Area Forecast Discussion
Issued by NWS Caribou, ME

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FXUS61 KCAR 161443
AFDCAR

Area Forecast Discussion
National Weather Service Caribou ME
1043 AM EDT Mon Apr 16 2018

.SYNOPSIS...
Low pressure will approach from the Great Lakes today and tonight
then slowly cross the area Tuesday into Tuesday night. The low
will exit into the Maritimes on Wednesday.
&&

.NEAR TERM /THROUGH TONIGHT/...
Update...
A wintry mix of snow, sleet and freezing rain will expand across
the region through the remainder of the morning into the
afternoon in advance of an approaching occluded front.
Precipitation will begin to transition to rain across Downeast
areas this afternoon, while a wintry mix persists across
northern and central areas. All Winter Weather Advisories remain
in effect. Winds will begin to increase across Downeast areas
this afternoon, where a Wind Advisory is in effect starting this
afternoon. High temperatures today will range from the lower to
mid 30s north, to the mid to upper 30s interior Downeast with
upper 30s along the Downeast coast. Have updated the forecast to
adjust for current conditions.

Previous Discussion...
A strong sfc high centered in northern Quebec continues to
drain cold and dry air into far northern Maine early this
morning with single degree dew points in the far north. The high
will weaken over the next 24 hours and elongate with centers
just east of Hudson Bay and south of the Newfoundland coast by
late tonight. An elongated area of low pressure extends from the
lower Great Lakes Region to the central Appalachians early this
morning. The low will deepen today and by tonight with the main
low center expected to be over Georgian Bay with a secondary
low to lift into the northern CT River Valley tonight. An
occlusion will lift north across the Downeast region late
tonight.

Many weather issues in the near term.  The first is the
precipitation that will lift north and east today. It will be
fighting dry air in far northern Maine toward the Saint John
Valley. Any snow Downeast will likely quickly change to sleet
this morning before transitioning to rain in the afternoon. As
the sleet changes to rain there could be a period of freezing
rain, especially from Bangor north and west. The winter weather
advisories were expanded to include Washington County and
central Penobscot County where there is high enough confidence
that there will be enough sleet and freezing rain during the
morning to cause some slick spots on the roads. Will keep the
advisories going until noon, but there is the concern if the
cold air hangs in that they might need to be extended into at
least the first half of the afternoon, and worst case into this
evening. To the north, the precipitation will have a hard time
getting going from Caribou north until this afternoon, and have
trimmed back the PoPs/QPF quite a bit for this morning. Although
air temps will likely hoover around freezing this afternoon,
the high sun angle should allow for most roads to just be wet as
they warm up a bit before the onset. Of course, this will need
to be monitored closely, and it is still possible that
advisories could need to be extended further north later this
morning. Sleet and any pockets of freezing rain from the
central highlands north to the Saint John Valley will gradually
transition to rain tonight, but with temperatures to remain near
freezing. There will be some concern that with the loss of
daytime heating that there could be slick spots well into the
night, especially in the Saint John Valley and in the valleys
of the north woods. When one looks at the model soundings there
is a deep layer above freezing from 850-700H, so confidence is
high that there will not be significant snowfall, but a
prolonged period of sleet with some freezing rain remains
possible in the north tonight. Downeast, temps will slowly rise
and it will be all rain tonight, although some local pockets of
sleet or freezing rain could persist into early evening well
inland. The next concern is the wind. The models have a 50 to
60 kt jet aimed right along the coast later this afternoon ahead
of the main jet that affects the region tonight. The current
wind advisory along the coast looks very reasonable, but with
the possibility of some mixing of the stronger wind aloft, a
decent gradient, and wet soils due to the rain will expand the
advisory into southern Penobscot County, interior Hancock
County, and central Washington County where wind gusts to 45 mph
are expected from very late in the afternoon through at least
the first half of tonight. Isolated to scatterd power outages
are possible.
&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY/...
Low pressure, both surface and aloft, will be centered just to our
west on Tuesday. A dry intrusion circulating into the low from the
south will taper rain off to spotty showers across the area by
midday and the sky may brighten at times. Showers may increase again
across western areas late in the day into Tuesday night in response
to the upper low working into the area. Some low level convection is
possible late Tuesday afternoon as the upper low moves in with
colder air aloft moving in over the warm intrusion in the low
levels. Low pressure, both surface and aloft, will be over our
region Wednesday bringing overcast skies and showers. The showers
should taper off Wednesday night as the low moves away and a weak
surface high moves over.
&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
Our attention on Thursday turns to a second wave of low pressure
sliding off the Mid-Atlantic coast, and then projected to track to
our south Thursday night. Boundary layer temperatures are expected
to be cold enough to support snow over central and northern areas
with rain likely Downeast. Precipitation output, however, is
expected to be light with this system, possibly giving a couple
inches of snow over the north with perhaps a band of moderate snow
across some parts of the central highlands Thursday night into early
Friday. Precipitation will taper off late Friday into Friday night
as the low moves away. A large high pressure system is then expected
to build in over during the weekend bringing a return of partial
sunshine late Saturday, clear skies Saturday night and a sunny
milder day on Sunday. Mild and dry weather look likely for much of
next week.
&&

