Area Forecast Discussion
Issued by NWS Portland, ME

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FXUS61 KGYX 161512
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
1112 AM EDT Mon Apr 16 2018

.SYNOPSIS...
Mixed precipitation, mainly in the form of freezing rain, rain,
and sleet will persist through at least this morning before
transitioning to rain this afternoon. As the system moves
through New England today, strong gusty winds are expected to
develop as well, especially on the coast as well as the western
slopes of the White Mountains. A broad area of weakening low
pressure will persist over the region Tuesday and will shift
east on Wednesday. Another area of low pressure will approach
from the west Wednesday night and will move east through the
region on Thursday. Low pressure will slowly shift east into the
maritimes for the remainder of the period.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Update...Adjusted winter wx advisories based on latest temp
trends.

The struggle is real...but we are finally seeing
ASOS/AWOS locations climb above freezing. Across the interior
however...typically favored cold air damming locations are stuck
at or below 32. That will continue the freezing rain threat into
the afternoon...as there is little mechanism for warming besides
weak diurnal heating and latent heat of freezing. I will be
trimming remaining winter wx advisories as temps climb above
freezing.

Otherwise...developing LLJ will ride up and over that cold dome
thru this afternoon. Strong isentropic lift will support fairly
widespread heavy rainfall. QPF still looking at around 2 inches
for much of the area...so localized poor drainage flooding is
possible...along with rivers rising mainly to action stage.

Previously...

Rare mid-April freezing rain event ongoing across much of the
forecast area this early Monday morning as overrunning continues
above an anomalous SFC cold wedge. So far, most roads are just
wet, but the combination of freezing rain and sleet continues to
cause slippery travel where road surfaces are a bit colder (like
bridges, overpasses, and portions of roadways that do not get
much sunlight during the day). Therefore, the winter weather
advisory continues until 15z today for most zones. However, we
have cancelled the advisory for coastal zones as temperatures
have warmed to above freezing.

Temperatures are expected to gradually climb today as the low
level cold air erodes from the western, eastern, and southern
edges. Therefore, we expect a transition to plain rain as the
morning progresses. This is a good thing, as the heaviest
rainfall is not expected to arrive until early afternoon at most
locations. Until then, expect slippery spots to persist. In
addition, widely scattered power outages will be possible
through early to mid morning as freezing rain accumulates on
trees and power lines.

Forcing for ascent and PWAT values maximize this afternoon just
ahead of eastward-advancing SFC low pressure. Heavy rain is
expected to be the result this afternoon into the evening hours
which could cause mainly minor flooding. In addition to the
maximum in forcing, this afternoon and early evening should
feature the strongest portion of the southeasterly LLJ. Based on
forecast soundings and model ensemble data, have expanded the
wind advisory to all of the Maine coast. Will also keep the
advisory up for western NH...but keep in mind this is mainly for
favorable downslope locations on easterly flow.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
Low pressure pulls away tonight with heaviest rainfall and
strongest winds ending this evening. The exception is for far
eastern zones where the heaviest precip and strongest winds will
linger into the overnight hours. Better weather is in the cards
for Tuesday, but plenty of clouds are expected with upper level
low pressure overhead.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Closed upper low will continue to meander over northern New
England Tuesday night and Wednesday. Expect mostly cloudy
skies through the period with scattered rain and snow showers.
Lows Tuesday night will be fairly uniform across the region in
the lower to mid 30s. Highs on Wednesday will range through the
40s north and lower to mid 50s south.

Upper low will drift off to the northeast Wednesday night as
another one moves in from the west. After partial clearing
during the evening expect increasing clouds in southwest zones
after midnight and a chance of rain or snow showers toward
daybreak. Lows overnight will range from the upper 20s to mid
30s.

Fairly weak area of low pressure will move east through the
region on Thursday bringing occasional rain showers through
the day and into Thursday evening. Highs on Thursday will
range through the 40s to near 50 in the south. Surface low
will continue east into the maritimes Thursday night.
Persistent cyclonic flow will keep skies mostly cloudy with
snow or rain showers likely in the north and scattered showers
in the south. Lows will again bottom out in the upper 20s to
mid 30s.

Upper low will remain parked over the area on Friday producing
mostly cloudy skies and scattered showers. Highs will once again
range through the 40s to near 50. Persistent upper trough will
keep skies mostly cloudy Friday night and Saturday with just a
slight chance of showers in northern zones. Lows will range from
the mid 20s to mid 30s and highs on Saturday will range from
the mid 40s north to the mid 50s south.

Cyclonic flow will gradually weaken Saturday night and surface
high will build in from the west on Sunday. Looking for
diminishing clouds through the period with highs finally
getting back to normal with readings in the upper 40s to upper
50s.

&&

.AVIATION /15Z MONDAY THROUGH FRIDAY/...
Short Term...IFR/LIFR ceilings/vsby today through tonight. VFR
Tuesday through Wednesday with areas of MVFR ceilings. MVFR/IFR
ceilings developing THursday...persisting through Thursday
night. VFR with areas of MVFR ceilings Friday.

&&

.MARINE...
Short Term...Winds gradually increase today...with gale force
gusts expected. Winds become more SEly late today...with some
gusts approaching 45 kts outside the bays. LLJ crosses the
waters tonight...with winds becoming Wly behind the cold front
and decreasing.

Long Term...
No issues expected Tuesday night through Friday.

&&

.HYDROLOGY...
A very moist air mass will continue to surge northward ahead of
a strong low pressure system in the Great Lakes today. The
heaviest precip is expected this afternoon and evening. A large
area of 1.5 to 2 inches QPF is expected...especially along and
southeast of the higher terrain. The question is mainly how much
snow melt we get in the headwaters...as temps are forecast to
remain near freezing for most of those areas. Ensemble river
guidance does forecast a couple locations in NH going above
flood...but not widespread enough threat for a flood watch at
this time. More likely there could be ponding of water in poor
drainage areas as well as river flows near flood.

&&

.TIDES/COASTAL FLOODING...
Beach erosion and splash over still possible for high tides
today and tonight...although more likely tonight. Current storm
surge forecasts keep tide gauges below flood stage today. With
E flow likely creating a storm surge up to or around 1 ft...this
could yield some minor flooding across the Seacoast of
NH...possibly into York Co tonight.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Winter Weather Advisory until 5 PM EDT this afternoon for
     MEZ007>009-012>014-020>022.
     Wind Advisory until 2 AM EDT Tuesday for MEZ023>028.
NH...Winter Weather Advisory until 5 PM EDT this afternoon for
     NHZ004.
     Winter Weather Advisory until 2 PM EDT this afternoon for
     NHZ001>003.
     Wind Advisory until 8 PM EDT this evening for NHZ001>003-005-
     007-011.
MARINE...Gale Warning until midnight EDT tonight for ANZ150>154.

&&

$$

NEAR TERM...Legro



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