Scientific Forecaster Discussion
fxus61 kbtv 161803
Area forecast discussion
National Weather Service Burlington Vermont
203 PM EDT Wed Oct 16 2019
moderate to heavy rainfall is expected to move into northern New
York later this afternoon and into Vermont this evening. This should
be a fairly long event with rainfall not expected to taper off until
Thursday night. Rainfall totals through Thursday night range between
1.5 to 2.5 inches for most locations with totals closer to an inch
across far eastern Vermont. Winds today will quickly strengthen to
20-30 mph before switching to the north Thursday morning at 25-40
mph. The combination of the heavy rain coupled with strong winds
could produce some power outages. As we head into Friday, we will
return to a more stable regime as high pressure begins to build into
the region. This period of drier and calmer weather will continue
through the weekend. The next chance for rainfall comes with another
strong front on Tuesday.
Near term /through Thursday/...
as of 155 PM EDT Wednesday...no real changes made with this
forecast other than to match latest trends in warming.
Otherwise, going forecast remains in real good shape at this
Previous discussion...other than a few high clouds moving
across the area, the first part of the day should be relatively nice
across the north country. Filtered sunshine will be seen through
late morning/early afternoon with the next storm system continuing
to track slower than previous runs showed. Surface high pressure,
which has brought US several nice days, has already shifted offshore
with a frontal system just beginning to work into western New York.
This is resulting in an increasingly strong pressure gradient which
will bring gusty winds ranging from 20-30 mph across the north
country by late this morning. Unlike previous model runs, rainfall
associated with the warm occlusion likely won't move into northern
New York until mid to late afternoon with rainfall moving into
Vermont this evening.
As has been the trend in previous nights, all numerical guidance has
shifted the developing coastal low off the virgina/Delaware coast
and its track even further westward. This westward trajectory shift
puts the north country in some of the most favorable areas for
seeing moderate to heavy rainfall heading into tonight. As the
surface low tracks inland over Long Island this evening, the
emphasis on moderate to heavy rainfall will exist over western New
York and the southern New England coastline. Through the evening and
overnight hours, the emphasis on this moderate to heavy rainfall
will shift northward into Vermont, New Hampshire and Maine. This
heavier precipitation will be associated with mesoscale banding
developing underneath a strong area of frontogenesis.
Thursday is when things really start to get interesting. A
combination of strong frontogenetic forcing, Champlain Valley
convergence and blocked flow will end up leading to some impressive
rainfall amounts across the region. We already discussed the
frontogenetically induced rain bands expected to develop tonight but
these banded precipitation structures are expected to continue
through the first half of Thursday afternoon. As the low level flow
begins to shift to the north, we will see some enhanced rainfall
rates across the Champlain Valley with some convergence within the
valley. This should also allow rainfall to continue well into
Thursday night. Looking at the Froude numbers for Thursday
afternoon, we shift from a free flow regime to a blocked flow
regime. What does this mean? Well, initially precipitation will have
no problem making it over the Green Mountains into Vermont and
northern New York but as we begin to stabilize, we will see some of
this moisture become trapped. Typically in blocked flow regimes, you
see enhanced precipitation on the windward (in this case eastward)
side of the mountain ranges (adirondacks in this case).
Additionally, precipitation can back build in the windward direction
which could further enhance rainfall amounts for the Champlain
Valley. With all of this said, rainfall amounts have generally been
increased the region with widespread 1.5-2.5 inches of rain expected
with slightly lower amounts across eastern Vermont as some
downsloping off the White Mountains will limit rainfall totals. Some
upslope locations across the Adirondack Mountains could see upwards
to 3+ inches based on the latest available data. Fun fact: snowfall
is still expected above 2500 ft across the Adirondack and Green
Mountains. It's tricky to get snowfall totals with temperatures
being near freezing at higher elevations but with heavy rainfall
rates expected, we could see 1-3 inches for The Spine of the Green
Mountains and 2-6 inches across the higher elevations of the
Another thing to watch out for over the next 36 hours will be the
winds. Earlier we mentioned gusty southerly winds developing this
morning in the 20-30 mph range. While this alone is not anything to
be concerned about, a lot of leaves will be blown off of trees
today. These leaves could in turn block drains and cause the
potential for some nuisance flooding. Winds will shift to the north
Thursday morning and be quite a bit stronger with many locations
seeing gusty winds in the 30-40 mph range thanks to a nice push of
isallobaric flow on the back side of the low pressure system. The
combination of the moderate to heavy rainfall and strong winds could
lead to some isolated power outages.
