NWS Forecast Discussion

For Fremont, NH

000
FXUS61 KGYX 230252
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
952 PM EST Wed Jan 22 2020

.SYNOPSIS...
High pressure brings fair weather and a warming trend to the
region through Thursday. A cold front will sink gradually south
into the area late Thursday through Friday accompanied by a few
clouds. A coastal storm may bring accumulating snow to much of
the region over the weekend into early next week, but rain and
mixed precipitation are also possible depending on system track.

&&

.NEAR TERM /OVERNIGHT/...
10PM UPDATE...
Have updated the forecast primarily to adjust overnight lows
based on latest observations and trends. Some higher level
clouds have drifted through the region, but they are more sparse
for now. They may thicken up especially in the north with time
overnight, but in general we`ve seen some decent cooling.
Overnight lows tonight should be warmer than the past few
nights, though, as low level dewpoints have climbed.

630 PM UPDATE...
Clouds are moving into the region as ridging aloft shifts to
the SE. Some ribbons of vorticity are allowing high clouds into
NH and northwestern Maine. These will eventually shift farther
east-southeast, allowing for another cold and mostly clear
night. Light southerly flow at the surface and the
aforementioned clouds will keep it from getting nearly as cold
as last night. Overnight lows were adjusted closer to the HRRR
and HREF, and range from the upper single digits to the mid
teens.

ORIGINAL DISCUSSION...
At 19z a 1035 millibar high was centered over the DELMARVA.
With the exception of some patchy low and mid clouds...GOES
imagery showed mainly clear skies across the area. Sunshine and
moderating 850 millibar temperatures have allowed the mercury to
rebound to near or slightly above normal for the date...with
readings in the upper 20s and lower 30s. For tonight...a few
high clouds will spill over the top of the ridge otherwise a
mainly clear and cold night with lows ranging from the single
numbers to mid teens.

&&

.SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/...
On Thursday...the high remains centered to our south. The ridge
will allow for more sunshine on Thursday and mild temperatures
as winds continue out of the southwest, both at the surface and
aloft. With nearly full sunshine, temperatures will reach the
lower 40s over southern areas. Mostly sunny skies...moderating
850 millibar temperatures...and light southwest flow will allow
temperatures to warm into the mid 30s to lower 40s...or a good
ten degrees above average for the date. Thursday night...an
east-west oriented cold front will begin to sag slowly southward
into the area as high pressure builds east into Quebec
province. We`ll see some clouds spread into northern and eastern
sections overnight with the front. Just how fast the clouds
arrive will determine when we put a lid on radiational cooling.
I`ve gone below machine guidance in many areas especially south
and west where the bulk of the night should be mostly clear.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
By Friday morning, a ridge of high pressure centered over
central Quebec will extend eastward across the Canadian
Maritimes, and will continue to bring fair conditions to New
England through early Saturday. This ridge will be anomalously
warm for this time of the year, with origins from the Pacific
Ocean, rather than northern Canada. This means that temperatures
will be above normal into the weekend, and that there will not
be a major source of cold air nearby or in place as a storm
system approaches for late Saturday through Monday.

The storm system is currently located over the Pacific northwest US.
It is expected to emerge over the central Plains and strengthen
until it becomes an occluded area of low pressure over the Ohio
River valley by late Friday. The low will slowly move eastward
and will likely cross through southern or central New England on
Sunday.

There has been a notable shift in the GFS, ECMWF, Canadian, and
their respective ensemble suites to a more northern and warmer
track of the low pressure over the last few model runs. This
shift in model output coincides with the actual system coming
ashore across the Northwest US and entering the RAOB network.
This means that the latest models runs have a better sampling of
the system itself than the previous runs did, so it`s difficult
to say whether the shift of the models to a warmer solution is
due to better sampling, or the beginning of a trend toward an
even warmer solution.

Regardless, with the better sampling, recent model trends, and
only marginally cold enough air across the region, there is
sufficient reason to believe that this system will feature a
considerable deal of mixing with rain, and a full blown
changeover is quite possible across the coastal plain. The
mountains stand the best chance of remaining all snow through
the event.

The storm is expected to move quite slowly, with the low pressure
center not expected to depart the Gulf of Maine until Monday
afternoon. With a slow track nearby, precipitation will likely
linger right through the day on Monday, but it will not be
continuous from late Saturday through Monday. Precipitation is
likely to be more showery and periodic across central and
southern zones by Sunday afternoon, with the mountains standing
the best chance of experiencing more continuous precipitation
with bands of snow rotating in on the backside of the low into
Monday.

Tides will also have to be watched closely during the Sunday
midday high tides. The astronomical high tide is 10ft in
Portland on Sunday. The slow progression and timing of the storm
could bring enough storm surge and large waves to cause some
minor coastal flooding concerns on Sunday.

After the system, high pressure will build across New England
through midweek next week, with temperatures returning to near
normal.

&&

.AVIATION /03Z THURSDAY THROUGH MONDAY/...
Short Term...Light winds expected tonight and Thursday as high
pressure moves through the region. Only some high level
cloudiness so expect VFR conditions all areas.

Long Term...
VFR conditions will continue into early Saturday as high pressure
persists across the region. A storm system is expected to bring
snow, likely mixing with rain across the coastal plain, which will
reduce visibilities and ceilings at times late Saturday through
Monday. Gusty winds will also accompany the system, with east winds
progressively shifting to the northwest from Sunday through
Monday.

&&

.MARINE...
Short Term...Light winds expected over the next few days as high
pressure moves across the region.

Long Term...
High pressure will persist through early Saturday. An area of
low pressure will slowly cross the waters Saturday Night through
Monday, likely bringing a period of easterly gales Sunday
morning. The system will then slowly exit the Gulf of Maine on
Monday morning, with freshening northerly winds on the backside.
High pressure will build in behind the system across the waters
early next week.

&&

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

&&

$$

NEAR TERM UPDATE...Kimble
SHORT TERM...Schwibs
LONG TERM...Clair

NWS GYX Office Area Forecast Discussion