Area Forecast Discussion
Issued by NWS Burlington, VT

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FXUS61 KBTV 270212
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
1012 PM EDT Fri Aug 26 2016

.SYNOPSIS...
Fair and seasonably warm weather will prevail across the region into
Sunday as high pressure dominates the sensible weather pattern. The
next chance for scattered showers will occur by later Sunday into
Sunday evening as a weak front crosses the area. Behind this system
a return to fair and dry weather is expected for early next week.

&&

.NEAR TERM /UNTIL 11 AM SATURDAY MORNING/...
As of 1012 PM EDT Friday...Current forecast on track. A quiet
24-hour stretch of weather is expected across the area as surface
high pressure across southern Canada combines with deep
subtropical upper ridging over the southeastern states to provide
broad-scale subsidence and mainly clear skies. Other than some
patchy mist/fog across favored locales later tonight skies should
be mainly clear through the period with no rain expected.
Temperatures generally a blend of bias-corrected model output
offering overnight lows in the 50s to near 60 and highs on
Saturday from 78 to 85 or so under moderate humidity levels. Winds
light.

&&

.SHORT TERM /11 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/...
As of 327 PM EDT Friday...

The mid-level pattern beginning on Saturday night will
feature geopotential height rises from an anomalous ridge
centered over the mid--Atlantic states. Increasingly more neutral
to weak mid-level height falls are then anticipated later Sunday
into Sunday night associated with more unsettled weather.

Saturday Night: Much of the area should remain dominated
by subsidence associated with building 500 mb heights. The
one exception will be along the outer periphery of the ridge
primarily across St. Lawrence County and along the Canadian
border counties where at least mid to high-level cloudiness is
expected. Due to the spatial differences in cloud cover, expect
central and southern areas to remain locally cooler with more
radiative cooling versus the more cloud-covered areas. Lows
should run about +5 to +10 degrees warmer than normal - in the
50s to mid 60s.

Sunday: Mid-level ridge axis begins to shift eastward with
variable cloud cover increasing through the day. I suspect that
precipitation chances through the first part of the day to be
limited given neutral heights and lack of a good trigger, with
chances ramping up into the high-Chance range for the afternoon.
NAM-based instability values are in the 500 J/kg range with LI`s
barely negative so there is  a limited potential for thunder,
with mainly showers predominating. Since areas to the south are
likely to see more early breaks, I`ve raised highs up some in
this area and correspondingly lowered them to the north. Highs
should then range in the upper 70s to mid 80s, above 30-year
climo normals by a couple degrees.

Sunday Night: Ongoing showers and/or thunderstorms to
progress eastward through midnight with PoPs decreasing into the
Slight Chance range, with a weak/nebulous frontal passage
anticipated during the overnight. 925 mb temps still around +18C
by 12z Monday and mostly cloudy skies keep temperatures in the
upper 50s to mid 60s.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
As of 327 PM EDT Friday...

500 mb shortwave trough associated with frontal passage
moves through early Monday with lingering slight-chance PoPs
trending dry by Monday afternoon. 12z GFS/ECMWF guidance then
point to a pattern change in mid-levels across North America,
with amplified ridging building into central North America and a
cyclonic gyre setting up across the Northeastern states beginning
around the end of August.Temperatures begin around 30-year climo
normals to end August,closing what has proven to be a warm
meteorological summer across the North Country, with a trend near
to below normal by early September as upper low and its thermal
trough overspread the area.The more active period of weather in
the extended is around Wednesday with a seasonably strong frontal
passage heralding the change toward cooler-than-normal temps.
Given the amplified nature to the upper-level pattern by mid-
week, I generally sided closer to the slower and cooler ECMWF
idea into Thursday and Friday.

&&

.AVIATION /02Z Saturday THROUGH Wednesday/...
Through 00Z Sunday...Mainly VFR but some patchy IFR/LIFR br/fg
possible at KMPV/KSLK 06-12Z. Mixed signals on potential br/fg
occurrence given dry advection regime with MOS-LAMP based
guidance most bullish. Confidence moderate on occurrence but given
morning rainfall, at least some added low level moisture input
will be present overnight with lightening winds aloft. Looking for
some scattered cumulus, most prevalent over the mountains, to
develop again tomorrow by mid morning with bases 4500 ft lifting
to 6000 ft by afternoon. Winds light and variable.

Outlook 00Z Sunday through Wednesday...

00Z Sunday through Wednesday...mainly VFR through the period with
high pressure. Two main threat periods for scattered showers and
brief MVFR conditions - Sunday afternoon/evening, then again
Tuesday afternoon/evening with weak trough passages.

&&

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

&&

$$
SYNOPSIS...JMG
NEAR TERM...JMG/Sisson
SHORT TERM...Loconto
LONG TERM...Loconto
AVIATION...JMG/Sisson


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