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Area forecast discussion 
National Weather Service Buffalo New York
232 PM EDT Wednesday may 6 2015

Synopsis...
high pressure settling across New York state this afternoon and tonight
will drift off the Atlantic coastline on Thursday...where it will then
remain through the upcoming weekend. This will promote a return to dry
weather for the remainder of the work week and middle summerlike warmth that
will last through the upcoming weekend...when slowly increasing humidity
levels should also allow some scattered showers and thunderstorms to
develop.

&&

Near term /through Thursday/...
as of 1830z...regional satellite imagery shows that high pressure
continues to bring clearing skies from northeast to southwest as
it builds across New York state...with the only lingering cloud
cover now found across the southern tier...which is situated along
and north of the remnant weak frontal boundary over Pennsylvania.
While a few scattered light showers will still be possible for a
while longer this afternoon across the southern tier...in general
the drying/clearing trend should continue to progress into this
latter region through the balance of the day. Elsewhere...expect
sun-filled skies and dry... pleasant weather to persist.

After that...the rest of the near term period will feature
surface-based high pressure remaining draped across the region
tonight...before gradually sliding off the New England coast on
Thursday...while the axis of its parent upper-level ridge slides
from the western Great Lakes to New York state. All of this should
promote fair and dry weather throughout...with the NAM/GFS
depictions of some spotty convective development across inland
sections Thursday afternoon looking to be spurious given both the
arrival of the upper level ridge axis/increasing capping
aloft...and what appears to be an overly aggressive increase in
surface dewpoints /particularly by the NAM...which is a typical
bias for that model/. In terms of cloud cover...expect mainly
clear/ mostly sunny skies to predominate...except for a potential
area of lingering low level moisture/expanding low clouds across
western New York tonight...which will then lift and transition to
diurnal cumulus as it advects eastward and strong diurnal influences
come into play during Thursday. Across the southern tier and
interior portions of The Finger lakes...there may also be enough
lingering low level moisture to allow for the development of some
patchy fog later tonight... any of which would be likely to
quickly dissipate following sunrise Thursday morning.

As for temperatures...expect nighttime lows to range from the
lower 40s across the north country to the upper 40s and lower 50s
across much of the area south of Lake Ontario tonight...with 850
mb temperatures of +10c to +13c then supporting a return to middle
summerlike highs in the upper 70s to lower 80s in most places on
Thursday. The one exception to this will be along the
lakeshores...where the weak surface pressure gradient will allow
for lake breeze circulations to develop on Thursday...which in
turn will help keep readings there significantly cooler.

&&

Short term /Thursday night through Friday night/...
on Thursday night surface high pressure across the middle Atlantic will
ridge back into our region. This will very gradually break down as
the 500 mb ridge axis shifts east from our region to New England by
Friday night. This will bring gradually warming temperatures
aloft...which will result in a very Summer-like pattern.

The vast majority of the period will be dry due to the influence of
the ridge and a relatively dry airmass. A consensus of model
guidance continues to forecast some quantitative precipitation forecast on Friday afternoon. This
does not seem feasible on and near the lakes where a lake breeze
should stabilize things...and the extent is also misleading with any
showers activity likely to be widely scattered in nature. Based on
consensus quantitative precipitation forecast/cape inland of the lake-breeze it/S hard to completely
rule out a few afternoon instability showers along the lake breeze
boundary...so will carry slight chance probability of precipitation. Without daytime
instability as a factor...both Thursday night and Friday night
should be dry.

Perhaps the bigger weather story is that highs on Friday will be
near the warmest so far this season. Except for the immediate
lakeshores...most areas should top 80 degrees...with middle 80s a bit
further inland across the Genesee Valley and Finger Lakes regions.
Overnight lows will be mainly in the 50s Thursday night...then
warmer on Friday night due to the developing southerly flow which
will limit radiational cooling and perhaps result in some modest
downsloping.

&&

Long term /Saturday through Tuesday/...
middle Summer warmth will likely continue through much of the long term
period. The chances for showers and thunderstorms will steadily
increase with each passing day as deeper moisture and an increasing
number of weak shortwaves cross the region.

Looking at the details...expect another very warm day Saturday with
850mb temperatures around +14c supporting middle 80s away from the lakeshores.
Humidity will continue to creep upward...making it feel like middle
Summer. The GFS is more aggressive in leaning a weak frontal zone
into the lower lakes by afternoon...while the European model (ecmwf) holds this
system farther north and west. Continue to favor the slower European model (ecmwf)
solution given the strength of the East Coast ridge. With this in
mind have continued with just a low chance of an afternoon shower or
thunderstorm.

Sunday through Tuesday the pattern will become more active as a deep
trough develops over The Rockies and moves slowly east across the
plains. A frontal zone will stall over the Great Lakes region...
while numerous convectively generated middle level vorticity maxima
move east across the Ohio Valley and Great Lakes. These systems will
be difficult to place in time and space...but will support periods
of enhanced large scale ascent and greater shower/thunderstorm
chances.

The GFS tries to drop the frontal zone just south of our area for
Monday and Tuesday...while the European model (ecmwf) holds the boundary just north
of Lake Ontario keeping our region in the very warm and humid air.
Again favor the European model (ecmwf) scenario with the warmth holding through
Monday.

By Tuesday both the GFS and European model (ecmwf) sweep the Central Plains trough
into the western lakes...with a cold front moving east across the
Ohio Valley and lower Great Lakes. This will support a chance of a
few more showers and thunderstorms...and also Herald the arrival of
somewhat cooler air.

&&

Aviation /19z Wednesday through Monday/...
high pressure over western and north central New York this
afternoon and tonight will slide off the New England coast on
Thursday. For the most part... this will promote a continuation of
fair VFR weather...save for some lingering lower clouds across the
western southern tier this afternoon/tonight...and possibly the
Niagara Frontier much later tonight and early Thursday. While the
majority of these will be MVFR...some IFR will be possible across
the higher terrain of the southern tier tonight. With nocturnal
cooling and some lingering low level moisture remaining in
place...some patchy IFR fog may also develop across the southern
tier and interior portions of The Finger lakes later tonight...
before dissipating after sunrise Thursday morning.

Outlook...
Thursday night and Friday...VFR.
Saturday through Tuesday...mainly VFR...with a chance of showers/
thunderstorms and attendant MVFR.

&&

Marine...
with a weak pressure gradient remaining in place across the lower lakes
region through the end of the work week...expect relatively light winds
and minimal waves to continue through Friday.

&&

Buf watches/warnings/advisories...
New York...none.
Marine...none.

&&

$$

Synopsis...jjr
near term...jjr
short term...apffel
long term...Hitchcock
aviation...jjr
marine...jjr

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