002
FXUS61 KBTV 192336
AFDBTV
Area Forecast Discussion
National Weather Service Burlington VT
736 PM EDT Tue May 19 2026
.WHAT HAS CHANGED...
As of 1045 AM EDT Tuesday...
Light showers are starting to develop. No lightning has been
observed at this time. A few rounds of thunderstorms will be
possible, with a stronger storm or two capable of gusty winds.
&&
.KEY MESSAGES...
As of 238 PM EDT Tuesday...
1. Warm and humid weather will promote a few strong storms
before a cold front drives cool weather back south.
2. A period of cool weather is expected the remainder of the
week.
3. A pair of weak systems will drive rain chances late Saturday
night into early next week.
&&
.DISCUSSION...
As of 238 PM EDT Tuesday...
KEY MESSAGE 1: The latest thinking from the Storm Prediction Center is
to reduce the likelihood of severe weather in the forecast. A
marginal risk outlook (Level 1 of 5), is now forecast for today. A
few strong storms may develop as a result of strong heating into the
80s with dewpoints in the lower 60s. CAPE of about 1000-1500 J/kg
will be possible, and there is also modest wind flow with 40 knots
of 0-6km bulk shear. Lapse rates are marginal, and there is not much
of a lifting mechanism in place today. Coverage of showers and
thunderstorms will be greatest in southern and eastern Vermont, with
relatively little outside these regions during the afternoon. The
main threat from any thunderstorm will be sending stronger winds
aloft to the surface.
Thunderstorm potential won`t end with the sunset this evening. We`re
in the season of piece meal frontal boundaries now. The first piece
arrives after sunset. Although surface instability will decrease,
the radiation of heat and mid-level warming should produce a sharp
inversion. Mid-level instability will increase along and ahead of
the front that will also coincide with a subtle upper jet and
vorticity max. Precipitation will expand northeast across the
Adirondacks. However, it will struggle as terrain shadowing and
dry air entrainment break up activity heading into Vermont.
However, the front will not yet be through the region until
Wednesday. So another warm, humid night it expected with upper 50s
to upper 60s tonight. A theta E boundary will cross mid-morning, and
cold produce some tiny, spot showers, and then the wind shift
finally crosses in the afternoon, which could also produce a
localized shower. Southern Vermont will still be in the 80s, but
most of the region will be in the 70s behind the theta E boundary.
If any activity can overcome strong mid-level drying in southern
Vermont, then a shower or two could briefly produce a few flashes of
lightning, but this isn`t expressly noted in the current forecast.
One last thing to note for Wednesday will be the breezy
northwesterly flow behind the system as the dry air filters in. With
afternoon mixing, it`ll bring in 20-25 mph gusts and RHs sinking to
30-40%. This may be most relevant in south-central Vermont, which
hasn`t seen quite as much rain over the last 3-4 days.
KEY MESSAGE 2: A rather strong batch of cold air will come in from the
north, and it will linger for awhile as the 1030mb surface high is
slow to move. Looks like we may be talking frost headlines based on
present low temperatures as the Adirondacks and Northeast Kingdom
enter the temperature-defined growing season. Min temperatures for
Wednesday night and Thursday night feature low to mid 30s for these
regions, and low to mid 40s for the rest of the area. Part of the
reason why we`ll observe such cool weather at night will come from
the very dry air mass overhead. Even with afternoon temperatures in
the 60s, minimum relative humidity values appear likely to drop
significantly during the day. Thursday`s cooler temperatures will
likely keep values closer to 25-35%, but Friday looks especially dry
around 20-30%. There`ll be steady winds Thursday, and light and
variable winds on Friday.
Even as high pressure begins to depart, it lifts towards the Gulf of
St. Lawrence rather than simply going off into the Atlantic. So
colder north flow will trend to cool, maritime east-southeast flow.
Conditions will be dry underneath this strong high. It`ll be
supremely pleasant weather through Saturday afternoon.
KEY MESSAGE 3: A weak, 1013mb low pressure will track towards the Great
Lakes region, and it will struggle mightily against the now 1035mb
surface high in the Canadian Maritimes. Guidance is consistent on a
warm front lifting northeast in association with the surface low but
also decelerating and decaying. A sharp gradient in rainfall amounts
is expected with steady rain setting up near or south of our
forecast area and dry the farther northeast you get. Some guidance
has the warm front and associated precipitation collapsing before it
even reaches the Northeast Kingdom of Vermont. The latest 12z GFS
doesn`t even allow the warm front to make it to our region of
responsibility.
Another area of low pressure will move towards James Bay, and it
will come with a well-defined upper trough that will begin to
acquire a negative tilt on. Yet another weak surface low will start
developing near Long Island. This will set the stage for strong
confluence while a moisture feed out of the Gulf and Atlantic are
positioned nearby. The doubling up of these features appears to last
for a very short time, and given that it`s relatively small, any
disconnect would disrupt precipitation efficiency. Regardless, this
feature will be progressive. A few showers cold linger into next
Tuesday as the backside of the upper trough makes it in during the
morning.
&&
.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
Through 00Z Thursday...Radar is showing a broken line of showers
and thunderstorms north of Lake Ontario and slowly approaching
the St Lawrence Valley. This activity is expected to impact KMSS
between 03-05Z with localized gusty winds, a brief heavy
downpour and some lightning, before shifting toward SLK by
midnight and slowly weakening. Eventually this activity will
enter the Champlain Valley after midnight and slowly weaken
across central VT. Tempo for brief MVFR conditions was used at
MSS with PROB30 groups for the rest of our taf sites. South to
southwest winds 5 to 15 knots will shift to the west/northwest
after passage of cold front with some lowering ceilings at SLK
toward IFR conditions possible around sunrise on Weds.
Additional MVFR cigs are possible at MSS/MPV and EFK on Weds
morning, before conditions improve to VFR with localized wind
gusts up to 20 knots possible.
Outlook...
Wednesday Night: VFR. NO SIG WX.
Thursday: VFR. NO SIG WX.
Thursday Night: VFR. NO SIG WX.
Friday: VFR. NO SIG WX.
Friday Night: VFR. NO SIG WX.
Saturday: VFR. Chance SHRA.
Saturday Night: VFR. Chance SHRA.
Sunday: VFR. Chance SHRA.
&&
.MARINE...
As of 238 PM EDT Tuesday...
A Lake Wind Advisory remains in effect for the Broad Waters of
Lake Champlain. Sustained winds have been lacking much of the
day, but have increased over the last couple hours. A few gusts
have hovered just under the 25 knot criteria as well. Given the
proximity to that threshold and cold water, the Lake Wind
Advisory will remain up. Some stronger wind gusts will be
possible on Lake Champlain around midnight following a boundary,
and then again once winds shift from south or southwest to
north later on Wednesday. Waves will likely range about 1-3
feet.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...None.
NY...None.
&&
$$
WHAT HAS CHANGED...Boyd/Haynes
DISCUSSION...Haynes
AVIATION...Taber
MARINE...Clay/Haynes
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