Area Forecast Discussion
Issued by NWS Portland, ME

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FXUS61 KGYX 250427

Area Forecast Discussion
National Weather Service Gray ME
1227 AM EDT WED MAY 25 2016

Low pressure surface and aloft will exit into the Canadian
Maritimes overnight. Warmer weather will return on Wednesday
ahead of a cold front. The cold front will bring clouds and a few
showers and thunderstorms to the area Wednesday afternoon and
evening. A ridge of high pressure will build over the area
Wednesday night and will hold over the region on Thursday as a
warm front approaches from the west. The warm front will stall
over the region Thursday night and Friday and will finally push
east of the region on Saturday. A cold front will cross the region
Saturday night followed by high pressure and dry air to round out
the holiday weekend.



1222 AM...minor ESTF update to reflect radar and satellite trends
and to ingest the 04z mesonet into near term grids.

1050pm update: Have refined cloud cover based on good fog product
imagery late this evening...helping to define the western edge of
the lower cloud cover over western NH. We continue to have a few
flare-ups of showers /and rumbles of thunder/ and have adjusted
the forecast as these graze my northwestern border. Noting that
K1V4 /St. Johnsbury, VT/ is fogging in at this hour with LEB
hinting at the same...feel good about /at least/ patchy fog
development west of the primary cloud shield overnight. Temps on
track with only minor adjustments here.

855pm update: Minor updates this hour to increase cloud
cover...and continue PoPs for a few hours along the NH/VT border
west of HIE. Temperatures remain in good shape. Noting gradually
decreasing visibilities along the coast...with evening webcams
corroborating current fog/drizzle area in the forecast well.

507pm update: Have updated this hour to clear out PoPs to the
east of exiting band of showers, with anything to the east of this
taking the form of drizzle. Have seen some improvement in sky
cover from recent visible satellite imagery and have also tried to
capture this trend heading through the evening hours. Temperatures
are generally on track.

Previous Discussion Below...
Upper level trough over Cape Cod continues to slowly migrate off
to the north and east. Band of precipitation extends from northern
Coos county in New Hampshire south and west across southern
Vermont. Instability under the trough will be just enough to keep
a mention of showers in the forecast overnight.

Onshore flow along the coast has been producing a very low cloud
deck along with fog and drizzle. Those conditions should persist
until the winds turn around to the west later tonight. Once the
winds switch then the drizzle should come to an end.
will likely take sunshine tomorrow morning before the fog


Upper level trough will finally pull away from the area tomorrow
and tomorrow night... leaving a more progressive and zonal upper
air pattern in place. A weak frontal boundary tries to nudge south
out of Canada and into the mountains of New Hampshire and western
Maine tomorrow afternoon. This feature may generate enough
instability to get some scattered thunderstorms going...but they
should be relatively weak and unorganized.


Warm weather continues Thursday as high pressure builds in
further at the surface and aloft. Temperatures should warm
quickly in a relatively dry airmass with some clouds remaining
over the higher terrain and mostly sunny skies across the coastal
plain. A warm front approaches from the SW during the late
evening hours...but it will take a while for the atmospheric
column to saturate so not expecting anything but sprinkles and
scattered showers over NH early on.

By the early morning hours Friday we should see more coverage over
NH and western Maine. The warm front will lift across
northern sections providing a focus for showers and thunderstorms
along the boundary with decent instability for areas far enough
away from the onshore flow.

PW values during the Friday to Saturday time frame jump from 1.4
inches areawide Friday to around 1.7 inches along the coast
Saturday as a cold front crosses the region. The cold front will
trigger more widespread convection with another chance at
thunderstorms Saturday.

The cool air regime continues with more air moving in from
the Canadian maritimes through early next week. In the upper
levels of the atmosphere we will shift to NW flow keeping skies
cloudy and a few showers around as weak impulses move SE. High
pressure builds in from eastern Canada Sunday with slightly
cooler temperatures as cool, dry air filters in. Likewise Monday
morning will be a little cool with temperatures primarily in the
40s. Preliminary guidance indicates ridging building in again by
midweek with increasing temperatures.


Short Term...

Summary: Low pressure nearly overhead this evening will lift north
and east through Wednesday with a cold front nearing the region from
the north and west Wednesday evening.

Restrictions: Conditions are widely varying at the terminals this
evening with IFR/LIFR along the coastal sites...with better
conditions as one moves inland.  Coastal locations will likely
deteriorate some overnight with thickening fog and some drizzle
anchoring VLIFR/IFR conditions at these locations.  Inland...with
ample low level moisture and light winds...any clearing will allow
fog to develop with local VLIFR/IFR at sites such as LEB and HIE as
well. Conditions will improve dramatically to VFR during the morning
hours Wednesday...with the last to see improvement likely being AUG
and RKD.  A shower/thunderstorm may approach HIE towards the very
end of the valid TAF period...but coverage is not expected to be
great enough to warrant mention in the TAFs at this range.

Winds: Light winds /less than 10kts/ cyclonically rotating around
low pressure just south of the region /mostly east and northeasterly
at the terminals/ will continue through tonight before becoming
increasingly westerly 5-10kts for the day on Wednesday.

LLWS: No threats this cycle.

Thunder: With shower activity pulling west of the evening...expect
little to no threat of thunder overnight through Wednesday morning.
Isolated/scattered showers and thunderstorms will likely past just
north and east of the terminals Wednesday evening...with low
probabilities of activity reaching HIE before 00z Thursday.

Long Term...VFR conditions Thursday with rain showers developing
across NH and northwestern Maine Friday. MVFR or IFR conditions
are most likely across KHIE and KLEB. TSRA is possible. On
Saturday more widespread showers and thunderstorms are possible
with MVFR or IFR conditions possible at all terminals through the


Short Term...No flags expected.

Long Term...Winds and seas will remain on the calm end of the
spectrum Thursday through next Tuesday. The pressure gradient will
increase Friday afternoon causing a few gusts to 20 kts.


Thursday will be one of the only dry days of the week. RH values
may hover near 30% but winds will be light. We are forecasting all
areas to receive rainfall this week albeit light.




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