Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Buffalo New York
1105 am EDT Wednesday Sep 17 2014
high pressure will keep dry and slightly cooler than normal weather
in place today. A weak cold front will then cross the region later
tonight and Thursday morning...and may bring a light shower or two
to areas east of Lake Ontario. Following the front...Canadian high
pressure and a reinforcing shot of noticeably cooler air will
briefly overspread our area Thursday and Thursday night...before a
moderating trend sets in for Friday and Saturday. The next more
widespread chance of rain will arrive this weekend...when a complex
frontal system is forecast to cross our region.
Near term /through tonight/...
sprawling high pressure will remain in control from the Ohio Valley
to New York state for the remainder of the day keeping dry
conditions in place. Late this morning visible satellite imagery
still showing a band of lake effect clouds along a convergent
boundary slicing down the middle of Lake Erie. Westerly winds just
off the deck are pushing lake clouds inland across southern Erie
County east into Wyoming County. Over far Eastern Lake Ontario...a
similar scenario is ongoing with a band of lake clouds extending
inland across southern Jefferson County and slowly moving northward.
There are a few very isolated light showers/sprinkles still showing
up on radar imagery along both boundaries...but expect these to
remain out over the lake waters and dissipate all together by early
afternoon. Expect both cloud bands to lift northward through the
late morning and eventually break up by sometime early this
afternoon thanks to the still strong middle September sun. Outside of
the lake clouds daytime heating should bring a period of diurnal cumulus
to form inland from the lakes late this morning across the
region...first across the higher terrain...then the lower
elevations. Cumulus will persist through the first part of the
afternoon...before drier air aloft mixes down which should start to
dissipate low level cloud cover later this afternoon. That
said...this afternoon there will also be some increase in middle
and high clouds across the north country as a weak cold front slowly
presses in our direction from Ontario/Quebec provinces...though even
there skies should become no worse than partly sunny. As for
temperatures...these will remain slightly cooler than average given 850 mb
temperatures of +4c to +7c...which will translate into surface readings
reaching into the middle and upper 60s in most locations.
Tonight...the weak cold front will slowly sag from southern Ontario/
Quebec into western and north central New York in response to a
subtle sharpening of the middle and upper level flow...with this
feature reaching or at least nearing a Buffalo-Rochester-Syracuse
axis by 12z Thursday. With the boundary appearing anafrontal in
nature...any noticeable increase in cloud cover should remain
confined to areas along and north of the boundary...while areas
further south remain mainly clear to partly cloudy.
Given the lack of significant upper level support and that the bulk
of any moisture should remain confined to the lowest 5-10 kft of the
atmosphere...precipitation chances attendant to the encroaching front still
appear to be fairly minimal tonight. This noted...a few light
showers still appear possible across the north country/Saint
Lawrence valley overnight...where moisture and low level convergence
will be the most favorable overall...and where some low chance probability of precipitation
will consequently be in play. Otherwise...expect another quiet and
dry night with overnight lows falling into the middle and upper 40s in
Short term /Thursday through Saturday night/...
a cold front will sag south across Lake Ontario and settle across
New York state on Thursday. While the front may bring a few
sprinkles...particularly across upslope areas south of Lake
Ontario...moisture will be very shallow due to the Arctic airmass
advecting into the region behind the front and aside from a few
sprinkles the main effects will be abundant lake enhanced cloudiness
across much of the forecast area. The exception will be the north
country which will escape the lake influences and have greater
exposure to the cool dry air flowing south out of Canada.
The combination of cold advection and abundant cloud cover will keep
temperatures in the 50s on Thursday. Temperatures will plunge
Thursday night as Arctic high pressure moves overhead and cloud cover
dissipates. With light winds...clearing skies and lowering
dewpoints...the potential for frost will extend across much of
western and north-central New York with the exception of areas
immediately adjacent to the lakes. The coldest readings will be
found across the north country which will be in closest proximity to
the coldest and driest air across Quebec. Here readings are likely
to dip below freezing inland from the lakes and a freeze watch has
been issued for late Thursday night and early Friday morning.
