Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Buffalo New York
1007 am EST sun Nov 29 2015
high pressure will keep cooler...yet seasonable... temperatures and
dry conditions across the region through Monday night. A low
pressure system will track across the Great Lakes on Tuesday
bringing above normal temperatures and rain. A cold front moves
through Tuesday into Wednesday bringing temperatures back to normal
with some lake rain/snow showers following behind the system through
Near term /through tonight/...
lingering low-level moisture and cloud cover will remain the main
forecast challenge today... and will impact high temperatures mainly
south of Lake Ontario.
The 12z buf sounding continues to show a sharp inversion with
-7c at 925mb warming to +1c at 900mb. Some higher resolution
guidance captures the current conditions. Across the southern
tier visible satellite shows clearing skies...which is consistent
with this guidance and likely to continue through this afternoon.
This is not the case south of Lake Ontario where lake moisture
should continue to maintain the cloud cover for the better part of
the day. High resolution guidance forecasts some light quantitative precipitation forecast
southeast of Lake Ontario this afternoon. Temperatures aloft are
slightly colder there...with the shallow moisture marginal to
support dendirtic snow growth. This probably will not be enough
for any precipitation to form outside of perhaps some light
flurries or sprinkles. The cloud cover should keep temperatures on
the cool side...with most areas not getting out of the 30s today.
While this seem quite cool in comparison to the temperatures we've
seen this fall... it is actually only a few degrees below normal.
By tonight... the surface high pressure will move over New
England... with winds turning more easterly then southeasterly into
Monday morning. This will finally help to disrupt the lake enhanced
cloud cover and allowing it shift out over Lake Ontario by Monday
morning. The best clearing will be in the southern tier and the
north country. The north country will be primed for optimal
radiational cooling tonight as winds may go calm for a period
overnight given the proximity to the surface high. Watertown may
actually crash into the low to middle teens tonight should winds go
calm as anticipated. Across the southern tier a bit more of a light
breeze should help keep temperatures will be in the lower 20s. South
of Lake Ontario... lingering cloudiness will keep lows in the middle
to upper 20s.
Short term /Monday through Tuesday night/...
on Monday surface high pressure will build across New England with a
ridge extending back into the lower lakes. This will provide another
sunny day with the airmass moderating slightly as weak warm
advection begins. Expect highs in the lower to middle 40s across
western and central New York with upper 30s across the north country.
Monday night the surface high will drift east into the Gulf of Maine
while the next area of low pressure and strong middle level closed low
move into the upper Midwest. Increasing warm advection and
isentropic upglide in the developing southerly flow between the two
systems will bring an increase in cloud cover from southwest to
northeast overnight. A few showers may develop across western New York and
the southern tier late. Expect early evening lows in the low to middle
30s in most areas with middle to upper 20s across the north country.
The combination of low level warm advection and increasing clouds
will then force rising temperatures overnight. Expect temperatures
to rise above freezing several hours prior to the onset of any
showers with very little risk of any freezing rain.
The vertically stacked low will cross the upper lakes Tuesday with
DPVA and diffluent flow aloft supporting increasing large scale
ascent across our region while an occluded front brings increasing
low level convergence during the afternoon. The increasing moisture
and ascent will bring increasing coverage of showers from southwest
to northeast through the day. 850mb temperatures surge to around +10c just
ahead of the front...and this will support highs in the middle to upper
50s across western New York despite the increasing showers.
Tuesday night the occluded front will move east across the area.
Showers during the evening will end from west to east overnight with
the passage of the frontal boundary. A well defined dry slot will
then bring a break in the rain and possibly even a period of partial
clearing overnight. Towards Wednesday morning the airmass will grow
marginally cold enough to support a Few Lake effect rain showers
northeast of the lakes.
Long term /Wednesday through Saturday/...
Wednesday a strong middle level trough will move east across the Great
Lakes region. The morning dry slot will give way to a rapid increase
in moisture and large scale ascent by early afternoon with the
approach of the middle level trough. The airmass will also grow
supportive of lake enhancement northeast of the lakes. The
combination of synoptic scale moisture and ascent along with lake
enhancement will produce numerous showers during the afternoon
northeast of the lakes...with a few showers likely even outside of
lake enhancement. Cold advection will bring falling temperatures
during the afternoon. The boundary layer will still be quite mild
with rain transitioning to a rain/wet snow mix at lower elevations
and possibly to all snow across higher terrain later in the
Wednesday night the synoptic scale moisture quickly pulls away...
with some lake effect showers of rain and wet snow lingering
southeast of the lakes overnight. Overall temperatures appear too
mild at lower elevations for any accumulation...with some minor
slushy accumulations possible across higher terrain. If Buffalo can
get through this period without measurable snow...this season will
likely shatter the record for the latest first measurable snow.
Any lingering lake effect rain and snow showers southeast of the
lakes Thursday morning will end by midday as high pressure and dry
air build into the lower lakes.
Friday and Saturday the GFS and European model (ecmwf) begin to diverge on timing
with the GFS bringing a middle level trough southward across New York and New
England Friday...while the European model (ecmwf) is much slower with the trough late
Friday night and Saturday. Regardless the system will be moisture
starved with nothing more than a few sprinkles or flurries at best.
For now have left both days dry with temperatures moderating to a
little above average.
Looking farther ahead...operational guidance and ensemble means show
a high confidence forecast for above normal temperatures to continue
through the middle of December with the upstream pattern across
the Pacific and high latitudes forcing mild Pacific air to flood
east across the nation while any cold air is locked up at very
high latitudes in northern Canada. It appears there will be little
chance for measurable snow through the middle of December.
Aviation /15z Sunday through Thursday/...
stratus will linger south of Lake Ontario through the afternoon
hours...while these clouds should mix/scatter across the southern
tier. This will result in mainly VFR conditions at jhw/Art while
buf/iag/roc are likely to remain MVFR. Eventually these clouds
should scatter out as high pressure builds in...however timing
this is problematic given the strength of the inversion in place.
By late this evening conditions should improve to VFR...however
confidence in timing is low.
Monday night and Tuesday...rain. Mainly MVFR.
Wednesday...mainly MVFR. Rain or snow showers likely.
Thursday...VFR/MVFR. A chance of rain or snow showers.
high pressure to remain in control through Monday... keeping winds
and wave minimal.
A low pressure system will then track across the Great Lakes Tuesday
into Wednesday resulting in a period of brisk southwesterly winds
ahead of the storm and west to northwest winds behind it. Small
Craft Advisory conditions will likely develop on area waters as this
weather system moves through.