581
FXUS61 KBTV 060733
AFDBTV
Area Forecast Discussion
National Weather Service Burlington VT
333 AM EDT Tue May 6 2025
.SYNOPSIS...
Damp weather conditions will continue. By Wednesday night, a
persistent upper low will begin to depart the region. Briefly
cooler and drier conditions will give way to additional rain,
mainly over Vermont Friday afternoon into Saturday. The
development of a broad upper ridge across the eastern US signals
a likely pattern change next week.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
As of 304 AM EDT Tuesday...Slow moving upper low pressure is
beginning to accelerate northeastwards. Currently, we are at the
confluence of a moist, southeasterly fetch off the Atlantic
Ocean. However, with just marginal forcing and 40-50 knot
southeasterly LLJ, we`ve been experiencing a large degree of
terrain shadowing. There should be a relative lull in
precipitation again late this morning and early afternoon as a
pocket of dry mid-level air encroaches. In that pocket of dry
air, partial clearing should allow temperatures to warm,
especially along the international border where southeasterly
flow should enhance downslope subsidence of that dry air. Near
70 to mid 70s should be prevalent in the Champlain Valley and
St. Lawrence Valleys while the rest of the region will linger in
the 60s. Daytime heating and dewpoints in the mid 50s should
allow for about 500 J/kg of CAPE, perhaps even 1000 J/kg over
the St. Lawrence Valley. Pulse convection should initiate mid-
afternoon and lift north in increasingly southerly flow. If
there`s anywhere that could have a stronger storm, it`d be the
St. Lawrence Valley due to better instability and shear of about
30-35 knots. Low-level flow is relatively weak and low-level
lapse rates are also poor. So if any storm is to produce much,
it`ll have to be sustained and breach a stable layer around
700mb. Some small hail and locally gusty winds could develop in
the St. Lawrence River Valley, but the rest of the region will
remain firmly garden variety.
The other thing that will need monitoring will be convection in
southern Vermont. The last two days has yielded 1-2 inches
across Rutland and Windsor Counties. 3 hour flash flood
guidances are about 1.6-1.8" and 6 hour is about 1.8-2". The
latest HREF forecast does not highlight this region, instead
emphasizing western St. Lawrence County, but that region is
tough to flood. Occasional HRRR runs have a narrow swath of 1-2"
cutting into Windsor County, and this suggests a watchful eye
kept there during afternoon convection.
By tonight, decreasing surface instability and entrainment of
dry air again will cause activity to wane, except continuing in
St. Lawrence County due to close proximity with the surface
low. Another warm mid-spring night with upper 40s to upper 50s
is expected Tuesday night. Upper level low pressure will be
overhead Wednesday with a surface cold front shifting southeast
late in the day. High res guidance has backed off some on
coverage and have mostly 40-70 PoPs once instability develops
Wednesday afternoon. With little wind shear, garden variety
thunderstorms are possible. Outside showers, it will be an
otherwise pleasant day in the mid 60s to lower 70s.
&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY/...
As of 304 AM EDT Tuesday...Scattered showers Wednesday night will
become increasingly isolated and confined to higher terrain going
into early Thursday, with the forecast eventually trending mainly
dry by the evening. Despite the diminishing shower threat, skies
will remain partly to mostly cloudy as an upstream shortwave
approaches from the west. Low temperatures Wednesday night will
range through the 40s, while highs Thursday will be in the 50s for
most locations. This will be noticeably cooler than the previous few
days, although the brief break in rain showers for most will make
Thursday a good day for those searching for some relief from the
persistent showers.
&&
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
As of 304 AM EDT Tuesday...The shortwave trough moving in from the
west will close off into another upper-level low Friday, which will
mean a return to the showery pattern for parts of the Northeast.
Highest confidence is in rain developing Friday and Saturday for
parts of southern and eastern Vermont, but there is some hope for a
drier conditions further west into northwestern VT and northern NY.
This setup will be due in part to the development of a coastal low
late Friday into Saturday under the upper low, with some question
remaining as to just how close to the New England coast the low
tracks as it moves northeast. The 24 hour model trend of the
deterministic GFS has been to generally shift the precipitation
further east with each consecutive run, supported by decreasing
probabilities for measurable precipitation in our western counties
amongst the GEFS ensemble guidance. Meanwhile, the ECMWF is holding
strong to a further inland track, resulting in (another) rainy
Saturday for most of our area. The 00Z deterministic run of the
Canadian is holding on to the faster trend as a whole with the
system, bringing some rain to eastern counties on Friday but keeping
Saturday mainly dry. A look at the ensemble QPF guidance shows a few
individual ensemble members clinging to a washout on Saturday, but
by and large the ensemble guidance is favoring lighter precip
amounts for northern NY and northern VT. Thus, have stuck close
to the National Blend forecast for PoPs for the weekend, keeping
25 to 40 percent PoPs for most of Vermont and into our eastern
NY counties for Saturday. As the low exits Saturday night,
confidence increases in a dry Sunday with drier air and surface
high pressure moving in from the west. Drier weather will last
into early next week with a warming trend in temperatures.
&&
.AVIATION /07Z TUESDAY THROUGH SATURDAY/...
Through 06Z Wednesday...Conditions are mainly VFR outside some
1500 ft agl ceilings at KRUT and KMPV with rain showers lifting
northwestwards. A stagnant weather pattern will result in
little change over the next 24 hours. Batches of light rain
continue to lift north, but upstream observations do not show
much in the way of visibility restrictions and intervals of MVFR
ceilings. A relative minimum in precipitation coverage is
expected from about 12z to 18z before additional shower activity
will lift up from the south. There could be a few embedded
thunderstorms, but mainly moderate rain is likely, with a few
PROB30 groups with 4SM indicating this idea. Showers again ebb
about 00z. Intermittent LLWS will also continue through the next
24 hours with winds around 2000 ft agl out of the southeast to
south at 35 to 45 knots.
Outlook...
Wednesday: Mainly VFR, with local MVFR possible. Likely SHRA,
Slight chance TSRA.
Wednesday Night: Mainly MVFR, with local IFR possible. Chance
SHRA.
Thursday: Mainly MVFR, with local VFR possible. Slight chance
SHRA.
Thursday Night: Mainly VFR, with areas MVFR possible. NO SIG WX.
Friday: Mainly VFR, with areas MVFR possible. Chance SHRA.
Friday Night: Mainly VFR, with areas MVFR possible. Chance SHRA.
Saturday: Mainly VFR, with local MVFR possible. Chance SHRA.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...None.
NY...None.
&&
$$
SYNOPSIS...Haynes
NEAR TERM...Haynes
SHORT TERM...Duell
LONG TERM...Duell
AVIATION...Haynes
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