Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Burlington Vermont
455 am EDT Wednesday Aug 27 2014
a weak cold front will move southeastward across the north country
today...producing a few scattered showers and thunderstorms. Cooler
and drier weather returns through the end of the work week as high
pressure builds over the region. The Holiday weekend will see
another chance for showers and thunderstorms.
Near term /until 8 PM this evening/...
as of 451 am EDT Wednesday...cold front entering Saint Lawrence
valley at this time. A line of showers in advance of the front
has diminished overnight due lack of instability and weak forcing.
As front makes its way slowly southeastward across forecast area
today...expect there to be some redevelopment of showers and
possible thunderstorms. Expect the front to be through northern
New York and northwest Vermont by midday...and through the
southern and eastern portions of forecast area by middle to late
afternoon. Highest probability of precipitation and best chance for thunder will be across
south-central Vermont where later arrival time of front will allow
for enough surface heating to generate cape values of around 1000
j/kg. Moisture limited however and trailing middle level shortwave
doesn't arrive till well after frontal passage...so have limited
probability of precipitation to around 30 percent. Maximum temperature forecast a tricky one...as
forecast area will be under gradual cold air advection with 850 mb
temperatures falling from 14-16c this morning to 11-14c by this evening.
Look for highs to range from the middle 70s in the Adirondacks to
the middle 80s south-central Vermont.
Short term /8 PM this evening through Friday/...
as of 451 am EDT Wednesday...cooling trend continues tonight into
Thursday. Series of middle level shortwaves moving across northern New
England will keep some clouds around...but it will be mostly dry
with just a low chance for a few light showers or
sprinkles...mainly across the higher terrain zones of northern
Vermont. Min temperatures tonight will be near seasonal levels...mostly in
the 50s. With 850 mb temperatures continuing to fall during Thursday to 6
to 8 c...it is shaping up to be a rather cool day with highs
ranging from the middle 60s to lower 70s.
Upper trough departs Thursday night into Friday while surface high
pressure builds east from the Great Lakes. The result will be
mainly clear skies Thursday night and Friday with below normal
temperatures. The combination of clear skies and light winds Thursday night
will allow for good radiational cooling. Expect lows in the 40s to
around 50...with temperatures rebounding into the lower and middle 70s Friday
with plenty of sunshine and light winds.
Long term /Friday night through Tuesday/...
as of 359 am EDT Wednesday...a relatively warm and humid weekend
and first half of next week is in store with multiple chances for
showers and thunderstorms.
High pressure will be sliding offshore Friday night allowing for a
return flow to develop and warm air advection to ensue on southwest
flow around the periphery of a building ridge over the southeastern
US. The region should stay mostly dry with lows generally in the 50s.
Changes are on the way beginning Saturday as broad southwest flow
continues and there is an appreciable increase in
moisture...warmth...and humidity. Should see dew points rise back
into the 60s (moderate mugginess) and precipitable water values rise
to near 1.5 inches. Pieces of energy will likely be riding around
the periphery of the ridge but with no real focus...should see a
mainly dry day for most. Will keep the chance of some scattered
showers/thunderstorms due to the increased moisture...warmth...and
therefore modest cape values. Looking at highs 77-82f. Chances for
some scattered showers continue Saturday night as the approaching
trough and frontal boundary near the region. Lows likely not falling
out of the 60s.
Sunday/Sunday night offer the best chances for widespread
shower/thunderstorm activity. A surface low and frontal boundary
will be nearing the region Sunday afternoon with the upper trough
approaching from the west. Latest trends in model guidance place the
majority of the region in the warm sector with increasing cape
values (up to 1500 j/kg) and around 30 knots of 0-6km shear. Thus with
boundary nearby could be looking at a threat of some stronger
storms. Heavy rain from any thunderstorms also likely with precipitable
water values over 1.5 inches and deep warm cloud depth. High
temperatures will be dependent on cloud cover and amount of shower
activity. Will show 75-82f for now...but if front is slower and
more sunshine occurs...these could be on the low side. Chances for
showers/storms continue through Sunday night as system passes
The upper trough and frontal system will be weakening by Monday and
heights may actually begin to build late in the day as a trough digs
into the northwest US and northern plains and a ridge strengthens over
the southeast US. Still will be some scattered showers around with
highs in the 70s and lows in the 60s.
Deep southwest flow returns late on Tuesday. Not looking at any
true focus for shower/thunderstorm development but with
warmth...humidity...and any pieces of energy riding around the
ridge...there will be the low chance for some scattered
showers/thunderstorms. Highs should reach the upper 70s to near 80
Aviation /09z Wednesday through Sunday/...
through 06z Thursday...primarily VFR expected through the period.
A cold front crossing the region this morning will bring with it
a few scattered rain showers 06z-08z at mss...and progressing south
and eastward...08z to 15z at btv...and then 12z-01z at rut where
an isolated thunderstorm cannot be ruled out either. Coverage is
expected to be minimal so will only show with vcsh for now.
Otherwise...ceilings will lower...but remain VFR at all sites
except for slk where a period of MVFR ceilings is likely between
08z and 15z. Some improvement is expected this afternoon.
Southerly winds early this morning from 5 to 10 knots will turn more
westerly and eventually north/northwesterly following frontal
passage later today.
Outlook 06z Thursday through Sunday...
06z Thursday-06z Sat: primarily VFR. Local IFR in patchy fog Thursday
06z Sat-00z Mon: mainly VFR although chances for scattered MVFR/IFR
showers and thunderstorms increase...especially late Saturday
night and Sunday where some brief periods of MVFR/IFR are