Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Buffalo New York
144 am EDT sun Jul 5 2015
high pressure will build across the region tonight and Sunday and
provide plenty of sunshine and warm temperatures to close out the
Holiday weekend. High pressure will remain in control Monday before
a weak area of low pressure moving north along the Appalachians
brings a chance of showers Monday night. A cold front will then
bring additional showers and thunderstorms later Tuesday through
Near term /through today/...
a quiet rest of the overnight time
period as high pressure builds across the lower lakes. Model
soundings continue to suggest some limited moisture moving back into
the area later tonight at around 5k feet which may be enough to
trend skies from mainly clear to partly cloudy. Temperatures will be
seasonable with overnight lows in the upper 50s on the lake plains
and lower 50s in the typically cooler interior southern tier and Tug
Hill region. Some patchy fog is likely in the river valleys of the
On Sunday...surface high pressure will build over the lower lakes
with a return to sunshine for the entire region. The airmass
continues to modify and warm under the long hours of early Summer
daylight...so expect highs to be about 5f warmer than today. This
will translate to lower 80s across lower elevations and upper 70s on
the hills and across the north country. Light synoptic scale flow
and strong differential heating will allow local lake breezes to
develop by afternoon with onshore winds keeping the lakeshores a
While it will be sunny on Sunday...there will once again be a
hazy...milky white look to the sky. This will be the effects of
wildfire smoke from western Canada and Alaska.
Short term /tonight through Tuesday night/...
as of 945 PM Saturday...have updated the forecast in the Monday to
Monday night time frame to increase cloud cover and insert chance
probability of precipitation across far western New York in conjunction with the middle/upper
level shortwave trough approaching from the Ohio Valley. The 18z
runs of the NAM/GFS have trended more aggressive with this feature
and also have support from the older 12z Gem global...all of which
suggest that enough moisture/lift/instability should be in place
to warrant a more substantial increase in cloud cover and precipitation
potential for the afternoon and evening hours...with at least
scattered convection now expected to develop across far western New
York during this time frame. Otherwise the forecast has been left
as is...still-relevant portions of the early afternoon short
term discussion follow below.
An area of high pressure will drift off the New England coast on
Monday bringing a light to modest southerly return flow across the
forecast area. The combination of initially mostly sunny skies and
850 mb temperatures to +16 to +17c will allow afternoon high
temperatures to spike into the middle to upper 80s across the forecast
area...the warmest readings we've seen since may. Temperatures
Monday night /within a continued light southerly flow/ will drop
only into the middle to upper 60s...with a few locations possibly
remaining at only 70f for a low.
On Tuesday an approaching shortwave trough over the upper Great
Lakes will steer a middle-level wave out of the middle-Atlantic region and
across the forecast area. An area of showers and thunderstorms is
possible across the area on Tuesday in the moist and unstable
southwesterly flow aloft. While 850 mb temperatures will remain
around +16 to +18c... anticipate that increased cloud cover and
shower activity will allow high temperatures to remain a few degrees
cooler than on Monday. By Tuesday evening... the surface cold front
associated with the upper-level shortwave passing north of the
forecast area will move into western New York. With the best
synoptic forcing with the wave passing well north of the forecast
area... expect that shower and thunderstorm activity along the front
will be rather scattered and disorganized. Some weak convectively
driven waves may propagate along the frontal boundary into Tuesday
night bringing periods of increased shower/thunderstorm coverage.
With the wave lifting north of the area... any deep layer shear will
likely remain weak into Tuesday evening... and thus expect that the
severe threat with any storms that do develop will be rather low.
Temperatures Tuesday night will bottom out in the middle 60s... with
the surface boundary and associated cloud cover stalling out as it
pushes south and east across the area. Thus some showers will
probably linger across the southern tier and Finger Lakes regions
Long term /Wednesday through Saturday/...
weak high pressure will build across the area Wednesday through
Friday... this will keep temperatures in the 70s to near 80 with
below normal chances of precipitation to end the work week.
Looking ahead to next weekend...forecast confidence remains below
normal...as various forecast models disagree on the timing of a
shortwave that could bring increased shower/thunderstorm chances
to one of the days of the weekend. While Saturday or Sunday could
see some shower/thunderstorm activity... the weekend looks far
from a washout.
Aviation /06z Sunday through Thursday/...
VFR flight conditions
were found across the region at 06z...and these conditions will be
predominate throughout this taf package. The exception will be
across the southern tier where some valley fog may expand across the
kjhw terminal. This fog should remain thin as dewpoints remain
several degrees lower than the air temperature...with generally MVFR
visibilities within the fog.
Expect a few middle and high level clouds to start to build northward
across wny Sunday evening...with a deck of middle level clouds reaching
the southern tier by dawn Monday.
Winds will remain light and variable through the taf period with an
area of high pressure passing across the lower Great Lakes region.
Tuesday and Wednesday...mainly VFR with a chance of showers and
a weak pressure gradient will remain in place across the lower Great
Lakes through the remainder of the Holiday weekend. This will
generally result in relatively light winds and minimal waves...with
local lake breeze circulations developing each afternoon and
producing weak onshore flow.