Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Burlington Vermont
156 am EDT Sat Aug 23 2014
the clouds and showers of the past couple of days will slowly
diminish overnight. Strong high pressure will build into the area
for the weekend and then stick around. Though there may be a spot
shower Saturday afternoon, the weather into the middle of next
week will feature lots of sun and increasing warmth.
Near term /until 8 am this morning/...
as of 105 am EDT Saturday...minor update to remove mention of
precipitation overnight and decrease cloud cover grids across the nek.
Latest infrared satellite trends show decreasing clouds entering northern Vermont
at this time...which will slowly expand southwest across our County Warning Area through early
this morning. Any clring will quickly be replaced by areas of
fog...especially central/northern Vermont valleys. Temperatures will fall back
into the l50s dacks/nek to near 60f cpv. All is covered in current
forecast in excellent shape and only minor adjustments to
probability of precipitation and sky cover needed as of 715 PM to nudge toward current
observational trends. Also felt fog/mist will could be prevalent
just about anywhere outside the Champlain Valley tonight so
increased areal coverage...including the slv where some partial
clearing has already occurred. Rainfall/showers continue to
gradually abate and lessen in areal coverage as we push toward the
8 o'clock hour. We did see another round of gullywashers out
across St Lawrence County earlier this afternoon however despite
only limited instability. Case in point our observer out in
Gouverneur reporting 1.70 inches between 1 and 4 PM earlier today.
Short term /8 am this morning through Sunday night/...
as of 320 PM EDT Friday...still looking like a pretty decent
weekend, with just one small bug-a-boo. With the upper air pattern
slow to evolve, we will continue to have cyclonic flow aloft. With
still a decent amount of low level moisture around, anticipate
daytime heating combined with topographic influences should result
in a few afternoon showers forming. Appears the best chance of
this will be across eastern Vermont. Have painted in low rainfall
chances, generally 15-25% for the afternoon hours in that area.
Certainly not going to be a washout.
Otherwise a good deal of sunshine is expected. With 850mb
temperatures of 11-12c, this should support lower elevation
temperatures well into the 70s. Winds will be light, and favor an
Surface high pressure sinking in from the north Saturday night
will set up a clear/calm night. With the boundary layer still
expected to be moist due to recent rains, this will set up a
perfect situation for locally dense fog to develop -- especially
in the river valleys. Temperatures will fall into the 50s, with
colder hollows into the 40s.
Sunday should be a spectacular weather day (well, for Summer
fans). High pressure overhead and a building upper level ridge
will lead to a dry day. 850mb temperatures rise a couple of
degrees into the 12-14c range. Thus lots of 70s to lower 80s will
be the common result.
Sunday night should be similar to Saturday night with clear/calm
conditions, so anticipate another round of patchy late night fog.
Temperatures will again fall back into the 50s (40s in the coldest
Long term /Monday through Friday/...
as of 352 PM EDT Friday...for first half of extended period the
full latitude ridge over the Mississippi basin shifts east over
the eastern US. Quiet weather during this time, with warming
temperatures. By middle week GFS develops higher amplitude ridge over
eastern US and trough to west, while European model (ecmwf) flattens out. As a result
GFS 1000-500mb thickness and 850 mb temperatures quite a bit warmer. GFS
850 mb temperatures up to 17f on Wednesday and Thursday which would support
temperatures well into the upper 80s in the Champlain Valley. European model (ecmwf)
somewhat in agreement with warmer temperatures on Wednesday...so felt
comfortable bumping up Wednesday maximum temperatures over superblend guidance. This
also matched previous forecast thinking.
European model (ecmwf)/GFS diverge more significantly from Thursday Onward...and
forecast confidence...especially in temperatures...is lower for the latter
half of the week. The shortwave trough sweeping out of the northern
plains states is taken by the GFS to dig an East Coast
trough...while the European model (ecmwf) flattens the ridge out and takes the
shortwave energy to the north. As a result GFS gives another day of
warmth while the European model (ecmwf) cools US down on Thursday. Hedged a little
warmer than guidance toward the GFS on Thursday...but kept the
forecast maxes Thursday out of the middle/upper 80s.
Both models bring probability of precipitation up into chance category with the approach of a
surface front despite dissimilarities at 500 mb. Orientation and
speed of the front varies...but using a broad brush in the far end
of the extended yielded chance for showers and thunderstorms
Thursday into Thursday night.
Aviation /06z Saturday through Wednesday/...
through 06z Sunday...VFR trending MVFR overnight...with periods
of IFR conditions possible in some spotty drizzle and patchy fog
through 13z. After 13z...scattered to broken clouds at or above 3000
feet are expected through the day on Saturday...with skies
becoming mainly clear Saturday evening. Winds will generally be
light and variable through the period.
Outlook 06z Sunday through Wednesday...generally VFR except areas
IFR/LIFR in fog each morning Sunday through Tuesday. Ridge builds
into region through this period with no precipitation and very few