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Area Forecast Discussion (AFD)

Issued by Caribou, ME (CAR)

FXUS61 KCAR 201057

Area Forecast Discussion
National Weather Service Caribou ME
657 AM EDT Tue Aug 20 2019

A cold front will push offshore early this morning. High 
pressure will build in from the west today and slide south of 
the region tonight. Low pressure will approach on Wednesday and 
track to our north Wednesday night.


7 AM Update...Both early morning visible satellite imagery and
observations indicate fog has dissipated across the area so did
a quick update to remove fog from the forecast. The rest of the
day will be sunny and dry. 

The cold front which brought some showers on Monday will be 
moving off the coast early this morning. High pressure 
approaching from the west will push cooler and drier air into 
the region today as dew points lower under a mostly sunny sky. 
High pressure will slide south of the region tonight with the 
sky remaining mostly clear. The drier air will allow 
temperatures to drop into the mid 50s across most areas. Our 
focus on Wednesday turns to a trough of low pressure approaching
from the west, supported by a strong upper trough sliding into 
Quebec. This will bring a southerly breeze, increasing clouds, 
and some low clouds lifting back into the area. A shower or 
thunderstorm may stray into western areas late on Wednesday 
supported by some low to mid level instability, light shear and 
some surface convergence ahead of the approaching trough.


Higher dewpoints will return Wednesday night into Thursday and
then cooler air is headed into the region by Thursday into

A warm front is expected to lift n across the region Wednesday
night bringing the higher dewpoints along w/showers and tstms.
There is a consensus among the NAM, GFS and ECMWF that the best
jet dynamics, high theta e and nose of waa reside across the
eastern sections of Maine. LLJ of 35 kts coinciding w/strong WAA
should be enough to get tstms going. PWs increase to 1.5 inches 
w/MUCAPE of 700-1200 joules. The 00z GFS and NAM showed the 
Maine Central Highlands, the Penobscot Valley into the Downeast 
to have the best potential for organized convection w/some of 
the storms possibly reaching near severe given the good 0-6km 
shear. The ECMWF favors more to the east showing the potential 
for heavy rainfall w/the llj and nose of warm air. The Canadian 
GEM showed heavy rainfall potential along the Downeast to the 
coast. Therefore, decided to ramp on precip chances(60%) 
playing for a more concentrated area across the Bangor region 
to the east. Used a blend for the QPF showing the potential for
heavy rainfall in the aforementioned area. Attm, decided to hold
off on enhanced wording since this is period 4. Attention needs
to be given to the potential for some storms to have possibly 
strong wind gusts and very heavy rainfall. Mdl soundings do 
support this as well. The daycrew can assess this further w/the
new model guidance. 

For Thursday, the activity winds down during the morning
w/leftover showers/drizzle and some fog. The ECMWF hangs on to 
more clouds into late morning while the GFS breaks things out.
The latest run of the ECWMF does hint at the potential for some
breaks, but it is short lived. Attm, decided to stay the course
as the daycrew played it, by keeping showers/tstms by late 
morning into the afternoon w/the pre-frontal trof ahead of the 
cold front. The is strong jet dynamics and llvl warming allowing
for destabilization. Confidence is low on severe potential due
to the drying in the mid and upper levels helping to squelch 
storm strengthening. Plus, lapse rates do not look steep enough 
to support organized updrafts. The cold front is slated to pass
through the region w/colder and drier air. Temps will really
start dropping back by the early Friday morning. Friday will be
a breezy day as the GFS and ECMWF support a llj of 35 kts out of
the NW. It will be much cooler. Heating in the llvls and cooling
aloft will allow for clouds and w/the upper trof over the
region, showers are expected mainly across the northern and
western areas. Daytime temps on Friday are forecast to be below


A chilly night Friday night w/overnight temps dropping back into
the 40s and low 50s. Saturday will see some clouds and chilly as
the upper trof will still have some influence on the region. 
There is a risk for some showers during the day. Improvement
looks to be on the way for Sunday as the upper trof passes to
the east and high pres builds in from the west. High pres is
forecast to remain into Monday w/temps showing a rebound closer
to normal readings.


NEAR TERM: Some patchy fog may be around early this morning.
Otherwise, the sky is expected to be mostly clear today and
tonight with VFR conditions. VFR conditions may lower to MVFR
and possibly IFR Wednesday afternoon as lower clouds spread
north across the area. Winds will be light today and tonight
then increase from the south on Wednesday. 

SHORT TERM: MVFR to IFR Wednesday night for all terminals
w/showers and tstms. Fog could hinder operations as well
lowering vsbys.

Thursday...IFR in the morning w/an improvement to VFR by mid to
late morning. There is a risk for tstms w/the cold front apchg.
This could bring conditions down briefly to MVFR. S winds 10 
kts will veer to the SW.

Thursday night through Saturday...VFR w/periods of MVFR,
especially across the northern terminals both Friday and
Saturday. WNW winds 10-15 kt w/some higher gusts.


NEAR TERM: Winds and seas are expected to be below SCA through
Wednesday. Some fog may limit visibility early this morning and
again late Wednesday afternoon. 

SHORT TERM: No headlines expected. S winds 10-15 kts Wed night 
w/tstms and fog. Winds will veer to the SW on Thursday w/a risk 
of a tstm. Cold front slides across the waters Thu night w/WNW 
winds 10-15 KTS. WNW winds to continue into Friday. Seas will 
gradually build to 4 ft by Thu and hold into Fri.





Near Term...Bloomer
Short Term...Hewitt
Long Term...Hewitt