Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Buffalo New York
1008 am EDT Fri Oct 28 2016
low pressure over New England will give way to high pressure today.
While this will allow for temporary improvement over our region...
the weekend will be unsettled. A cold front will stall just south of
our area while several waves of low pressure will pass along it.
This will support more rain showers during the weekend...especially
Near term /through tonight/...
a Few Lake effect and upslope rain showers, mixed with wet snow
across the higher terrain, will continue east and southeast of Lake
Ontario through midday. The most concentrated area of showers will
persist over eastern Oswego County. Elsewhere a few sprinkles will
continue through midday southeast of Lake Ontario from the eastern
suburbs of Rochester to western Oswego County, and also in a plume
between Buffalo and Rochester into the western Finger Lakes near
what remains of a Georgian Bay connection. Expect the sprinkles over
the west to end by late morning, with activity across eastern Oswego
County ending by early afternoon.
Weak low pressure in the vcnty of the Thousand Islands early this
morning will continue to Transfer to the New England coast...while
high pressure based over the upper Ohio Valley will gradually nose
north and cross our region. This scenario will offer improving
weather for our forecast area...although clouds will be relatively
slow to clear for The Finger lakes and Eastern Lake Ontario regions
with cyclonic northwest upslope flow.
The gradual return to at least partial sunshine will be accompanied
by a cooler than normal airmass...as 850 mb temps within a couple
degrees of zero c will only support afternoon Max temps in the mid
40s. It will be cooler east of Lake Ontario where highs across Lewis
County will struggle to climb above 40 f.
The narrow surface high and its flattening mid level support will
push to our east tonight...while a broad surface low will make its
way across the province of Ontario. Fairly strong warm advection
will be in place between these two features...with the tightest
baroclinic zone crossing by just to the north of our forecast area.
While this will lead to an increase in cloud cover for our region...
the lift needed to generate showers should generally remain north of
the border. The exception will be across the north country where
showers will become likely towards daybreak. This while scenario
will largely be driven by an anomalously strong 125kt h25 jet that
will plow across the upper Great Lakes.
The onset of the strong warm advection across our region will result
in a non-diurnal temp trend. That is...most areas can expect their
low temperatures to occur relatively early. This will be followed by
a pronounced rise in temperatures during the wee hours of the
morning as our forecast area is enveloped within the warm sector of
the sfc low over Ontario. Temperatures that will bottom our between
35 and 40 should climb by at least 10 deg by daybreak.
Short term /Saturday through Monday/...
on Saturday...a robust northern stream shortwave and its attendant
surface low will slide from a position a little south of James Bay
to the middle Saint Lawrence valley. In the process...this feature
will push an initial prefrontal trough across the area between the
morning and early afternoon hours...before slowly dragging its
trailing cold front into our region late in the day. Increasing
moisture and lift attendant to these features will help to generate
some scattered showers across our region...with somewhat more
numerous activity found east of the lakes where overall forcing/
uplift will be a bit stronger. It will also be a breezy to windy day
owing to a tighter pressure gradient and the passage of a 45-55 knot
low level jet across the area...though with temperature profiles
suggesting that the low levels will remain fairly stable...expect
that the bulk of the stronger winds will remain confined aloft...with
gusts in the 25-30 knot range the most likely outcome at the surface.
With a much warmer airmass in place...we can also expect a return to
decidedly above normal temperatures in spite of the increased cloud
and shower coverage...with highs ranging from the 55-60 range across
the north country to the mid 60s across many areas south of Lake
During Saturday night...the aforementioned cold front will slowly
sag across our region during the first half of the night...before
stalling along or just south of the New York/PA border overnight as an
elongated secondary surface wave takes shape along the portion of
the boundary draped across the Midwest and central Great Lakes.
With the passage of the boundary followed by diminishing forcing
and some temporary drying in the mid levels...showers should tend
to become more scattered in coverage for a good chunk of the night
following the frontal passage...before ramping up a bit again across
the southern tier late as the secondary surface wave approaches
from the Central Lakes. Otherwise we can expect a fairly cloudy night
as plentiful low level moisture will linger behind the front...and
this in conjunction with a lingering mild airmass will support rather
mild overnight lows ranging from the mid 40s across the north country
to the upper 40s/lower 50s south of Lake Ontario...or readings which
will be some 10 degrees above normal for this time of year.
On Sunday the secondary surface wave will quickly ripple along the
slowly sagging frontal boundary...with the center of the wave
reaching the New Jersey coastline by evening. Compared to 24 hours
ago...the various guidance packages have come into much better
agreement on the overall track and timing of this feature...with
the wave passing by just to our south during the morning hours.