Short term /Thursday night through Friday/...
as of 315 am EDT Wednesday...rainfall will finally begin to taper off
Thursday night as the now stacked low pressure system slides
northeastward. Lingering shower activity is expected across
northwest facing slopes with good upslope flow continuing into
Friday. Additional rainfall amounts will generally be a quarter of
an inch or less through the remainder of the rainfall event. Winds
will also weaken heading into Friday as the gradient begins to
weaken but we should still see winds in the 15-25 mph range through
much of Friday. Some of the rain showers will mix with snow across
northeastern Vermont but should only yield a dusting of snow
Long term /Friday night through Tuesday/...
as of 315 am EDT Wednesday...the long term will be characterized by
drier conditions and temperatures warming from near normal to above
normal temperatures with the next best chance for precipitation next
For Saturday, broad surface high pressure will be positioned just to
our south. Clearing skies are expected as the last vestiges of
moisture exits the region. Then on Sunday, a narrow shortwave trough
will lift across the region along a stretched out cold front. The
moisture feed is fairly tenuous and ridging looks to persist in the
face of this feature, so anticipate showers will largely dissipate
before crossing into northern New York as the feature moves eastward.
For Monday, ridging will amplify ahead of another high amplitude
trough that will develop across the central US. Thus, a pleasant day
is expected. As we head towards evening though, tightening pressure
gradients ahead of the next cold front will lead to increasingly
gusty winds later in the day with 850mb winds increasing to 50 to 55
knots. Bulk of the tropical moisture streaming along those fast mid-
level winds should arrive overnight Monday into Tuesday morning
based on latest model data. Should be a good soaker, but it will be
a bit more terrain dependent than the event that will unfold
tomorrow. A few lingering showers will be possible until the upper
trough departs around next Wednesday.
Aviation /18z Wednesday through Monday/...
through 18z Thursday...currently VFR at all terminals with bkn/ovc
skies between 5-10k ft. Southeasterly winds are beginning to
pick up across the area with sustained winds between 10-15 kt,
with gusts upwards of 20-25 kt, with localized gusts up to 30
kt, especially at krut through 05z tonight. After 06z, winds
will shift out of the north/northeast at 10 to 15 kt. Gusts
will increase towards 12z, especially for the Champlain Valley
where a strong 40-50 kt 925mb jet sets up...gusts for kbtv &
pbg could be upwards of 35 knots. Elsewhere, expecting gusts in
the 20-25 kt range. Rain moves in from west to east around 21z
to 00z. Periods of moderate to heavy rain will begin to impact
all terminals at 03-06z through the remainder of the taf period
with visibilies between 3-4 miles. Ceilings will deteriorate
overnight tonight, dropping to MVFR after 00z areawide, with IFR
ceilings expected between 05-10z.
Thursday night: mainly MVFR, with local IFR possible. Chance
Friday: mainly MVFR, with areas VFR possible. Chance rain showers.
Friday night: mainly VFR, with local IFR possible. No sig weather.
Saturday: mainly VFR, with local MVFR possible. No sig weather.
Saturday night: VFR. No sig weather.
Sunday: VFR. No sig weather.
Sunday night: VFR. No sig weather.
Monday: VFR. Slight chance rain showers.
there is the possibility for urban and small stream flooding
tonight throughout Thursday as moderate to heavy rainfall will
move through the north country. Looking at the meteorological
model ensemble river forecasts (mmefs), a few locations
including but not limited to ausable Forks and Center Rutland
could approach or exceed minor flood stage. Rainfall totals
through Thursday night will range from 1.5 to 2.5 inches with
around an inch for far eastern Vermont as downsloping off the
White Mountains will reduce rainfall totals. Upslope locations
of the Adirondacks could see 3+ inches but these totals should
be very isolated. Flashier rivers and streams will respond
quickly to this rainfall but should largely remain within
bankful. Another concern for the potential of localized flooding
will be Leaf debris. Strong winds will develop this afternoon
and continue through Thursday which should blow many leaves off
of trees. These leaves could partially or fully block storm
drains which could lead to some localized flooding. Stay tuned
for later forecasts for any updates to flooding concerns.
winds are expected to ramp up quickly this morning as the
pressure gradient begins to strengthen. By noon, southerly winds
around 15-25 knots are expected to develop with seas building
upwards to 4 ft. A brief lull in the winds are expected this
evening as winds begin to shift to the north. Winds will
increase rapidly again Thursday morning with winds of 25-35
knots expected along Lake Champlain with higher gusty up to 40
knots possible. Seas will build to 4-6 ft with some 7 ft waves
in the broad sections of the lake. Winds will slowly ramp down
Thursday night and Friday but will likely remain around 25 knots
until Friday night.