Area Forecast Discussion
Issued by NWS Portland, ME-- Highlight Changed Discussion --
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FXUS61 KGYX 251044
Area Forecast Discussion
National Weather Service Gray ME
644 AM EDT THU AUG 25 2016
High pressure will remain anchored well to our south today
allowing for warm southwesterly flow to continue. A few
thunderstorms may move into New Hampshire late this afternoon but
most of the region will remain dry. A cold front will approach
late tonight and Friday with more chances for showers and
thunderstorms during this time. High pressure will return for
Friday night and Saturday with a drier air mass. Showers and
thunderstorms may return early next week as another frontal system
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
-- Changed Discussion --640 AM Update...Little change to the going forecast. Just a few
minor adjustments to sky cover and temperatures based on latest
trends in observational data. Forecast remains on track.
Cirrus associated with a weak short wave trough and some higher-
level warm air advection will allow for mostly cloudy skies for a
portion of the region early this morning. However, this should
move out early and allow for a good amount of sun for the balance
of the morning. Another impulse will then approach from the west
allowing for a return to a fair amount of clouds this afternoon.
Forcing for ascent will be pretty weak this afternoon so most of
the region is expected to be dry. However, a couple of showers or
thunderstorms may move into western zones late in the day. Lapse
rates will be weak as well as the deep layer shear so we are not
expecting severe weather. However, any storms that do move in late
would likely have torrential downpours as precipitable water
values rise to around 1.75 inches and warm cloud depths deepen.
Again, most of the region will likely remain dry however.
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.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/...
Fairly low confidence exists in the PoP/Wx forecast for late
tonight and Friday morning as models differ on strength of forcing
and resulting potential convection. A few of our mesoscale models
as well as global models (ECMWF most robust) indicate that
convection will develop across Upstate NY overnight as a weak
short wave trough provides modest forcing for ascent in an area of
positive theta-e advection. The resultant cluster of showers and
possibly thunderstorms then moves into western NH late tonight or
early Friday morning, then dies out as it tries to push into
Maine. Not completely sold on this as some convective feedback may
be at play there, but can`t completely rule out the scenario put
forth by the 00z ECMWF, RGEM, and to some extent the ARW and NMM.
Have therefore gone with chance PoPs for much of NH late tonight
into early Friday morning to allow for the possibility of showers
and thunderstorms. We wouldn/t expect severe weather with this at
this point, but a frequent lightning and very heavy downpours
would be on the table. Again, this is conditional upon development
in the first place.
PoPs for the remainder on Friday are a little tricky as the
aforementioned short wave trough moves through fairly early and
deep layer westerly flow dries things out. This may leave much of
the region high and dry and quite hot for much of Friday. However,
if the SFC front hangs back long enough, another round of showers
and thunderstorms will be possible on the coastal plain swwd to
southern NH. Another possible scenario is if convection does
indeed develop to our west late tonight and arrives later than
expected, it could potentially continue eastward into Maine during
the morning and early afternoon hours as the atmosphere
destabilizes as heating takes place. Again, confidence is not high
in any one of these scenarios at this time.
.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Expect a drying northwest flow Friday night as high pressure
builds in from Ontario and Quebec. High pressure then crosses into
northern New England on Saturday with cooler temperatures, but
still above normal for late August. The high moves east on Sunday
with a south to southeasterly flow developing. This will keep
temperatures a little bit cooler especially toward the coast.
Meanwhile, a shortwave trough moving through Quebec and toward
northern Maine will set up another frontal passage Sunday night
with showers possible with the front. Models seem to be in a
little better agreement on the timing of this, with the shower
chances ending by Monday morning. High pressure building in from
the west next week will keep conditions dry with temperatures a
few degrees above normal.
.AVIATION /12Z THURSDAY THROUGH MONDAY/...
Short Term...VFR conditions are expected today outside of widely
sct showers and thunderstorms in western NH late this afternoon.
Some stratus and fog may affect the coastal plain late tonight and
early Friday morning as the low levels moisten up. In addition,
there is a low probability of showers and thunderstorms late
tonight and early Friday morning, particularly across NH.
Long Term...Generally expect VFR conditions across the area
through the weekend, though some showers are possible as a cold
front arrives Sunday night which could bring MVFR conditions
especially in northern areas.
Short Term...A small craft advisory has been issued for later this
afternoon and tonight for the ocean waters as winds increase and
seas build. Infrequent marginal SCA conditions may occur in the
bays as well, but lower confidence there. Winds and seas gradually
Long Term...High pressure crosses the Gulf of Maine this weekend
with light winds expected. A cold front will arrive from the
northwest Monday morning, though winds with the front should
remain below advisory levels.
MARINE...Small Craft Advisory from 5 PM this afternoon to 8 AM EDT
Friday for ANZ150-152-154.