123
FXUS61 KBTV 062357
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
757 PM EDT Mon May 6 2024

.SYNOPSIS...
Beautiful weather conditions is expected. After a foggy and
cool morning tomorrow, temperatures will rise into the mid 60s
to mid 70s again under clear, blue skies. By Wednesday, rain
chances will return to the forecast with a trend towards cool
temperatures struggling to rise above 60 over the weekend.
Friday appears most likely to be the wettest day. Temperatures
will begin to moderate at the start of next week.

&&

.NEAR TERM /THROUGH TUESDAY NIGHT/...
As of 659 PM EDT Monday...A thin layer of cirrus clouds is
covering much of the southern half of the forecast area, so have
adjusted sky cover to account for this. Overall, minimal impact
with breaks in the cirrus this evening. This cirrus is expected
to shift southeastward tonight, allowing for fog to develop,
especially in valley locations prone to fog. After a
particularly warm day, temperatures are running a bit higher
than forecast, but they should drop off quickly as the sun sets
and skies clear. Previous discussion below:

Previous discussion...With moisture out of the region, we`re
left with fair weather cumulus and thin cirrus. Observed
temperatures are in the 60s to lower 70s with a light breeze out
there. Truly a gorgeous spring day. Efficient cooling is
expected underneath surface high pressure and ample mid-level
dry air. In fact, parts of Ontario Province were below freezing
last night. With that, it seems highly likely the Adirondack
Airport at Saranac Lake hits 32 tonight. Elsewhere, mainly upper
30s to mid 40s is expected with upper 40s near Lake Champlain.
There`s plenty of ground moisture available, and this should
produce valley fog across climo favored spots.

Another great weather day should unfold tomorrow. Temperatures
should be a couple degrees warmer compared to today due to
somewhat drier air in place. There will be some more wind
tomorrow afternoon out of the northwest, but nothing that should
exceed 15 mph. Overnight, a compact surface low will approach
the region with rain chances increasing from the southwest.
Initially, skies will be partly cloudy, and we could observe
brief radiational cooling before clouds and southeast flow
develop ahead of the low and precipitation. Temperatures will
likely be in the 40s Tuesday night into Wednesday.

&&

.SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/...
As of 256 PM EDT Monday...On Wednesday morning, the omega block
breaks down, allowing for a piece of shortwave energy from a
huge meandering upper level closed upper low out west to
approach our region. PWATs rise from 0.4 to 1.1 inches, which is
equivalent to the 25th and 90th percentile of SPC sounding
climatology for the Albany, NY upper air site. Expect shower
coverage to become more widespread by Wednesday morning. Then
the upper level pattern gets a little more complicated. Models
show that upper low over Newfoundland retrograding into New
Hampshire/Maine. As it interacts with the aforementioned
relatively weak shortwave energy from out west, there are some
signals it becomes a neutrally to even slightly negatively
tilted H5 trough. Looking at the 250mb level, there is a small
window parts of New England gets into the favorable left exit
region of an anomalously strong 110 kt jet. A belt of 7 to
7.5C/km mid-level lapse rates cross the area around mid day into
the afternoon hours from west to east.

