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Area Forecast Discussion (AFD)

Issued by Caribou, ME (CAR)

                            
000
FXUS61 KCAR 241016
AFDCAR

Area Forecast Discussion
National Weather Service Caribou ME
616 AM EDT Mon Jun 24 2019

.SYNOPSIS...
High pressure will build toward the region from the west and
will settle into the area tonight. The high will move east of
the area Tuesday. A series of frontal boundaries and
disturbances will cross the area Tuesday night through Friday.

&&

.NEAR TERM /THROUGH TONIGHT/...
6:15 am update: Satellite pictures and web cams show a sunny
start to the day.  A cool start with a low of 31F early this
morning at Estcourt Station. Updated with the past few hours of
observed data, and made only some very minor tweaks based on 
the latest observations and expected forecast trends.

Previous discussion:
The area will remain in northwest flow aloft today between an 
upper low in the eastern Maritimes and an upper ridge building 
across western Quebec. Model soundings show steep low level 
lapse rates up to around 800H. The surface pressure gradient 
weakens during the day. Expect that with full sunshine and good 
mixing that the wind picks up for a time this morning into early
this afternoon before diminishing later in the day. It will not
be nearly as windy as it was over the weekend, but some wind 
gusts of up to 25 mph are expected for a time today. The air 
mass is on the cool side for late June with 925H temps around 
+12-14C, and expect highs to top out near 70 degrees in the 
Saint John Valley to the mid 70s in the Greater Bangor Region 
and upper Penobscot Valley. The upper ridge axis builds toward 
the western Maine/Quebec border late tonight as weak surface 
ridge settles over the area late in the evening and begins to 
slowly shift east overnight. The combination of a clear sky, a 
dry air mass, and calm wind in the valleys will allow the 
normally colder northwest valleys to drop in the l/m 30s, with 
40s for most of the remainder of FA. Did lower the temps in the 
normally colder nw valleys and have added in some patchy frost. 
The patchy frost is not expected in the more agricultural areas 
and mainly the very rural valleys, so will hold off on a frost 
advisory.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
Our prolonged active weather pattern will begin later on Tuesday
as a weak 500mb shortwave trough swings through the state.
Showers will hold off for most of the day timing wise with
chances increasing later in the afternoon for Central Maine and
not until late evening further east along the New Brunswick 
border. Onshore flow will develop with a marine layer expected 
to push into Downeast Maine. Model soundings aren't supporting 
any surface based CAPE at this point with very weak upper level
instability, so thunder threat is very low at this point. 
Warmest temperatures on Tuesday will be across the Crown of 
Maine with the least amount of clouds, cooler along the coast 
with the onshore flow developing. On shore flow continues with 
broad cyclonic flow aloft over the state Tuesday night through 
Wednesday. Looks like a prolonged marine layer push with coastal
fog development likely Tuesday night through Wednesday. Should 
be a mostly cloudy day for all areas with low stratus clouds 
most likely hanging on for most of the area. Could have some 
breaks across the higher terrain of the Central Highlands and 
Northwoods Wednesday afternoon. This could lead to some showers 
and even a few isolated thunderstorms across this area, with 
Downeast remaining dry. It will be cool with below normal 
temperatures expected.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
Active weather period expected through the extended forecast
with a progressive upper level cyclonic flow pattern across the
Northeast. Virtually every day from Thursday through Sunday 
currently has the chance for daily showers and isolated 
thunderstorms. This period could have the potential for above 
average precipitation with slightly below normal temperatures. 
It will be difficult to time the numerous shortwave troughs for 
this period, but currently Thursday and Saturday afternoons look
like the best chance for convection. Thursday will most likely 
have the best shear dynamics, with lower atmospheric shear 
possible Friday into the weekend depending exactly where the 
upper level low develops. One thing that looks to have higher 
confidence is the cool pool aloft allowing for daytime 
instability. As of now next weekend isn't looking the best with 
upper level low progged to be centered over the state among most
ensemble mean guidance. Still time for this to change though.

&&

.AVIATION /10Z MONDAY THROUGH FRIDAY/...
NEAR TERM: VFR through 12Z Tuesday morning.  A NW wind will gust to 
20-25 knots this morning and into early afternoon before beginning 
to diminish. 

SHORT TERM: VFR conditons expected Tuesday morning with ceilings
lowering through the day as a weak system approaches from New
Hampshire. Shower activity will begin to impact KBHB/KBGR
Tuesday afternoon, with showers reaching the Northern Maine TAF
sites by the evening. Marine layer will push in Tuesday night
and Wednesday with LIFR conditions possible for KBHB and KBGR,
conditions could be better further north. Showery activity is
expected both Thursday and Friday afternoon, with a slight
chance for thunder at this point.

&&

.MARINE...
NEAR TERM: The wind and seas will remain well below small craft 
advisory levels through tonight as high pressure builds over the 
waters. 

SHORT TERM: Seas will remain below SCA conditions for this
period with waves generally remaining in the 2 to 3 feet range.
South winds expected on Tuesday as a weak frontal boundary
crosses the coastal waters Tuesday night. Southerly winds will
allow for the development of fog Tuesday night into Wednesday.
Very light winds by Wednesday afternoon with generally westerly
winds expected by Thursday with the chance for showers later
Thursday evening as another weak frontal boundary travels across
the coastal waters.

&&

.CAR WATCHES/WARNINGS/ADVISORIES...
ME...None.
MARINE...None.

&&

$$

Near Term...CB
Short Term...Dumont
Long Term...Dumont
Aviation...CB/Dumont
Marine...CB/Dumont