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Area Forecast Discussion (AFD)

Issued by Caribou, ME (CAR)

FXUS61 KCAR 221113

Area Forecast Discussion
National Weather Service Caribou ME
713 AM EDT Thu Aug 22 2019

A cold front will cross the area today. The cold front will 
exit across the Gulf of Maine tonight into Friday. High 
pressure will build across the region Saturday through Tuesday. 
A frontal system will approach the region later Wednesday.


711 AM Update...

Fog and drizzle have set up per the latest obs and satl
analysis. The RAP soundings confirm this w/the llvl moisture
tucked under an inversion. The fog and drizzle is expected to
lift/burn off later this morning w/the northern areas being the
last to clear out. Adjusted the hrly temps and wx element to
keep the fog/drizzle. Rest of the forecast looks on track.

Previous Discussion...
Sctd tstms may contain strong wind gusts this afternoon into 
the early evening.

The latest radar trends showed batch of showers across the
eastern areas pushing into New Brunswick. Another batch of
showers and sctd tstms in Quebec were moving to ene. The latest
HRRR showed this activity weakening as it runs into a more
stable airmass currently in place across the region. Low clouds
and fog around this morning looks to hold in through at least
mid morning, before starting to lift and break out. The latest
RAP and HRRR show the warm front lifting to the n by late
morning w/the central and southern sections breaking into the
warm sector w/some heating. This will help to allow for
destabilization as sfc winds veer to the SW. Further n, airmass
will take some time to destabilize. Temps are expected to rise
quickly into the low/mid 80s. 

A blend of the NAM/RAP and HRRR shows a pre-frontal trof out 
ahead of the cold front moving across the region by the 
afternoon. This feature will be the focus for tstms to develop 
across the n and w and the migrate se during the afternoon into 
the evening. The areas to focus on for any organized tstm 
development will be from the Houlton- Millinocket region down 
into Hancock and Washington County. CAPE potential, especially 
MUCAPE is forecast to be in the range of 800-1200 joules. 
0-3/0-6km shear 30+ kts w/a strong upper jet moving across the 
area this afternoon. Lapse Rates in the llvls do steepen to > 
8.0 c/km in the aforementioned areas along w/mid level lapse 
rates hitting near 6.5 c/km. This should be enough to aid in 
convective development sufficient updrafts. Given the lack of 
sufficient moisture through 700 mbs, thinking is that any near 
severe tstms will be isold. The main threat will be strong wind 
gusts and this wording has been added to the forecast. SPC has 
this region in a Marginal Risk for severe tstms. 

The activity will wind down after 9 PM w/the cold front sliding
across the region. Drier and cooler air will start filtering
into the region w/winds shifting to the WNW. Decided to hold off
on mention of fog as the blyr will stayed mixed. Overnight temps
will be some 5 to 10 degrees cooler than readings attm this


The cold upper trough and building surface high from Canada will
be the dominant features. Temperatures in this regime will be
cooler than normal with low humidity as dew points fall into the
40s in northern zones. Expect a decent amount of cumulus clouds
on Friday. Can't rule out some fairly low topped
around 600mb...on Friday afternoon, but will only paint PoPs in
northern Aroostook and the North Woods at this time. The upper
level trough axis crosses Friday night into Saturday morning.
Will increase cloud cover during this period...mostly in
northern zones...but not include PoPs. Can't rule out a few
sprinkles. On Saturday, the upper trough will generate more
cloud cover than Friday with a slight chance of some sprinkles
along the eastern border. For Saturday night, the cold air mass
will be fully in place with clear skies and light winds. Lows in
the upper 30s to lower 40s are expected in northern zones and
frost is not totally out of question. Further south towards
Bangor, lows won't be a chilly with upper 40s to lower 50s
anticipated. Patchy river/lake fog will occur later in the


This period is currently expected to feature fair weather under
a building blocking ridge. As the block evolves into a Rex
block, there is some question as to where the closed upper low
migrating under the block will end up, but will not include any
significant PoPs now. Development of an inverted trough towards
the coast would be the worst case scenario.  Temperatures will 
slowly recover towards normal readings by Tuesday or Wednesday. 
Nights will continue to be on the chilly side Sunday and Monday 
nights with this dry Canadian air mass. The block breaks down 
later Wednesday into Thursday. A warm occlusion will eventually 
cross the area by Thursday.


NEAR TERM: IFR/LIFR this morning w/stratus and fog across the
air fields. Conditions will improve to VFR for KBGR and KBHB
by mid-late morning. The northern terminals will take a bit more
time to improve to VFR til early afternoon. This will limit the
tstm threat north of KPQI. South of KPQI, tstms may contain 
strong wind gusts to 40+ kts. Winds will be from the SW at 10 
kts or so. 

VFR all terminals tonight w/some patchy fog this evening which 
could bring VSBYS down to MVFR briefly. Any fog should clear out
w/winds shifting to the WNW. 

Thursday night...chance of IFR along the coast in the
evening...otherwise VFR


Friday night into Saturday morning...MVFR cigs tempo IFR cigs
north of HUL...otherwise VFR

Saturday afternoon into Monday...VFR outside of patchy shallow
fog around sunrise


NEAR TERM: S winds to turn to the SW this afternoon w/speeds of
10 kts or so. Dense fog will burn off by early afternoon as the
winds increase. There is a risk of a tstm or two into early
evening. Winds will turn to the W tonight as the cold front
moves into the waters. Seas of 2 ft will build to 3 ft w/the
outer zones possibly reaching 4 ft. Local wave model was used
for the winds 

SHORT TERM: Fog will depart the waters Thursday night and
probably not return through the rest of the period. Winds will
pick up Saturday night with some gusts to 20 kts, but no
advisory is expected. A low pressure system may be forming over
the Atlantic south of the Gulf of Maine Monday into Tuesday. The
evolution and track of this system remains very uncertain, but
has potential to cause elevated winds and seas.





Near Term...Hewitt
Short Term...MCW
Long Term...MCW