday for ANZ052.
Small Craft Advisory until 5 AM EST Tuesday for ANZ050-051.
Storm Warning from 5 AM to 1 PM EST Tuesday for ANZ050-051.