Scientific Forecaster Discussion
fxus61 kbtv 151515
Area forecast discussion
National Weather Service Burlington Vermont
1015 am EST Fri Nov 15 2019
warmer temperatures are in store for the north country today
with highs in the lower to upper 30s. These warmer temperatures
will be short-lived with a strong Arctic cold front expected to
move through the region this afternoon and evening. Convective
snow showers and snow squalls are expected to move across
northern New York and northern Vermont during the late afternoon
and evening commute. These squalls will produce white-out
conditions and could create very slick Road surfaces as
temperatures plummet quickly after the front moves through.
Record breaking cold temperatures are then expected tonight and
again on Saturday night with temperatures beginning to moderate
as we head into the beginning of next week.
Near term /through Saturday/...
as of 1002 am EST Friday...main story for today continues to be
snow squalls with potential Road impacts, beginning around 21z
in the St. Lawrence Valley, and 22-00z across the remainder of
nrn New York and nrn Vermont. Axis of precipitable water values 0.25-0.35" across the nrn
Great Lakes into nrn New York and northern New England exists in
advance of approaching Arctic boundary. These moisture values
are generally consistent with more significant snow squall
cases, especially as Road temperatures drop below freezing
quickly with onset of squalls and Arctic frontal passage. Btv
snow squall parameter shows a strong signal, and low-level
mixing behind the front supports north-northwest winds gusting to 30 mph as
the front passes through. We'll continue to message 1/4mi or
less vsby along with quick 0.5" to 1.5" snowfall accumulation
with the squalls, along with timing with the late afternoon/evening
commute. Appears best SBCAPE (60-150 j/kg) and 925mb
frontogenesis occurs across the northern half of the forecast
area. Snow squall warnings may be needed later today. Should see
snow squall activity diminish south of Montpelier into
S-central Vermont as instability and frontal-scale forcing weakens
after 00z to 01z.
Previous discussion...persistent southwesterly flow across
Eastern Lake Ontario has caused a weak lake effect band of
snowfall to develop across the St. Lawrence Valley this morning.
This has brought snow showers to Massena and Ogdensburg with
little in terms of accumulations thus far. As winds begin to
shift more westerly during the mid to late morning hours, the
snow band will shift further east into northern New York and
bring chances for snow showers to Essex, Franklin and Clinton
counties in New York. Temperatures today will be on the mild
side when compared to recent days with highs in the lower to
upper 30s (still 7-10 degrees below normal). High temperatures
today will likely be achieved by early afternoon as a strong
Arctic cold front will quickly descend across the north country.
Speaking of the strong Arctic cold front, everything remains on
track for the development of snow squalls this afternoon across
northern New York and the northern half of Vermont. All of the
ingredients remain present and more impressive than they did
yesterday: a strong Arctic cold front, instability ranging from 75
to 150 j/kg of cape, strong frontogenetic forcing due to the strong
temperature gradient along the front and moisture pooling out ahead
of the cold front. Looking at the latest high-res guidance, it looks
like snow squalls could form as early as 3 PM in Massena and move
into the Saranac Lake, Burlington and St. Albans area around 5 PM.
Given the latest timing, these squalls will likely impact the
evening commute across northern New York and northern Vermont. All
commuters are urged to keep an eye on the skies and be ready for
rapidly deteriorating conditions as the squalls push through the
region. Snowfall amounts won't be overly problematic with most
places seeing less than an inch of snowfall. However, the fact that
many places will be above freezing this afternoon is a bit
concerning as roads will likely be wet from melting snow.
Temperatures behind the Arctic cold front will drop very quickly
which could create a flash freeze on roadways that aren't treated
which could lead to very slick travel conditions.
Skies will quickly clear tonight following the passage of the cold
front with a plethora of dry air moving into the region. When you
couple the clearing skies with very strong cold air advection behind
the front, you get a favorable set-up for radiational cooling. Given
that both the 850 mb temps and 500 mb temps are in the 99th
percentile for below average values, this is no Ordinary cool down.
In addition, hysplit backward trajectory models show this air mass
originated at the North Pole. Near record to record low temperatures
are expected tonight and again Saturday night while we could see
record low high temperatures on Saturday. Bundle up folks, another
record breaking cold snap is on the way.