.AVIATION /15Z MONDAY THROUGH FRIDAY/...
NEAR TERM: Conditions will lower to IFR levels today at the
Downeast terminals with a wintry mix this morning transitioning
to rain this afternoon. VFR at the northern terminals will
lower to MVFR this afternoon in sleet and freezing rain then to
IFR tonight in sleet, freezing rain, and rain. LLWS is expected
across the entire region tonight.

SHORT TERM: IFR conditions in low clouds are expected Tuesday
through Wednesday with some possible breaks of MVFR during the
midday or afternoon Tuesday. conditions should improve to MVFR
Wednesday night then possibly VFR on Thursday as low pressure
moves away.
&&

.MARINE...
NEAR TERM: A Gale Warning is in effect on the waters today
through tonight. Wind gusts to 45 knots are expected with the
seas building up to 15 feet. Visibilities will be reduced in
rain and a wintry mix this morning, with rain and patchy fog
this afternoon and tonight.

SHORT TERM: Winds are expected to be below SCA Tuesday through
Thursday as low pressure over the area slowly weakens and moves
east into the Maritimes. However, a few gusts may reach 25 kt on
Wednesday as the low moves away. A SCA may be needed Thursday
night or Friday in response to a new low tracking south of the
area.
&&

.HYDROLOGY...
Rivers will be on the rise this week due to the combination of rain
and snowmelt in the north, and rain in the south.  Open water
flooding appears unlikely given the amount of precipitation that is
expected. The main concern will be on the northern rivers, i.e. the
Saint John, Aroostook, and Allagash Rivers that still have
significant ice.  The rising waters levels will cause the ice to
break up later this week and could lead to the potential for ice
jams, and possible localized ice jam flooding.
&&

.TIDES/COASTAL FLOODING...
Minor coastal flooding is possible at the time of high tide around
midnight tonight.  Minor coastal coastal overwash and minor beach
erosion are expected with some small rocks likely to be washed up on
coastal roads.  Overall looks to be a relatively minor event. This
should be the only tidal cycle that a flood threat exists for and
we are not expecting any inundation flooding in coastal areas.
&&

.CLIMATE...
The low temperature of 12F at Caribou, Maine Sunday morning
broke the previous record low of 13F, set in 1981. Caribou has
now had the 5th coldest first half of April on record. The high
temperature at Houlton Sunday of 31F tied with 1971 for the
lowest high temperature on April 15th.
&&

.CAR WATCHES/WARNINGS/ADVISORIES...
ME...Winter Weather Advisory until noon EDT today for MEZ010-011-
     015>017-029>032.
     Wind Advisory from 5 PM this afternoon to 5 AM EDT Tuesday for
     MEZ015>017.
     Wind Advisory from 2 PM this afternoon to 5 AM EDT Tuesday for
     MEZ029-030.
     Coastal Flood Advisory from 10 PM this evening to 2 AM EDT
     Tuesday for MEZ029-030.
MARINE...Gale Warning until 6 AM EDT Tuesday for ANZ050>052.

&&

$$

Near Term...Norcross/CB
Short Term...Bloomer
Long Term...Bloomer
Aviation...Norcross/CB/Bloomer
Marine...Norcross/CB/Bloomer
Hydrology...CB
Tides/Coastal Flooding...CB
Climate...CB


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