Area Forecast Discussion
Issued by NWS Caribou, ME

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FXUS61 KCAR 230606

Area Forecast Discussion
National Weather Service Caribou ME
106 AM EST Thu Feb 23 2017

High pressure will cross the region overnight. Low pressure
will track through Quebec on Thursday and track to our north
Thursday night. High pressure will return on Friday.


107 AM Update...
Clear skies have allowed for temps to drop off quickly w/low
lying spots dropping into the lower 20s across portions of
northern and western areas. As a matter of fact, temps have
fallen into the mid/upper 20s all the way to the downeast
region. Adjusted the overnight lows down some to take into
account the latest trends. Some fog showing up on the latest
metars and webcams confirm this to be the case. Temp/dewpoint
spread down below 3 degrees w/llvl moisture allowing for fog
potential. The latest RAP and NAM12 caught on to this setup.
Decided to add fog into the fcst into morning commute. Slick
spots on roads due to the fog and cold surface temps. This will
be addressed w/a Special Weather Statement and in the
HWO(Hazardous Weather Outlook). Still looking for some light
freezing precip by morning hrs w/warm front lifting across the

Previous Discussion...
Low pressure north of the Great Lakes will move to the north of
the state Thursday. Light precipitation is possible across the
northern most part of the state as the low passes by. Expect
Warmer air aloft so after a brief period of snow expect a
mixture of sleet and freezing rain. QPF amounts are mostly under
a tenth of an inch before changing to rain so accumulation of
ice is expected to be minimal. Have used the precipitation from
thickness tool run on a blend of the NAM and GFS for
precipitation type Thursday. All precipitation should change to
rain later Thursday morning as surface temperature warms.


A sfc low associated with an upper-level shortwave is forecast
to pass north of the CWA at the start of the period, dragging a
weak cold front across the state Thu night. The front then
stalls over the Gulf of Maine during the day Fri. Some rain may
be ongoing at the start of the period, especially up north, but
this will quickly diminish and move off to the east with the
front. Highs will be a few degrees lower on Fri, but still well
above normal for late Feb.

A more powerful low pressure system backed by a deep upper-level
trough will lift NE`ward across the Great lakes and into
western Quebec Fri night and Sat. As this happens, the stalled
front will lift back north as a weak warm front late Fri night.
As it does so, some is likely to develop from Downeast to the
central highlands Fri eve and night. Warm moist air overrunning
sfc sub-freezing air will likely lead to some sleet and freezing
rain, mainly north of a Bangor-Eastport line, before the warm
air moving north turns everything to rain after sunrise Sat AM.
As warm, moist air streams northward over the statewide snowpack
on Sat and dewpts get above 30F, will need to watch out for
potential of fog, which could be locally very dense.


At 00z Sat, the cold front associated with the potent low will
just be reaching the eastern border of NY, and will then quickly
advance across the state by 12z Sat. Moderate to heavy rain is
possible ahead of and with the front. Given the rather deep
snowpack remaining across the state, much of this rain will
likely get absorbed, though it`s too early to say for sure what
the hydrologic impacts may be. Most of the precip will be clear
of the state by Sun PM, but a few showers could linger into the
evening, until the base of the upper trough crosses the state.

A weak front crossing the state Mon afternoon & evening could
trigger some snow showers, perhaps even a snow squall, before
pushing out of the area. Meanwhile, a more potent low may pass
well to the south, keeping clear of the CWA. The ECMWF, GFS, and
CMC are all in relatively good agreement on the next significant
system impacting the CWA Wed into Thu, so will just have to wait
and see how the details unfold. Did go for some low-end likely
POPs with this system, due to good agreement between the models.


NEAR TERM: Expect VFR conditions across northern areas into the
early morning hours, with MVFR conditions developing overnight.
A light wintry mix is possible across northern areas late
tonight through early Thursday morning before a transition to
rain. Conditions will lower to IFR/LIFR levels across northern
areas Thursday. VFR conditions are expected Bangor and Downeast
overnight into Thursday morning, with MVFR conditions
developing during the afternoon.

SHORT TERM: IFR to MFVR conditions are expected Thu night,
improving to all MVFR and VFR during the day Fri. Conditions
will deteriorate again Fri eve and night, with widespread IFR
CIGs likely. IFR vsbys also psbl in snow for KCAR thru KFVE,
with ocnl freezing rain possible from KBGR northward Fri night.
Sleet and FZRA will change to rain from south to north Sat AM,
with areas of dense fog likely to cause patchy IFR to LIFR into
Sat night. The fog will break up Sat night, though IFR CIGs may
remain thru Sun PM in lingering snow showers. Improvement to
MVFR or VFR may occur Sun night, but another round of snow
showers and psbl squalls may cause areas of IFR conditions Mon
morning and afternoon.


NEAR TERM: Conditions are expected to be below small craft
advisory levels overnight through early Thursday. Small craft
advisory conditions could then begin to develop later Thursday
afternoon. For sustained winds Thursday have used the NAM. For
waves: Currently a medium period southwesterly swell is being
observed at buoy sites. This wave system was generated last
night from a fetch confined to the Gulf of Maine. Wind speeds
have been well below 10 knots today so wind wave is small. South
to southwesterly wind wave will build later Thursday to 3 to 4
feet/6 seconds as wind speeds increase late in the day. Will use
the Near Shore Wave Model to populate wave grids.

SHORT TERM: Borderline winds and gusts Thu night into Fri AM may
require an SCA, though seas will likely be on the low side.
SW`ly winds Thu night will shift E-SE`ly by Fri eve as low
pressure approaches from the west. Winds will turn more SE-S`ly
and increase by Sat as a warm front pushes from the Gulf onto
the mainland.





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