Area Forecast Discussion
Issued by NWS Caribou, ME

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FXUS61 KCAR 232215
AFDCAR

Area Forecast Discussion
National Weather Service Caribou ME
615 PM EDT Tue Apr 23 2019

.SYNOPSIS...
Low pressure will exit the Gulf of Maine this evening and move
across Nova Scotia tonight. Another low from the Great Lakes
region will approach late tonight and move east across the
region Wednesday. High pressure will cross the region Thursday.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
Update 6:15 PM: Have adjusted wind speeds higher based on
latest observations. Also adjusted temperature and dew points.
No other changes.

An unusual succession of back to back cold core closed upper
lows will affect the region this evening through Wednesday. The
first compact vertically stacked closed upper low is moving
across the Gulf of Maine this afternoon. Atlantic moisture being
wrapped northward on the cyclonic side will continue to cause
rain into the evening. A lot of this moisture will remain
trapped under an inversion tonight and cause low clouds and
drizzle across the entire area. High pressure in northern Quebec
will help maintain the cool easterly flow and the subsidence
inversion. The reign of the high pressure will be very short
lived as the second compact cold core closed upper low will
swing eastward from the Great Lakes. This system will remain in
the northern stream and won`t tap into deeper moisture. As a
result, QPF amounts will be a quarter inch or less again. In
spite of the very cold air aloft, convection is not
expected, in large part due to the steep low level inversion
and resulting cold air at the surface. Elevated instability
doesn`t look like a factor. Most of the rain, or sleet for the
far north, will be with an occlusion that will approach late
tonight and enter the area Wednesday morning. This occlusion`s
northward and eastward progress will be stunted by the
development of a triple point low in the Gulf of Maine towards
midday. This will maintain the cool east flow and limit
tomorrow`s highs to the upper 30s north and low to mid 40s
towards Bangor and the coast. As the cold upper low moves over
the state later Wednesday, the inversion will decay, along with
warmer air aloft. At this point the threat in the far north
changes from sleet back to snow. At this point, thicknesses are
marginal, cloud tops are expected to be below the DGZ and time
of day is not favorable. However, there are always uncertainties
with cold core upper lows in the spring and it`s not hard to
envision a worst case scenario of some higher elevation sites
seeing an inch or two of wet snow in northern Aroostook County
by the evening.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
Low pressure will exit across the Maritimes Wednesday night,
with high pressure building toward the region late. Will have a
chance of evening rain/snow showers north, with a chance of rain
showers Downeast. Skies will then remain mostly cloudy across
northern areas overnight, with decreasing clouds Downeast. High
pressure will cross the region Thursday, then begin to exit
across the Maritimes Thursday night while low pressure
approaches from the west. Expect mostly/partly cloudy skies
across northern areas Thursday, with partly cloudy skies
Downeast. Clouds will increase across the region Thursday night.
Rain will develop Friday in advance of the approaching low.
Near normal, to slightly below normal, level temperatures are
expected Thursday/Friday.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
The intensifying surface low will lift across the region Friday
night through Saturday while being captured with the upper low
though how rapidly this occurs is still uncertain. Rain will
occur Friday night into early Saturday, then taper to showers
during the afternoon. Rainfall totals with this system are
still uncertain. The surface/upper lows will lift toward
Labrador Saturday night. Expect mostly cloudy skies along with
a chance of rain/snow showers across the north and mountains
Saturday night. Across Downeast areas, expect partly cloudy skies
along with the slight chance of evening rain showers.
Significant uncertainty then exists Sunday into Tuesday
regarding the track and timing of several possible lows along
with rain chances and total rainfall. Generally expect near
normal, to slightly below normal, level temperatures Saturday
through Tuesday.

&&

.AVIATION /22Z TUESDAY THROUGH SUNDAY/...
NEAR TERM: The prevailing condition will be IFR cigs through
tomorrow for all sites. There will be temporary increases to low
MVFR cigs at times this evening. Tempo IFR vis is possible
through this afternoon with low pressure over the area and
again Wednesday morning with another frontal system. There is a
risk of sleet and snow at locations such as FVE and Clayton Lake
during Wednesday.

SHORT TERM: Occasional MVFR conditions will occur across the
north and mountains Wednesday night, with occasional MVFR
conditions possible early Downeast. Could have occasional MVFR
conditions across the north and mountains early Thursday.
Otherwise, expect generally VFR conditions across the region
Thursday through much of Thursday night. Conditions will begin
to lower to MVFR levels later Thursday night, then to IFR/LIFR
levels with developing rain Friday. IFR/LIFR conditions are
expected Friday night into early Saturday. MVFR/IFR conditions
are expected later Saturday, with VFR/MVFR conditions Saturday
night. Uncertainty then exists Sunday regarding possible low
pressure.

&&

.MARINE...
NEAR TERM: Have extended the Small Craft Advisory until 7 pm
this evening. Winds are steadily declining, but seas will stay
up well into the night and the expectation will be to convert to
a Small Craft Advisory for Hazardous Seas upon expiration of
the current advisory. Otherwise, rain this afternoon and early
evening will end, but a new round of rain will arrive late
tonight into early Wednesday morning as low pressure forms over
the waters.

SHORT TERM: Conditions are expected to be below small craft
advisory levels Wednesday night into Thursday night. Small
craft advisory conditions are then expected to develop Friday.
Showers are possible Wednesday evening. Visibilities will then
be reduced in rain and fog Friday.

&&

.HYDROLOGY...
River Flood Warnings remain in effect for the Saint John and
Fish Rivers at Fort Kent, along with the Mattawamkeag River near
Mattawamkeag. The Saint John and Fish Rivers near Fort Kent
appear to have started to slowly fall. The Mattawamkeag River
remains near steady. All the rivers are ice free with the
exception of the headwaters of the Saint John.

Areal Flood Advisories remain in effect for Eastern Aroostook
County and along the East Branch of the Penobscot River below
Grand Lake Matagamon Dam. Some roads remain closed due to
flooding in the advisory areas including along portions of Route
11 near Grindstone. Many rivers and streams in the advisory
areas remain at or near bankfull with flooding in lowland areas.

Will continue to keep a close eye on the Fish River chain of
lakes through the next week or two since water levels are
rising and this area typically peaks late. Concerned about
potential for flooding possibly similar to last spring in this
area.

&&

.CAR WATCHES/WARNINGS/ADVISORIES...
ME...None.
MARINE...Small Craft Advisory until 7 PM EDT this evening for ANZ050-
     051.

&&

$$

Near Term...Mignone


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