Given this track and the presence of a narrow but fairly impressive
ribbon of deeper moisture and forcing to its north...this system
appears primed to bring the bulk of our region another shot of
rainfall through the morning and early afternoon hours...with this
then quickly diminishing from northwest to southeast through the
rest of the day as the wave/frontal boundary rapidly pulls off to
our southeast. With this in mind...have indicated a fast-moving
swath of categorical pops passing across areas south of Lake Ontario
during Sunday...with precip chances sharply tapering to the likely
and chance ranges across the north country...and to below slight
chance across the bulk of the Saint Lawrence valley. As for temps...
with our area on the cooler side of this system and subject to
a considerable amount of shower activity and cloud cover...daytime
highs on Sunday will be much cooler than those of Saturday...and
will largely range from the mid to upper 40s across the north country
to the lower 50s across the remainder of the region.
Following the passage of this system...the axis of expansive Canadian
high pressure and much drier air will build from the upper Great Lakes
to New England Sunday night and Monday. This will result in fair and
dry weather returning to our region...along with diminishing cloud
cover later Saturday night and Sunday morning as both drying and
subsidence increase over the area. Meanwhile temperatures will average
out a little below normal...with lows ranging through the 30s Sunday
night followed by highs in the mid 40s to lower 50s Monday.
Long term /Monday night through Thursday/...
as we move into the longer-term portion of the forecast...the surface
ridge responsible for monday's fair weather will quickly slide east
and out to sea Monday night and Tuesday...allowing another northern
stream shortwave and surface low to quickly slide eastward across
Ontario and Quebec. Rapidly strengthening warm air advection out
ahead of this next system will likely result in another night with a
noticeable non-diurnal temperature trend Monday night...followed by
a rather warm day on Tuesday when readings will likely surge into
the 65 to 70 degree range south of Lake Ontario...and into the upper
50s and lower 60s across the north country.
While this system will push its trailing cold front across our region
late Tuesday and Tuesday night...this feature still appears to be
rather weak and greatly starved for both moisture and upper-level
support...which should result in it coming through dry for the bulk
of our region...save for the north country which will lie closer to
the low track and where a few isolated showers may thus be possible.
Following the frontal passage...another bubble of high pressure and
somewhat cooler air will build across our region for Wednesday...but
even then temperatures will remain solidly above average with afternoon
highs in the upper 50s to lower 60s anticipated for most locations.
Looking out toward the end of the period...the medium range models
remain in decent agreement on another weak low crossing our region
sometime in the Wednesday night to Thursday time frame. This system
will bring US our next real chance for some showers...while temps
should continue to average out a bit above normal.
Aviation /14z Friday through Tuesday/...
MVFR cigs will gradually give way to VFR conditions during the
midday and afternoon hours as a weak storm system over New England
will give way to high pressure over the Ohio Valley. Cigs east of
Lake Ontario though will take the majority of the day to improve.
Tonight...the area of high pressure will push east as the next storm
system will track across the province of Ontario. While there will
be a gradual increase in cloud cover overnight...mainly VFR
conditions will remain in place. The main issue for tonight will be
the likelihood of low level wind shear during the wee hours. A low
level jet of 50-55 knots will move in after 08z.
Saturday...VFR/MVFR with scattered to numerous showers developing.
Sunday...MVFR with showers likely. IFR cigs will be possible
across the southern tier.
Monday and Tuesday...VFR.
small craft advisories will remain in place for Lake Ontario through
the afternoon as moderate northwesterlies continue. During the
course of the afternoon...high pressure centered over the upper Ohio
Valley will nose northward across the lower Great Lakes. This will
allow winds to weaken and waves to subside so that all sca's should
be allowed to expire by nightfall.
Winds will start to freshen later tonight though...as the nose of
the surface high will push east while a storm system will track
across the province of Ontario. Small Craft Advisory conditions are
likely to develop on Lake Erie by daybreak...while an offshore
southerly flow over Lake Ontario will keep the strongest winds and
highest waves in Canadian waters.
As the aforementioned area of low pressure moves from Ontario to
Quebec on Saturday...its associated cold front will approach the
lower Great Lakes. This will continue to support freshening winds
with Small Craft Advisory conditions likely for most...if not all...of the New York
In the wake of the cold frontal passage later Saturday night and
Sunday...winds will shift to the north and northeast. Sub advisory
conditions can be expected regionwide.
Marine...Small Craft Advisory until 7 PM EDT this evening for loz043-
Small Craft Advisory until 3 PM EDT this afternoon for
Small Craft Advisory until 5 PM EDT this afternoon for