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Area Forecast Discussion (AFD)

Issued by Caribou, ME (CAR)

FXUS61 KCAR 170751

Area Forecast Discussion
National Weather Service Caribou ME
351 AM EDT Sat Aug 17 2019

Surface high pressure will remain over the region into Monday while
multiple upper level disturbances move across the state this weekend.
A weak cold front will move through late Monday followed by weak
high pressure for Tuesday. A stronger cold front is expected 
late Wednesday night and Thursday.


Broad cyclonic flow aloft will advect two shortwave troughs over
the state today, which will bring scattered showers and maybe a
few isolated thunderstorms. At the surface the flow will be out
of the south as a surface ridge remains centered just to the
east over Halifax. This is allowing for a persistent southerly
push moving a higher dewpoint airmass in the low 60s over the
cold Gulf of Maine waters. The end result is a persistent marine
layer push through the next 24 hours bringing with it low
stratus and fog to Downeast and the Penobscot Valley. Overall
this will lead to a cool gloomy day for most of the area. There
could be some breaks in the clouds across the north, but there
will also be more showers across Northern Maine this morning as
the first shortwave trough moves through. Small break in shower
activity is possible midday today before a stronger 500mb vort
max approaches from New York this evening. This could bring a
better chance for showers again tonight across the entire region
and even a few elevated thunderstorms could be possible with
MUCAPE values just high enough. The HRRR is already hinting at
this possibility, so added the mention of isolated thunder 
later tonight in the forecast. Overall not the best Saturday, 
especially if you are on the coast. 


The short and long terms will be dominated by a progressive 
WSW flow alf pattern with fqt s/wv systems.

Sun begins with exiting shwrs in the morn, with ptly sunny 
skies advcg ewrd from QB prov durg the aftn, reach the NB border
latest. Sun eve will begin fair, then clds will increase late 
at ngt as a s/wv trof from the great lks apchs. Shwrs and enough
CAPE for aftn/eve tstms is xpctd msly across the N hlf of the 
FA as the s/wv crosses the Rgn. Behind this system, a brief 
surge of slightly drier air is xpctd for Tue, with albeit warm 
aftn hi temps.


Tue ngt will begin fair, with increasing clds late and a chc of
shwrs alg the coast by erly Wed morn as more humid air begins 
to return. The rest of the Rgn will see ptly clds skies Wed morn
then mcldy skies Wed aftn/eve with shwrs likely alg with sct
tstms. Shwrs will linger across the FA late Wed ngt and perhaps
even into Thu across the FA with longer range models uncertain
about the arrival and passage of a cold front thru the FA durg
this tm. All long rang models agree that the cold front 
completely clears SE of the FA by Thu ngt, allowing for sig
cooler and much drier air to enter the FA from Cntrl Can. 


NEAR TERM: Variable weather conditions sums up the aviation
forecast over the next 24 hours with a deep marine layer push
expected to impact KBHB/KBGR through tonight with low IFR 
conditions. Ceilings could increase a bit this afternoon to IFR 
conditions before dropping again tonight. Further north 
expecting MVFR conditions today at the Aroostook County TAF 
sites before dropping tonight as lower ceilings are expected to 
push in. Scattered rain showers are also expected along with 
light southerly winds. 

SHORT TERM: Mainly VFR and light winds all TAF sites xcpt brief
MVFR/IFR in tstms and heavier shwrs Mon aftn/eve and Wed
aftn/eve and patchy ngt fog Sun ngt, Mon ngt, and Wed ngt. 


NEAR TERM: Seas and winds will remain below SCA conditions with
a persistent light southerly breeze moving a humid airmass over
the cold waters. This will keep low stratus and areas of fog
over the coastal waters through Saturday night. Winds will
generally remain in the 5 to 8kt range as a weak surface high
remains to the east of the region, waves will generally be in
the 2 to 3 foot range. 

SHORT TERM: No marine hdlns for these ptns of the fcst with
marine fog likely Sun ngt thru Mon ngt and again late Tue ngt 
thru Wed ngt. Went with about 80 to 90 percent of WW3 wv
guidance for fcst wv hts for outer MZs and a blend of WW3/NWPS
for near shore waters. Spectral wv components consist of a short
srly wind fetch nwrd propagating 5 to 7 sec wv group and a NW
propagating background swell wv group of arnd 10 sec. 





Near Term...Dumont
Short Term...VJN
Long Term...VJN