Area Forecast Discussion
Issued by NWS Portland, ME

Home | Current Version | Previous Version | Text Only | 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 261448
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
1048 AM EDT Fri May 26 2017

.SYNOPSIS...
Low pressure is developing in the Gulf of Maine this morning...bringing
an area of heavy rainfall and some thunderstorms to New Hampshire
and western Maine. Low pressure will continue northeast into the
maritimes through tonight. Weak high pressure will build over the
area on Saturday and will shift offshore on Sunday...but at least
allow for a window of dry weather. The next system over the eastern
Great Lakes will lift north into Quebec Sunday night and will drag
a front toward the region on Monday. That front will slowly cross
the area late Monday night and Tuesday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
940 am Update: The center of the low/mid level center of low
pressure, show nicely on Satellite loops, now to the north of
Cape Cod moving slowly northeast and will exit through the Gulf
of Maine late today and into the Maritimes tonight. The heavy
rains in the broad cyclonic flow have exited the region but
bands of light rain and some drizzle will continue to rotate
through the rest of the morning and into the afternoon. Thus, will
keep forecast as is. Temps will only move up a few degs today
and remain in the 50s as forecast.

Update...No major changes to the current forecast based on
latest observational trends.

LLJ is starting to back as low pressure squeezes under
New England. This is slowing its progression and as a result I
have updated and raised PoP thru mid morning across much of the
forecast area. Deformation precip and precip associated with the
low center will also gradually move Nwd into parts of SW
NH...but that should slowly weaken thru the morning as best
forcing for ascent moves E. I have also upped QPF amounts to
better match latest observations and reports.

Previous discussion...Well developed warm conveyor belt is
moving up the New England coast this morning. A strong Ely LLJ
is helping to force an area of heavy rain and embedded
thunderstorms. The instability is elevated...so I have not seen
much in the way of wind with the storms...but some cloud to
ground strikes have been noted in addition to the in cloud
flashes. That elevated instability really tapers off to the
N...so thunder is only in the grids for another hour or so. PoP
may need to be delayed in exiting in future updates...as the low
pressure slips under New England and the warm conveyor begins
to stall its Nwd movement. It is looking like a fairly
widespread 1 to 2 inches of rain...with locally higher amounts

Once the LLJ forced precip does finally lift N...the area will
be left under the upper low. This will continue showery weather
into the afternoon...with only gradually decreasing PoP
expected. I also dropped high temps...as little sunshine and
lingering precip should help keep us much cooler than normal.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...
We remain in cyclonic flow on the backside of departing s/wv
trof tonight. That should keep clouds around...though
downsloping off the mtns may help to lift those a little bit
towards the coast. Significant height rises are not forecast
until Sun...so much of the day Sat could be leftover low level
moisture and slowly scattering cloud cover. There is no real
forcing for showers...but there is also no real forcing to move
clouds out quickly. That should keep temps on the cool side of
normal.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
The deterministic models are in decent agreement on the longwave
pattern through late next week. We begin the period with a weak
shortwave ridge traversing the area. This ridge is quickly kicked
offshore by Monday in response to a deepening upper trough over
the Great Lakes. The upper trough axis will shift gradually
eastward and remain across the northeast CONUS through the end of
next week. Temperatures this period should average below normal as
troughing will dominate across New england. In the dailies...a
weak ridge of high pressure will cross the area on Sunday before
retreating offshore. Low pressure centered north of the Great
Lakes will push a slow-moving occluded front across the region
Monday and Tuesday with onshore flow and the advancing baroclinic
zone providing a damp start to the new work week. Behind this
frontal system...the unsettled weather will continue as an upper
trough remains across the northeast and a series of weak cold
fronts or surface troughs cross the area.

&&

.AVIATION /15Z FRIDAY THROUGH TUESDAY/...
Short Term...IFR/LIFR conditions mainly near the coast this
morning...as low pressure moves thru the Gulf of ME. There
should be very slow improvement today with daytime heating...but
feel that at least MVFR CIGs linger thru the day. Drier air
moving in Sat should allow for VFR CIGs finally. For the next
couple of hours LLWS is a possibility at RKD...as strong LLJ
moves NE up the coast. TSRA will also be possible at
PWM...AUG...and RKD as the jet lifts NE. TSRA are generally
lasting about an hour with the heaviest RA.

Long Term...

Mon - Tue...MVFR in shra with lcl IFR in fog and drizzle.

&&

.MARINE...
Short Term...SCA conditions will continue thru the afternoon.
Winds will diminish early today...with seas taking longer to
drop below 5 ft outside of the bays.

Long Term...

Mon - Tue...Conditions could approach Small Craft outside the
bays.

&&

.TIDES/COASTAL FLOODING...
Have issued a Coastal flood statement for isolated minor
flooding along the coast near the time of high tide shortly
after noon today. The storm surge is currently running 1.3 feet
above which will allow the high tide to approach 12 feet.
Combined higher seas in the exposed coastal areas may cause some
splashover.

For tonight...The astronomical tide in Portland is 12.0 feet
mllw just after midnight tonight. Winds should be offshore by
that time...however the high water condition may require a
coastal flood statement or maybe even an advisory for a couple
hours around the high tide.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...Small Craft Advisory until 8 PM EDT this evening for
     ANZ150>154.

&&

$$

NEAR TERM...Marine
SHORT TERM...Marine
LONG TERM...Cempa



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