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000
FXUS61 KGYX 092309
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
709 PM EDT Tue Apr 9 2024

.SYNOPSIS...
Increasingly unsettled weather returns for the back half of the
week with showers on Wednesday escalating to rounds of
widespread rainfall Thursday through Friday as low pressure and
an associated cold front cross the region. The system will bring
about gusty, potentially strong winds on Friday as well.
Scattered showers are then expected through the weekend.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
7 PM Update...No changes needed to the forecast at this time
other than two adjust temperatures downward initially as onshore
flow has been significantly cooling.

Previously...

High level moisture will increase during the overnight hours
tonight as a warm front approaches from the west. Atmospheric
soundings remain very dry, so any light precipitation that
attempts to approach the forecast area will not survive the
trip. Very low dew points will allow for a large diurnal range
from the mild readings of today. Min temperatures will drop into
the lower to mid 30s in most areas by morning.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
A warm front continues to move eastward across the region on
Wednesday. This will bring plenty of clouds along with
precipitation in the form of showers to northern portions of the
forecast area during the morning. The rain showers will
gradually move towards the coast during the day with time
despite a ridge located over eastern New England aloft. It will
still remain relatively seasonable for this time of the year,
but not as warm as Tuesday. Afternoon highs will reach it into
the 40s with lower to mid 50s over southern New Hampshire.
Reading may be warmer in the Granite State if breaks in the
cloud cover occur.

Scattered showers will continue Wednesday night as a moist
southeasterly flow continues off the Gulf of Maine. The
additional moisture will allow for at least patchy fog at a
minimum which is supported by the latest HREF solution. Patchy
drizzle may be possible as well, especially as we head towards
Thursday morning as a weak disturbance exits the region. It
looks to be relatively mild with overnight lows in the 30s and
40s.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Overview: A dreary end of the week in the forecast as rain
chances increase Thursday, with additional wind and potentially
heavy rain Friday. See Hydrology section for information about
flood potential. Warm temperatures remain in the region into
next week, with active weather pattern remaining.

Details: The main focus of long term is looking at the next wet
and windy weather maker late this week. This will bring some
hydro concerns to the foreground, which are outlined in the
Hydrology section.

The pattern will be one we are familiar with over the past
year, but fine details will vary. Current guidance suggest a
slow ramp up in precipitation before the main flush of heavy
rain Friday. Typically these lead to hydro issues both on rivers
and flash flooding, but in addition antecedent surface
conditions will be saturated with ripe snow from the past week.
This is well apparent in NASA LIS relative soil moisture, and
NOHRSC modeled snow temperatures.

SW flow will be underway at the surface Thursday morning, with
upper/mid level ridging just cresting and moving east through
the afternoon. This will result in deeper moisture advection
beginning with only a few breaks through Friday night. PWAT
values climb over an inch for much of this period. Low level
moisture will be present for the duration, with mid and upper
level moisture fluctuating. This will result in periods of rain
up to Friday morning and afternoon. In between, light rain is
expected. The most susceptible area for greatest QPF looks to be
the SE and E facing slopes of higher terrain where orographic
lift should prolong and enhance rain rates. This isn’t in a good
spot considering up to 6” of SWE locked up in melt-able
snowpack currently. Not all of this may come out, but winds,
rain, and dewpoints are expected to drive a good portion.

Main forcing arrives Friday as elongated front pushes through
the area. This will bring gusty to strong winds to the immediate
coast, but weak inversion inland should spare some of the
stronger gusts from these locations. Will need to keep an eye on
this component, especially as it can modify snowmelt. This will
also drive increased temperatures and dewpoints into the
region, with highs climbing into the 60s for southern NH and
upper 50s for Maine.

Will see periods of light precipitation into the weekend, but
the main flush will have occurred Friday. Unfortunately,
temperatures remain warm enough for runoff to continue vs.
freezing temps slowing this down. Another quick moving system
approaches towards the beginning of next week, but focus will
remain on the late week system at this time.

&&

.AVIATION /23Z TUESDAY THROUGH SUNDAY/...
Short Term...VFR conditions in all areas with an increase in
high level moisture during the overnight hours. VFR conditions
continue into Wednesday before ceilings lower further Wednesday
night, with showers and patchy fog. IFR conditions and possibly
LIFR can be expected. Patchy drizzle remains possible as well.

Long Term...IFR to LIFR ceilings likely amid moist low levels
Thursday and Friday. Vis will also be restricted in fog and rain
across the area. Can`t rule out some breaks, but these will
become more apparent in the near term. Cigs improve into the
weekend, but some local area may still be MVFR/IFR. LLWS may be
a factor considering a temperature inversion across much of the
area Thursday night through Friday.

&&

.MARINE...
Short Term...Winds and seas will remain below SCA thresholds
tonight. On Wednesday, a southeasterly gradient increases in the
afternoon. There could be a few gusts near 25 kt along the
outer waters, however confidence levels for raising flags per
coordination with our neighbors is not high at this time. Fog
may be reducing visibilities over the waters Wednesday night.

Long Term...Winds will increase to Gale and high end Gale
Thursday into Friday. This will result in wave heights
increasing as well. Waves to 10ft are currently forecast, but
higher will be possible considering some east coast fetch. Winds
trend to SCA Friday night into Saturday morning.

&&

.HYDROLOGY...
Confidence is increasing in the potential for new and renewed
river flooding Thu-Fri across the region. A storm system will
bring warm, humid, and breezy conditions to produce snow
ripening/melt, and then periods of moderate to heavy rainfall.
Rainfall totals of 1-2" are expected, with amounts up to 2.5"
across the mountains. This will all occur over a ripened
snowpack, adding a snowmelt component. Windy conditions,
particularly in the higher terrain, will combine with the warm
dew dewpoints to exasperate the snowmelt which could reach 3"
SWE loss in 48 hours.

Antecedent conditions ahead of this event are saturated due to
repeated rounds of rainfall over the past month, and this
additional rainfall and snowmelt will likely eliminate any
remaining infiltration capacity, causing immediate runoff
directly into streams and rivers and generating small stream and
river flooding. The culmination of vulnerable antecedent
conditions, the atmospheric setup, snowmelt, elevate the risk
for flooding. At this time the conditions favor minor river
flooding with the potential for isolated significant flooding,
particularly in the mountain regions.

Outside of the snow covered areas, locally heavy rainfall may
elicit poor drainage and nuisance flooding in urban areas,
especially if heavier rainfall totals were to materialize.

&&

.TIDES/COASTAL FLOODING...
The highest astronomical tide of the month will occur tonight
around midnight. A modest southeasterly flow over the coastal
waters may allow a few locations from Portland and points south
through the NH Seacoast to reach flood stage tonight. Minor
flooding is likely.

Otherwise, astronomical tides reach their monthly maximum this
week with forecast tidal stages reaching action stage with each
cycle. Late night/early morning cycles are the higher of the two
cycles, and have potential to touch flood stage through late
Friday. Surge should increase, even if just subtly as high
pressure settles south of Nova Scotia and sets up an onshore
flow through mid-week. A storm surge is then possible on Friday,
however timing of this surge will be critical in determining
what if any impacts occur as astronomical tides will start to
trend downward at that point.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Coastal Flood Advisory from 11 PM this evening to 2 AM EDT
     Wednesday for MEZ023-024.
NH...Coastal Flood Advisory from 11 PM this evening to 2 AM EDT
     Wednesday for NHZ014.
MARINE...None.

&&

$$


NEAR TERM...Ekster
SHORT TERM...Cannon
LONG TERM...Cornwell