Short term /Saturday night through Sunday/...
as of 319 am EST Friday...bitter, potentially record-breaking cold is
expected Saturday night/Sunday morning as high pressure crests
directly overhead. With light winds, clear skies, and a relatively
fresh snowpack, radiational cooling will be optimized, allowing
temperatures to drop dramatically overnight. Have trended a bit
downward from the previous forecast, closer to MOS guidance, which
is going quite cold (ie met says -11f at slk). Have gone with single
digits above zero in the wider valleys, and zero to a few degrees
below in the mountains. Later shifts will need to monitor trends and
make adjustments as needed.
For Sunday...the high shifts east and warm advection starts with the
flow turning to the south/southeast. Hence expect temperatures will
rebound nicely, eventually topping out in the upper 20s north to mid
30s south. May see an increase in mid and high clouds through the
day, but overall expect sunshine and dry conditions.
Long term /Sunday night through Thursday/...
as of 319 am EST Friday...turning warmer (but still cooler than
normal) through next week. It'll be unsettled as well with chances
for precip for much of the period. First will come an upper
shortwave and associated surface low, which will traverse up along
the East Coast, remaining east of the benchmark. Timing/placement of
the northern fringe of the precip associated with this system's warm
air advection is in question; the NAM spreads a decent slug
northward into the north country Sunday night into Monday, while the
GFS and European model (ecmwf) are slower, holding any precip off until daytime
Monday. Given the cold, dry air that will be in place, feel that
it'll take a while for the column to saturate; have therefore leaned
toward the slower guidance and kept Sunday night mostly dry.
Regardless, precip type will be a concern with the aforementioned
cold air locked in at the surface. Meanwhile, warm air moves in
aloft, though the extent of the warm nose differs between model
solutions. Still, expect precip would start out as a wintry mix,
especially if the earlier NAM solution is correct. The precip may
mix with or change over to rain for a time Monday afternoon into the
evening. Things will then change back over to snow Tuesday as the
low shifts east and colder air follows in its wake. Thereafter,
another upper trough digs into the Great Lakes, forming a closed low
which will move over or just south of our region Tuesday night
through Wednesday. Brief ridging follows Wednesday night, but
another upper trough approaches from the west to end the week. Given
all this, have a lot of chances of precip, mainly rain and snow, for
mid to late week.
Aviation /15z Friday through Tuesday/...
through 12z Saturday...a weak band of snow showers has set up
over the St. Lawrence Valley and should continue through about
15z or so which could produce some brief periods of low MVFR at
kmss. Otherwise, sites are generally VFR this morning with
winds from the south at 10 to 17 knots. We will see winds
gradually shift to the southwest during the morning hours while
increasingly in magnitude ahead of a strong cold front. This
cold front will bring strong convective snow showers and snow
squalls to much of the north country late this afternoon and
early evening hours with kmss seeing near whiteout conditions
around 20z and Burlington closer to 22z. These showers will
weaken as they track west to east but there will be some strong
gusty winds coupled with brief heavy snow as these squalls move
through. Following the front, we will see winds quickly shift to
the northwest with sustained winds in the 15 to 18 knot range
and gusts around 25 knots continuing into the early evening
hours. Following the front, we will see skies quickly clear
leading to VFR conditions at all terminals by the end of the
Saturday: VFR. No sig weather.
Saturday night: VFR. No sig weather.
Sunday: VFR. No sig weather.
Sunday night: mainly VFR, with local MVFR possible. Slight chance
Monday: mainly VFR, with areas MVFR possible. Chance fzra, chance
ra, slight chance pl.
Monday night: MVFR/IFR conditions possible. Chance pl, chance
fzra, chance snow.
Tuesday: mainly MVFR, with areas IFR possible. Chance ra, chance
here are some min and low Max temperature records which could be broken over
the next few days.
Min temp records
date kbtv kmpv k1v4 kmss kpbg kslk
11-16 6|1967 4|1967 10|2003 0|1967 11|1967 -11|1933
11-17 7|1924 5|1972 20|2017 12|1980 14|1972 -10|1933
Low Max temp records
date kbtv kmpv k1v4 kmss kpbg kslk
11-16 22|1933 22|1967 31|2018 20|1967 29|1967 16|1933