Area Forecast Discussion
Issued by NWS Burlington, VT-- Highlight Changed Discussion --
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FXUS61 KBTV 240816
Area Forecast Discussion
National Weather Service Burlington VT
416 AM EDT TUE MAY 24 2016
-- Changed Discussion --An upper level low pressure system just off the mid-Atlantic coast
will move northeast today and reach eastern Maine tonight. This will
bring clouds to the area along with the threat of showers across
Vermont and parts of the northern Adirondacks. Dry weather is
expected Wednesday morning...but then an upper level disturbance
will move across the area Wednesday afternoon and bring a chance of
showers and thunderstorms to the North Country. Above normal
temperatures are expected today and Wednesday with highs in the mid
70s to lower 80s.
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.NEAR TERM /THROUGH WEDNESDAY/...
-- Changed Discussion --As of 415 AM EDT Tuesday...We will see a gradual increase in
clouds across most of the area today as an upper level low
pressure system off the mid-Atlantic coast moves slowly northeast.
There will be a sharp gradient of precipitation with this system
across our area because of the track of the system. Looking at
most of northern New York remaining dry today with a chance of
showers across Essex County New York and most of Vermont. There
could even be an isolated thunderstorm...mainly over southern and
eastern Vermont. High temperatures today will be in the mid 70s
east to lower 80s west.
Upper level low continues to move northeast tonight and reach
eastern Main by Wednesday morning. Still looking at some lingering
showers over eastern Vermont tonight...but eventual dry conditions
develop over the entire area later tonight through Wednesday
morning. Eventually a shortwave trough moves across eastern Canada
and the Northeast Wednesday afternoon. This will increase dynamic
support over the area and bring a cold front into the region late
Wednesday afternoon. Instability should also increase ahead of the
front with highs getting into the mid 70s to lower 80s. Dew points
will also be increasing...but feel model forecasts are doing their
usual overforecast of dew points which in turns creates more
instability. Feel CAPE values will be closer to 500 J/kg versus the
model forecasts of 1000 J/kg. This should be sufficient to enhance
the potential for convection and during this time of maximum
instability...deep layer shear is increasing. Neither the instability
or shear are strong...but enough to increase the potential for
thunderstorms and have included in the forecast.
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.SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY/...
As of 355 PM EDT Monday... tuesday night: showers/isolated
t-storms mainly for vermont will quickly fade by mid evening with
the loss of heating. maybe a touch of patchy fog for late night,
though confidence not high enough to include that in the forecast.
wednesday: hi-res models are all pretty similar with overall
scenario of a shortwave and associated weak surface front pushing
into the region from the northwest. with temperatures well into
the 70s, we`ll have some surface based instability. models suggest
cape values of 500-1000 J/kg. nam also showing 0-6km shear of
roughly 30-40kt developing during the afternoon especially across
northern ny. looks like enough ingredients coming together for
convection to develop during the afternoon -- perhaps with semi-
organization to them. model radar reflectivity output from various
hi-res models suggests a broken line of t-storms will rapidly
develop mid-day across northern new york and push southeast and
then quickly fade by early evening as they reach southern vermont
where less instability will be available. have blended the
reflectivity outputs to form the basis of the PoP forecast for the
day. basically a 30-50% chance of t-storms for the afternoon,
especially across northern ny and extending into northern vermont.
thursday: will be a transition day. for most of us, it will be
dry and fairly sunny. perhaps some showers or isolated t-storm
across northern ny later in the day as a developing southwest flow
sends a surge of moisture our way. stuck with the model blend with
highs well into the 70s for the region.
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
As of 355 PM EDT Monday...
looks like a summer pattern for the holiday weekend. that means
warmth, moderately humid and the chance for thunderstorms each
day. GFS and ECMWF are in "okay" agreement with the large scale
synoptics, however there will be a "back-door" front setting up
somewhere probably just to our east thanks to the still quite
chilly atlantic ocean. depending on how far inland this front will
push will greatly affect the weather we see. considerable
differences in this subtle but important detail in the global
models, so there is some bust potential in parts of the forecast.
thursday night: southwest flow and associated moisture advection
will lead to scattered showers. clouds and precipitation will keep
it rather mild overnight, with lows in the 50s to lower 60s.
friday: we`ll be solidly into a warmer and slightly more humid
airmass. both GFS and ECMWF indicate a decent amount of surface
based instability, with cape values likely topping out over 750
J/kg by the afternoon. not a lot of dynamic forcing, but the
atmosphere will be fairly moist (precipitable water values over
1.25"). looks like a typical early August weather pattern, so
I`ve gone ahead with a typical forecast for that part of the
summer. 35-50% chance of afternoon thunderstorms looks good. will
probably initially form over the higher terrain and then push east
during the afternoon. with 850mb temperatures rising to around
15C, that would support support highs in the lower to mid 80s for
the region. went a little warmer than the first guess model
saturday: looks a lot like friday, except the surface dewpoints
are a little bit higher. i think this will be the first day that
we`ll really start to notice the humidity. some differences in the
overall temperature fields as denoted by the GFS and ECMWF. ECMWF
wants to slide in slightly cooler air from the north, as it has
the ridge axis suppressed slightly further south than the GFS. the
GFS has 925mb temperatures rising to 20-23C, which would mean we
could approach 90f in some valley areas. ECMWF is cooler (17C
across the Canadian border to 22C in far southern vermont). took
the blend of the models, but that still results in temperatures
solidly into the 80s. based on those temperatures and a little
higher humidity, afternoon thunderstorms will be a good bet once
again. no strong focus other than terrain, so t-storms will be a
hit and miss proposition.
sunday & memorial day (monday): both GFS and ECMWF indicate that
cooler atlantic airmass will pool to our east and try to make a
westward push as a small high pressure develops east of new
england. this "back door" front will be shallow, and just how much
the terrain (white mountains and green mountains) restrict it`s
westward movement is just a little beyond the resolution of the
global models. for sunday, this backdoor front should still be to
our east, so sunday looks to be a repeat of saturday (temperature
wise and t-storm chance-wise). for monday, if anything, the models
suggest a cooler airmass will push into eastern vermont. if this
happens, we could see a pretty significant temperature variation
(60s far east to mid 80s far west) across the forecast area. those
specific details, as mentioned, are tough to pin down this far
out. thus stuck with straight guidance blend for monday, which
indicates an overall cooler day than sunday. still a rather moist
airmass around, so will maintain 30-40% PoPs. given the cooler
forecast, surface instability will be less, so probably not as
many t-storms around for memorial day. still doesn`t look like a
total washout of a day, so i think most outdoor activities/bar-b-ques
should still be okay.
.AVIATION /08Z Tuesday THROUGH Saturday/...
Through 06Z Wednesday...VFR through the forecast period. Winds
variable less than 10 kts. After 15Z Tuesday, increasing moisture
from the east/south will bring sct/bkn VFR cigs in the 050-100 AGL
range with an increasing threat of a shower/isolated storm,
especially at KMPV/KRUT terminals.
Outlook 06Z Wednesday through Saturday...
06z Wed - 00z Thu: VFR with chance of afternoon/early evening
showers and/or isolated thunderstorms each day. Activity generally
scattered in nature with long periods of VFR/dry weather. Brief
gusty winds and/or MVFR visibilities possible with any heavier
Thu: VFR under high pressure.
Thu night-Fri: VFR/Chance MVFR in SHRA/TSRA with a warm front.
Sat: Mainly VFR. SCT pm SHRA/TSRA.