Area Forecast Discussion
Issued by NWS Portland, ME

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FXUS61 KGYX 241329 AAC
AFDGYX

Area Forecast Discussion...UPDATED
National Weather Service Gray ME
929 AM EDT Wed May 24 2017

.SYNOPSIS...
High pressure over the region will shift east today. Low
pressure over the Ohio Valley will slowly lift northeast
tonight through Thursday and will reach the vicinity of Cape Cod
by Friday morning. Low pressure will continue northeast into the
maritimes Friday through Friday night. Weak high pressure will
build over the region on Saturday. Low pressure will approach
from the west on Sunday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
920 AM Update...
Minor changes were made to the forecast for temperatures, dew
points, and sky cover. Rain associated with low pressure
offshore will stay out of NH and ME outside of a few sprinkles
with high pressure providing subsidence over the region. A weak
sea breeze is expected to form later this afternoon along the
coast.


11z update...
Quick update to to adjust temp/td grids. Cirrus shield
associated with low pressure passing offshore will gradually
shift east this morning leaving a scattered to broken mid level
deck in its wake for most of the day. Radar indicating some
light echoes across southern New Hampshire but this is not
reaching the ground and expect any showers to remain south of
the forecast area today. No other changes planned attm.


Previous discussion...
Weak high pressure will hold over the region today as low
pressure passes well offshore. Much of the day will feature
variable high and mid level cloudiness along with filtered sun.
A weak sea breeze this afternoon will cap temps in coastal zones
in the mid to upper 60s. Farther inland highs will top out in
the lower to mid 70s.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/...
High pressure will build in from the northeast overnight.
NAM suggesting some ocean stratus developing in increasing
onshore flow but other models not showing this moisture getting
into the region until Thursday so at this point just looking for
variable to partly cloudy skies. Lows will range from the mid
40s north to the lower 50s south.

Clouds will be on the increase on Thursday as a warm front over
the mid Atlantic coast lifts northward. Will see an increasing
chance of showers in southern zones as over-running shifts
northward. Expect QPF to be light and spotty during the day.
Highs in coastal and southern zones will only reach the upper
50s to near 60. Farther north...highs will top out in the lower
to mid 60s.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
On Thu the upper low will round the base of the trof and move
into the OH Valley. Models are in good agreement that the
occlusion will run out ahead of it and towards the forecast area
overnight. It will be battling the departing high pressure...so
precip should mainly hold off until after 00z Fri. The trailing
s/wv trof will help to redevelop low pressure at the triple
point...in the Gulf of ME early Fri. This will likely be the
period of heaviest precip for NH and Wrn ME. 06z thru about 18z
should be pretty wet...with the dry slot working in after that
time. PWAT values should be pushing 200 percent of normal...so
rainfall may be heavy at times Fri. Expect generally 1 to 2
inches of rain before it is all said and done. Also of note are
the high astronomical tides starting Thu night. With tides right
around 12 ft...any amount of surge will likely lead to minor
flooding. And Thu night especially should see the best overlap
of high water levels and onshore flow. Coastal flood headlines
may be necessary for this time period.

S/wv ridging moves in for Sat and tries to hold thru Sun. The
next trof drops in out of Canada to close out the holiday
weekend. The unofficial start of summer does not look very
summery...as another occlusion looks to push thru late Sun or
early Mon. The follow up wave looks delayed this time...so model
forecasts are not suggesting any sort of coastal redevelopment.
However with trofing remaining in place over the Ern
CONUS...unsettled wx will linger...with any sunshine tending to
lead to afternoon clouds and showers.

&&

.AVIATION /13Z WEDNESDAY THROUGH SUNDAY/...
Short Term...VFR today through tonight. IFR/LIFR ceilings
developing on Thursday in the south. Areas of MVFR ceilings in
the north.

Long Term...Areas of IFR conditions or lower will persist in RA
and onshore flow Fri. There may be pockets of higher CIGs...like
at HIE...where downsloping off the mtns may help a little.
Significant improvement likely will not occur until Sat...when
low pressure begins to pull away. Weak ridging Sat into Sun will
allow for VFR conditions to return.

&&

.MARINE...
Short Term...SCAs will likely be needed on Thursday.

Long Term...SCA conditions will continue into Fri as a coastal
storm strengthens in the Gulf of ME. Low pressure will not pull
away until Sat...so winds and seas will only gradually diminish
into the weekend.

&&

.TIDES/COASTAL FLOODING...
Astronomically high tides begin tonight with an 11.5 ft peak
forecast overnight. With increasing onshore flow may see some
minor splash-over but will let the day shift make the decision
on any statements or warnings. Coastal flooding still more
likely with higher tides Thursday and Friday nights.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...None.

&&

$$

NEAR TERM...Hanes
SHORT TERM...Legro
LONG TERM...Sinsabaugh



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