019
FXUS61 KBTV 061728
AFDBTV
Area Forecast Discussion
National Weather Service Burlington VT
128 PM 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 119 PM EDT Tuesday...Little change needed with crnt fcst.
Radar showing rain showers with heavier embedded showers angling
acrs SLV attm. Also, additional precip wl expand acrs
central/southern VT over the next 1 to 3 hours, per upstream
radar trends. Timing of rain showers and associated pops/qpf
continues to be the challenge with deep closed vertically
stacked cyclonic circulation over the Ohio Valley. As weak sfc
instability develops associated with several narrow dry slots
rotating acrs our cwa, expect the areal coverage of showers with
embedded rumbles of thunder to increase in areal
coverage/intensity this aftn/evening. The highest probability of
CAPE values near 500 J/kg continues to be located over the
SLV/western Dacks and have the highest potential for thunder is
in this area. Otherwise, sounding analysis shows the potential
for some training/back building showers/storms, given the
unidirectional flow aloft and small MBE velocities <10 knots, so
we wl cont to monitor hydro threat. As instability wanes this
evening, intensity/coverage of showers should decrease by 03z.
Did make some minor tweaks to pops/qpf, but kept temps the same,
even thou we are running several degrees too cool. A bit more
humidity noted this morning with sfc dwpts climbing into the mid
50s to lower 60s per obs.
Previous discussion below:
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. A 40-50kt LLJ and a
pocket of mid-level dry air evident on water vapor will lift
northeast with scattering of precipitation. 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 TUESDAY/...
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 /17Z TUESDAY THROUGH SUNDAY/...
Through 18Z Wednesday...A mix of MVFR/VFR conditions acrs our
taf sites this aftn with intervals of rain showers expected to
prevail into this evening. As southeast flow continues at MPV,
CIGS will hover near IFR thresholds thru this aftn, with some
lowering toward IFR cigs by 00z possible, as steadier rain
showers arrive. Thinking periods IFR cigs are likely for MPV
overnight as southeast flow prevails with plenty of moisture
below 2500 feet. Other taf sites utilizing mostly a persistent
fcst with a mix of MVFR/VFR conditions. A stronger shower or
embedded thunderstorm could produce brief IFR vis at MSS this
aftn/evening. Winds remain south/southeast at 5 to 10 knots with
localized gusts up to 15 to 20 knots at RUT/EFK, which wl shift
to the southwest btwn 09z to 12z on Weds associated with sfc
boundary.
Outlook...
Wednesday Night: MVFR/IFR conditions possible. Chance SHRA.
Thursday: Mainly MVFR, with areas VFR possible. Slight chance
SHRA.
Thursday Night: Mainly VFR, with areas MVFR possible. Slight
chance SHRA.
Friday: Mainly VFR, with areas MVFR possible. Chance SHRA.
Friday Night: Mainly VFR, with areas MVFR possible. Chance SHRA.
Saturday: VFR. Chance SHRA.
Saturday Night: MVFR/IFR conditions possible. NO SIG WX.
Sunday: VFR. NO SIG WX.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...None.
NY...None.
&&
$$
SYNOPSIS...Haynes
NEAR TERM...Haynes/Taber
SHORT TERM...Duell
LONG TERM...Duell
AVIATION...Taber
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