Scientific Forecaster Discussion

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Area forecast discussion 
National Weather Service Burlington Vermont
155 am EDT Friday Apr 25 2014

Synopsis...
high pressure over the north country overnight will result in
mainly clear skies and cool temperatures. Friday will start with
plenty of sunshine but clouds will develop during the afternoon
hours with showers arriving for Friday night into Saturday.
Temperatures will be near normal for Friday...but below normal
with clouds and showers on Saturday into Sunday.

&&

Near term /until 6 am this morning/...
as of 123 am EDT Friday...cloud cover has given way to clear
skies this morning...but there will be an increase in high clouds
over northern New York in advance of next weather system. This
will start with mostly scattered-broken middle and high level clouds before
12z. Light to calm winds continue as pressure gradient relaxes and
high pressure crests over the region. Expect light winds and clear
skies to allow temperatures to fall into the 20s most areas...with some
upper teens in the adks.

&&

Short term /6 am this morning through Saturday night/...
as of 320 PM EDT Thursday...mid/upper level ridge across the NE Continental U.S.
Will quickly shift into eastern New England by 00z Saturday...as
progressive westerly flow aloft continues across the northern tier of
the United States. Deep dry layer and strong subsidence per
latest water vapor trends will result in mostly sunny skies on
Friday morning...but middle/upper level relative humidity increases after 18z from SW
to NE. Best 850 to 700mb Omega fields and associated ribbon of
850 to 500mb relative humidity >80% arrives after 00z Sat...so will keep Friday dry
at this time. Prognosticated 850 mb temperatures range from 0c nek to 4c southwest
slv...resulting in temperatures ranging from the l/M 50s nek/mountains to
l60s slv and warmer/uhi areas of the cpv.

Friday night into Saturday...850 to 500mb relative humidity quickly overspreads
the forecast area with modest upward vertical velocities associated with 500 mb vorticity and development
of middle/upper level trough. Still feel initial 500 mb vorticity and moisture will
dissipate across our County Warning Area on Friday night...with leading edge of
precipitation falling as mostly virga...especially given very dry lvlls.
Better dynamics and deeper relative humidity arrives associated with closed
500 mb/7h circulation between 06z-12z Saturday...with a band of light to
moderate rain anticipated. Have noted pockets of cooler prognosticated
850 mb temperatures <0c across central/northern Vermont/nek on Saturday
morning...which could result in some wet snow in the mountain summits.
Cold pool aloft associated with closed system moves directly
overhead on Saturday...with cooling profiles aloft anticipated.
This combined with some limited surface heating will result in
additional instability for more scattered showers to develop.
Bottom line Sat will be cool and damp with occasional rain showers
and high elevation snow showers likely. Total quantitative precipitation forecast will range between
0.10 and 0.50 of an inch. Temperatures will range from the u30s/m40s
nek/mountains to m40s/l50s valleys on Sat.

Saturday night...closed middle/upper level circulation continues to deepen
as several embedded S/w's interact with this large synoptic scale
system. This will slow overall movement of system down with it
becoming stationary off the New England coastline by Sat
night...and numerous ribbons of moisture rotating across our
central/eastern County Warning Area. This combined with developing west to
northwest follow will result in additional showers. Given the
deepening cold pool aloft and associated cooling of low level thermal
profiles...thinking snow levels will drop to around 2000 feet by
Sunday morning. However...accumulations should be light. Temperatures
with clouds/wind and precipitation will hold mainly in the 30s to near
40f...fairly uniformed across our region.

&&

Long term /Sunday through Thursday/...
as of 336 PM EDT Thursday...extended range forecast continues to
looks very uncertain as much of the Continental U.S. Will be impacted by a
developing Omega block late this weekend. Upper low low which
will have brought rain/snow showers to the region Saturday and
Saturday night will shift offshore Sunday with a generally dry
yet cool and brisk end to the weekend. Highs will run about 5-10
degrees below normal in the middle 40s to lower 50s. As the low
shifts further offshore Sunday night...Omega block setups up
across the Continental U.S. With another closed low developing over the
central rockies and a highly amplified ridge across much of the
eastern Continental U.S.. this pattern remains fairly persistent for Monday
through Wednesday with a slow progression eastward and some
slight modification to the amplitude of the ridge. At this
time...the forecast does look generally dry for the north
country...but depending on the exact track of all the above said
features...things could change. Temperatures will be highly variable
based on ridge/low placements...but in general look to run at or
below normal. As we get closer to Thursday...signs are that the
ridge begins to break down and rockies low shifts eastward into
the Great Lakes renewing chances for precipitation across the northeast.

&&

Aviation /06z Friday through Tuesday/...
through 06z Saturday...VFR conditions expected through the period. A
ridge of high pressure over the region early today will move
slowly east and be off the New England coast by 00z Saturday.
Satellite loop through 0530z Friday showing middle and high clouds
across the Great Lakes and Ohio Valley streaming eastward...so expecting
an increase of middle and high clouds across Vermont and northern New
York today. A low pressure area and a frontal system will approach
the region tonight with ceilings continuing to lower. Expecting
light rain showers to develop across northern New York between 04z-06z
Saturday.

Outlook 06z Saturday through Tuesday...

06z Sat through 00z Monday...mix of MVFR/VFR with periods of showers
associated with upper low passage.

00z Monday through 00z Tuesday...MVFR trending to VFR as upper low pulls
away from the region.

00z Tuesday through 00z Wednesday...VFR under high pressure.

&&

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

&&

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