Scientific Forecaster Discussion
fxus61 kbtv 131125
Area forecast discussion
National Weather Service Burlington Vermont
625 am EST Wed Nov 13 2019
high pressure will build into the region today with dry and
unseasonably cold weather expected. Temperatures gradually
moderate on Thursday into Friday before another strong cold
front crosses the area Friday evening with scattered rain and
snow showers. Behind this front a brief return of cold weather
returns for Saturday, after which temperatures moderate
considerably into next week.
Near term /through Thursday/...
as of 625 am EST Wednesday...forecast remains on track as of
600 am. Small adjustments were made to hourly sky cover,
temperatures and dewpoints through late morning to account for
current observational trends. No significant changes to
thinking however. Have a great day!
mainly quiet weather returns over the next 42 hours as 1030 hpa
sfc high pressure builds into the region and slides east by
Thursday. Departing upper polar trough exits into the Canadian
Maritimes with another very cold day on tap by November
standards as highs struggle into the mid teens to lower
20s...perhaps a few mid 20s far south. Any clouds/northern mtn
flurries this morning to erode to mainly clear skies by mid to
late afternoon as west/northwesterly flow trends light.
This evening begins with clear skies. However, as the high slides
east return southwesterly flow aloft will allow increasing mid to
upper level clouds to spread quickly west to east across the area
after midnight. This in advance of a dampening mid-level upper
trough progressing east from the Great Lakes/southern Canada. Dry
weather is generally expected, though will maintain slight chance
pops for a few snow showers across the slv later at night or toward
morning. Temperatures will take on a typical non-diurnal trend,
especially west of The Greens where light south/southwesterly low
level flow will become established overnight. Thus coldest readings
will likely occur in the evening, then trend steady or slowly tick
up a few degrees overnight. Record minima will be threatened once
again at a few sites (see climate section below).
On Thursday aforementioned upper shortwave dampens and lifts out to
the north and east over time as southerly flow deepens across the
area. Lower-end chances for a few snow showers will exist across the
slv during the morning hours, though a largely dry day is expected
across the majority of the forecast area despite ample mid level
cloud cover. Temperatures moderate by some 8-15 degrees from today's
readings, reaching the 27 to 34 range by late afternoon. These
values are still some 15 degrees below normal for the second week in
Short term /Thursday night through Friday night/...
as of 317 am EST Wednesday...temperatures will be quite a bit warmer
on Thursday night as cloud cover and southwesterly flow in the low
and mid levels couple to moderate our temperatures. Under this warm
air advection regime, we will see overnight lows only dropping into
the lower to upper 20s which is a good 10-15 degrees warmer than
previous nights but still puts US a couple degrees below normal.
Snow showers associated with a weak shortwave disturbance will
linger across the St. Lawrence Valley through the overnight period
Thursday into Friday morning. Overall snowfall totals looks to be
rather marginal (less than half of an inch or so) due to the lack of
moisture and weakening dynamics. However, a strong Arctic cold front
will push into northern New York early Friday afternoon and bring a
higher chance of snow showers with it.
Digging deeper into the snow chances Friday afternoon with the
Arctic cold front, there appears to be a nice band of instability
developing out ahead of main area of convergence. Now, this isn't
like anything we will see during the Summer months but cape values
of 100 to 300 j/kg catches our attention when you mention a strong
cold front during the winter months. Due to the strong temperature
gradient expected on the back side of the Arctic front, the NAM and
GFS are both depicting a strong band of frontogenetic forcing moving
across northern New York into northern Vermont during the late
afternoon/early evening hours. When you combine all of these
ingredients, you have the potential for not only convective snow
showers but also the potential for snow squalls. Given that we
should have background wind fields in the 15 to 25 mph, it would not
be surprising to see some strong convective showers or even a few
snow squalls that could briefly cause white out conditions. This
should be monitored in the coming days as this could impact the
evening commute for parts of the north country. Stay tuned for more
information in the coming days.
The aforementioned showers will dissipate Friday evening with high
pressure quickly building into the region. This should allow
temperatures to cool quickly under increasingly clearing skies with
low temperatures expected to drop back near zero to the lower teens
with yet another strong cold snap.
Long term /Saturday through Tuesday/...
as of 317 am EST Wednesday...the new cold snap will last through
Saturday with afternoon high temperatures struggling to climb into
the 20s across the north country. However, the surface high pressure
will be transient and will begin to push offshore Saturday night.
This will allow for one more well below normal night Saturday night
with lows once again near zero to around 10 degrees. Winds in the
mid-levels will shift to the southwest on Sunday and begin to usher
in some much warmer air to the region. Afternoon high temperatures
will be around 32 across much of the region with mostly clear skies
prevailing throughout the day on Sunday.
The long term forecast begins to get tricky and challenging as we
head into early next week with the potential for several storm
systems to impact the region. The key feature to be watching during
the weekend period will be an upper level low off the coast of the
Carolinas and how it phases (or doesn't) with the longwave pattern
over the East Coast. The GFS, at this time, shows this low weakening
into an open wave and then getting absorbed by the longwave pattern
and mainly pushes offshore while the European model (ecmwf) and Canadian but show
this feature remaining independent and tracking just to the east of
Cape Cod Monday night. Interestingly enough, all of the
deterministic and ensemble guidance shows a significant warm trend
by Tuesday with highs back into the 40s across the whole region
regardless of how this system plays out.
Another system will be possible on Wednesday with the GFS and European model (ecmwf)
both showing this feature but lack on the position of the low as it
tracks offshore. It has all the signs of a developing nor'eastern
which puts a lot of weight on the position to potential impacts to
the region. However, should this situation pan out, there is a high
likelihood that this would be a rain event and not a snow event with
850 mb temperature +3 to +5. There could be some upslope snow on the
back side once we see some cold air advection but we will have to
wait and see what models show in the coming days. In the mean time,
enjoy the cold because it looks like we return to seasonal
temperatures for the foreseeable future.
Aviation /12z Wednesday through Sunday/...
through 12z Thursday...mainly VFR through the forecast period
as gusty northwest winds abate and high pressure builds into
the area. Cigs to range from sky clear to sct035-040 above ground level. Only
exception will be at kslk and to a lesser extent kmpv where
more persistent MVFR will be possible through mid-morning and
cigs range from scattered-bkn015-025 above ground level. After 00z increasing high
level as/cs from 150-250 above ground level builds east, gradually lowering to
050-100 above ground level after 06z. No precipitation is expected overnight.
Winds west/northwest 6-12 kts and occnly gusty to 18kt at Vermont
terminals through 15z, slowly abating into the afterrnoon hours
before trending near calm by 00z Thursday.
Thursday: VFR. Slight chance shsn.
Thursday night: VFR. Chance shsn.
Friday: mainly VFR, with local MVFR possible. Chance shsn, chance
Friday night: VFR. Chance shsn.
Saturday: VFR. No sig weather.
Saturday night: VFR. No sig weather.
Sunday: VFR. No sig weather.
below are daily record minimum temperatures for November 14.
Burlington: 10 (1996)
plattsburgh: 12 (2004)
montpelier: 5 (2018)
Saranac lake: -4 (2018)
massena: 8 (1971)