Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Buffalo New York
159 PM EDT Thursday Oct 8 2015
fair weather this evening will fade as a storm system tracks across
our region tonight and tomorrow with rain. A cold front will advance
across the region later Friday...ending rain showers from west to
east as well as marking the leading edge of cooler air temperatures.
Expect a chilly Saturday...but dry before warmer temperatures return
to the region to close out the Holiday weekend.
Near term /through tonight/...
visible satellite imagery this
afternoon displays sunny skies with some fair weather cumulus
across the southern tier and The Finger lakes region. Previous Disco
Surface high pressure will move from southern Quebec off the New
England coast today as the next wave of low pressure moves into the
upper Great Lakes. This will allow light and variable winds to
become more easterly late in the day. With little change in the
airmass other than a general drying trend... expect another day of
pleasant seasonable temperatures with much more sunshine than we
have seen so far this week.
Widespread soaking rain will move into the area tonight as a
deepening low pressure system moves from northern Michigan to
Eastern Lake Ontario by daybreak Friday. The greatest rainfall
amounts will be concentrated along a line through the long axis of
Lake Ontario into the north country... where quantitative precipitation forecast amounts to around 1
inch are expected into Friday morning. This axis of moderate to
heavy at times synoptic precipitation will develop along the warm frontal
push ahead of the deepening surface low... with integrated vapor
transport values around the 90th percentile for this time of year.
Any hydrologic concerns in the north country are mitigated by the
progressive nature of the low... with this focused area of
precipitation moving through in less than 12 hours. Forecast
precipitation amounts taper off to around a half inch along the New York
thruway corridor... and down to around a quarter inch across the
southern tier... owing to the more showery rainfall that develops
just ahead and along the cold frontal push and upper-level trough
passage. Regardless of the exact details the entire forecast area
will see a soaking rainfall tonight into Friday morning.
Temperatures will initially cool after sunset this evening... but
will bottom out before midnight... then will follow a warming trend
through sunrise Friday as strong warm advection moves across the area.
So even though overnight lows are advertised generally in the 50s to
upper 40s... western New York will be pushing 60 by sunrise Friday with
some middle 50s still in the north country.
Short term /Friday through Sunday night/...
a shortwave...seen this morning in WV imagery over the Canadian
Maritimes...will plow across the upper Great Lakes to eastern Canada
for the start of this period. This will briefly amplify an otherwise
near zonal flow along the Canadian border so that our region will
experience a quick shot of true autumnal air. The cooling will be
preceded by a period of widespread showers...with steadier...
possibly heavy rain expected across the Eastern Lake Ontario region.
A relatively broad surface low over Lake Ontario Friday morning will
track east across the Adirondacks to New England Friday afternoon.
The attendant cold front will push across our region in the
process...with moderately strong frontogenetic forcing and
assistance from a h25 jet interacting with a moisture rich
environment (max precipitable water 1.5") to generate widespread rain showers. As
mentioned above...the showers will fall as steadier rain near and
east of Lake Ontario in the vicinity of the stronger forcing. Total
rainfall amounts are forecast to range from a half to three quarters
of an inch over the western counties to nearly an inch east of Lake
Ontario. Despite significant middle level drying leading to the
tapering off of the rain from west to east during the midday and
afternoon...near saturated air in the low levels within an
increasingly northerly flow at h925 will inhibit any clearing. In
fact...much of the low cloud cover is expected to persist deep into
Friday night...especially across the southern tier.
Meanwhile...strong cold advection in the wake of the cold front
should encourage fridays maximum temperatures to occur around lunchtime...with
slowly falling Mercury readings forecast for the afternoon. 850 mb
temperatures will then bottom out near zero c late Friday night/Saturday
morning. This will lead to mins in the lower 40s across the western
counties and upper 30s across the Eastern Lake Ontario region.
On Saturday...a large surface high will extend from the lower Great
Lakes to the lower Mississippi Valley. While it will be a notably
cooler day with temperatures only reaching the low to middle 50s...we
can anticipate the return of mostly sunny skies.
Conditions will continue to improve as we progress through the
second half of the weekend. The axis of the surface high will push off
the East Coast while flat ridging in the middle levels will cross the
lower Great Lakes. This will result in a fairly strong southwest
flow of mild air...with 850 mb temperatures expected to easily climb into the
double digits. Afternoon temperatures should have no trouble making
it into the 60s...with ample sunshine likely providing a beautiful
day for taking in the fall foliage.
Long term /Monday through Thursday/...
a low amplitude flow will generally be in place across the country
for the first half of next week...although a significant kink in the
flow will keep US from having fair dry weather for all three days.
This pattern will support above normal temperatures...especially on
Monday when a deep southerly flow ahead of a cold front will likely
send our temperatures to within a few degrees of 70.
The aforementioned cold front will cross the upper Great Lakes
during the day Monday with 850 mb temperatures climbing to 12c or better over
our forecast area. The southerly flow ahead of the cold front will
not only Promise very mild conditions...but will work against the
eastward progression of the cloud cover associated with the
Clouds will then thicken across the western counties late Monday and
Monday evening...with the front producing scattered showers as it
will pass over our forecast area Monday night. Given the consistency
of this scenario by the operational versions of the GFS and European model (ecmwf)...
have raised probability of precipitation to 40.
The supporting shortwave will cross the lower Great Lakes on Tuesday
while the front will make its way across New England. While the
showers will end from west to east...a northerly upslope h925 flow
in the wake of the front will likely keep a fair amount of clouds in
Ridging is then expected to briefly move across our region Tuesday
night and Wednesday...promoting fair weather for the middle week
Aviation /18z Thursday through Tuesday/...
at 18z mainly VFR flight
conditions were found across the region. Several patches of MVFR ceilings
were found across the southern tier...especially the western portion.
High level cirrus is beginning to spill across the taf region...but it
should be later this evening before we see the lower deck of stratus
ahead of the next storm system reach US.
Expect rain showers to reach the western taf sites between 02z and
06z...with a then 12 to 18 hour period where rain showers will be
likely. Expect mainly MVFR/VFR flight conditions early within the
rain...along with minimal low level wind shear. The longest duration of rain along with
the heaviest rain activity is expected over the north
country...including the kart airfield.
Later tonight and early Friday more widespread IFR flight conditions
are expected in not only the higher terrain...but also downwind of the
lakes across kiag/kbuf/kart.
Outlook... Friday afternoon and night mainly MVFR with rain showers
Saturday through Tuesday...mainly VFR. There will be a chance for
showers late Monday night and early Tuesday morning creating MVFR
high pressure sliding off the northeast coast by tonight will
promote easterly winds across the lakes especially be later in the
day. Wave action on Eastern Lake Erie is expected to remain light...
while some 1 to 3 foot wave remain on Western Lake Ontario in the
A storm system will bring an increase in southwesterly winds late
tonight through Friday along with widespread rain...with Small Craft
Advisory conditions likely on portions of the eastern Great