After a chilly start to the day Friday morning...temperatures will
moderate nicely as the high moves off to the east and the
combination of abundant subsidence from the high and increasing warm
advection on the western flank of the high pushes temperatures back
into the mid-60s...making for a pleasant autumn day across the
Warm advection will continue to increase Friday night into Saturday
as the high moves off the East Coast and developing low pressure
moves into the upper Midwest. Increasing moist return flow across
the region and warm advection aloft will bring increasing cloud
cover Friday night will yield much more mild readings Friday night
with lows in the 50s. It will feel almost summerlike Saturday as a
warm front slides by to our north and southerly flow
strengthens...with associated downsloping helping to push readings
into the middle to upper 70s across the Genesee Valley and north of The
Finger lakes with low to middle 70s elsewhere across western New York
and slightly cooler temperatures in the north country. The mild
weather should hang on for more night Saturday night with dewpoints
rising into the middle to upper 50s with overnight lows in the upper
50s to around 60.
Long term /Sunday through Tuesday/...
the quiet stretch of weather across the lower Great Lakes will
come to an end Sunday as a potent shortwave dropping out of
northwestern Canada reinforces an existing shortwave trough and
weak surface low over the western Great Lakes. The reinvigorated
surface low will track into Quebec Sunday while the shortwave digs
a deep upper level trough across the Great Lakes. While there is
broad agreement that the resultant cold front will swing across
western/north-central New York sometime Sunday into Sunday
evening...there continue to be differences in detail and timing of
specific features. Nonetheless given very strong synoptic forcing
at work am confident that most areas will see precipitation
sometime during the Sunday/Sunday night time frame. Future model
runs will allow for more refinement of timing of the frontal
passage and associated precipitation.
The passage of the aforementioned cold front will mark a transition
back to cooler autumnal weather across the lower Great Lakes as upper
level troughing once again becomes established across the region.
Look for temperatures to fall from pre-frontal highs in the 70s
Sunday back into the 60s Monday...with highs possibly only reaching
the 50s by Tuesday as the upper level trough moves overhead. The
cold air aloft and synoptic scale west-northwest flow through the
period will keep plenty of lake-enhanced cloud cover and potentially
rain showers in the mix for Monday and Tuesday.
Aviation /15z Wednesday through Sunday/...
VFR conditions generally continue across the bulk of the region.
There are a couple areas of lake clouds still immediately downwind
of lakes Erie and Ontario where some lower-end VFR...5-6k feet decks
lake effect clouds persist. These may decks may make it into the
kbuf/kart terminals by noon...before starting to break up.
With renewed daytime heating/mixing...the lingering lake effect
clouds should mix out by early afternoon. Otherwise...expect VFR
conditions to prevail through the day with some diurnal cumulus
developing away from the lakes...and some middle and high cloudiness
eventually working into the north country in advance of an
approaching cold front.
Tonight...the aforementioned cold front will slowly press southward
into New York state...bringing lower-end VFR ceilings and the chance of
a few light showers to the north country overnight. By late in the
night...some of the lower VFR ceilings will may push as far south as a
Thursday through Saturday...generally VFR...with the possible
exception of some Post-frontal MVFR ceilings Thursday morning. Some
localized IFR southern tier valley fog will also be possible Friday
and Saturday mornings.
Sunday...VFR/MVFR with showers becoming likely.
late this morning visible satellite imagery shows a band of lake
effect clouds along a convergent boundary slicing down the middle of
Lake Erie. Westerly winds just off the deck are pushing lake clouds
inland across southern Erie County east into Wyoming County. Over
far Eastern Lake Ontario...a similar scenario with a band of lake
clouds extending inland across southern Jefferson County and slowly
moving northward. There are a few very light showers/sprinkles now
showing up on radar imagery along both boundaries out over both
lakes. Szilagyi waterspout index (swi) shows a very small chance for
a waterspout along these bands of lake clouds until they break up
late this morning/early afternoon. Inversion heights are low...so
will opt to keep out of the grids unless we receive a report.
High pressure draped from the Ohio Valley to New York state will
drift southeastward today...allowing a weak cold front to cross the
lower lakes later tonight and Thursday morning. Following this
front...another area of high pressure will build from central
Ontario province to the New England coastline Thursday through
In the immediate wake of the cold front...a brief period of
moderate northerlies could bring conditions close to advisory levels
on Eastern Lake Ontario very late tonight and Thursday morning.
Otherwise...winds and waves should remain below advisory criteria
New York...freeze watch from late Thursday night through Friday morning