671
FXUS61 KBTV 131722
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
122 PM EDT Tue Aug 13 2024

.SYNOPSIS...
After some morning fog burns off, mostly sunny skies develop
today with temperatures warming into the mid 70s to lower 80s
most locations. A cool and comfortable night is anticipated with
lows in the upper 40s to upper 50s across our region. The
chances for afternoon showers and thunderstorms increase again
on Wednesday into Thursday with temperatures warming into the
upper 70s to mid 80s.

&&

.NEAR TERM /THROUGH WEDNESDAY NIGHT/...
As of 111 PM EDT Tuesday...Weather conditions remain quiet. As
some smoke models suggested, subsidence has allowed it to
descend to the surface. Real time air quality observation sites
suggest some degradation in air quality, but nothing
significant, nor have weather stations been observing
appreciable drops in visibility. Satellite shows most of the
smoke is lingering in eastern Vermont at this point. Little
weather grid changes were necessary. Have a great day!

Previous discussion below:
A beautiful day is on tap with developing sunshine, mild temps,
and comfortable humidity values, resulting in a classic North
Country Chamber of Commerce type day. Water vapor shows large
scale subsidence directly overhead, which is confirmed by area
soundings indicating a deep dry layer btwn 850-300mb. After some
morning fog/clouds burn off plenty of sunshine is anticipated
with just a few fair wx cumulus clouds over the trrn. Progged
925mb temps btwn 18-20C support highs mid 70s to l/m 80s acrs
our region.

Tonight mid/upper lvl trof prevails as sfc high pres remains
anchored acrs the central Great Lakes. Some high level moisture
may advect into our cwa from the north aft 06z, but given
lighter wind fields and temps dropping to near cross over values
anticipate some areas of fog, especially climo favored areas.
Have continued with previous fcster thinking for fog with most
likely areas valleys of the northern Dacks and mtn valleys of
central/northern VT, including the NEK and CT River area. Lows
range from the upper 40s to upper 50s with comfortable humidity.
For Weds continued a 15 to 30% probability of showers/storms,
with highest pops over the eastern Dacks and mtns of VT btwn
21-00z. Latest NAM solutions indicate sfc based CAPE values in
the 1200-1800 J/kg, which maybe a bit overdone, especially if a
dry pocket near 850mb mixes toward the sfc. Either way, a weak
disturbance in the northerly flow aloft drops south acrs our cwa
after 18z, which should provide enough lift for widely scattered
showers/storms. Temps warm back into the upper 70s to mid 80s, a
few degrees warmer than today. Deep layer shear is very weak
and unidirectional on Weds, so not anticipating a severe threat,
maybe a brief stronger storm is possible, but coverage wl be
limited.

&&

.SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/...
As of 335 AM EDT Tuesday...Daytime showers may linger Wednesday
night, with a diminished opportunity for lightning, as sufficiently
steep lapse rates and cyclonic flow promote scattered shower
activity. At the surface, weak high pressure will remain over the
area. So aside from any precipitation, expect another round of
patchy dense fog to develop.

While not a washout, Thursday is likely to be showery. The latest
model guidance continues to suggest we will se numerous showers with
a chance of thunder to redevelop after a lull, peaking Thursday
afternoon, before again winding down Thursday night. A very weak
surface trough approaching from the west will aid in surface
convergence with some southerly winds developing in Vermont and
northern New York while the upper level low over Maine continues to
spin and bring impulses pinwheeling on its western flank across our
area.

Six hour thunderstorm probabilities are fairly robust in the 32 to
41% range between 2 and 8 PM areawide, with slightly greater chances
centered near Orange County and lowest in southernmost St. Lawrence
County. Thunderstorms are unlikely to be severe, but stronger ones
will be capable of small hail and gusty winds. Fairly low freezing
levels, perhaps down to 8000 feet, suggest a taller storm could
produce some brief small hail. While low level flow will be weak,
moderate northerly winds aloft suggest in a stronger updraft, a
taller thunderstorm would have sufficient deep layer shear for a
cell to be balanced such that gusty winds could make it to the
surface in a downdraft, aided by dry low level air and the
associated steep lapse rates.

High temperatures will probably end up very close to seasonal
normals. However, compared to the previous forecast, these
temperatures have trended a touch cooler, especially in many Vermont
locations, probably due to greater likelihood of numerous showers.
The cloud cover associated with these showers will limit solar
radiation, although a partly cloudy sky generally is still
indicated; periods of mostly sunny skies will be interspersed with
cloudy ones. Precipitation chances will wind down Thursday night as
mid-level ridging slides in from the west. Nighttime temperatures
will be seasonable again, probably ranging from the low 50s to low
60s.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
As of 335 AM EDT Tuesday...Friday will be the pick of the long term
for outdoor activities, easily. High confidence of dry weather with
a ridge of high pressure cresting overhead.

Then Saturday, Sunday, and Monday look unsettled, to say the least.
While none of these days currently is favored to see any significant
event, the potential for heavy rainfall will need to be monitored. A
potentially deep trough will only slowly move eastward through the
weekend, as a Rex block in the western Atlantic develops due to the
track of what is now Tropical Storm Ernesto. The longwave pattern
will maintain the trough near or west of the region into Monday.
Through the period, the 500 millibar heights continue to show some
variability in global models. These differences don`t change the
rainfall chances much, but they will have subtle effects on the
amount of instability and shear available for thunderstorms each
day. As an example, with the 00Z LREF, the combination of these
parameters in each of the four ensemble clusters Saturday afternoon
varies. The mean of only one of the four scenarios suggests a low
end severe weather threat, and even that would be primarily in the
southwestern portions of northern New York. That is consistent with
the pattern of NBM probability of 24 hour rainfall exceeding 0.5"
through Sunday morning. Rainfall totals through Monday currently
have a 10 to 30% chance of exceeding 2" using the same model
guidance. While not dramatically so, there generally is a consensus
on deep moisture and forcing for precipitation peaking on Sunday
across our area; That may be the day to focus on with regards to any
potential impactful weather, so stay tuned.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
Through 18Z Wednesday...VFR conditions expected for the next 6
to 9 hours. Fair weather cumulus clouds with bases around
3000-5000 ft agl will dissipate beyond 22z. Outside a southeast
lake breeze at KPBG, all terminals have shifted to northwest
winds, which should continue through about 00z before winds
become light and terrain driven. Some fog will develop across
the valleys, but some competing factors should present it from
being prolific. For now, have just indicated 2-4SM visibility at
KMPV and KSLK. After 12z, northwest windds return at 5 to 10
knots. Isolated showers and storms will develop towards 18z
Wednesday, but appear unlikely to impact any terminals at this
time.

Outlook...

Wednesday Night: VFR. Slight chance SHRA, Patchy BR.
Thursday: VFR. Scattered SHRA, Isolated TSRA.
Thursday Night: VFR. NO SIG WX.
Friday: VFR. NO SIG WX.
Friday Night: VFR. Slight chance SHRA.
Saturday: Mainly VFR, with local MVFR possible. Chance SHRA,
Slight chance TSRA.
Saturday Night: Mainly MVFR, with local IFR possible. Likely
SHRA, Slight chance TSRA.
Sunday: Mainly MVFR, with local IFR possible. Likely SHRA, Slight
chance TSRA.

&&

.BTV WATCHES/WARNINGS/ADVISORIES...
VT...None.
NY...None.

&&

$$
SYNOPSIS...Taber
NEAR TERM...Haynes/Taber
SHORT TERM...Kutikoff
LONG TERM...Kutikoff
AVIATION...Haynes