Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Burlington Vermont
935 PM EST Thursday Dec 5 2013
a cold front will move across the region tonight into Friday
morning. It will bring rain showers to the north country...which
will transition to a wintry mix and then snow showers late tonight
into Friday morning before ending. More snow showers are possible
Friday night...especially over southern Vermont...as a weak wave of
low pressure passes south of New England. Dry and cold weather is
then expected over the weekend.
Near term /until 6 am Friday morning/...
as of 935 PM EST Thursday...zones updated to reflect continued
slow movement of front/precipitation through the County Warning Area. Temperatures fairly stagnant over
the area and have made adjustments to trend down after midngt. Added
patchy fog in for the slk area and kept fog from previous issuance
in as well. Rest of forecast slow...but on track.
Previous discussion...low pressure near James Bay will lift
further northeast tonight. Forecast area will remain in the warm
sector this evening...and then a cold front now over the eastern
Great Lakes will make its way east across the area overnight. 850
mb temperatures ranging from +6 to +10c this evening with surface temperatures
ranging from only the middle and upper 30s over much of eastern
Vermont where low clouds and fog have prevailed today...to the
lower 50s across the Champlain Valley and much of northern New
York. So precipitation that falls this evening will be in the form
of just rain. By morning however...850 mb temperatures will range from
around 0c over southern Vermont to around -5c over the Saint
Lawrence valley...with surface temperatures falling below freezing across
much of northern New York and into the lower to middle 30s in
Vermont. As the colder air arrives...rain will change to a wintry
mix of sleet and snow with perhaps a brief period of freezing rain
as well...especially over the Adirondacks. Expecting the bulk of
the precipitation to fall in the form of rain before the colder
air arrives. Not anticipating more than a coating of ice
anywhere...and any snow/sleet accumulations by morning will be
light as well (a dusting to 2 inches) and confined to northern
areas. Southern and central Vermont can expect mainly rain as cold
air arrives very late.
Short term /6 am Friday morning through Saturday night/...
as of 341 PM EST Thursday...cold air continues to filter into forecast
area during Friday as front pushes slowly southeast. Temperatures
not expected to climb much above the early morning lows over
northern areas...with temperatures falling a bit over the south.
Changeover from rain showers to sleet/snow continues across
Vermont during the morning before precipitation comes to an end as
drier air works into the region. Any snow/sleet accumulations will
be limited to a dusting to around an inch. Cloud cover will also
decrease briefly before a weak wave of low pressure moves along
the cold front and passes out south of New England Friday night.
Moisture associated with this disturbance returns north into
forecast area Friday evening...before exiting by Saturday morning.
The result will be some light snow...which will affect mostly
southern half of Vermont with 1 to 3 inches of snow. Lower probability of precipitation
and less snow expected across the north. Outside of perhaps a few
mountain snow showers or flurries on Saturday...it will be dry
with partly sunny skies. Temperatures expected to be several
degrees below normal with valley highs mostly in the lower 30s.
Continued dry and Cold Saturday night as a ridge of high pressure
builds into the north country.
Long term /Sunday through Thursday/...
as of 318 PM EST Thursday...overall trends of all extended range
guidance continue to favor another mixed precipitation event to
begin the work week...followed by generally quiet conditions
thereafter. Model consensus remains very good...and thus
forecaster confidence is high.
Extended forecast begins on Sunday with a ridge of high pressure
over the region and dry conditions but cool temperatures with highs only
in the 20s...about 10 degrees below normal. Forecast then becomes
more active going into Sunday night as the high drifts east off
the Atlantic coast and a developing low coming out of the Midwest
approaches the Great Lakes. As the low tracks northeastward into
southern Ontario/Quebec the north country will once again be put
into the warm sector with mixed precipitation likely. Precipitation
should begin as snow late Sunday night into Monday
morning...before transitioning a mix of rain/sleet/snow Monday
afternoon...and back to snow Monday night. Vertical temperature profiles
even support some areas of freezing rain...but confidence is low
on those exact details at this time.
For the remainder of the forecast period for Tuesday through
Thursday...colder temperature profiles return as a broad upper trough
settles over the northeast. We'll be under fast west/southwest
upper flow with several weak shortwaves moving through supporting
some low chance probability of precipitation here and there for snow...but no real big
accumulations on the horizon...sigh. Highs during the period will
generally be in the 20s...and lows in the lower teens to single
numbers...all well below normal for mid-December.
Aviation /03z Friday through Tuesday/...
through 00z Saturday...mix of flight categories expected from this
evening into Friday morning...improving to VFR during the day on
Friday. Low ceilings and increasing precipitation will lead to a
mix of VFR/MVFR/IFR/LIFR through Tuesday morning...with the heaviest
precipitation centered 07z-12z. This will be in the form of rain
at rut...rain/snow/sleet mix at mpv/btv/pbg...and snow/sleet mix at
slk. Mss may escape without any significant precipitation.
Greatest threat for IFR/LIFR will be at mpv this evening and then
slk overnight...with periods of MVFR likely elsewhere. Conditions
improve on Friday with VFR expected for most...except some MVFR
ceilings lingering at slk.
Outlook 00z Saturday through Tuesday...
00z Saturday through 12z Saturday...generally VFR with areas of
MVFR/IFR in light rain and snow...mainly south and east of btv.
12z Saturday through 06z Monday...VFR under high pressure.
06z Monday through 12z Tuesday...IFR/MVFR in developing snow and
mixed precipitation...as surface low pressure area moves into the
Tuesday...generally MVFR with isolated to scattered snow showers.