Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Buffalo New York
426 am EDT Wednesday Sep 2 2015
high pressure will remain draped across the region right through
the Labor Day weekend. While a series of weak upper level
disturbances could generate some isolated to widely scattered
showers and thunderstorms through Thursday... conditions should
otherwise be rain free.
Near term /through tonight/...
on the synoptic scale...the zonal flow currently in place across
the Great Lakes and northeast will buckle a little and turn weakly
cyclonic today and tonight due to the passage of a series of weak
upper level disturbances. Meanwhile at the surface...broad high
pressure will remain dominant across our region into this
evening...before gradually giving way to a weak surface trough/
cool front that will sag in our direction from Ontario and Quebec
Through the course of this morning...expect dry and quiet weather
to continue across our region...with any areas of fog/stratus that
developed overnight dissipating over time with increasing daytime
heating and mixing. This should result in a return to partly to
mostly sunny skies areawide by late this morning.
This afternoon...a very subtle upper level shortwave will work
across our region...and this in conjunction with developing lake
breeze boundaries and continued heating of our warm and humid
airmass could be enough to pop an isolated shower or thunderstorm
or two across western New York during the afternoon. Judging from
a consensus of available guidance...the best chances for these
would be along the typically favored Lake Erie/Lake Ontario lake
breeze convergence zone north of Buffalo...and across interior
portions of the southern tier. Even in these areas though...coverage
should remain fairly sparse...with the vast majority of the time
likely to remain rain free. Otherwise...expect warm and humid
conditions to continue...with 850 mb temperatures of around +17c
supporting widespread highs in the middle to upper 80s away from any
Tonight...any limited diurnally-driven convection still ongoing
at the start of the evening should tend to weaken and largely fall
apart with the loss of daytime heating. As a result...mostly quiet
and largely dry weather should continue to prevail for a large
chunk of the night... before another weak shortwave and the
aforementioned surface trough/ cool front begins sagging across
Lake Ontario late. At that point... the combination of subtle lift
from these features and warmth and moisture contributions from
Lake Ontario could be enough to generate some additional scattered
showers and thunderstorms over the lake and its adjoining
areas...for which some low chance probability of precipitation will remain in play from
our existing continuity. Otherwise...warm and humid conditions
will continue to prevail...with the combination of partly cloudy
skies and light winds allowing for the development of some patchy
fog just about anywhere...along with the typical areas of fog
within the southern tier valleys. With respect to
temperatures...overnight lows will mostly be in the middle to upper
60s...with lower 60s across interior portions of the southern
Short term /Thursday through Friday night/...
what will likely be the most exciting weather of the entire
period will occur on Thursday as an amplifying ridge upstream over
the Midwest backs the flow to the north across eastern Canada...in
turn forcing a back door cool front south across the lower Great
Lakes on Thursday. As eluded to in previous discussions...the
combination of weak synoptic forcing and upslope flow should
trigger widely scattered showers and thunderstorms across portions
of the forecast area Thursday afternoon and early Thursday
evening. Activity should be confined to higher terrain inland from
the lakes due both to the timing of the frontal passage as well as
the fact that greater heating over the higher terrain will be
needed to overcome a weak middle-level cap.
Any activity will wind down quickly Thursday evening with the
loss of diurnal heating. Clearing skies behind the front should
allow for the development of the ubiquitous valley fog Thursday
night. Look for lows to run in the low 60s with the north country
as well as a few sheltered southern tier locales dipping into the
While temperatures Thursday will still be in the low to middle
80s...cooler air filtering south into New York from Ontario behind
the front should produce a slightly cooler end to the work week on
Friday with highs in the upper 70s to around 80. This combined
with abundant sunshine courtesy of high pressure building out of
Canada and dewpoints that will run in the upper 50s across many
areas should make for a very pleasant conclusion to the work week
indeed. Light southeasterly flow developing Friday night as high
pressure drifts across New England will bump dewpoints up a couple
of degrees...producing a slightly warmer night with lows in the
60s and valley fog once again.
Long term /Saturday through Tuesday/...
the Holiday weekend will be warm and sunny as the axis of the
upper level ridge shifts across the Great Lakes with strong
surface high pressure dominating at the surface. Highs will run in
the middle 80s Saturday and Sunday with the warmest temperatures of
the period falling on Monday as the center of the high shifts to
the Middle- Atlantic States and southwesterly flow returns to the
lower Great Lakes...in turn advecting warmer air out of the Ohio
Valley and generating downsloping that will push temperatures on
Labor Day into the middle to upper 80s across the Genesee Valley and
north of The Finger lakes with middle 80s elsewhere. Lows through the
period will continue to run in the 60s.
Looking ahead to Tuesday...differences continue to still exist
between the global models on the timing of a cold front that is
expected to slide across western and north-central New York as
upper level energy currently over the Pacific northwest eventually
makes its way to the vicinity of James Bay. The European model (ecmwf) brings the
front through Tuesday afternoon while the GFS holds off until
Wednesday. For now will keep a chance of showers and thunderstorms
in for Tuesday with the knowledge that this could easily end up
being delayed by at least 24 hours. Warm air advecting poleward
ahead of the front should result in another very warm September
day with highs in the middle to upper 80s.
Aviation /09z Wednesday through Sunday/...
areas of fog and attendant LIFR/IFR that developed overnight
will dissipate this morning with increasing daytime heating/
mixing...yielding widespread VFR conditions from late this
morning on through the rest of the day.
Tonight conditions will start off VFR...with localized reductions
to IFR/MVFR in fog then developing again as the night progresses...
with the greatest potential for these found across the southern
tier. There will also be a chance of showers and thunderstorms
late over and around Lake Ontario as a weak surface trough presses
into our region.
Thursday...VFR with a chance of showers and thunderstorms.
Localized IFR in fog developing Thursday night.
Friday through Sunday...VFR. Localized IFR in overnight/early
high pressure will remain draped across the lower lakes region
right through the Labor Day weekend...resulting in continued
light to modest winds and minimal waves. With a humid airmass
also remaining in place...there will also be the potential for
areas of fog each night and morning.