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  Tuesday May 23, 2017

 

NWS Area Forecast Discussion


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FXUS61 KBTV 181918
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
318 PM EDT Thu May 18 2017

.SYNOPSIS...
Near record high temperatures expected today, along with gusty
southwest winds, especially the Saint Lawrence Valley. The heat
will help to fuel strong to locally severe thunderstorms late
this afternoon into the overnight hours. The primary threat will
be damaging winds and one inch hail. Much cooler and drier
weather returns to the North Country on Friday into the upcoming
weekend.

&&

.NEAR TERM /UNTIL MIDNIGHT TONIGHT/...
As of 1103 AM EDT Thursday...Overall elements in good shape this
morning as temps quickly warm into the l/m 80s with 86 already
here and 88f at PBG at 11 am. Expecting highs in the upper 80s
to lower 90s in most locations.

Still looking at convection to fire this
afternoon/evening...with some uncertainty on areal coverage and
placement. Water vapor shows weak 5h vort in southwest flow
aloft across ohio valley/western ny with associated EML. This
energy and instability will interact with lake breezy boundaries
and higher terrain to help in development of isolated to
scattered storms this afternoon after 18z. Thinking storms
develop over the eastern dacks between 18z-20z...and impact
parts of central/southern VT...where CAPE values will range
between 1500 and 2000 j/kg and 0 to 3 km shear of around 40
knots. CAPE/Shear would support organized convection...but the
lack of significant forcing at the surface and aloft will limit
magnitude and coverage. Thinking pulse like convection with
some potential for isolated wind/hail between 20z-24z.
Meanwhile...better dynamics and surface convergence approaches
the SLV btwn 00-03z. Expecting additional storms to
develop...but still uncertain on impacts from cooler lake
ontario waters and timing in late evening...will have on
instability. Thinking a broken line of storms with damaging
winds will be the primary threat...mainly across northern ny
between 00-04z. Finally wind advisory looks good...as latest RAP
shows 925mb of 50 to 55 knots around 00z across the SLV. Expect
surface wind gusts between 45 and 50 mph.

Previous discussion below:
Temperatures starting in the 60s to low 70s this morning with
dewpoints in the 50s. Both temperatures and dewpoints will
increase in SW flow today, resulting in hot and muggy
conditions. Active weather day is on tap for today. Pre frontal
trough will approach this afternoon, followed by a cold front
overnight. Strong southwesterly flow will be in place across the
area, with a wind advisory in place for the St Lawrence Valley.
Temperatures will also approach record high values today with
upper 80s to lower 90s across the area. Surface dewpoints climb
into the 60s this afternoon with deep layer moisture being
advected into our region on the southwesterly flow.

Warm temperatures and high dewpoints will create surface
instability, Cape values will be around 1500 during the
afternoon with 0 to 6 km shear 45-55 kts. Hi res models showing
first round of convection starting up around 4 or 5 pm,
spreading from Essex County NY southeastward across Vermont.
Gusty winds and small hail are possible and potential to become
severe will need to be monitored. Not a lot of large scale lift
yet though, maybe a limiting factor as previous forecaster
noted. By about 8-9 pm a more organized line of storms, strong
to severe, will approach the St Lawrence valley. With these
storms the primary threat will be strong gusty winds, possibly
damaging, with very strong low level wind fields noted. These
storms will have better forcing with cold front and accompanying
surface convergence. Think that these storms will cone through
in the form of a line. Best chance for damaging winds will be
across Northern New York and edging into the Champlain valley,
but the air mass will generally be more stable across Vermont
and storms may not hold together. Have continued with mention of
enhanced wording, gusty winds small hail and heavy rain. Wind
advisory also remains in effect from 18z to 03z for the Saint
Lawrence valley with strong gradient flow out of the Southwest.
Wind gusts in the 40 mph range are expected, with wind gusts in
the 30s across the rest of the forecast area. Surface cold front
continues to push across our forecast area overnight, and
should clear our forecast area by about 12z. Lots of ingredients
in place for some potentially severe weather today, though
still a bit of uncertainty with proximity to cold waters of Lake
Ontario as storms cross that area, as well as unfavorable
timing of surface cold frontal passage. Very hot windy day for
sure though with at least some strong storms.

&&

.SHORT TERM /MIDNIGHT TONIGHT THROUGH SATURDAY NIGHT/...
As of 445 AM EDT Thursday...Last bit of shortwave energy in
upper level trof kicks across our forecast area early Friday,
showers are likely through about 18z. From Friday afternoon
through Saturday surface and upper level ridges will build over
our area, much drier and cooler air will be in place. This time
period will be much cooler than the previous 2 days, but much
closer to seasonal normals, generally highs in the 60s and lows
in the 40s. There may be areas of frost in the deeper/protected
valleys of the Adirondacks and Northern Vermont.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
As of 317 PM EDT Thursday...Upper level ridge and exiting
surface high pressure off the Atlantic seaboard will keep dry
conditions across the North Country to end the weekend with
increasing clouds ahead of our next system encroaching from the
west during the afternoon. Deep low pressure over southern
Ontario tracks eastward into central Quebec Sunday night through
Monday dragging a cold front through northern New York and
Vermont with showers developing late Sunday evening across
western areas and becoming widespread after midnight through
Monday as a weak wave of low pressure forms over the mid-
Atlantic states and rides northeast to the Gulf of Maine by
Monday night. In contrast to the previous forecast, the 12z
model suite indicates very little instability both at the
surface and aloft to support thunder so I`ve removed all
mention. Is a rumble or tow of thunder possible, sure. Just not
enough to justify it in the forecast.

Brief break in precipitation occurs Tuesday as we`ll be in
between systems, with the next chance for showers and potential
thunderstorms coming Wednesday/Wednesday night as deepening low
pressure over Great Lakes Tuesday night tracks northeast through
the St. Lawrence Valley.

Temps through the period will be very seasonal with highs in
the mid 60s to low 70s, and lows in the mid 40s to low 50s.

&&

.AVIATION /19Z THURSDAY THROUGH TUESDAY/...
Through 18Z Friday...Primarily VFR conditions are expected
through 12Z Friday with 2 rounds of scattered showers and
thunderstorms this afternoon and evening briefly reducing
vsby/cigs to MVFR/IFR. After 12Z, there will be a gradual trend
towards MVFR as cigs lower behind a cold front passage. For
winds, gusty to locally strong south-southwest with gusts in the
20-35kt range persist through about midnight before shifting to
the west-northwest at 8-15kts.

Outlook...

Friday Night: VFR. NO SIG WX.
Saturday: VFR. NO SIG WX.
Saturday Night: VFR. NO SIG WX.
Sunday: VFR. Slight Chance SHRA...TSRA.
Sunday Night: VFR. Likely SHRA...TSRA.
Monday: MVFR. Likely SHRA...TSRA.
Monday Night: VFR. Slight Chance SHRA.
Tuesday: VFR. Slight Chance SHRA.

&&

.CLIMATE...
Max Temp Records for 5/18/17

KBTV...89 set in 1989
KMPV...90 set in 1962
K1V4...92 set in 1906
KMSS...90 set in 1962

&&

.BTV WATCHES/WARNINGS/ADVISORIES...
VT...None.
NY...Wind Advisory until 11 PM EDT this evening for NYZ026-027-087.

&&

$$
SYNOPSIS...Neiles
NEAR TERM...Neiles/Taber
SHORT TERM...Neiles
LONG TERM...Lahiff
AVIATION...Lahiff
CLIMATE...WFO BTV



 
 
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