Area Forecast Discussion
Issued by NWS Caribou, ME

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FXUS61 KCAR 271737

Area Forecast Discussion
National Weather Service Caribou ME
1237 PM EST Thu Feb 27 2020

Intensifying low pressure will cross the region today, then
exit across the Maritimes Friday through Saturday. High
pressure will build across the region later Sunday into Monday.


1230 PM Update...
Just small tweaks to account for current conditions. Biggest
change was to bump up freezing rain some in central Washington
County based on spotter report and latest model soundings. Winds
are cranking Downeast, strongest near the coast, with a decent
number of outages reported. Expect the winds to weaken in a few
hours and forecast had this well covered. Over the next few
hours, expect the warm layer aloft to erode from west to east
and can see this happening now as Southern Piscataquis has gone
mostly from sleet back to snow based on correlation coefficient
and webcams. This erosion of the warm layer aloft will allow for
just rain or snow mid to late afternoon and no more sleet or
freezing rain. All snow from Millinocket and Moosehead Lake
north with snow intensifying and winds picking up.

Previous Discussion...
A strong storm is expected today with blowing snow across the
northern half of the forecast area and a very sharp gradient in
snowfall across the Bangor Region and Downeast Maine. Surface
analysis as of 9z shows an elongated area of low pressure in the
low 990s stretching from eastern Ontario to near New York City,
moving northeast ahead of the negatively tilted upper level
trough. The strongest pressure falls are underway along the
coast, indicating a secondary low pressure is forming and the
initial low over Ontario is becoming occluded. Temperatures have
remained fairly steady overnight just below freezing across the
north and above freezing across Downeast Maine. Mesoanalysis at
9z currently shows the surface wet bulb zero line bisecting
forecast zones 31, 11, and 32. Reduced snow totals slightly
around the Bangor area, where forecast soundings from the NAM
and HRRR also show a substantial warm nose changing
precipitation over to rain even if surface wet bulb temperatures
decrease enough to support snow.

The secondary low is expected to strengthen over the Gulf of
Maine, with potential for a band of heavier precipitation
forming across northern Washington and Southern Aroostook
Counties as the main precipitation axis moves away. Upgraded
northern Washington County to a Winter Storm Warning with this
update due to a combination of around 6 or 7 inches of snow and
sleet accumulation from this band. The strong easterly low level
jet will also enhance terrain effects and snowfall totals in
this area, as well as eastern facing slopes of northern Maine
where up to a foot of snow is possible. Likewise, areas downwind
of higher terrain may see a reduction in totals. In any case,
the primary impacts will be near whiteout conditions due to a
few hour period with snowfall rates in excess of one inch per
hour and winds gusting to around 40mph. Winds of this magnitude
will also reduce snow ratios, so opted to cap ratios at 11:1.

A dry slot will rapidly sweep in by 0z, quickly reducing
precipitation and snowfall rates. Forecast soundings continue to
indicate drying above 10,000 feet AGL, which includes the DGZ.
While models do reduce QPF and the TROWAL does remain in the
vicinity of northern Maine, their amounts are still questionably
high given the lack of deeper moisture. Reduced QPF from 0-6z
and limited areas to around an inch or less of accumulation
during this time. The DGZ may briefly saturate again as a mid
level front swings through around 6z Friday and shifts winds out
of the southwest, but by this point the best forcing and the
TROWAL will be north/northeast of the forecast area.


A surface trof and deformation zone aloft will lift north of
the region Friday, while an upper low approaches from the west.
The upper low will then cross the region Friday night through
Saturday night. Unsettled conditions with the upper low will
keep mostly cloudy skies along with a chance of snow showers
across the north and mountains Friday through Saturday night.
Across Downeast areas, expect mostly cloudy skies with a slight
chance of snow showers Friday. Partly/mostly cloudy skies are
then expected Friday night through Saturday night, with also a
slight chance of snow showers Saturday. Temperatures will be at
slightly below normal levels Friday/Saturday.


The upper low will exit across the Maritimes early Sunday, with
surface high pressure building toward the region late. Expect
mostly cloudy skies along with a slight chance of snow showers
across the north and mountains Sunday, with partly cloudy skies
Downeast. High pressure moves east of the region early Monday
with a warm front then crossing the region. A cold front then
approaches later Monday night. Generally expect partly cloudy
skies north, mostly sunny Downeast, Monday. Clouds then increase
Monday night along with a chance of snow showers, possibly
mixed with rain showers along the Downeast coast. Uncertainty
then develops Tuesday regarding whether the cold front stalls
across the region, or if low pressure moves along the front
eventually drawing the cold front south in the wake of the low.
Expect a chance of rain/snow showers across the region Tuesday,
with steadier precipitation possible if a more organized low
moves along the front. A stronger low will approach from the
southwest later Wednesday, though the timing/track remain
uncertain. Current indications are that this system should draw
enough warm air north to keep precipitation mostly in the form
of rain Downeast. Across northern areas, precipitation should
start in the form of snow or a snow/rain mix then possibly
transition to mostly rain dependent on the eventual track of the
low. Near normal, to slightly below normal, level temperatures
are expected Sunday. Temperatures will then warm to above normal
levels Monday through Wednesday.


NEAR TERM: IFR or low MVFR throughout. Windy, with low level
wind shear as well. Significant improvement KBGR and KBHB to VFR
early evening or late afternoon, with slackening winds and
ceilings to VFR. Slower to improve north of KBGR, but expect
VFR or locally MVFR by late evening. Generally VFR Friday except
some MVFR in scattered snow showers mainly central areas.

Friday...MVFR conditions with snow showers north, MVFR/VFR with
a slight chance of snow showers Downeast. Southwest winds
gusting up to 25 to 30 mph.

Friday night through Saturday night...Occasional MVFR
conditions possible north. Mostly VFR Downeast.

Sunday...Generally VFR. MVFR conditions possible across the
north early.

Sunday night through Monday...Generally VFR. MVFR conditions
possible later Monday into Monday night with a chance of
snow/rain showers.


NEAR TERM: No changes to marine headlines were made with storm
force winds expected today. A brief break is expected during the
evening before winds shift WSW and increase to Gale force, so
expect the storm warning to be replaced with a Gale Warning upon
its expiration this afternoon. Seas will be very hazardous and
well in excess of 10 feet, becoming choppy as winds shift,
creating multiple swells overnight.

SHORT TERM: Gale conditions expected Friday into Friday
night, with small craft advisory conditions Saturday into
Saturday night.


In spite of relatively low astronomical tides, the intersection
of high tide with a storm surge over 2 feet early Thursday
afternoon raises the possibility of minor coastal flooding and
overwash. A coastal flood statement has been issued for the
upcoming early afternoon high tide cycle.


ME...Winter Storm Warning until 5 AM EST Friday for MEZ001>006-010-
     Winter Weather Advisory until 10 PM EST this evening for
     Wind Advisory until 3 PM EST this afternoon for MEZ029-030.
MARINE...Storm Warning until 1 PM EST this afternoon for ANZ052.
     Storm Warning until 3 PM EST this afternoon for ANZ050-051.



Near Term...Foisy/Strauser
Short Term...Norcross
Long Term...Norcross
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