897
FXUS61 KBTV 290730
AFDBTV
Area Forecast Discussion
National Weather Service Burlington VT
330 AM EDT Wed Jul 29 2026
.WHAT HAS CHANGED...
As of 300 AM EDT Wednesday...
Forecast rainfall totals have been increased slightly. The
isolated to scattered flash flooding risk remains on track, and
a Flood Watch remains in effect for portions of the area through
this evening.
&&
.KEY MESSAGES...
As of 300 AM EDT Wednesday...
1. Waves of locally heavy rain will continue to move through
the forecast area through tonight. Isolated to scattered flash
flooding is possible and a Flood Watch remains in effect for
portions of the area through tonight.
2. Briefly dry conditions are expected on Saturday, and then
chances for showers and thunderstorms will increase again.
&&
.DISCUSSION...
As of 300 AM EDT Wednesday...
KEY MESSAGE 1: A slow-moving low pressure system to our south
with continue to send waves of rain through our forecast area
through tonight. A Flood Watch remains in effect for portions
of southern and central Vermont, as well as Essex County New
York, where isolated to scattered flash flooding is possible.
Observed rainfall amounts so far have been highly variable across
the CWA as expected, with localized areas that have multiple heavy
showers and thunderstorms move through having picked up 1-2 inches
so far. These areas include higher elevations of the southern
Greens in eastern Rutland County, a narrow swath of northern
Chittenden County to southern Franklin County near Milton
towards St. Albans, and an area between Hammond and Gouverner in
Southern St. Lawrence County. Outside of these areas, reported
storm total rainfall amounts as of early Wednesday highly
variable but generally under an inch. Overall, the area has been
able to absorb these precip amounts with no reported issues
thus far in our CWA.
After a brief break in precipitation overnight, the next wave of
light to moderate rainfall is moving northward over western VT
and eastern NY early this morning. Rainfall rates within this
wave are expected to generally stay between a tenth and a
quarter inch per hour, but some isolated higher rates are
possible.
The heavier rainfall threat increases later this morning, when
the center of the low will shift closer to our forecast area.
As the low moves north, southerly flow will become easterly.
This will direct moisture upslope over the eastern slopes of the
southern and central Greens. As this happens, expect a window of
steady precipitation over these upslope areas with rainfall
rates between 0.25 to 0.5 inch per hour, with the potential for
briefly higher rates. While the heaviest precipitation of the
event is forecast to stay to the south of our CWA boundary,
there will be a window this morning through mid- afternoon where
the low will pivot to our south and we have the potential to
see some impressive rainfall accumulations in portions of our
area. More specifically, an additional 1-3 inches of rain
through tonight is forecast over portions of southern and
central Vermont, along with the eastern slopes of the northern
Adirondacks. Higher additional amounts, with localized 3-4
inches of additional precipitation today, cannot be ruled out
over the higher elevations of the southern Green Mountains.
Current one hour Flash Flood Guidance from the NERFC ranges from 1.5
to 2.5 inch/hour across most of our CWA...lowest in the previously
mentioned areas that have received the most rain out of the event so
far. Six hour flash flood guidance is 2-3.5 inch/6 hour. The
anticipated additional QPF in comparison with the flash flood
guidance does suggest that some isolated to scattered flash flooding
is possible today, but flash flooding is not expected to be
widespread. The area of highest concern in our CWA remains
higher elevations of southern Rutland and Windsor counties. Much
of the area included in our Flood Watch is included within the
Slight (at least 15% risk) of flash flooding today as per the
latest Excessive Rainfall Outlook issued by the Weather
Prediction Center. Given antecedent dry conditions leading up to
the event, rivers are generally forecast to remain within
banks, though some flashier streams will run high.
The threat for flash flooding will decrease tonight as the low
begins to exit to the east. Showers will wane in intensity and
coverage through the day Thursday, eventually fully coming to
an end by Thursday night.
KEY MESSAGE 2: An upper ridge will settle over the area Friday night
into Saturday. Could be a foggy Saturday morning, especially after
our recent wet period. A digging trough along the Corn Belt will
allow warm, humid air to return. Temperatures will climb into the
80s across the forecast area. A few afternoon showers may try to
develop. A range of forecast soundings suggest a mid-level warm
layer around 600mb should prevent convection, but that it erodes
Saturday evening. So a late showing of afternoon convection seems
possible Saturday, mainly along the mountain spines with limited
forcing and light flow in place.
On Sunday, a northern stream trough will provide some focus for
precipitation Sunday afternoon-Monday while the trough over the Corn
Belt gets dragged farther south. The northern stream system will
usher in somewhat dry and stable air into the region. As the
southern trough lingers across the southern US and a Bermuda high
develops, we`ll be just north of the tropical plume of moisture this
combo will produce. So Tuesday appears to be somewhat drier, but
then that plume appears likely to shift north some on Wednesday.
With this regime, we`ll likely be somewhat warmer than average, with
upper 70s to mid 80s for daytime highs and mid 50s to mid 60s for
nighttime lows.
&&
.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
Through 00Z Thursday...The initial portion of the forecast has been
faring well enough, but did make some modest changes based on
shifts to the south and east. The first six hours are of
relatively good confidence, with periods of moderate rain
producing 2-6SM visibility. Ceilings are gradually falling
towards 2500-5000 ft agl, albeit somewhat slower than expected.
The worst surface conditions around 09z-15z with most terminals
MVFR or IFR at that time frame. This will be timed with heavy
rain associated with a surface low expected to pass north. Winds
will go calm or variable on its approach. Southeast winds will
transition to northeast, and then north approaching 06z. Wind
speeds will be strongest about 12z-22z at 6-11 knots, and a few
gusts up to 20 knots is possible at KRUT. Eventually, secondary
low pressure will develop more strongly off the New England
Coast. Surface winds will begin to diminish, but the flow aloft
will remain easterly to southeasterly at 30-40 knots at 2000 ft
agl across much of Vermont. Some LLWS is noted. As the surface
low decays, conditions are expected to improve some, and then
trend towards steady state. There will likely be some
redeveloping convection 18z Wed to about 03z Thurs, which could
produce locally heavy rain reducing visibilities, and it is
possible another swath of precipitation arcs northwest, but
confidence is lower at this time.
Outlook...
Thursday: Mainly VFR, with areas MVFR possible. Chance SHRA,
Slight chance TSRA.
Thursday Night: Mainly VFR, with areas MVFR possible. NO SIG WX.
Friday: Mainly VFR, with local MVFR possible. Slight chance SHRA.
Friday Night: VFR. NO SIG WX.
Saturday: Mainly VFR, with local MVFR possible. NO SIG WX.
Saturday Night: VFR. Slight chance SHRA.
Sunday: MVFR/IFR conditions possible. Chance SHRA, Chance TSRA.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...Flood Watch through this evening for VTZ009>011-018>021.
NY...Flood Watch through this evening for NYZ034-035.
&&
$$
WHAT HAS CHANGED...Duell
DISCUSSION...Haynes/Duell
AVIATION...Haynes
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