Area Forecast Discussion
Issued by NWS Caribou, ME

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FXUS61 KCAR 221722

Area Forecast Discussion
National Weather Service Caribou ME
1222 PM EST Wed Feb 22 2017

High pressure will build to our south today and tonight. Low
pressure will track through Quebec on Thursday and track to our
north Thursday night. High pressure will return on Friday.


Update 12:20 PM: Have adjusted wind, temperature, and dew point
based on latest observations. No other changes.

A weakening occluded front moving across the region early this
morning may bring some very light showers or freezing rain,
sleet or snow early this morning. Otherwise, the morning will be
mostly cloudy and mild. High pressure building to our south
will then bring a light southerly flow and a very mild day today
with partial sunshine and highs reaching near 40 north to the
low 40s Downeast. A small low will approach from the great lakes
tonight bringing increasing clouds and a light southerly flow.
Temps will remain mild, only dropping a couple degrees below
freezing. Precipitation may begin to push into northwestern
areas toward dawn. Boundary layer temps will be warm enough to
support rain but surface temps will be just below freezing so
will have a small chance of light freezing rain in the northwest
toward morning. The light southerly flow and some increase in
low level moisture may produce some patchy fog toward morning.


A continuation of the warmer temperatures expected.

A warm front will lift across the region on Thursday as low pres
moves across Quebec. Some light freezing rain/drizzle looks
possible mainly north of the Bangor-Calais region in the
morning. The NAM and GFS soundings support this potential w/dry
air above the llvl moist airmass that will be in place. Warmer
air is expected to allow for temps to rapidly rise above 32F
after 8 AM and continue their climb during the day. The
associated cold front is forecast to apch the region from the
west later in the afternoon. The region looks like it gets into
a pseudo-warm sector in the afternoon w/temps rising well into
the 40s and possibly lower 50s in the downeast region. A pre-
frontal trof looks like it could develop ahead of the cold front
w/the airmass destabilizing. Decent shear at the 0-6km layer of
35_ kts w/elevated instability. The NAM/GFS soundings support
this to be the case and point to some elevated CAPE of around
100 joules across the n and w in the afternoon. The NAM is the
most robust w/this potential. This could lead to some squalls
action of heavy showers w/graupel and brief wind gusts to 30
mph or so.

The cold front is forecast to slide across the region Thursday
night w/a cooldown by Friday morning. Any leftover rain showers
could go to snow showers before ending. No accumulation
expected. Temps in the upper 20s by 7 AM Friday across the n and
w while central and downeast will see low/mid 30s. Friday will
start out sunny followed by increasing clouds during the day
ahead of the next weather system to affect the region through
the weekend. High pres nosing down from Quebec will allow for
the llvl cold air to get trapped near the surface. Decided to
undercut the guidance for Friday`s max temps and leaned w/upper
30s to around 40 across the northern 1/2 of the CWA while
central and downeast will see low to mid 40s. The long range
guidance was offering some differing solutions w/the ECMWF and
Canadian Global bringing some measurable precip by late Friday
afternoon while the GFS and NAM keep precip shield at bay until
Friday evening. Decided to use a blend and brought precip
chance to 60% across swrn areas late in the day and have 40%
elsewhere. The precip will be in the form of light rain starting
out but as evap cooling takes hold, some light snow or sleet
and possibly freezing rain later in the night. This will be
discussed further in the long range section below.


A challenging forecast shaping up this term through Sunday.

Light rain Friday evening could go to a period of light snow or
even sleet/freezing rain later in the night ahead of the main
system w/evaporative cooling taking hold and continuing into
Saturday morning. This would be especially true from the
Central Highlands northward. The 00z runs of the NAM and GFS
point to this scenario while the ECMWF and Canadian Global show
warm air streaming in aloft w/llvl cold air eroding more
quickly. Decided on a colder solution attm w/the sleet and
freezing rain Saturday morning given the position of the high
and cold air right at the surface. The warmer air wins out by
mid morning w/precip going to all rain. Areas of fog expected as
the warm air moves over the snowpack.

There looks to be a lull in the activity by Saturday afternoon
w/the main thrust of rain expected Saturday night. The latest
cycle of the long range guidance points at the potential of a
2nd low developing on the apchg frontal system Saturday evening
and moving across eastern Maine. This would bring a good slug of
rainfall to the region w/anywhere from 0.50 to 1.00" of liquid
precip. The deep snowpack in place should be able to absorb
much of the rain especially for the northern 1/2 of the CWA. The
downeast region could see some runoff as snowpack continues to
erode. This would also allow for some rises on rivers and
streams w/the potential for any ice movement. Duration of
rainfall and warm air will be key. Another item of concern
will be the sse winds Saturday night. A 925mb jet of 45+ kts is
forecast to move across the downeast region w/the potential for
winds gusts to 40 mph. Guidance was showing colder air to
filter into the region by Sunday morning w/a period of snow
before the precip ends. The daycrew can assess this potential
today w/the later guidance. Sunday looks to be a windy and
colder day w/snow showers and a wnw west wind. Wind gust
potential of 35 to 40 mph possible especially across the open
and high terrain. Temps will be falling throughout the day on

High pres is expected to briefly ridge across the region Sunday
night w/increasing clouds later at night w/another weaker system
apchg from the w. This weaker system could bring a round of
light snow to CWA on Monday w/daytime temps back to more
seasonal norms.


NEAR TERM: VFR conditions are expected today into tonight.
Conditions may lower to MVFR in some sites late tonight in some
mist or light fog and, across the north, some lowering ceilings.

SHORT TERM: IFR conditions expected on Thursday w/some MVFR
Thursday afternoon but a return to IFR Thursday evening as the
front slides across the region. LLWS potential is there for
Thursday especially in the afternoon. Conditions to gradually
improve to VFR by mid to late Friday morning. Another frontal
system is expected to affect the region later Friday night into
the weekend. This will bring lowering cigs and vsbys to IFR
w/some fog and rain. There is potential for some light icing
across the northern terminals early Saturday morning.


NEAR TERM: Winds and seas are expected to remain below SCA today
and tonight. Some fog may spread across the waters late tonight.

SHORT TERM: No headlines expected through Friday. Some gusts to
25 kts for the outer zones possible later Thursday into Thursday
evening. Attm, kept sustained wind 15-20 kts and seas 3-4 ft for
these zones. Closer in along the intra-coastal zone, 10-15 kts
and seas 2-3 ft. Things expected to change come Saturday,
especially Saturday night into Sunday w/sustained winds of 2-25
kts and gusts apchg 30+ kt. Sunday will definitely be the windy
day w/25 kt sustained winds and gust potential of 30-35 kts as
colder air moves over the warmer Gulf of Maine waters.





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