Scientific Forecaster Discussion
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Area forecast discussion
National Weather Service Buffalo New York
454 PM EDT Tue Sep 26 2017
high pressure will keep dry weather and midsummerlike warmth across
our region through most of Wednesday. An approaching cold front may
finally bring a few showers late Wednesday afternoon and Wednesday
evening...with much cooler temperatures then following in its
wake for Thursday right on through the upcoming weekend.
Near term /through Wednesday/...
ridging at all levels will remain draped across the region for the
rest of this afternoon. This will provide our region with dry weather
and fairly plentiful sunshine...with only some passing thin cirrus
and scattered afternoon diurnal cumulus expected for cloud cover.
While there will be a bit more moisture in place at the lower
levels...am still not at all impressed with the potential for any
showers inland from Lake Erie this afternoon...as both substantial
dry air and a cap will be in place at the mid levels. Have thus kept
pops confined to around 10 percent in this latter area. Even if a
couple of pop-up showers do somehow manage to form...these would be
rather brief in nature and very isolated in coverage.
Otherwise...the big story this afternoon will be the continued
midsummerlike warmth and humidity. While 850 mb temps will be a
little cooler than yesterday across far western New York (+17c to
+18c)...these will still support widespread highs in the mid to
upper 80s (and a few isolated 90-degree readings) west of the
Genesee Valley this afternoon. Meanwhile further east...850 mb
temps will remain warmer (+18c to +19c)...and will thus again be
supportive of highs mostly in the upper 80s to lower 90s. As of
this writing...the previous record high for Watertown for this
date (82 in 1970) has already been broken...and the records for
both Buffalo (87 in 1959) and Rochester (89 in 1900) have at least
Tonight...high pressure will continue to linger across our region
while slowly weakening. This will result in continued fair dry
weather...with some patchy radiation fog redeveloping in the southern
tier valleys and east of Lake Ontario overnight...though with a light
southerly flow in place this will be of lesser coverage and lighter
in nature when compared to previous nights. Otherwise...we can expect
another warm and muggy night with lows mostly in the lower to mid
On Wednesday leftover weak surface-based ridging will still be in
place from the Ohio Valley to New England through the morning hours...
while maintaining dry weather and mostly sunny skies across our
region. As we move through Wednesday afternoon...things will finally
begin to change as this ridge slips further southeastward and gives
way to mid-level troughing and an associated cold front approaching
from the northwest. As has been previously discussed...both moisture
and upper-level support along the cold front look to be pretty meager
at best...leaving just low level convergence along the front (and to
a lesser extent lake breeze boundaries) as the only appreciable forcing
mechanism available. As a result...any convection that develops during
the mid to late afternoon hours should be largely in the form of
scattered showers...and perhaps an isolated weak thunderstorm or two
given the presence of just enough diurnal instability. Temperature-
wise...we can expect one last unseasonably warm day with 850 mb temps
of +16c to +17c supporting highs in the lower 80s across far western
New York and in the mid to upper 80s further east. Record highs for
sept 27th are 87 at Buffalo (1946)...88 at Rochester (1920)...and 82
at Watertown (2011)...with only the Watertown record looking to be in
serious jeopardy at this time.
Short term /Wednesday night through Friday night/...
the cold front that will be moving east-southeast through western and central
New York Wednesday night will continue to weaken as its parent surface low
and upper level forcing speed eastward through Quebec. The result
will be a mostly dry night while cold air on a northwest flow spreads
across the region. Temperatures aloft will drop enough for dry
adiabatic lapse rates and lake forced convection, but moisture aloft
will be almost non-existent. The result should be lake-induced and
upslope clouds with limited lake fetch, lasting well into Thursday.
The continued cold air advection however will result in temperatures
about 20f cooler than days past, with highs mostly in the 60s. This
may feel like a cold spell to many, but climatically it will be
right about normal for this time of year. This pattern will
continue into Thursday night.
The next feature of interest will be coming from the northwest
territories, and should be dropping into the Great Lakes region by
Friday. Primed with lake-induced buoyancy and forced with
synoptic moisture, expect a hybrid between synoptic rain showers
and lake induced showers for Friday. The probability of
measurable precipitation has been notched up to 60-70%, and
would not be surprised to see this upward trend continue over
the next day or so. Without a long fetch (nw flow), single
plumes of course are unlikely but high equilibrium levels may
allow for some embedded thunderstorms.
Surface high pressure should begin to move in Friday night, marking
the end of any precipitation potential. The coldest air aloft will
be just about overhead Friday night. The result should be More Lake-
induced cloud cover with upslope/north flow (really limited lake fetch).
Long term /Saturday through Tuesday/...
Saturday another broad area of high pressure will bear upon US. The
850 hpa temperatures will still be cool (low single digits) and
lingering moisture trapped beneath a subsidence inversion will
likely continue a fair amount of stratus clouds to start the
weekend...especially south of Lake Ontario.
As these clouds, and lake effect clouds clear Saturday night,
overnight lows will drop and potentially drop to the mid 30s with
areas of frost in clearing areas east of Lake Ontario, and across SW
New York state.
Saturday night and through next Tuesday this surface high will
sprawl across the region, bringing yet another period of abundant
sunshine and warming temperatures.
Highs Saturday in the mid 50s to around 60f will moderate...and rise
back above normal by the end of the period.
Aviation /21z Tuesday through Sunday/...
lingering high pressure will largely maintain dry VFR conditions
through early Wednesday afternoon...with just some patchy fog and
attendant reductions to IFR/MVFR possible in the southern tier
valleys and also east of Lake Ontario overnight and early Wednesday
As we move through the rest of Wednesday...a cold front will sag
into our region from the northwest...bringing thickening/lowering
clouds along with some scattered showers. While some brief/localized
MVFR conditions could develop in association with the frontal
boundary and its showers...by and large VFR conditions should
continue to prevail.
Wednesday night...mainly VFR with a chance of showers in the
Friday...VFR/MVFR with some showers becoming likely.
Saturday and Sunday...mainly VFR.
high pressure will remain in place across the lower Great Lakes
through tonight and into early Wednesday morning...with light
winds and minimal waves continuing.
During Wednesday southwesterlies and westerlies will freshen in
advance of an approaching cold front...before giving way to brisk
northwesterlies in the wake of the front late Wednesday afternoon
and evening. This will likely result in a round of advisory-worthy
winds and waves from late Wednesday afternoon through Thursday
morning...particularly on Lake Ontario where winds appear to be