537
FXUS61 KBTV 210545
AFDBTV
Area Forecast Discussion
National Weather Service Burlington VT
145 AM EDT Sun Apr 21 2024
.SYNOPSIS...
Scattered showers will persist into the evening hours, with any
stronger activity capable of producing gusty winds and small hail or
graupel. Sunday and Monday will be mainly dry, but cooler,
especially Monday after a strong cold frontal passage Sunday night.
Temperatures will warm briefly on Tuesday, with rain chances
increasing as we head into the middle of the week.
&&
.NEAR TERM /THROUGH MONDAY/...
As of 123 AM EDT Sunday...A quiet night across the region this
evening with mostly clear skies. The current forecast remain in
good shape, with only some small tweaks to sky cover to reflect
latest satellite.
PREVIOUS DISCUSSION...Scattered showers have developed across
the region as anticipated this afternoon. Given the dry airmass
that is now in place (dewpoints are currently in the 20s to
around 30F in most locations), some showers have already
produced wind gusts up to 45 mph as they`ve moved through
northern NY. This trend will continue through the evening hours,
along with the potential for pea-sized hail or graupel.
Temperatures have dropped sharply under the showers as well, as
much as 5-10F in just 20 minutes.
All this activity is associated with a potent upper trough which is
swinging overhead. This feature will shift east of our region
overnight, and this along with the loss of daytime heating will
allow showers to wane. Winds will subside overnight as well, though
some occasional gusts will continue to be possible. Skies will
briefly clear out early, but clouds will increase later tonight into
early Sunday as lingering low-level moisture becomes trapped under a
weak inversion. This along with the winds will help limit
radiational cooling overnight; lows will range from the upper 20s to
the mid 30s.
Partly to mostly cloudy conditions will linger into early Sunday
afternoon, but expect the daytime hours to be dry. Daytime mixing
will bring increasing winds and lowering dewpoints during the
afternoon. Highs will be in the mid 40s to mid 50s, but brisk winds
could make it feel a bit on the chilly side, especially where clouds
linger. Another robust upper shortwave trough will swing down toward
the international border Sunday night while a strong cold front
pushes southward across our region. Moisture will be quite limited,
but given the strong dynamics, a few showers will be possible as the
front moves through, mainly over the northern mountains. Any
precipitation would likely fall as snow or a rain/snow mix, and some
light accumulation will be possible. A reinforcing shot of cold and
dry air will follow the front, and temperatures will drop into the
low 20s to around 30F by early Monday morning.
&&
.SHORT TERM /MONDAY NIGHT/...
As of 344 PM EDT Saturday...Expect a sunny sky with below normal
temperatures on Monday in the wake of a strong cold front. The main
story for the day will be very low humidity, likely dropping to near
or below 20% during the day in many locations. The synoptic pattern
of surface high pressure to our west and surface trough over the
Canadian Maritimes is consistent with local studies for fire danger
in April and May. A strongly anomalous lobe of Arctic air will be to
our north, characterized by 500 millibar heights more than 3 sigma
below normal in central Quebec and 850 millibar temperatures more
than 20 degrees Celsius below normal Monday morning. We will be
avoid the brunt of the cold air as the upper level low gyres back to
the north during the day. Still, with low level cold air advection
temperatures will only warm through the 40s, resulting in highs
roughly ten degrees below normal despite full sunshine. Deep mixing
due to the very dry air and sunshine will contribute to the lower
relatively humidity values, probably bottoming out in the mid
afternoon hours. While we should see gusty winds, the surface
pressure gradient looks weak enough to keep the magnitude of gusts
relatively low, near 20 MPH for most spots.
As the upper trough retreats, we will gradually become influenced
instead by an air mass of Pacific origins that will be moving
eastward across the northern Plains. As a broad zone of surface high
pressure sets up out across the southeastern US Monday night,
lowering pressure across our region will induce increasingly breezy
south winds in a dramatic reversal from the previous night. If these
breezes materialize on the earlier side, low temperatures will occur
well before sunrise. Expect strong warm air advection, with 12 hour
850 millibar temperature rises of 4 to 9 degrees Celsius between 2
PM Monday and 2 AM Tuesday, greatest in northern/western areas and
smallest in southern Vermont, but with dry air and ridging aloft no
precipitation will occur during this period.
&&
.LONG TERM /TUESDAY THROUGH SATURDAY/...
As of 344 PM EDT Saturday...Tuesday will be a much warmer day than
Monday due to continued warm air advection and sunshine. A tongue of
warm temperature anomalies will rapidly shift eastward across the
Great Lakes into our region during the day, with surface
temperatures likely to surge into the upper 50s to mid 60s by mid-
afternoon. Southerly winds ahead of an approaching significant
trough will channel through the wide valleys and could be stronger
than currently indicated. NBM probabilities of peak wind gusts
reaching 40 MPH are above 40% in locations such as Massena, NY and
Burlington, VT. Probabilities of wind gusts reaching advisory level
are much lower; we don`t expect any wind hazards at this time.
If you`re looking for warm spring weather, make sure to spend time
outdoors by midday Wednesday because it dramatically colder weather
will arrive after that time. In fact, a stretch of winterlike
weather may make an unwelcome return behind a well-predicted cold
front. The extent of any snowfall is highly uncertain as model
guidance continues to be rather divergent on how a low pressure
system evolves in our region. As a result, the degree of cold air,
let alone precipitation amounts, ranges wildly as illustrated in
mean 850 millibar temperatures in the most likely outcomes. The
coldest solution features a very deep trough and closed upper level
low due to phasing of Pacific and Polar jets. This idea, similar to
the operational GFS, shows temperatures well below the interquartile
range of global ensembles and supports measurable snow in the valley
floors. Even two other reasonable solutions bring some snow to even
the lower elevations late Wednesday into Thursday.
It`s still too early to jump onto a single outcome, but some heavy
wet snow is possible, particularly in westerly upslope favored
locations. While highly unlikely to be on its scale, the timing is
similar to the heavy snowfall on April 27-28, 2010 in northern
Vermont that produced locally around 2 feet of snow. Given the low
predictability of the period and plenty of time to hone in on
details, will continue to stay with the NBM for weather elements in
the Wednesday afternoon through Thursday night period. Thereafter,
dry weather is favored to end the week with little indication of
precipitation on Friday or Saturday at this time.
&&
.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
Through 06Z Monday...VFR conditions currently prevail across all
sites, with mostly clear skies across the forecast area. VFR
conditions will prevail at all terminals for the forecast
period, with some increasing clouds throughout the day and
little to no precipitation. Winds this evening have be westerly
to southwesterly and will generally remain less than 10 knots.
Between 13Z to 15Z, winds will become breezier, with wind gusts
between 15 to 25 knots. No LLWS is currently expected during the
forecast period.
Outlook...
Monday: VFR. NO SIG WX.
Monday Night: VFR. NO SIG WX.
Tuesday: VFR. NO SIG WX.
Tuesday Night: Mainly VFR, with local MVFR possible. Chance SHRA.
Wednesday: Mainly MVFR, with local VFR possible. Definite SHRA.
Wednesday Night: Mainly VFR, with local MVFR possible. Chance
SHRA, Slight chance SHSN.
Thursday: VFR. Slight chance SHRA, Slight chance SHSN.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...None.
NY...None.
&&
$$
SYNOPSIS...Hastings
NEAR TERM...Hastings/Kremer
SHORT TERM...Kutikoff
LONG TERM...Kutikoff
AVIATION...Kremer
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