Area Forecast Discussion
Issued by NWS Portland, ME

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FXUS61 KGYX 290722 AAA
AFDGYX

Area Forecast Discussion...UPDATED
National Weather Service Gray ME
322 AM EDT Mon May 29 2017

.SYNOPSIS...
Low pressure centered north of the Great Lakes will push an
occluded front eastward across New england through Tuesday. This
front and an onshore flow will produce cool unsettled weather
with showers from time to time along with areas of drizzle and
fog. Warmer weather returns for the second half of the work
week, but with the chance of showers each day.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
At 06z...a 1000 millibar low was over the upper Great Lakes with
associated warm front through the mid atlantic region and a
trailing cold front through the Mississippi valley. GOES water
vapor showed an upper low vicinity of Lake superior and a
shortwave impulse upstream of the forecast area over the upper
Mississippi valley racing northeastward. NWS Doppler Radar
mosaic showed an area of broken convection stretching from the
eastern Great Lakes through the mid Atlantic region. For
today...the warm front will lift slowly northward into New
England while the shortwave impulse races northeast across the
forecast area this afternoon and evening. The band of showers
will lift northeast and cross the area during the afternoon and
early evening. Otherwise...a mostly cloudy day with onshore flow
contributing some patchy drizzle and fog mainly along the
coastal plain. Today will be chilly by late May standards with
high temperatures limited to the 50s.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
Shower activity will trail off tonight as the weakening
shortwave impulse exits into the maritimes by late evening.
We`re left with the persistent onshore flow with widespread
stratus and fog along with patchy drizzle for the remainder of
the overnight period as the warm front remains hung up to our
south and west. Lows tonight will be in the 40s. On
Tuesday...the occluding frontal system remains to our south and
west with onshore flow continuing. Another weak shortwave
impulse will ride northeast and bring another round of more
widespread showers during the afternoon. Otherwise...mostly
cloudy and cool with some patchy drizzle and fog in the onshore
flow. Highs tomorrow will range from the upper 50s to lower 60s.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Overall the global models are in pretty good agreement with the
continued blocky pattern through Thursday. It is after this
point that the GFS and Euro begin to have very different
solutions for the extended mainly concerning how to deal with
the East Coast closed low. Looking at long term blocking indices
and Hovmoller plots, the blocking pattern should start to break
up around day 10 (6/8).

Around mid week the large cyclone on the east side of the Rex
block which has been affecting our weather will shift east, closer
to central Quebec Province but still to our west. The low takes
on a negative tilt allowing a series of basal short waves to
affect northern New England more directly. With the atmospheric
river in place/rich moisture still being pumped north from the
tropics, this results in several rounds of showers and
thunderstorms this week with at least a couple moderately strong
frontal passages. The mountains will be closest to quasi-
stationary forcing and this combined with orographic effects
will keep clouds and rain showers in the forecast for northern
zones for much of the time.

The rainiest periods look like Wednesday and again Saturday.
There will be chances for more organized convection with thunder
given the strength of the cold pool aloft and especially if the
timing of frontal passages is favorable for peak heating. In
particular Wednesday and perhaps Friday look possible for
thunderstorms.

Overnight lows this week will generally be in the upper 40s to
mid 50s, or slightly above normal. Highs will be in the 60s and
70s with some warmer spots possible over southern and interior
sections in westerly flow and also those times when the sun is
able to break through the clouds.

&&

.AVIATION /07Z MONDAY THROUGH FRIDAY/...
Short Term /through Tuesday/...MVFR in shra with areas of IFR
along the coastal plain in drizzle and fog throughout the period.

Long Term...Rainy conditions with MVFR or lower ceilings and low
visibilities especially overnight and in the morning are
expected Wednesday Friday. Fog may be a concern Thursday
morning.

&&

.MARINE...
Short Term /through Tuesday/...Quiet on the waters with winds
and seas below SCA. However...we will see vsby restrictions on
the water in showers and fog.

Long Term...The next chance of SCA conditions for gusty winds
and increasing seas may occur Friday into Saturday as a strong
cold front crosses the waters.

&&

.TIDES/COASTAL FLOODING...
The astronomical high tide in Portland is 11.1 feet MLLW at
3:08 AM Tuesday. Last night`s tide was about 0.6 feet above
predicted levels. With winds and seas virtually unchanged, we
may be issuing something for tonight`s tide later today as water
conditions may exceed their minimal benchmark levels to produce
isolated minor flooding.

&&

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

&&

$$
SYNOPSIS...Schwibs
NEAR TERM...Schwibs
SHORT TERM...Schwibs
LONG TERM...Hanes
AVIATION...Schwibs
MARINE...Schwibs


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