Area Forecast Discussion
Issued by NWS Portland, ME

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000
FXUS61 KGYX 240004
AFDGYX

Area Forecast Discussion...UPDATED
National Weather Service Gray ME
704 PM EST Thu Feb 23 2017

.SYNOPSIS...
A weak cold front will try and push south across the area this
evening with a few rain showers in the mountains before
returning north as a warm front by late Friday. A strong cold
front and more widespread showers will move across the region
Saturday night followed by a drier and colder air mass for
Sunday into Monday. A disturbance will approach from the west
late Monday and Monday night.

&&

.NEAR TERM /THROUGH FRIDAY/...
658 PM Update: Forecast generally evolving as planned this
evening...with primary changes being to reduce sky cover through
the first half of the overnight based on evening satellite
imagery...and increase overnight temperatures somewhat based on
evening observations. Expect the overnight to largely remain dry
as weak cold front settles into the region despite robust mid
level lapse rates. HRRR/RAP suggest that llevel westerly flow
may limit fog development initially with a downslope component
developing overnight...but with dewpoints above freezing...and
well above where they were 24 hours ago...will continue patchy
fog mention in the forecast at this time.

Previous Discussion below:
A weak front will try and move through the area this evening
but for the most part it gets washed out. A few light showers
with this front may occur in the mountains but no precipitation
is expected elsewhere. The light southwest flow will diminish
overnight. The problem of the night will be how widespread fog
develops. With light winds and another day of melting snow lower
levels will become increasingly moist. With shallow inversions
setting up overnight due to the warmer air aloft and shallow
cold surfaces due to snow cover its a recipe for some areas of
dense fog. Temps will be very mild tonight and went above
guidance.

&&

.SHORT TERM /FRIDAY NIGHT/...
On Friday and strong push of warmer air with high dewpoints
pushes north as a warm front...this will allow a band of light
stratiform rain or drizzle to spread from south to north. By
later in the day most of the overrunning light rain will be
north of the forecast area, but low clouds will persist. Temps
will be mild once again but not as warm over southern areas due
to widespread clouds.

Friday night Widespread low clouds and fog is expected as a
broad and very warm southerly flow develops with higher
dewpoints and overrides the cooler snow covered surface.
Supersaturation should occur. Also with higher dewpoints over
the cooler ocean waters additional fog/stratus will be advected
to inland areas on the increasing south to southeast flow.
A very mild night expected and min temps may end up warmer than
forecast even though we went above the blended models.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
Extended period begins with a rather robust cold front in place
over central New York state and very warm air advection
occurring over northern New England. Temperatures on Saturday
will average around 20F degrees above normal. By 00z Sunday the
cold front and associated convection will be on our doorstep.
Strong dynamics will likely produce some isolated thunderstorms
as it moves through. QPF amounts could be as high as an inch in
some isolated locations while the majority of the region should
see around a half inch or so. The combination of very warm
temperatures followed by rain will likely get rivers moving and
we have issued a Flood Watch with this package. Please see the
Hydrology segment for more information. Rapidly moving system
pulls off the north and east Sunday morning as much colder air
streams in from the northwest. Although this will bring
temperatures down from Saturday, they will remain 5F to 10F
degrees above normal for most of the next week.

Another system is expected to move out of the mid Atlantic
states Monday night and Tuesday. This system will bring more
precipitation to the area, although confidence with amounts
right now is not strong. It will be another fast moving system
and looks like it will still be developing as it moves across
the Gulf of Maine. Best chance for significant precipitation
will be over southern New Hampshire and extreme southern Maine.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
Short Term...

Summary: A weak cold front will stall as it settles into the
region tonight...before returning north as a warm front on
Friday... yielding deteriorating flying conditions due to low
clouds... fog...and rain showers. Low clouds and some drizzle
are likely to continue through Friday night into Saturday ahead
of an approaching cold front.

Restrictions: VFR attm...but do expect deterioration after
midnight as weakening flow aloft...and elevated dew points over
a snowpack should yield some fog development although confidence
is only moderate. Am also watching stratus over the Gulf of
Maine that will make a run at RKD this evening. Otherwise expect
MVFR/IFR restrictions in showers as warm front lifts north on
Friday with a murky period of MVFR/IFR /and eventually LIFR/ fog-
stratus-drizzle for Friday night/Saturday in southerly flow
ahead of approaching cold front.

Winds: Southwesterly winds less than 10kts will diminish to
light and variable tonight and through the first half of the day
Friday before returning southwest 5-10kts by Friday afternoon.
Flow becomes southeasterly 5-10kts for Friday night and
Saturday.

LLWS: 30-35kt southwesterly winds near 1kft this evening will
produce a period of LLWS through about midnight before
diminishing. Strengthening southerly flow Friday night will
likely yield another period of LLWS.

Long Term...IFR/LIFR conditions Saturday morning should improve
quickly to VFR as temperatures begin to soar. Expect conditions
to drop once again to IFR/LIFR in the evening as a cold front
moves through. The cold front will likely generate some isolated
thunderstorms as well as briefly heavy rain. VFR conditions
return on Sunday as colder air works into the area behind the
cold front.

&&

.MARINE...
Short Term...Southwest flow develops over the waters tonight
allowing winds to briefly approach SCA conditions and seas to
reach 5 feet. Have issued a SCA for these conditions overnight. after
With very warm moist air riding over the cool waters should also
see some developing fog/stratus thru Fri night.

Long Term...Will likely meet SCA conditions Saturday night and
Sunday as winds before and after a fast moving cold front pick
up.

&&

.HYDROLOGY...
A flood watch has been posted for interior portions of Maine and new
Hampshire from 00Z Saturday through 00Z Monday. Temperatures are
soaring into the 50s and lower 60s today and this trend will likely
continue tomorrow and Saturday. Temperatures in the mountains will
be more subdued on Friday with highs there in the lower to mid 40s
but bounce back on Saturday. Light rain will move in Friday as a
warm front moves north producing around 0.25 inches across mostly
central and northern locations. Saturday night the cold front moves
through with another 0.50 to 0.75 possible. The warmth will ripen
and melt the snowpack starting rivers and streams to rise today and
and continuing the rise tomorrow. The rainfall will cause additional
runoff Friday night and Saturday morning. At the current time the
main threat is ice jam flooding. The threat is higher in New
Hampshire where temperatures are warmest and precipitation will be
higher than in Maine.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Flood Watch from Friday evening through Sunday evening for
     MEZ007>009-012>014-020-021.
NH...Flood Watch from Friday evening through Sunday evening for
     NHZ001>009-011-012-015.
MARINE...Small Craft Advisory until 5 AM EST Friday for ANZ150-152-154.

&&

$$

NEAR TERM...Arnott/Marine
SHORT TERM...Marine
LONG TERM...Pohl
AVIATION...Arnott/Pohl
MARINE...Marine/Pohl
HYDROLOGY...Hawley



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