Scientific Forecaster Discussion

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Area forecast discussion 
National Weather Service Burlington Vermont
626 am EDT Thursday Apr 24 2014

Synopsis...
high pressure will build into the north country today...bringing
clearing skies and gusty winds. The next chance for showers will
be Friday night into Saturday along with the arrival of cooler
air for the weekend. A few mountains snow showers will be
possible on each night over the weekend...with only minor
accumulation anticipated.

&&

Near term /until 7 PM this evening/...
as of 626 am EDT Thursday...northwest winds continue around 5-15kts with
gusts in so locations of 20-25kts this morning. Clouds slow to
erode from northern Vermont. This may help to keep relative humidity values from falling
as much...but areas expecting lowest relative humidity already clear across southern
half of cpv and southern Vermont. With gusts already 20-25kts this
morning...would not be surprised to see an isolated gust in
excess of 45mph this afternoon in southeastern Vermont. Overall forecast in good shape.

Previous discussion...tight pressure gradient continues over the
north country as surface low heads further into the Atlantic and surface
high pressure builds into the region today and tonight. Low level jet
of 35-50kts at 850mb will affect eastern Vermont...producing northwest winds of
15-25kts with gusts up to 40kts...centered along the eastern slopes
of the Green Mountains into the CT valley. Downsloping may see
isolated higher gusts. BUFKIT soundings show mostly clear skies
with mixing to around 5kft should keep widespread wind gusts just
below advisory criteria.

In addition to windy conditions today...northwest flow will also bring
drier air over the north country...with relative humidity values falling into
the m20 to m30 percent range. See fire weather section for more
details. Threat of dry air and strongest winds will be centered
around 18z- 22z.

Otherwise...upper level trough which helped to produce overcast skies
yesterday has for the most part move east...with only nek still
seeing cloudy skies which will gradually erode eastward today. Northwest flow
will keep slightly cool influx of air so maximum temperatures will generally
be about 5 degrees below normal today.

&&

Short term /7 PM this evening through Saturday/...
as of 505 am EDT Thursday...level jet quickly exits east this
evening...as surface ridge sets up to crest over the north country by
early Friday morning. This will result in light to calm
winds...mostly clear skies and chilly overngt min temperatures. Expect
valleys to see Friday morning lows in the m20s...with hir terrain in
the middle teens to l20s.

Friday will be warmer as winds shift out of the S ahead of surface
low pressure system approaching from Ohio River valley. This low
will track east-northeast...increasing clouds throughout the day on Friday.
Friday maximum temperatures will be slightly above normal before precipitation begins
to edge its way into the north country from the west Friday
night. Exact track and evolution of this system still unsure as
models suggest double barrel system taking most of its energy off
the Long Island coast. This would affect how much quantitative precipitation forecast the north
country would receive. Expect moisture to linger into Saturday as
the upper low moves across the north country...making for a
dreary first half of the weekend. Temperatures will be near
normal before cooler air begins to filter in for the rest of the
weekend.

&&

Long term /Saturday night through Wednesday/...
as of 407 am EDT Thursday...European model (ecmwf) and GFS models show a closed
upper low will be over the region Saturday night...so will
continue with a chance of showers. The closed upper low will move
east of the region by Sunday...but the forecast area will still
be under cyclonic flow...so have slight to chance probability of precipitation for
showers in the forecast for Sunday. Expecting mainly dry
conditions Sunday night with just some slight chance probability of precipitation for
showers over northeast Vermont. A mainly dry day on Monday as a
ridge of high pressure builds south from Canada and remains over
the region through Monday night.

European model (ecmwf) and GFS models showing some major differences for the
Tuesday and Wednesday forecast. Thus...forecaster confidence is
low. European model (ecmwf) model has a ridge of high pressure at the surface and
aloft over the region with a dry forecast indicated for Tuesday
and Wednesday... as European model (ecmwf) model suggesting the region will be
under an Omega block with a closed upper low over the middle
Mississippi Valley with another closed upper low over the
Atlantic south of the Canadian Maritimes. However...GFS model
shows a closed upper low also over the middle Mississippi Valley
with the other closed upper low much further east in the Atlantic
than depicted by the European model (ecmwf) model. GFS model brings moisture
northeast into the region from the southeastern U.S. Tuesday and
Wednesday with a chance of showers. For now...will use super
blend probability of precipitation and keep a chance of showers in the forecast for
Tuesday and Wednesday...but given model differences forecaster
confidence is low at this time.

&&

Aviation /12z Thursday through Monday/...
through 06z Friday...VFR conditions expected through the
period...as a ridge of high pressure builds slowly east into the
region from the Great Lakes and Ohio Valley. Surface pressure
gradient to tighten across the region today as a low pressure
area south of Nova Scotia deepens. This tight pressure gradient
will produce gusty northwest surface winds across the region
today with northwest surface wind gusts of 20-30 knots expected
through 23z Thursday. After 23z Thursday expecting clear skies
and northwest surface winds diminishing to less than 10 knots.

Outlook 06z Friday through Monday...

06z Friday through 00z Sat...VFR under high pressure.

00z Sat through 00z Monday...mainly VFR with chance of MVFR showers
associated with a weak low passage.

Monday...mainly VFR under scattered-broken skies.

&&

Fire weather...
as of 505 am EDT Thursday...fire weather concerns increase this
afternoon for elevations below 1500 feet across the Champlain
Valley...and portions of southern Vermont...due to the combination of
the recent dry spell...expected breezy winds...and low min relative humidity
values.

Most the cpv and southern Vermont have seen less than a quarter
inch of rainfall in the past five days...this has resulted in
significant drying of the fine fuels per local Forest contacts
below 1500 feet...where green up has not occurred.
Meanwhile...above 1500 feet most of the fine fuels and Leaf
litter is compressed from recent snow pack or still wet. Most of
central/northern Vermont mountains and northern New York have received measurable
precipitation over the past 2 to 5 days or snow pack is still on the
ground above 2000 feet...resulting in limited threat.

Breezy west to northwest winds of 15 to 25 miles per hour with gusts to 35
miles per hour are expected across the higher terrain...parts of the CT River
Valley...and Champlain Valley this afternoon. Isolated stronger gusts
up to 45 miles per hour will be possible along the eastern slopes of the Green
Mountains due to downsloping and stronger low level jet near
southeastern Vermont.

In addition...min afternoon relative humidity values will drop between 25% and 35% between 1
PM and 5pm across northern New York...the cpv and southern Vermont...with isolated
readings of 20% near Springfield Vermont possible.

These conditions combined with the overall drying of
grasses...twigs...and debris such as dead leaves from last fall
will allow any fires that do occur to spread quickly...burn
intensely...and be difficult to contain. Pay close attention to
any outdoor burning you may be attempting today. Monitor weather
conditions...do not leave your brush or debris pile
unattended...and heed any advice from your local fire Warden.

Will continue t0 highlight threat for this afternoon in the
Champlain Valley and southern Vermont in severe weather potential statement...as well as a
Special Weather Statement.

&&

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

&&

$$
Synopsis...kgm/Taber
near term...kgm
short term...kgm
long term...wgh
aviation...wgh/lahiff
fire weather...Taber/kgm