Area Forecast Discussion
Issued by NWS Portland, ME

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000
FXUS61 KGYX 251440
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
1040 AM EDT Wed Apr 25 2018

.SYNOPSIS...
Low pressure moves north into the area today allowing rain to
overspread the area from the southwest in the morning and work
northeast by afternoon. A good soaking rain is expected for most
of the region. This system will slowly exit the region
Thursday. A cold front Saturday evening will allow cooler air to
push back into New England. A warming trend is expected early
next week however.

&&

.NEAR TERM /UNTIL 10 PM THIS EVENING/...
1030 AM...Fine tuning pops a little bit into this afternoon
based on current trends, and meso models. The HRRR seems to hit
a on abit of a convective cluster moving across SE NH and the
ME coastal plain between 22Z and 04Z, so hit this period with
the mention of heavy rain. I left thunder out, but would not be
surprised for a few rumbles near the coast at this time as well.


645AM UPDATE...
Rain now moving into southwest New Hampshire. Have updated the
forecast to adjust the timing of rain arrival as well as adjust
morning temperatures.

ORIGINAL DISCUSSION...
First batch of rain already trying to move into the area from
the southwest. Expect top-down moistening of the air mass as
this moves in, with likely some evaporational cooling into the
40s as rain begins. Rain becomes steadier and more widespread as
the day goes on and low pressure approaches from the southwest.
High temperatures today will not be that far from current
temperatures, except perhaps northeastern areas which could warm
up a bit this morning before rain arrives. Went below most
guidance on highs today, more in line with higher resolution
guidance due to the onshore flow from the cold Gulf of Maine as
well as evaporationally cooled low level inversion expected.

&&

.SHORT TERM /10 PM THIS EVENING THROUGH 6 PM THURSDAY/...
Axis  of steadier rain shifts east across the area tonight,
moving into eastern Maine on Thursday. With increasing moisture
levels and limited cooling we could see fog developing as well.
When it`s all said and done, most areas on the coastal plain and
into the eastern foothills will see about an inch of rainfall.
Worth noting that there is a fairly broad range in model
forecast rainfall amounts, with the NAM generally being dry
(maybe a half inch?) and the Canadian and GFS being the wettest
(1.5 inches?). Current forecast is a bit of a blend, with some
emphasis on terrain-enhanced areas as well as higher amounts
along the immediate coastline.

As steady precipitation moves east on Thursday, expect more
showers to develop under the cold core upper low moving in from
the west during the day Thursday. So although the steady rain
ends, more showery weather continues. With better mixing
expected on Thursday, temperatures make another run at 60, with
southern areas most likely to top this threshold while northern
areas stay cloudier and may not reach it.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
The extended forecast looks progressive with a large cutoff low
centered near Nunavut offering continued chances for
precipitation this weekend and into next week. Several spokes of
energy cycle through the Northeastern CONUS the next several
days. Friday evening surface low pressure will develop over the
east coast and move northeast. Models are not in agreement with
the location of the dominant surface low, but a warm front
should arrive sometime Friday evening with a cold front
following for Saturday evening. This will produce widespread
rain showers across the region.

Friday and Saturday will be relatively warm with upper 50s to
mid 60s in southerly flow ahead of the system. Increasing clouds
and precipitation will cool things off with 850mb temperatures
dropping about 10 degrees by Sunday morning. Highs at the
surface will struggle into the mid 40s over the mountains and
foothills, with mid 50s elsewhere. This is not overly cool for
this time of year, but after warmer weather recently, it will
feel more than a couple degrees below normal.

A warming trend looks on tap for next week with modified high
pressure pushing up from the south and skirting fast moving flow
to our north. This looks like a good stretch of precipitation
free weather...except for the mountains which may see just
enough short wave energy to produce partly cloudy skies and
showers.

&&

.AVIATION /15Z WEDNESDAY THROUGH SUNDAY/...
Short Term...Expect deteriorating conditions from southwest to
northeast today, with conditions becoming IFR by evening in
rain. Could stay MVFR on the other side of the mountains up in
Whitefield. There is the potential for fog to develop this
evening into tonight which would cause further reduction in
visibility, possibly as low as 1/4 mile. Conditions improve
fairly rapidly Thursday morning from west to east, with
scattered showers moving in from the west especially during the
afternoon.

Long Term...Prevailing VFR is expected Thursday night through
Friday morning, but conditions may deteriorate to MVFR or IFR at
times late Friday into Saturday in rain showers. Lingering
-SHRA/-SHSN are possible for KHIE and KLEB Saturday night into
Sunday with other sites VFR. Gusty NW winds are forecast for
Sunday afternoon and evening.

&&

.MARINE...
Short Term...Increasing onshore southeast flow expected today
and tonight, likely topping out at about 30 KT. Prolonged
southeast fetch will also increase the wave heights to over 5
FT, and as high as 10 FT in the central Gulf of Maine waters
near Matinicus. Winds shift to the west and decrease on
Thursday, though it will take a little while for seas to
subside.

Long Term...Waves may increase in southerly flow Saturday. Winds
and seas also approach SCA conditions in west flow behind a
cold front Saturday night into Sunday.

&&

.HYDROLOGY...
There is still a good amount of snow left especially in the
higher terrain. Warm temperatures yesterday brought rises to
many of the headwater gages. Expect continued snow melt to
combine with about an inch of rainfall to bring further rises to
all rivers, but especially the headwaters that drain eastward
out of the mountains toward the Atlantic. These are the areas
most likely to see minor flooding, and some locations are
currently forecast by the RFC to reach minor flooding. Because
of this, we have issued a Flood Watch covering the most likely
impacted areas, including the upper Saco River as well as
tributaries of the Androscoggin River. Flooding cannot be ruled
out on the upper Pemigewasset River as well as along the
Kennebec.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Flood Watch from 8 PM EDT this evening through Thursday
     afternoon for MEZ007>009-012>014-021.
NH...Flood Watch from 8 PM EDT this evening through Thursday
     afternoon for NHZ001>006.
MARINE...Small Craft Advisory from 5 PM this afternoon to 8 PM EDT
     Thursday for ANZ150-152-154.

&&

$$
SYNOPSIS...
NEAR TERM...Cempa/Kimble
SHORT TERM...Kimble
LONG TERM...Hanes
AVIATION...
MARINE...
HYDROLOGY...


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