Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Buffalo New York
1052 am EDT Tuesday Sep 30 2014
an upper level disturbance will interrupt the fine stretch of autumn
weather we have been experiencing recently. This disturbance will bring
clouds and scattered showers to the area today and tonight. There
will be fair weather and again becoming mostly sunny on Wednesday
with the sunshine and pleasant warmth lingering into Thursday.
A strong cold front is then expected to cross the region on
Friday...bringing a greater likelihood of showers followed by
much cooler temperatures for the upcoming weekend.
Near term /through tonight/...
current forecast is working out nicely. Have upped the probability of precipitation over
Chautauqua County during late morning and removed slight chance
thunder as most of support for deep convection will likely slip to
the south of our forecast area by afternoon.
Clouds will thicken over our region with rain showers associated
with the upper level disturbance and area of weak surface low
pressure reaching our far western areas late morning. This upper
level feature will dive southeastward such that the core of the cold
air aloft will brush by the southern tier. Under this cool pool
aloft steeping lapse rates and SBCAPE upwards to 500 j/kg may allow
for some thunder this afternoon south of the state line. Farther
northward and away from the influences of the upper level low and
weak surface low chances for showers will diminish...with just
slight chances for showers over the north country today.
Tonight the surface low will open up to a weak wave...with an
inverted surface trough extending northward from near West Virginia
northward across western New York. A few showers may form on
convergent boundaries associated with this inverted trough through
the night. A northeast wind flow will ensue overnight from a strong
area of high pressure over Quebec Canada. This flow over the waters
of Lake Ontario will add low level moisture such that low
clouds...perhaps a sprinkle and patches of fog are possible south of
Lake Ontario. Likeliest areas for this fog formation would be around
Rochester westward across the Niagara Frontier and then down into
the southern tier.
Temperatures today will not be as warm as recent days due to the
thicker cloud cover. Highs will range across the lower to middle 70s
today. Tonight temperatures will fall back into the low to middle 50s.
Coolest spots will be across the north country where some brief
clearing may develop.
Short term /Wednesday through Thursday night/...
an upper level low will move eastward across southern New England on
Wednesday while a 500 mb ridge axis builds across the lower lakes.
This ridge axis will remain across our region into Thursday night
with dry conditions.
NAM/sref guidance continue to Show Low level moisture trapped
beneath an inversion in a northeast flow south of Lake Ontario. This
will result in lingering cloud cover Wednesday morning which should
gradually dissipate during the afternoon hours. Otherwise...the
close proximity of the departing upper trough may spark a stray
shower on Wednesday...but the vast majority of the region will stay
dry. Temperatures will climb into the upper 60s to lower 70s...which
is still above normal for the date.
Surface high pressure centered in the Canadian Maritimes will ridge
across our region Wednesday night...with this ridge axis eventually
moving east Thursday and Thursday night. This will set up a
southerly flow which will limit lake breeze development Thursday
afternoon. This will result in a sunny and warm early fall day on
Thursday. The combination of warm 850mb (around +11c) and downslope
flow should allow buf-roc and much of the Genesee Valley to warm
into the middle to upper 70s...with elsewhere topping out in the lower
to middle 70s.
The southerly flow will increase Thursday night...with 925mb winds
increasing to 30 to 35 kts by 12z Friday. This will keep the
atmosphere well mixed and continued downsloping will result in
unseasonably warm overnight temperatures in the 60s north of I-90.
00z guidance (nam/GFS/ggem) is slightly slower with the next system
with this pretty much keeping our region dry through early Friday
Long term /Friday through Monday/...
our stretch of Indian Summer will come to a close during this period
as much cooler air will invade the Great Lakes region. Daytime highs
will be some 20 degree f lower during the weekend than from readings
during the previous week.
Synoptically...this period will be highlighted by a deepening cutter
storm that will lift almost due north from Chicago Friday...while
sweeping a pattern changing cold front across the lower Great Lakes
late Friday and Friday night. A consensus of 00z guidance
(gfs/ECMWF/ggem) is slightly slower with this system. Our region is
likely to stay dry for a good part of Friday which will allow
temperatures to warm well into the 70s with breezy conditions. A swath of
moderately heavy showers will sweep across the region...entering
Friday afternoon...then moving across the region Friday evening and
Much cooler air will then charge across our region as the axis of
the negatively tilted 500 mb trough will become aligned over the lower
Great Lakes from Saturday through Monday. Showers with this trough
will linger into Saturday...especially across eastern portions of
the County Warning Area. 850 mb temperatures will average within a degree or so of zero
c...which will not only result in below normal temperatures...but
will also support some nuisance lake induced rain showers for sites
east of both lakes.
Aviation /15z Tuesday through Saturday/...
at 12z southern tier valley fog has brought LIFR visibilities across the
valleys...including the kjhw terminal. Elsewhere localized low
clouds over the north country have brought the kart terminal down to
IFR ceilings. Otherwise mainly VFR to start the taf cycle with some
patches of MVFR visibilities in fog.
Clouds are slowly thickening through the morning hours. These clouds
coupled with daytime mixing should erode the valley fog by middle
morning. Also the localized low clouds over the kart airfield should
pass within the first hour or so of the taf cycle such that the taf
site returns to VFR for the remainder of the period. Expect much of the
region to be back to VFR by middle to late morning.
A few showers will pass across the region today. Will maintain vcsh
as this activity is expected to be scattered south of Lake Ontario.
The exception will be across the southern tier which will lie closer
to the upper level shortwave and cold pool aloft. Here there may
even be a few thunderstorms early afternoon with daytime
Tonight clouds will lower south of Lake Ontario as winds veer around
to northeasterly. A still convergence boundary in the low levels may
serve as a focus for sprinkles and low MVFR or IFR clouds south of
Lake Ontario as the northeast winds maintain ample low level
Wednesday through Thursday...VFR...except for localized IFR in
southern tier valley fog between 06z-15z each day.
Friday...VFR lowering to MVFR with showers becoming likely.
Saturday...MVFR with a chance of showers.
an upper level low...and weak surface low will dive southeastward
across Lake Erie and towards Pennsylvania today and tonight. A
light wind today will become northeasterly tonight and increase to
around 15 knots on Lake Ontario...and 10 knots on Lake Erie. These
stronger winds on Lake Ontario will bring waves 2 to 4 feet tonight.
Weaker winds will allow for 1 to perhaps 2 foot waves on the eastern
end of Lake Erie tonight.
Waves and winds will diminish through the day Wednesday as high
pressure again builds across the lower lakes region.
Late in the week...a strong area of low pressure is expected to lift
across the Great Lakes region on Friday...while swinging a strong
trailing cold front across the lower lakes. The tightening pressure
gradient associated with the low will lead to a period of stronger
winds...with advisory-level winds and waves becoming possible.