FXUS61 KBTV 111717
Area Forecast Discussion
National Weather Service Burlington VT
117 PM EDT Sun Apr 11 2021
A weak occluded front will bring increased cloud cover and chances
for rain to portions of northern New York and southern Vermont this
afternoon. However, most locations are expected to remain dry with
cooler temperatures as a backdoor cold front approaches from the
northeast. Scattered showers will remain possible through Tuesday
but it appears we are in for another quiet week of weather with high
pressure once again building back across the region. Temperatures
won`t be quite as warm this week as they were last week with high
temperatures each afternoon in the upper 50s to lower 60s.
.NEAR TERM /THROUGH MONDAY/...
As of 1006 AM EDT Sunday...Only changes to the forecast this
morning were to continue backing off on PoPs/QPF along our
forecast border across northern New York and southern Vermont.
Looking at the big picture, the occluded frontal boundary
already appears to be stalling with the backdoor cold front
making more progress than initially thought. The combination of
these two factors should yield mainly dry conditions except the
far southern reaches of our forecast area. For most locations,
another nice spring day is on tap although it woulnd`t hurt for
a few rain drops given the developing drought conditions.
Previous discussion...A couple of weak fronts will make a run
at each other from opposite sides of the forecast area today and
Monday, with the overall result being the chance for scattered
showers over portions of our area. The first front will be a
backdoor cold front, which currently lies poised just to our
north and east. Cooler maritime air will spread into eastern VT
as this front makes its way westward. Meanwhile, an occluded
front positioned to our southwest will push toward our region,
spreading showers northeastward as it does so. Unfortunately,
with the drier air behind the cold front and ridging aloft will
work against the occluded front, limiting the forward progress
of the precipitation. Showers will make it into northern New
York and portions of southern Vermont, but expect most areas
will be dry, particularly east of a line from Ellenburg Depot to
Waitsfield to Stafford. West of this line, scattered showers
will come and go this afternoon through Monday, with total
rainfall amounts generally a few hundredths to perhaps up to a
third of an inch in far western St Lawrence County. Note that
some of the hi-res CAM guidance is indicating some pop up
convection ahead of the occluded front in portions of far
northern NY/Champlain Valley. There will be a bit of elevated
instability, but overall convective threat is minimal so have
left out any mention of thunder. Temperatures are a bit tricky
given the two boundaries that will be at play. Areas from the
Champlain Valley westward will top out in the upper 60s to lower
70s. East of the Greens, the backdoor front will keep
temperatures in the lower to mid 60s. It will be even cooler
tomorrow, generally in the mid 50s to mid 60s. This is near
normal for mid May, but it will feel cool compared to the recent
warmth we`ve had. Lows tonight will be in the upper 30s to
upper 40s, coolest in the sheltered valleys in the higher
.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY/...
As of 358 AM EDT Sunday...Retrograding pattern with a stable air mass
advancing in from the east remains the expectation for Monday night,
with any lingering rain showers over western portions of the
forecast area being shunted to the west as the upper level energy
tracks across the Mid- Atlantic states. The east or northeast low-
level flow will support development of a thick overcast over eastern
Vermont where surface winds will be negligible. During the daytime,
neither surface heating nor dry air aloft will be sufficient to mix
out the clouds, which will be trapped under a relatively high -
several thousand foot - inversion. Elsewhere, skies generally should
be partly to mostly cloudy, although where the easterly mid-level
flow results in downsloping, such as in the eastern Champlain
Valley, the clouds should dissipate more quickly and temperatures
recover a little better. Highs will end up roughly 5 degrees above
normal in many areas from the Green Mountains west, with near or
possibly below normal temperatures east of the Greens. While
measurable rain not expected, very light showers are possible over
eastern Vermont during the day as a subtle upper-level wave moves
southwestward, causing enough vertical motion in the clouds to
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
As of 442 AM EDT Sunday...Another occluded front will advance towards
the area Tuesday night, and yet again have trouble moving eastward
through the whole region. Currently good agreement from model
guidance that again only northern New York gets precipitation from
this boundary before it fizzles out. However, during the day on
Wednesday, it appears the occluded low pressure system will be large
enough and track far enough north to support surface convergence in
much of the North Country, enough so to result in scattered showers.
The broad, disorganized system will not have much in the way of
thermal gradients or strong wind fields, so precipitation will be
light. Temperatures should be near normal or a few degrees above
normal, reaching into the mid and upper 50s in most areas.
Things may get more interesting on Thursday, as the latest guidance
strongly suggests that the upper-level troughing moving eastward
Wednesday night will phase with southern stream energy, with rapid
cyclogenesis taking place somewhere east of the central
Appalachians. The latest global deterministic models have this low
pressure area somewhere between the DelMarVa and Cape Hatteras early
on Thursday, with the GFS relatively far south and east. As a
result, the circulation stays offshore and well south of our area,
with dry, mild northeast winds across the North Country. However,
both the Canadian and European solutions are far enough north and
west to bring steady rainfall to at least portions of the forecast
area. However, very little support for a large rain event in excess
of 1" exists at this time. In fact, even with a relatively favorable
track near Cape Cod in the Canadian model, the ensemble system
suggests even rainfall exceeding 0.1" is relatively unlikely. The
ECMWF ensemble is a little more encouraging for significant
rainfall, with about a 50% chance of rainfall exceeding 0.5" across
much of Vermont and northeastern New York. Since a cloudy and wet
period from Thursday into early Friday would mark a dramatic shift
from the previous forecast, the current forecast does not yet call
for this rainfall. But if the next cycle has more support for an
east coast low pressure system sufficiently north and west, expect
to see precipitation chances come up a bit.
The remainder of the forecast period really will be determined by
what happens with the potential storm on Thursday. The weekend looks
potentially unsettled with additional shower chances if the low
pressure system lifts northward along the coast, which would help
establish a synoptic pattern featuring the mean trough sitting over
the northeastern US. Areas of low pressure would then dumbbell
around the trough, with better chances of showers along with
cooler conditions will probably holding off until Sunday.
However, if the storm on Thursday goes harmlessly out to see, we
will not only miss out on rain then but we will likely remain
in light flow pattern with weak surface high pressure keeping us
high and dry, with temperatures trending a bit warmer. Stay
.AVIATION /17Z SUNDAY THROUGH FRIDAY/...
Through 18Z Monday...VFR conditions continue to prevail across
the North Country with ceilings generally 20,000 ft our higher
as high clouds in advance of a frontal occlusion overspread the
region. Winds have been out of the north to northeast this
morning and early afternoon at 7-15 knots with some gustier
winds at Rutland and Massena but we should see winds flip to the
south to southeast between 21Z and 22Z. At Massena, it looks
like winds will stay from the northeast with bouts of gusts to
20-25 knots through much of the forecast period. Precipitation
continues to look lackluster with rainfall struggling to advance
northward. In response, we have lowered PoPs and have just a
mention of VCSH at KRUT and KSLK tonight. Otherwise, dry weather
with VFR conditions will persist through the next 24 hours.
Monday Night: VFR. NO SIG WX.
Tuesday: VFR. NO SIG WX.
Tuesday Night: VFR. Chance SHRA.
Wednesday: VFR. Slight chance SHRA.
Wednesday Night: Mainly VFR, with areas MVFR possible. NO SIG WX.
Thursday: Mainly VFR, with areas MVFR possible. Slight chance RA.
Thursday Night: Mainly VFR, with local MVFR possible. NO SIG WX.
Friday: Mainly MVFR, with local VFR possible. NO SIG WX.