St. Johnsbury, Vermont 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

639
FXUS61 KBTV 231715
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
1215 PM EST Mon Dec 23 2024

.SYNOPSIS...
Very cold conditions are ongoing with temperatures below zero
for most locations this morning before clouds increase west to
east around sunrise. A clipper-type system will move through the
North Country this evening through tonight bringing moderate
snow totals and potential impacts for holiday travelers. Dry
conditions are expected Tuesday through the end of the week with
continued colder than average temperatures, but not as brutally
cold as the last couple of days.

&&

.NEAR TERM /THROUGH TUESDAY/...
As of 929 AM EST Monday...After a very cold start to the
morning, temperatures have begun to moderate although most
places still remain near or below zero. The one forecast change
for this morning was to lower high temperatures today as the
latest MOS guidance shows temperatures steadily warming through
the day and even through the overnight hours. The net result was
to lower high temperatures by about 4 degrees but to warm low
temperatures by 2-3 degrees. The overall impact on the forecast
was minimal with the snow event tonight and tomorrow still on
track.

Previous Discussion...

* A Winter Weather Advisory is in effect for much of northern
  New York, northern Vermont, and portions of central Vermont.
  Areal coverage of 3 to 6 inches has expanded over the previous
  forecast. Moderate snowfall could impact holiday travelers
  this evening through late morning Tuesday.

Frigid conditions are ongoing with widespread lows below zero
degrees and -24 being observed at Saranac Lake. However, mid
level clouds are increasing west to east and will aid in
limiting further cooling for northern New York with the deck
arriving in Vermont by daybreak.

A clipper-type system will move through the region this
afternoon through Tuesday morning bringing breezy winds and
accumulating snow. Two facets of the forecast have changed and
generally resulted in increasing snowfall amounts: QPF has
increased, and the overall 850mb low-level jet has weakened
below 40kts for most locations. Moisture is still projected to
be mainly along and behind the lljet supporting more snowfall
than usual for downslope locations along the eastern
Adirondacks while limiting the eastward extent of shadowed
precipitation. As such, snowfall amounts were increased pretty
much everywhere leading to more widespread cover of 3 to 6
inches of accumulating snow. One foil, which moderated my
forecast a bit, is that the dendritic growth zone is rather
high for many locations and coincident with 35+kt winds. These
winds will likely fracture a good portion of dendrites resulting
in more of a mixed snow-crystal structure reaching the ground
favoring a dry, but relatively more dense snowpack that could
limit snow depth. Should winds decrease further, however,
another couple of inches could accumulate. On a positive note,
southerly flow today will increase temperatures with highs
expected to be in the 20s. Locations with breezes, like the
northern Champlain Valley, will still feel like 10 degrees when
wind chill is taken into account. Models seem too warm Tuesday
with high pressure over the region and continued northerly flow.
Have continued the trend of limiting temperatures and cooled
highs from around 30 degrees for northern valleys down to the
mid/low 20s.

&&

.SHORT TERM /TUESDAY NIGHT/...
As of 346 AM EST Monday...Precipitation will quickly come to an end
by Tuesday night as the upper low continues to trek eastward. Behind
the departing low, high pressure will begin to build into the
region, marking the start of a quieter weather pattern. Overnight
lows will be seasonably cold, with temperatures generally in the
teens and single digits above zero, unlike the last few nights.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
As of 346 AM EST Monday...High pressure will be the dominant feature
for the remainder of the week, bringing a period of quieter weather.
A strong surface inversion looks to build under the high pressure,
which may lead to some air quality concerns through the week.
Additionally, this inversion will keep temperatures in the valley
quite cool, while the mountain summits will likely be a few degrees
warmer. Overall, the high pressure overhead will make for a welcomed
stretch of benign weather, especially for those traveling for the
holidays. Temperatures will be rather seasonable through the week,
with a gradually warming trend towards the weekend.

There is still the question of how quickly the ridge will break down
towards the weekend, with a wide range of solutions amongst global
deterministic models. Precipitation chances look to increase Sunday
heading into the beginning of next week with increasing moisture
streaming into the region, but there is still is still a lot of
uncertainty so stay tuned.

&&

.AVIATION /17Z MONDAY THROUGH SATURDAY/...
Through 18z Tuesday...VFR conditions will continue through the
afternoon hours with a steady decline in ceilings and
visibilities as snowfall spreads west to east across the North
Country. Snow is expected to begin at KMSS around 22Z with a
sharp reduction to IFR visibilities with falling snow with snow
entering the western Vermont terminals around 00Z-01Z. IFR
visibilities are expected through the duration of the snow event
with ceilings steadily dropping to 2500 ft by 06Z and 1500 ft
by 12Z. MVFR ceilings will likely linger through the morning
hours on Tuesday with the chance for some scattered snow showers
through 18Z. A modest low level jet will also develop tonight
with around 30 knots of winds at the 2000 ft level and we have
included it at the TAF sites most likely to be impacted by the
stronger winds aloft.

Outlook...

Tuesday Night: VFR. NO SIG WX.
Christmas Day: VFR. NO SIG WX.
Wednesday Night: VFR. NO SIG WX.
Thursday: VFR. NO SIG WX.
Thursday Night: VFR. NO SIG WX.
Friday: VFR. NO SIG WX.
Friday Night: VFR. NO SIG WX.
Saturday: VFR. NO SIG WX.

&&

.EQUIPMENT...
The sensor at the Newport, Vermont airport has not been
reporting since Sunday morning. Techs will be taking a look into
what is causing the communication issue.

&&

.BTV WATCHES/WARNINGS/ADVISORIES...
VT...Winter Weather Advisory from 5 PM this afternoon to 1 PM EST
     Tuesday for VTZ001>008-016>018.
NY...Winter Weather Advisory from 5 PM this afternoon to 1 PM EST
     Tuesday for NYZ026>031-087.

&&

$$
SYNOPSIS...Boyd
NEAR TERM...Boyd
SHORT TERM...Kremer
LONG TERM...Kremer
AVIATION...Clay
EQUIPMENT...