Area Forecast Discussion
Issued by NWS Portland, ME

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS61 KGYX 150725
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
325 AM EDT Tue Aug 15 2017

.SYNOPSIS...
A cold front will move south out of Canada today triggering
scattered showers and thunderstorms, especially this afternoon.
High pressure builds in Wednesday before another low pressure
system affects the region Friday with the potential for a
period of beneficial rain. Drier conditions develop Saturday
with fair weather continuing into early next week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
A short wave trough will approach from the west today, likely
delivering a bout of scattered showers and thunderstorms this
afternoon. However, before then, WAA ahead of the approaching
trough is allowing for a batch of showers across southern New
England as of 07z. Some of these will move northeastward
affecting southern NH and portions of coastal ME through mid
morning. The HRRR seems to have a decent handle on this, so
blended in a healthy dose of it for the morning hours. In
addition, there will likely be some early morning fog and low
clouds.

For this afternoon, some SBCAPE should develop given moistening
low levels along with breaks of sun. However, it should remain
on the weak side mainly owing to weak mid level lapse rates.
Nevertheless, as the short wave trough approaches, scattered
showers and thunderstorms are expected to develop, with the
greatest coverage expected across northern and central zones.
Moderate deep layer shear should allow for some storm
organization which may allow for a couple of strong to severe
storms, with damaging winds being the main threat. Again,
central and northern zones seem to be the main target as best
forcing for ascent will ride northeastward into that region this
afternoon. However, areas further south may see a few as well.

Took a blend of available guidance for high temperatures today,
which puts most locations in the upper 70s. However, if clouds
and showers linger longer than expected this morning then highs
may end up being a little bit lower than forecast.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/...
Short wave trough pushes off to the east this evening bringing
an end to the threat for thunderstorms early on. A few showers
may linger over the mountains overnight, but most of the region
should be dry. However, some fog may once again develop and
become locally dense, especially where it rains this afternoon.

Cooler and drier for Wednesday as high pressure moves in.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
The end of the week will start off with high pressure overhead
but by the end of the week and upper level blocking pattern
breaks down allowing low pressure to move in from the Great
Lakes by Saturday. The upper level trough remains overhead
through the end of the weekend before long wave ridging finally
returns to the area for the start of the week.

Wednesday night will see high pressure in place overhead with
relatively modest 500mb heights as the strong low which had been
forming the eastern end of the omega block begins to move into
Labrador. With dry conditions throughout the atmosphere this
will be a nice night for radiational cooling and as a result the
low temperatures have been pushed downwards towards the lower
end of guidance. 1000-500 thickness values are forecast to drop
to near 550 dm through the north. The last time we saw similar
values (July 23) low temperatures in the 30s were reported
across interior northern Maine. Dewpoints will be the key factor
in determining the low temperature and have opted to keep lows
in the mid 40s across the north for now.

Moving into the day on Thursday we see brief ridging make an
appearance with sunny skies and a sea breeze. By Thursday night
low pressure developing over the Great Lakes will begin to
approach the area bringing southerly flow and increasing clouds.
The arrival of the rain has shifted later in time when compared
to last nights model runs, however this is consistent with the
climatology of blocks being slow to break down. While there is
now much better agreement amongst deterministic guidance on rain
starting to reach the CT valley by Friday morning I would not
be surprised to see this consensus drift further in time with
rain starting late morning or afternoon. No matter the start
time by Friday night and Saturday look for widespread rain
showers to move into the region. Some of the rain showers could
be heavy at times, due to the high precipitable water values and
southerly flow bringing tropical moisture into the region,
however a bit leery of any of the higher amounts shown in
models as the trend recently has been dry and convection is by
nature hard to pin down.

Most of the rain will move out of the area on Saturday, however
Sunday may again see some showers or even thunder in the
mountains as the upper level trough pulls through.

By Monday high pressure will move in, keeping most areas of
Northern New England under clear to mostly clear skies for the
eclipse. Areas where clouds could become a concern include the
northern mountains where upslope flow and afternoon
destabilization may generate some scattered cumulus and the
midcoast and Penobscot bay where onshore flow could generate
some local stratus along the coast.

&&

.AVIATION /07Z TUESDAY THROUGH SATURDAY/...
Short Term...Low clouds and stratus should lift by early to mid
morning most terminals although some MVFR conditions may linger
through the morning across southern NH and coastal ME. VFR
conditions are expected this afternoon, but a few showers and
thunderstorms will bring briefly lower ceilings and vsbys. VFR
other than some fog overnight. VFR Wednesday.

Long Term... VFR conditions for Wednesday through Friday
morning. Friday will see rain move in from west to east dropping
conditions to MVFR with patches of IFR possible during the day.
Overnight Friday into Saturday look for rain and IFR fog at all
terminals. A return to VFR will happen on Saturday afternoon for
all but the northern mountains where MVFR ceilings will linger.


&&

.MARINE...
Short Term...Conditions are expected to remain below small craft
thresholds through Wednesday.

Long Term... High pressure builds over the waters Wednesday and
Thursday before a low pressure system and cold front brings rain
across the region on Friday night. Winds and seas will increase
modestly with this system but should remain below small craft
criteria. High pressure builds in for the end of the weekend.


&&

.EQUIPMENT...
The weather radar at Gray (GYX) is up and running as of early
this Tuesday morning and should be available for this
afternoon`s showers and thunderstorms. However, techs are still
testing the new parts so it still could go down from time to
time today.

During any outages, radar coverage is available from adjacent
radar sites including Burlington-Vermont (KCXX), Taunton-
Massachusetts (KBOX), and Hodgdon-Maine (KCBW).

Also, the radar at Albany (KENX) suffered a failure that has
been attributed to azimuthal motor/gear issues. It is expected
to be down for several days. See FTMENX for updates.

&&

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

&&

$$

NEAR TERM...Ekster
SHORT TERM...Ekster
LONG TERM...Curtis


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.