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Area forecast discussion 
National Weather Service Burlington Vermont
410 am EDT Thursday Jul 30 2015

Synopsis...
widespread showers and thunderstorms are expected today as a cold
front moves across the region. These thunderstorms will have the
potential to become strong to severe with gusty winds and heavy
downpours possible. Cooler weather returns on Friday as the cold
front exits the area.

&&

Near term /until 6 PM this evening/...
as of 410 am EDT Thursday...forecast remains on track for the
potential for strong to severe storms today as a cold front shifts
through the region. Current radar and surface analysis show the
boundary currently over the western tip of Lake Erie while
convection is firing up on the Eastern Shore. Doesn't matter which
model you pick, they all show just about the same timing for
convection shifting into the btv County Warning Area today. Current arrival/exit
timing looks to be 13-17z in the Saint Lawrence valley and
northern Adirondacks, 16-20z in the Champlain Valley, and 17-21z
across central and eastern Vermont. With this timing in mind, the
greatest threat for any severe storms will be from the Champlain
Valley and points eastward where the best surface heating will
take place. Still looking at roughly 1000-2000 j/kg of cape
developing by middle-day from the Champlain eastward, with 0-6km
shear of about 30-40 knots which should be enough to develop a
narrow band of organized thunderstorms. Wind shear is mostly Uni-
directional from the southwest and parallel to the front, so the
primary severe threat will be damaging winds from bowing segments
with a fairly minimal hail threat due to high freezing levels.
Secondary threat will be the potential for heavy downpours with
precipitable waters pushing close to 2", but storms should be moving quick
enough to mitigate any flash flood concerns. Highs today will
range through the 80s to near 90 in some places. Based on
convective timing, high temperatures are expected to be reached around
middle-day across Vermont, and late afternoon across northern New
York.

&&

Short term /6 PM this evening through Saturday/...
as of 410 am EDT Thursday...as the aforementioned surface front
clears the region to our east convection will quickly die off this
evening with clearing skies expected after 00z. Southwest flow
continues aloft as a large-scale closed low takes residence over
James Bay resulting in a slow arrival of the cooler Post-frontal
air. Overnight lows will remain above normal but cooler than the
previous 2 nights with temperatures falling into the 60s for most, except
some 50s in the Adirondacks.

For Friday and Saturday the closed low over James Bay remains the
dominant weather maker across the north country with several pieces
of shortwave energy moving through the generally west/southwest flow
aloft. First piece of weak energy shifts through Friday with a few
isolated showers possible across the northern tier of the cwa, but
more scattered showers and isolated thunderstorms are possible
Saturday as a stronger shortwave shifts east from the Great Lakes.
Highs both days will be very seasonal in the upper 70s to middle 80s,
with Friday night lows in the middle 50s to low 60s.

&&

Long term /Saturday night through Wednesday/...
as of 312 am EDT Thursday...this morning's global operational
runs and supporting ensemble members remain in overall good
agreement on the large-scale synoptic features from Sunday Onward.
This will feature a slowly evolving and broad upper trough across
the northern Great Lakes and Canadian prairies eastward into the
northeastern tier of the country into east-central Canada.
Northern New York and New England will generally lie on the
southern periphery of this feature with a rather active weather
pattern taking shape as fast flow aloft brings several shortwaves
and chances of showers/storms to the region. No widespread severe
weather is expected, but confidence on timing and strength of
individual shortwave features is modest at best, typical under
such scenarios. In general the best threat of precipitation will
occur during the afternoon and early evening hours when weak to
modest instability will exist. With low to middle level flow
remaining west to southwesterly, near seasonal temperatures and
tolerable humidity levels are expected with a slight cooldown by
the middle of next week as upper trough makes its furthest inroads
south.

&&

Aviation /08z Thursday through Monday/...
through 06z Friday...other than patchy MVFR/br visibilities at
kslk and kpbg VFR conditions expected through 12z. After 12z
frontal boundary pushes through the area with showers/storms
possible from west to east in the 14-20z time frame. A few storms
may trend strong to locally severe with turbulence/wind from
kpbg/kbtv and points east. Brief IFR visibility/MVFR ceilings possible
with this activity. Showers/storms to clear eastern terminals by
21z. Winds light through 12z, then southerly from 6-12 kts and
occasionally gusty from 12z Onward, trending light once again by
00z Friday.

Outlook 06z Friday through Monday...
06z Friday - 12z Sat: mainly VFR. Chance MVFR/IFR fog mainly at
mpv/slk.

12z Sat onward: mainly VFR. Chance shra/tsra.

&&

Marine...
as of 410 am EDT Thursday...boaters should exercise caution if
planning on recreating on Lake Champlain today as a cold front
shifting through the region will produce a line of potentially
strong thunderstorms. We currently expect storms to impact the
Lake Champlain basin between noon and 4 PM where the greatest
threat will be strong to locally damaging winds in excess of 50
miles per hour. Winds of this magnitude can easily overturn vessels so be
prepared to seek safe Harbor should severe thunderstorms develop.
Monitor National oceanic and atmospheric administration weather radio for updates through the morning.

&&

Btv watches/warnings/advisories...
Vermont...none.
New York...none.

&&

$$
Synopsis...lahiff
near term...lahiff
short term...lahiff
long term...jmg
aviation...jmg
marine...lahiff

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