Area Forecast Discussion
Issued by NWS Portland, ME

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FXUS61 KGYX 230217 AAD
AFDGYX

Area Forecast Discussion...UPDATED
National Weather Service Gray ME
917 PM EST Wed Feb 22 2017

.SYNOPSIS...
Low pressure moving east through southern Canada will allow a
mild southwesterly flow to continue tonight through Thursday.
Highs will climb into the 50s to near 60 across New
Hampshire...with 40s to lower 50s over western Maine. A weak
cold front will try and push south across the area Thursday
night with a few rain showers 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.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
915 PM Update: Have continued to lower temperatures for most
locations based on evening trends that show a few sites /RKD-
SFM-BML/ already in the upper 20s. No signs of fog at this
juncture...but HRRR is now starting to pick up on coastal
stratus potential so will maintain previous forecast changes.
Finally...issued a SPS earlier based on re-freezing of water on
roads due to the quickly falling evening temperatures.

716 PM Update: Following rapid 1-2 hour temperature drops as
winds decouple this evening. Overnight lows were tweaked
downward as a result. Otherwise...primary changes to the
forecast are to adjust fog/low cloud wording overnight with some
patchy fog pretty much possible anywhere while NARRE-TL and
HRRR/RAP BUFKIT profiles along with statistical guidance signal
some coastal stratus potential after midnight. Moved the
forecast in this direction...and will monitor late evening
trends before making further adjustments.

513 PM Update: Minor changes to match late afternoon
temperatures and reduce cloud cover based on the last few
visible images of the late afternoon.

Previous discussion below...
The evening will start out mostly clear as per satellite
imagery. By later tonight patchy valley fog is expected to
develop due to the residual low level moisture from the snowmelt
this afternoon combined with calm winds. Tonight`s overnight
lows will be mild with temperatures in the upper 20s to lower
30s.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
Thursday models show a mild southwest flow to develop with h85
temps aloft to reach +6 to +8C. This flow should allow temps to
reach near 50 in the mountains and southern Maine and could
reach near 60 over southern NH. A weak cold front tries to push
south across the area but weakens and then washes out as it
moves through the area by Thu evening. A few showers are
possible in the mountains with its passage Thursday afternoon
and evening but it should remain dry elsewhere. Patchy fog may
once again form overnight due to the snowmelt. Temps will once
again be mild with overnight lows ranging from near 30 in the
mountains and mid 30s to lower 40s elsewhere.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Models are in fairly good agreement in the long term. A frontal
boundary will stall just south of the region Friday...then start
to push back through the area as a warm front Friday night as
low pressure moves northeast through southern Quebec. This will
lead to a rather warm day Saturday. As the low continues
northeast Saturday night the trailing cold front will cross the
region with rain showers which will change to snow showers in
the mountains overnight Saturday night as colder air pushes
into the region. At this time it appears that the moist system
moving northeast in Atlantic will not phase with the northern
frontal system until after it passes through the region. The
models continue to show the heaviest showers with the frontal
passage in the mountains...and combined with the snowmelt caused
by the warm temperatures may produce some ice movement on the
rivers.

Drier air moves into the area Sunday but with a northwest flow
there will be a persistent threat of snow showers in the
mountains through Monday. Weak systems pass north and south of
the region late Monday and Tuesday with the next threat of
significant precipitation for the area on Wednesday.

&&

.AVIATION /02Z THURSDAY THROUGH MONDAY/...
Short Term...

Summary:  Southwesterly flow continues through Thursday as low
pressure passes north of the region with a few showers arriving as
an attendant cold front pushes through the area Thursday night.
High pressure then noses into the region from the north on Friday
before stalled frontal boundary to our south returns north as a warm
front.

Restrictions: VFR attm and this will continue through the evening.
Lots of ground moisture out there from recent melting and there are
some signs given good radiational cooling that this will result in
some fog development...particularly with continued good moisture
advection in the southwest flow aloft.  NARRE-TL points to low
ceiling potential over southern NH/coastal ME as well...with good
agreement from the LAV/MAV/MET.  Thus...expect IFR fog and some
coastal low stratus to develop after midnight with conditions a bit
better /MVFR/ at HIE/LEB.

For the day on Thursday...expect gradual improvement to VFR outside
of LEB/HIE where nearby approaching front will help MVFR cloudiness
linger longer...potentially through the day.  MVFR restrictions
possible in a few light rain showers Thursday night before a return
to VFR conditions on Friday morning.  Front to our south returns
north Friday afternoon...with restrictions in rain showers again
possible towards evening.

Winds: Calm/light-variable winds overnight will become southwest
5 to 10kts for the day on Thursday before diminishing to 5kts or
less Thursday night and shifting northwest overnight.  Light
northwesterly winds /less than 10kts/ expected Friday.

LLWS: LLWS possible Thursday evening in southwesterly flow ahead of
approaching surface cold front. Frontal passage will end the threat
from north to south overnight.

Long Term...MVFR to IFR conditions possible in showers and fog
Friday night into Saturday night. MVFR to IFR conditions
will persist in the mountains in scattered snow showers through
Monday.

&&

.MARINE...
Short Term...A warm front moves north across the waters tonight.
A developing southwest flow Thu will begin to build seas to
near 5 ft by evening and continue Thu night. SCA`s may be
needed for Thu night due to seas over the outer waters.

Long Term...SCAs likely outer waters late Saturday through
Monday and again on Wednesday.

&&

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

&&

$$
SYNOPSIS...
NEAR TERM...Arnott/Marine
SHORT TERM...Marine
LONG TERM...Jensenius
AVIATION...Arnott
MARINE...


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