Area Forecast Discussion
Issued by NWS Caribou, ME

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FXUS61 KCAR 202228
AFDCAR

Area Forecast Discussion
National Weather Service Caribou ME
628 PM EDT Thu Sep 20 2018

.SYNOPSIS...
High pressure will crest over the area this evening then move east
late tonight. Strong low pressure will track northwest of the
area Friday and pull a strong cold front through late Friday
night. Cool high pressure will build in from the west on
Saturday.

&&

.NEAR TERM /THROUGH FRIDAY/...
615 PM Update: Trrn influences were added to cld cvr this eve
alg with wind Fri into Fri ngt. Otherwise, latest obs were used
to update fcst hrly temps/dwpts into the ovrngt with no chgs to
ovrngt fcst lows attm. Lastly, lgt shwrs from mid to late aftn
are dissipating erly this eve, so this element will likely be
removed for the next fcst element.

Orgnl Disc: A chilly airmass over the land, lakes and waterways
that have been warmed by a very warm summer has resulted in
persistent stratus and some spotty showers and drizzle again
today. Some breaks in the overcast are possible early this
evening as the upper ridge axes moves through. However, mid and
high clouds will increase later tonight as a warm front lifts
north ahead of approaching low pressure. A strong autumnal low
will lift northeast from east central Ontario into Quebec on
Friday. The gradient between high pressure to our east and the
big low to our northwest will result in increasing south winds
on Friday. Wind gusts Friday afternoon into Friday evening could
reach 40 to 50 mph at times. The wind advisory will be extended
through the entire region given impact potential with leaves
still on the trees, and wet ground Downeast. The strongest winds
Friday will likely be during the very late afternoon as some of
the wind from the low level jet mixes down.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
As an unusually powerful low pressure system tracks across
northern Quebec on Friday night, all guidance shows very strong
H925-H850 winds ahead of the cold front that will cross later
Friday night into early Saturday morning. H850 winds may reach
60 to 65 kts ahead of the front. The loss of daytime heating
will mitigate winds mixing to the surface, but both a pre-
frontal trough and the actual cold front have the potential to
mix the 50+ mph winds to the ground. Furthermore, with
temperatures rising all night, even nominal mixing to H925 could
pull down some 50 mph gusts. When leaves are on the trees,
frequent gusts over 35 mph usually cause problems. As a result,
power outages remain a concern for Friday night. A Wind
Advisory will be issued for the remainder of the forecast area
as the strongest winds aloft shift southward during the night.
During Friday evening, elevated instability increases with an
H850 thermal ridge and have maintained a chance of
thunderstorms with gusty winds with the pre-frontal trough. It
may be one of those situations that requires severe thunderstorm
products for squall lines...even without thunder. Temperatures
will fall sharply with the front early Saturday morning and
won`t rise too much on Saturday. Saturday will continue to
feature strong gusty northwest winds hitting 35 mph, but these
winds will die off in the afternoon as high pressure builds and
skies clear across the entire area. High pressure continues to
build Saturday night. With the cold air in place, frost will be
a concern and have added it to the forecast. A reinforcing cold
front arrives Sunday and will bring the coldest air of the
season to date. This front will be dry. H850 moisture will
generate some frontal cu/sc in northern zones while the cold air
advection and mixing will generate 20 to 25 mph wind gusts.
Highs will be up to 5 degrees cooler in northern zones for
Sunday.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
A hard freeze seems likely Sunday night at this point with a big
1038mb high building over the area. Have expanded mention of
frost in the forecast for Sunday night. Winds may be slow to die
off and allow decoupling, but the cold air advection alone will
provide sub-freezing temps. Monday will remain chilly with highs
in the 50s, but skies will be clear with little wind. Another
night of frost is a threat Monday night and have added this into
the forecast. This frost could extend to the coast. Three
consecutive days of frost may put an end to the growing season
for much of the area. The high will remains in place Tuesday but
the upper ridge axis will cross and high overrunning clouds
will increase. A warm front will approach Tuesday night into
Wednesday on the back side of the departing high. A maritime
flow and frontal inversion will ensure widespread cloud cover
developing during this time...along with increasing temperatures
and dew points. Dew points will steadily rise Tuesday into
Wednesday until topping out back in the low to mid 60s. Strong
southerly low level winds on the backside of the departing high
are showing up in guidance again and heighten concerns about
another potential wind event...with leaves remaining on the
trees. This would occur during the Tuesday night into Wednesday
evening time frame. There`s still some question as to how fast
the cold front will cross the area. Most guidance is now showing
a slower progression due to a higher amplitude blocking ridge
and the cold front may become parallel to the flow later
Wednesday into Wednesday night. As a result, will keep pops in
the forecast into Thursday morning...but consensus wind and temp
fields produce a fropa late Wednesday. High pressure will build
behind the front Thursday into Friday.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
NEAR TERM: MVFR conditions in low stratus clouds should improve
to VFR for a period through mid evening, except the far north
where some stratus will linger. Ceilings will then lower to
MVFR again late tonight as the warm front lifts into the area.
MVFR conditions should drop to IFR Friday morning and remain IFR
on Friday. Wind shear is likely across the area Friday for SSW
winds around 45kt at 2K ft.

SHORT TERM: LLWS, isolated embedded thunderstorms and gusty
southerly winds reaching over 45 mph are the issues for Friday
night. Cigs may also drop to MVFR in rain. VFR returns Saturday
morning and persists into Tuesday. Patchy shallow river valley
fog will be a risk near sunrise...most likely Tuesday morning.

&&

.MARINE...
NEAR TERM: A gale warning will be issued beginning early Friday
afternoon for increasing south winds. Seas will rise in
response to the winds and some fog may reduce visibilities.

SHORT TERM: Gale conditions wind down quickly Saturday
morning...followed by a Small Craft Advisory into the afternoon.
High pressure will provide quiet conditions over the waters
until Tuesday when another advisory may be needed later in the
day.

&&

.CAR WATCHES/WARNINGS/ADVISORIES...
ME...Wind Advisory from 2 PM Friday to 8 AM EDT Saturday for
     MEZ001>006-010-011-015>017-029>032.
MARINE...Gale Warning from 2 PM Friday to 8 AM EDT Saturday for
     ANZ050>052.

&&

$$

Near Term...Bloomer
Short Term...MCW
Long Term...MCW
Aviation...Bloomer/MCW
Marine...Bloomer/MCW



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