Area Forecast Discussion
Issued by NWS Portland, ME

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FXUS61 KGYX 240747

Area Forecast Discussion
National Weather Service Gray ME
347 AM EDT Mon Jul 24 2017

Low pressure will move up the coast bringing widespread rain to
the area through tonight. Wet conditions and showers will
persist through Tuesday. The unsettled weather slides off to
the east for Wednesday. High pressure will build into the area
with comfortable temperatures and sunny skies.


Expect rain to spread through the region from Southwest to
northeast today as low pressure develops off New Jersey and
tracks through the Gulf of Maine.

At 3am height falls indicated the low beginning to take shape
just off the Jersey Shore. A second broader area of low pressure
over New York state was headed up the St. Lawrence valley.
While many models continue to suggest these two lows will be of
about equal strength I expect the coastal low to dominate and
eventually gain strength at the expense of the northern stream
resulting in a generally southward shift of the heavier
precipitation which is reflected in teh forecast package.

Rain will move into Southwest New hampshire by daybreak. With
dewpoints still in the 40s to low 50s along the Canadian border
expect it to be slow to saturate and it will take until early
afternoon for rain to reach the ground across the entire
forecast area.

While overall this is a rather weak storm compared to the ones
we typically see on this pattern in winter there is some
potential for heavier pockets of rain especially this afternoon
across southern New Hampshire.


By this evening the low center will be well into the Gulf of
Maine with the maine precipitation shield out over the water.
Meanwhile the northern Mountains will begin to see some upslope
continuing showers. Along the coast the forcing for any sort of
steady or heavier rain has passed, but the moist saturated
airmass remains and patchy drizzle along with fog can be
expected overnight.

The damp conditions will remain through the morning on Tuesday.
By tuesday afternoon the upper level low will finally pull east
of the area allowing the surface flow to switch around to the
west and move dryer air and high pressure in on Wednesday.


Upper trof axis swings thru the region early Wed...allowing
things to clear and dry out. Surface ridge axis is forecast to
settle over the forecast area prior to valley fog could
be fairly widespread. Once that should be a sunny and
pleasant day.

Upper ridging is short lived the next s/wv trof
will be approaching from the W early Thu. Timing of the wave is
favorable for diurnally assisted...scattered showers and
thunderstorms. Late in the day global model guidance is being
dominated by Mid MS Valley convection. Models develop a surface
reflection that propagates downstream towards New England. At
this time the CMC and GFS remain S...while the ECMWF is a Nrn
outlier. Given that this is convection...and convection that is
still some 48 hours from developing...I will maintain with the
multi-model consensus and at least let convection develop
tonight before making any large changes to PoP grids.

Once that front pushes thru the region...we will return to a
general pattern of a l/wv trof over the Ern CONUS. This will
keep precip chances more or less confined to the passage of cool
fronts every other day or so.


Short Term /through Tuesday/...While conditions remain VFR for
the moment expect to see a decrease from southwest to northeast
into MVFR in showers this morning. By nightfall the fog and low
stratus will become more widespread resulting in IFR across most
of the region. The IFR fog will be slow to lift on the coast on
Tuesday but elsewhere we`ll see a return to MVFR by daybreak
with the entire region moving towards VFR by Tuesday night.

Long Term...Conditions are expected to improve Wed to VFR as
high pressure builds in. Confidence decreases during the latter
half of Thu into the next chance for precip arrives. A
cold front approaching from the W and a possible convective
complex may bring MVFR or lower conditions to much of the area.
If sufficient moisture can return N behind the departing high
pressure...a period of IFR conditions is possible for coastal


Short Term /through Tuesday/... Increasing easterly flow ahead
of the developing low will result in wind gusts to around 30kt
as a low level jet mixes down over the waters. The prolonged
easterly flow will also result in waves building to around
5-6ft. A small craft advisory has been issued with the strongest
winds and waves expected along the new hampshire coast closest
to the low center.

Long Term...Winds and seas expected to remain below SCA
thresholds thru late in the week. Convectively enhanced low
pressure may try and develop in the Gulf of ME late in the week
and bring a period of SCA conditions to the outer waters.


High astronomical tides tonight may contribute to some
localized minor coastal flooding right around the times of high
tide during the late evening hours. Last night the portland tide
gauge reached 12.1ft. With increasing easterly flow and a
similar tide prediction for tonight have opted to issue another
Coastal flood advisory. High tide at Portland is forecast to be
11.5ft at 12:46am, which combined with the easterly flow and
existing anomaly will likely result in a tide once again just
cresting 12ft. This will cause minor nuisance flooding in
Portland along the wharfs as well as along coastal roads in York
county, and along back coves and low lying areas of New


MARINE...Small Craft Advisory from 11 AM this morning to 2 AM EDT
     Tuesday for ANZ150-152-154.



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