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Area Forecast Discussion (AFD)

Issued by Caribou, ME (CAR)

                            
000
FXUS61 KCAR 232132
AFDCAR

Area Forecast Discussion
National Weather Service Caribou ME
532 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/...
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 /21Z 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...MCW
Short Term...Norcross
Long Term...Norcross
Aviation...MCW/Norcross
Marine...MCW/Norcross
Hydrology...Hewitt/Norcross