Area Forecast Discussion
Issued by NWS Portland, ME
FXUS61 KGYX 301322
Area Forecast Discussion
National Weather Service Gray ME
922 AM EDT Sun Apr 30 2017
High pressure will crest over the region today before shifting
offshore. A warm front will remain south of the region tonight
and Monday and will be followed by an occluded front Monday
night. A trough of low pressure will approach from the west on
Tuesday and will slowly cross the region on Wednesday. High
pressure will gradually build in from the west Wednesday night
and will shift offshore on Thursday as low pressure approaches
from the southwest. Low pressure will slowly move up the east
coast Thursday night through Friday.
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
9am update... have increased Pops for this afternoon across the
north as the slug of precip currently over Cornwall Ontario
moves east towards our area. A few more convective showers to
the south of this main warm frontal band may also move through
southern portions of the region.
615 AM Update...Little change to the going
forecast. Based on near term mesoscale models, will maintain
change to low likely pops across southern NH midday.
High pressure at the sfc will continue to build into our region
this morning before shifting offshore late in the day. This high
will deliver much cooler temperatures today. WAA aloft will
quickly get started late this morning and early afternoon and
will result in an increase in clouds. Light rain should begin to
break out across northernmost zones this afternoon and WAA
forcing for ascent increases. Further south, it should be mostly
dry today, although we did include some chance pops across
southernmost NH midday/early afternoon as the HRRR continues to
develop showers over Upstate NY which then move eastward,
possibly affecting southernmost NH early this afternoon.
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...
Forcing for ascent increases tonight across our northernmost
zones - mainly Coos County into the western ME mountains. This
is where a band of rain - locally heavy - will likely set up
later tonight. This band could drop up to an inch of rain
tonight through Monday morning before shifting northward. The
air mass in the western ME mountains may actually be cold enough
so that some light icing occurs tonight between 1 and 3 kft as
seen on NAM BUFKIT profiles.
For the rest of the region to the south of the mountains, we
expect mainly dry weather although some drizzle is likely to
develop later tonight as easterly flow moistens.
The same story can be told for Monday - with an even colder day
in store except perhaps the CT River Valley. Cool high pressure
ridging from the northeast will remain entrenched Monday as WAA
continues overhead. This will mean cool, cloudy, and drizzly
conditions for most of the area east of the mountains with
highs in the 40s and 50s. In the CT River Valley, temps will
likely warm as downsloping occurs...possibly into the 60s.
.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
Warm front will continue to slowly lift northward
Monday night and will be quickly followed by an occlusion
forecast to shift into western zones by Tuesday morning. Moist
onshore flow will keep low clouds and drizzle going for much of
the night before showers and possibly a few thunderstorms
associated with the occlusion push in from the west after
midnight. Increasing southwest flow will push low level moisture
eastward by Tuesday morning. Lows overnight will range through
the 40s to near 50 degrees.
Upper low and trapped surface reflection will
gradually push in from the west on Tuesday. First
half of the day not looking too bad with a mix of sun and
clouds. Expect clouds and showers to edge into northwestern
zones during the afternoon. Highs will top out above
normal...generally ranging through the 60s to near 70.
Upper low will continue to press in from the west
Tuesday night and Wednesday keeping clouds and showers in the
forecast through the period. Lows Tuesday night will range
through the 40s and highs Wednesday in the 50s north and lower
to mid 60s south.
Upper low will gradually lift off to the northeast
Wednesday night as surface high pressure builds in from the
west. Expect clouds and a few stray showers to give way to
partial clearing in the north and clearing skies downwind of the
mountains after midnight. Lows will range through the 30s to
Weak ridging will edge in from the west on Thursday
as low pressure approaches from the southwest. After a partly
to mostly sunny morning high clouds will push into southern
zones during the afternoon. Highs will range from the mid 50s
north to mid 60s south.
Low pressure moving in from the southwest will bring
rain back into the region Thursday night and Friday.
Good tropical connection will bring plenty of moisture
along with this system and both the ECMWF and GFS in fairly goo
agreement in placing axis of heaviest precip across southern
New England into the Gulf of Maine. This would keep flooding
threat low for the area but this situation will have to be
monitored closely through the week in the event models shift
this rainfall axis farther north.
Models diverge for the weekend with the new GFS spinning up
another area of low pressure over the mid Atlantic states and
slowly moving this system up the coast bringing more rain to the
area. 12z ECMWF not showing this so forecast confidence rather
low for the weekend.
.AVIATION /13Z SUNDAY THROUGH THURSDAY/...
Short Term...VFR conditions are expected today. Conditions are
expected to deteriorate to MVFR tonight followed by IFR or lower
during the day on Monday in low clouds and drizzle.
Long Term...IFR/LIFR ceilings Monday night...improving to VFR
Tuesday. Areas of MVFR ceilings in the mountains Tuesday night
through Wednesday. VFR Wednesday night through Thursday.
Short Term...SCA for the ocean waters until 12z this morning for
gusts around 25 kt. Otherwise, sub-sca conditions expected today
SCA`s likely Monday night into Tuesday.
Cooler conditions are expected today with light winds expected
by late morning. Things moisten up substantially tonight and
Monday with low clouds and drizzle expected - especially Monday.
Rainfall of around an inch is possible across northern NH and
the western ME mountains late tonight and early Monday.