977
FXUS61 KGYX 292244
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
644 PM EDT Mon Apr 29 2024

.SYNOPSIS...
Cool winds off the Atlantic will develop for Tuesday and Wednesday
with a few showers and temperatures below normal as the calendar
changes from April to May.  Shower chances continue for later this
week with temperatures slowly climbing.  An early look at the coming
weekend shows seasonable temperatures with a shower or two
possible.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
640 PM Update...Little change to the going forecast at this
time. Mostly thin clouds will continue to advect in this
evening. Have increased Pops across far western zones for late
tonight as several new CAMs have a few bands of WAA-induced
showers moving in or forming over western NH. Not out of the
question there could be a rumble of thunder with these, mainly
after 4 am.

Previously...

High Impact Weather Potential: Minimal.

Pattern: Longwave ridge axis to the west of New England this
afternoon with surface high pressure centered well to our north
towards Hudson Bay and northwest flow aloft continuing over our area
with a wedge of dry air centered towards northern Maine with PWATs
increasing to the south and west reaching over 1" as you move into
southern New England and much of New York state.  Within the
moisture gradient overhead...a weakening band of showers has moved
from northwest to southeast across the area bringing with it a
few hundredths of an inch of rainfall.

Through this Evening: This band of showers will continue to
weaken as it exits the region to the south and east. This
will allow for a dry evening across the area with temperatures
ranging from the low 50s in the mountains to around 60 to the
south under a mix of sun and clouds.

Tonight: A quiet night is expected with building mid level heights
and surface ridge axis overhead.  With the surface warm front well
to our south and west...any forcing for ascent/shower activity
should remain well west of the area with skies becoming partly
cloudy with overnight lows largely tied to the degree of cloud
cover...warmest /near 50/ over southwestern NH where there will
be more clouds... with lower/mid 30s over the western Maine
mountains where clearer skies will allow for more radiational
cooling.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
High Impact Weather Potential: Minimal.

Pattern: Longwave ridge axis flattens as it moves east and overhead
through daybreak Tuesday. Warm front/moisture gradient mentioned
above will push it/s way towards northern New England through this
period east of low pressure that will track north of the western
Great Lakes through the day. Weak waves of low pressure along the
warm front to our west pass southwest of the region through Tuesday
night...but warm/moist advection over the quasi-stationary frontal
boundary will bring shower chances by later Tuesday through Tuesday
night which will form the focus for this forecast period along with
cool temperature potential on Tuesday.

Tuesday: Moisture gradient / warm front aloft will be overhead as H5
ridge axis pushes in from the west. Given the mid level ridge
placement...deep forcing for ascent will not be plentiful during the
day...but in the llevels...a westerly LLJ will continue to impinge
on the sloped frontal boundary which could allow showers/sprinkle
development through the day.  Otherwise...there will be a good deal
of cloudiness with weak onshore flow suggesting a very cool day with
mesoscale guidance insisting some spots will struggle to hit 50.
Continued to trend the forecast in this cooler direction.

Tuesday Night:  There is modest mesoscale model/ensemble agreement
that convection will develop across upstate New York Tuesday
afternoon and evening given instability southwest of surface warm
front and weak forcing from ascent given llevel convergence around
wave of low pressure and a shortwave north of that region.  This
convection will weaken as it pushes east in the mid level flow...
becoming removed from surface-based instability. Still...expect
shower activity to increase in coverage and pass through the region
during the overnight and will move PoPs in the the high likely
category in line with the guidance consensus.

Ensemble based QPF probabilities suggest a wetting rain /0.10"/ is
likely for all of NH and into far western ME before probabilities
diminish as you work north and east deeper into the cooler/drier
air. Rainfall in all areas is expected to remain below 0.5"
with no hydro concerns.

Temperatures will be cool with the rain and onshore flow...falling
into the lower 40s with some fog possible given the abundant
boundary layer moisture.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
The 500 mb pattern through the long term period will be
characterized by troughing through the Rockies and Plains with
ridging across the eastern third of the US and troughing near
Atlantic Canada. A system moving through the ridge will be exiting
the East Coast Wednesday morning with the ridge trying to rebuild
into New England Wednesday night. A disturbance tracking over the
ridge will bring chances for showers Thursday. The ridge will
rebuild to the west of New England Friday while surface high
pressure builds in from the north. This ridge axis will then slowly
slide east over the weekend suggesting a warming trend, although the
presence of troughing near Atlantic Canada makes for low confidence
in temperatures through the end of the period.

The 12Z model suite suggests that precipitation associated with a
poorly organized system exiting the East Coast will end by Wednesday
morning. Weak troughing and moisture will linger south of New
England leading to skies remaining mostly cloudy. Steady east to
southeast winds combined with limited sunshine will keep highs in
the 50s with the warmest locations along the CT Valley where highs
approach 60 degrees. Heights start to build over the Ohio Valley
Wednesday night into Thursday while a disturbances tracks over the
ridge into New England Thursday afternoon. There is a fair amount
spread amongst ensembles regarding this feature with the likely
cause being that it originates from convection that is expected
across the Plains tomorrow. Have stuck close to the NBM for
PoPs which brings 20-30 percent chances for showers across the
area.

In the wake of Thursday`s system global models are in decent
agreement in a ridge axis building to the west of New England with
an upper low developing near Atlantic Canada. Beneath the ridge
temperatures will climb above normal while the presence of the upper
low threatens the invasion of cool maritime air. Ensembles show
a large spread in temperatures Friday through the weekend with
the overall pattern suggesting a warming trend as the ridge axis
migrates east into New England. The incoming ridge favors
mostly dry conditions Friday into Saturday while moisture
advecting northward through the Ohio Valley will introduce
chances for showers to close out the forecast period.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
Short Term...

Summary: A warm front south and west of the area will spawn a few
showers through Tuesday with little in the way of impacts before a
more widespread area of shower activity brings deteriorating
conditions Tuesday night.

Restrictions: VFR across the terminals early this afternoon with a
few light showers/sprinkles impacting LEB-CON and possibly MHT-PSM
before they end.  VFR through tonight with gradually deteriorating
conditions on Tuesday with MVFR cigs developing at LEB/HIE and
slowly spreading north and east. A few showers are possible
during the day Tuesday. Tuesday night...more widespread rain
showers are expected across the terminals bringing a period of
IFR CIGS and MVFR VSBYS throughout the terminals.

Winds: Northwesterly winds /except ESE seabreeze at PSM/ continue
into this evening with light/variable winds expected for the
overnight.  Southeast winds 5-10kts are expected for the day on
Tuesday...becoming light and variable again Tuesday night.

LLWS: No LLWS is expected through Tuesday night.

Long Term...MVFR cigs Wednesday morning will lift resulting in VFR by
Wednesday afternoon. Chances for -SHRA increase Thursday
bringing the potential for a period of MVFR conditions late
Thursday into Thursday night with a return to VFR Friday into
Saturday.

&&

.MARINE...
Short Term...With high pressure ridge axis centered over the
waters through the short term forecast period...winds and waves
are expected to remain below SCA levels through the period.

Long Term...Winds and seas remain below SCA thresholds Wednesday
through Saturday.

&&

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

&&

$$

SYNOPSIS...Arnott
NEAR TERM...Arnott/Ekster
SHORT TERM...Arnott
LONG TERM...Schroeter
AVIATION...Arnott/Schroeter
MARINE...Arnott/Schroeter