Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Buffalo New York
415 am EDT Thursday Jul 28 2016
a weak cold front across the region will produce a few stray showers
and thunderstorms across western New York and The Finger lakes region
today. Weak high pressure across the region Saturday should limit
any shower activity to near the PA state line, while scattered
shower and thunderstorm chances increase again Saturday night
through Sunday night as a wave of low pressure tracks through the
Near term /through tonight/...
a broad cyclonic flow aloft with a nearly 100 knot, 250mb jet will
persist across the region today with a corresponding weak surface
cold front. In the right entrance region of this jet streak, a wave
of low pressure seen on WV imagery across the Ohio Valley this
morning will track just to our south and east by later this
afternoon and overnight tonight. Mid-level lapse rates under the
upper-level broad trough will be enough to support a few spotty
showers and thunderstorms inland from the lakes with diurnal heating
today. However, forcing across our forecast area will remain very
weak, and thus convection will be tied to enhanced low-level
convergence from orographic and lake breeze influences. Thus have
chance pops for the interior southern tier and northern Finger
Lakes. The low chance for afternoon convection will also linger over
the Saint Lawrence valley closer to the broad upper trough over
Quebec. With all of this, today will be, by and large, a dry day
across the region, with 850 mb temps +16/+17c supporting high
temperatures in the mid to upper 80s and increasing cloud cover
through the day. Winds will also remain fairly light and mainly
driven by local lake breezes.
By tonight, the aforementioned wave will track through central PA
and into central and eastern NY, largely skipping the forecast area
to the south and east. However, cannot rule out a few isolated to
scattered showers and thunderstorms mainly limited to the interior
southern tier. Temperatures will remain in the upper 60s in the lake
plains with low 60s across the higher terrain and north country.
Short term /Friday through Sunday/...
on Friday a southern stream shortwave and associated surface low
will move from the northern mid Atlantic states into southern New
England. This system will produce significant rainfall along its
path, but unfortunately for drought stricken western New York this
rainfall will remain well to our southeast. Our region will be left
with a modest increase in deep layer moisture Friday well to the
north of the surface low. A very weak northern stream surface cold
front will sag slowly south across the area on Friday and may
provide a focus for isolated to widely scattered showers and
thunderstorms. A multi-model consensus places the best chances for
these scattered showers across the southern tier where better
moisture and instability will be found, with lesser chances
extending northward to the Niagara Frontier and greater Rochester
areas. High pressure over Quebec will likely keep the Saint Lawrence
Any showers that form on Friday will end from northwest to southeast
Friday evening as the surface low moves east into the North
Atlantic, with the northern stream cold front moving south into PA.
Drier air will advect into the region overnight on low level north
to northeast flow with clearing skies and lowering dewpoints.
Model guidance begins to diverge as early as Saturday with the track
and timing details of the next wave. In a general sense, another
wave of low pressure is forecast to move through the Ohio Valley and
towards the northeast states. A fair number of operational and
ensemble models take this second wave a little farther north than
the first, giving some hope for rainfall across our region. The GFS
is closest to previous forecast continuity, with a weak wave moving
through PA later Saturday night and Sunday with showers crossing
western and central New York. The new 00z European model (ecmwf) has trended faster with
this system, with most of the rain arriving Saturday and Saturday
night. The Canadian Gem has slower timing like the GFS, but is much
stronger and farther northwest with the surface wave. Given the
model differences, the best option at this time is to stick close to
previous continuity, with a mainly dry Saturday followed by
increasing rain chances Saturday night and Sunday, with the greatest
chances across the southern portion of the area.
Temperatures will be a little cooler than recent weeks and very
close to mid Summer averages, with highs in the lower 80s across
lower elevations and upper 70s higher terrain Friday through Sunday.
Lows Friday night and Saturday night will be in the low to mid 60s
in most locations, with mid to upper 50s in the cooler southern tier
valleys and east of Lake Ontario.
Long term /Sunday night through Wednesday/...
a progressive low amplitude pattern will remain in place along the
Canadian border through early next week with dominant ridging
remaining in place from the Central Plains to the southeast states.
The wave of low pressure passing near the region over the weekend
will move to the East Coast Sunday night with any showers and
scattered thunderstorms ending from west to east. High pressure will
then build into the Great Lakes region Monday and Tuesday with a
return to dry weather. The surface high will drift to the East Coast
by Wednesday and still remain close enough to keep the next system
and deeper moisture at Bay, with a continuation of dry weather.
Temperatures will start next week not far from average with highs in
the lower 80s on Monday. The heat will build again by midweek as the
surface high moves to the East Coast and deep southwesterly return
flow develops. This will boost high temps into the upper 80s by
Aviation /08z Thursday through Monday/...
expect mainly VFR conditions today. The exception is at jhw where
patchy fog is possible through the early morning, resulting in
variable vsby through daybreak. This should average around 2sm, but
could range wildly.
A front will gradually drop south across the area today, and this
combined with lake breeze boundaries may result in scattered showers
and possibly a thunderstorm Thursday afternoon. Coverage should be
quite spotty, and largely avoiding taf sites.
Tonight...mainly VFR with a chance of showers and thunderstorms.
Friday through Sunday...VFR/MVFR with a chance of showers and
weak flow today will keep mainly lake breeze dominated winds and
minimal waves on the lakes through this evening. Then, a wave of low
pressure will track from central PA to east central New York supporting a
freshening northeasterly wind, especially on Lake Ontario where
waves may approach small craft criteria toward Friday morning.
Otherwise high pressure will build in across the lower Great Lakes
later Friday and into Saturday resulting in diminishing winds and