While the best chance for organized convection and stronger
storms should remain south of our CWA, CAMs forecast soundings
(namely the 12z NAM 3km since we are just getting into the CAM
time range for Wednesday afternoon) hint at the potential for
some marginally severe storms capable of isolated large hail and
perhaps some wet downburst across the southern zones of our
CWA. The main limiting factors include the marginal and
conditional surface-based instability and dew points in the low
to mid 50s. But with surface to 6km shear in the 40-50 kt range
as well as 0-1km storm relative helicity of over 100 m2/s2, an
isolated strong to perhaps severe storm cannot be totally ruled
out. Nonetheless, given the conditional nature of the storms,
have kept with the mention of slight chance of thunderstorms.
The key take home message at this time remains to monitor the
forecast for Wednesday afternoon if you have outdoor plans.
Heading into overnight Wednesday, any thunderstorms and locally
heavy downpours will taper off and mainly dry conditions should
prevail after midnight. Given plenty of moisture trapped in the
boundary layer up to 750mb, patchy fog is possible in sheltered
locations overnight Wednesday into early Thursday morning.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
As of 256 PM EDT Monday...We briefly get into zonal flow on
Thursday but there remains plenty of moisture trapped under an
inversion at the 850-700mb level and cool light northerly or
northeasterly flow below 925mb level owing to a weak surface low
off the New England coast. So expect isolated to scattered
showers and plenty of clouds on Thursday, although no washouts
are expected. There remains the possibility for breaks in
sunshine and where they do occur, current forecast daytime highs
would be a tad too cool. Heading into Friday, global guidance
shows a sub-550mb upper low shifting east from the Ohio River
valley into the interior Atlantic seaboard. There remains
considerable differences in the evolution of the upper low and
how far south it digs. At this time, most of the ensemble
members have it too far south for any organized convection,
although another round of garden variety thunderstorms is
certainly on the table for Friday. What we can be currently more
confident is the potential for anomalously cool temperatures to
prevail across North Country Friday afternoon into at least the
first part of the weekend. The sub-550mb upper low moves
overhead with unseasonably cold temperatures aloft. For
perspective, the sub-freezing 850mb temperatures late Friday
into Saturday would be around the 10th percentile of SPC
sounding climatology for the Albany, NY upper air site for
middle of May. So hikers could certainly encounter snow showers
for the High Peaks of the Adirondacks above 4500 ft elevation
Friday afternoon into Saturday.

Highs on Friday or Saturday could struggle to get out of the
50s for the valleys and 40s in the higher elevation. For
reference, typical highs for North Country are in around 62 to
68, so a day with highs around 10-15F below normal is on tap.
Unsurprisingly, the CPC 8-14 day temperature outlook favors
below normal temperatures for our region. As for rainfall and
hydrologic considerations, while the most aggressive members of
the Model-Based Ensemble Forecast System (MMEFS) guidance are
hinting at a non-zero chance of river flooding in the
Friday/Saturday time frame, the consensus of members is for area
rivers to rise but remain below action stage. Typically flashy
basins such as East Branch of the Ausable River (ASFN6) could
experience sharp water level rises late Friday into Saturday but
remain below action stage or bankfull. The probability of
widespread convection, which is required to drive the rainfall
rates for flooding to be a concern, is extremely low and mainly
confined to the south of our CWA given the unseasonably cool
regime as depicted by the upper level pattern. Therefore, the
rainfall is expected to be mainly showery and manageable in
nature. As for a sneak peek into the weekend, after an
anomalously cool start to Saturday, a brief period of drier and
warmer conditions are possible for at least parts of the weekend
before a deeper and broader 540mb upper low anchors itself
somewhere across the eastern U.S. For warm weather lovers,
unfortunately the odds do favor an extended period of cooler
weather but it does look like severe weather potential remains
negligible to nil.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
Through 00Z Wednesday...Clouds will decrease through the
overnight period. Mostly VFR conditions are expected the next
24 hours, outside nighttime fog. West to northwest winds at 5
to 10 knots trend light and variable or terrain driven after
03z. Fog appears likely across favorable river valleys
impacting SLK, MPV and EFK between 08z and 14z, with lower
chances at other terminals with no explicit mentions noted at
this time. Beyond 12z, mainly clear skies prevail with north to
northwest winds steadily increasing at 5 to 8 knots. Some clouds
will develop again during the daytime hours.

Outlook...

Tuesday Night: VFR. Chance SHRA.
Wednesday: Mainly MVFR, with areas VFR possible. Likely SHRA,
Slight chance TSRA.
Wednesday Night: Mainly MVFR, with local IFR possible. Chance
SHRA.
Thursday: Mainly VFR, with areas MVFR possible. Chance SHRA.
Thursday Night: Mainly MVFR, with areas VFR possible. Likely
SHRA.
Friday: Mainly MVFR, with areas IFR possible. Likely SHRA.
Friday Night: Mainly IFR, with areas MVFR possible. Chance SHRA.
Saturday: MVFR/IFR conditions possible. Chance SHRA.

&&

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

&&

$$
SYNOPSIS...Haynes
NEAR TERM...Haynes/Storm
SHORT TERM...Chai
LONG TERM...Chai
AVIATION...Neiles