Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Burlington Vermont
128 am EDT Sat Jul 4 2015
high pressure will provide mainly fair weather and seasonably
warm temperatures for the Holiday weekend. Outside of a few
scattered showers Saturday afternoon into Saturday night, dry
weather is expected. The next chance of more widespread showers
looks to occur by Tuesday into Tuesday night with passage of a
weak frontal system.
Near term /until 6 am this morning/...
as of 108 am EDT Saturday...several changes made to current
forecast based on observations and latest radar trends. Have
increased the cloud cover as latest infrared satellite shows middle/upper level
clouds overspreading our County Warning Area ahead of next system. In
addition...with more clouds and higher surface dewpoint than
expected...have increased temperatures by 3 to 5 degrees. Thinking lows
will range from middle 40s dacks to middle 50s cpv/slv. Last change was
to increase probability of precipitation for Saturday/Saturday evening time period...as
guidance shows moisture over central PA/New York advecting into our
central/southern County Warning Area today. Expecting a few light showers
associated with this precipitation...as heavier returns now on radar will
weaken as moisture encounters deep dry layer per 00z Albany
sounding. Rest of forecast in good shape.
Short term /6 am this morning through Sunday night/...
as of 310 PM EDT Friday...high pressure continues to slide east
into Saturday allowing a northern stream shortwave trough to
approach and cross the area by Saturday night. As was the case
yesterday, believe model dewpoints, resultant planetary boundary layer instability and
quantitative precipitation forecast output is overdone with this feature. Low to middle level back
trajectory analysis from today's hysplit runs suggest our source
air tomorrow originates from southern New York into Pennsylvania so
slightly higher dewpoints on light southerly return flow seem
reasonable, just not to the extent of the deterministic runs. Best
shot at seeing a stray shower tomorrow afternoon appears to occur
across the higher terrain of the Adirondacks where weak planetary boundary layer flow
will support slope flows and localized Theta-E convergence.
Outside of this area just a token 10-20% threat with most areas
remaining dry over the course of the day. Highs tomorrow generally
in the 70s under variable middle to high cloud cover.
By tomorrow night aforementioned shortwave trough swings through the
region with clouds and perhaps a few showers across our northern
counties. Again, quantitative precipitation forecast will be light with coverage being scattered
at best and many areas remaining dry, especially south.
Low temperatures a bit milder given variable clouds, mainly in the
50s to around 60.
By Sunday into Sunday night upper trough swings east with deep layer
high pressure returning in earnest across the region. Other than a
few lingering morning showers far northeast dry weather is expected.
Temperatures will average very close to early July normals with
highs in the upper 70s to lower 80s and overnight lows in the middle
50s to lower 60s.
Long term /Monday through Friday/...
as of 322 PM EDT Friday...
A hint of Summer next week as heights and temperatures rise to or
just above normal with a surge of moisture and some thunderstorms
Models in agreement that short wave ridging Monday should bring a
nice warm and dry day in the 80s with 850 temperatures rising to 14-15c.
Models similarly increasing humidity and instability
(1000-2000j/kg cape) on Tuesday ahead of a frontal system as
southwest flow advects moisture into the region. So that will
increase our chances of showers and thunderstorms through through
Tuesday night. Little change in 850 temperatures so temperatures again in the
Where models differ is on how fast the frontal system moves
through with GFS bringing front through by Wednesday morning while
European model (ecmwf) is slower and brings it through later in the day. Both
models show upper trough weakening and lifting north, so not
expecting a deepening trough like we've had lately. The timing of
the front would make a significant difference in the convective
probabilities, so went with a blend with showers and a slight
chance of thunderstorms hanging around on Wednesday. Temperatures a bit cooler
Some uncertainty continues Thursday-Friday as flow aloft is generally
westerly with weak troffing so can't completely rule out a shower
with temperatures near normal for this time of year (80/60).
Aviation /06z Saturday through Wednesday/...
through 06z Sunday...primarily VFR expected through the
period...with the exception of some IFR/LIFR fog/br early this morning
at mpv/slk. Will see increasing High Deck of clouds through
today with some additional cumulus development by afternoon.
Areas of fog/br will likely develop 08z-11z at mpv/slk...but
density and coverage not expected to become widespread. An
isolated shower or brief thunderstorm may also develop this afternoon...but
left out for now as coverage not expected to be widespread.
Otherwise...light and variable winds tonight (except southeast 7-10 knots
at rut) turn southerly at 5-10 knots on Saturday.
Outlook 00z Sunday through Wednesday...
06z Sat-sun...mainly VFR. Isld MVFR -shra over the higher
terrain. Monday...mainly VFR under high pressure. Local LIFR fog possible
kmpv/kslk. Tuesday..mainly VFR. Scattered MVFR thunderstorms and rain with frontal passage Tuesday
night. Wednesday...mainly VFR. Scattered MVFR Post frontal -shra.
ktyx radar will be out of service until Tuesday or later.