NWS Forecast Discussion

For Fremont, NH

000
FXUS61 KGYX 061618 AAB
AFDGYX

Area Forecast Discussion...UPDATED
National Weather Service Gray ME
1118 AM EST Fri Dec 6 2019

.SYNOPSIS...
A weak area of low pressure will cross the region this
afternoon. Much colder air will sweep across the forecast area
tonight and Saturday. Warmer temperatures and some rain are
expected early next week before a cold front brings in another
dose of Arctic cold during the second half of the next work week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
1115 AM Update... Dry air is still eroding the leading edge of
the precipitation shield, which is making its way across
southern NH and into SW Maine. We should start seeing snow reach
the ground shortly in southern and central NH, but it may take a
little bit longer in ME. Still expecting minor accumulations as
most guidance deepens the low only once its offshore. So we
could see some accumulations over the islands and Downeast
along the Maine coast.



930 AM Update... GOES satellite and radar imagery are showing
snow moving across NY State and into Vermont this morning. Have
only changed weather and QPF/snow amounts lightly as near term
CAM models are still indicating 1-3" across southern NH through
tonight, with less coverage north and east. Short of an
advisory, we will likely issue an SPS for slick commutes this
afternoon. Still we have a little way to go with top-down
saturation with dew points only in the lower teens in NH and ME.



Update...Have updated the forecast based on current observations
and latest radar imagery. Have upped snowfall amounts slightly
over southern portions of the forecast area. Latest mesoscale
model trends have increased the QPF for southern New Hampshire
and extreme southwest Maine overnight. Otherwise, just minor
changes to the latest forecast package.

Prev Disc...Scattered upslope snow showers will gradually end
over the mountains this morning.

A clipper type system will then cross the region this afternoon.
Have leaned closely towards the higher pops of the latest HRRR
as snow will likely develop over southern New Hampshire during
the late morning hours before pushing east. With the track of
this system, expect an inch or two snow accumulation across
southern New Hampshire and into portions of York County in
Maine. Some of the higher elevations over southern New Hampshire
may pick up a little more in the way of precipitation. Further
to the north, there may be a only a coating of snow.

Winds will become light this afternoon in advance of this weak
system with highs in the 20s to lower 30s in most areas.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY/...
Light snow continues for a short period along and near the
coastline as the low slowly intensifies as it exits into and
through the Gulf of Maine.

Much colder air will follow this system on northwesterly breezes
tonight with upslope snow showers continuing in the mountains.
By Saturday, the core of the cold air will be over the region.
There will be good mixing with temperatures in the
-14C to -18C range, yielding highs only in the teens and 20s
across the region.

Saturday night will likely be the coldest night over the next
few days as high pressure crests over the region. There is the
potential for good radiational cooling in some areas with a
fresh snowfall and clear skies. Question will be the gradient
and whether or not winds can go calm during the night as a ridge
of high pressure remains to our west during much of the night.
Nevertheless, expect readings in the single numbers in many
areas.

Sunday will remain fair and dry as high pressure begins to exit
off the coastline. A gradual warm up will begin as well which
sets us up for the long range portion of the forecast.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
The high pressure ridge will crest across New England on Sunday
and continue eastward into the Central Atlantic and strengthen
on Monday and Tuesday. A shortwave will dive southeast through
the High Plains over the weekend and will lead to the
development of low pressure across the Great Lakes on Monday.
The low will strengthen as it rides east-northeastward through
the eastern Great Lakes and down the Saint Lawrence River Valley
through late Tuesday. Moisture will ride north on the western
periphery of the ridge, and the strengthening low pressure
center will lead to the development of widespread precipitation
across the northeast. Some spotty precipitation is possible by
the late morning hours Monday, but the bulk of the precipitation
looks to arrive late in the afternoon and evening Monday. The
steadiest precipitation from this round looks most likely to
wind down by Tuesday Morning, but showers may linger through the
afternoon on Tuesday.

The progression of the frontal boundary has been the subject of
some disagreement between the models late Tuesday and into
Wednesday. The GFS has been progressively slower with the
frontal passage over the past several runs, and the latest ECMWF
has lurched to a slower fropa solution. This has implications
for precipitation, with another round of moisture riding north
along this front late Tuesday and into early Wednesday. This
would lead to another period of predominantly rainfall, with
very little if any break from the first round.

An extended period of warm air advection will initiate on Sunday,
occuring above the surface earlier on Sunday. Temperatures will be
slow to rise above freezing near the surface across interior
sections through Monday morning, but the threat for any light
freezing rain at the onset of the precipitation appears to be
diminishing with the arrival of the precipitation not being until
later on the day Monday. Additionally, with the extended period of
WAA lasting into Tuesday, warming above freezing appears inevitable
at this point across the entire CWA, with temperatures warming into
the 50s across the coastal plain.

Once the frontal boundary passes, CAA will take hold on
Wednesday as an Arctic high pressure center builds across the
region Thursday and Friday. Long range deterministic models and
ensembles support below normal temperatures late in the week,
perhaps aided by a secondary cold front. Unsettled weather is
likely to persist after cold FROPA under mean troughing, most
likely relegated to the upslopes.

&&

.AVIATION /16Z FRIDAY THROUGH TUESDAY/...
Short Term...VFR conditions in the north with MVFR and areas of
LIFR conditions in snow over southern sections today. Conditions
improve tonight outside the mountains on brisk northwesterly
breezes. VFR conditions will then dominate through Sunday.

Long Term...Ceilings lower and rain overspreads the area Monday
with likely degradation to MVFR CIGS, IFR CIGs/VSBY in pockets
of heavier rainfall. Southerly surface winds generally 

NWS GYX Office Area Forecast Discussion