Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Buffalo New York
413 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 likelihood of showers followed by much cooler
temperatures for the upcoming weekend.
Near term /through tonight/...
we will have an interruption in the streak of fine autumn weather
today as an upper level disturbance brings scattered showers and
perhaps a thunderstorm to the region today.
This morning an upper level shortwave is seen on water vapor imagery
over central Michigan. At the surface a weak area of low pressure is
near Lake Huron and the western end of Lake Erie...with a frontal
boundary extending eastward to the south of Lake Ontario. Regional
radars display a swatch of rainfall ahead of the upper level
shortwave with the rain showers over Georgian Bay to near Detroit
and the western end of Lake Erie.
Before the clouds arrive fog will fill the valleys across the
southern tier this morning. Recent surface observations display some
quarter mile visibility within this fog...with a half to one mile
predominate. Will hold off on a dense fog advisory as fog is likely
restricted to the valleys. Some patches of fog are possible across
the northern Niagara Frontier where temperatures are cooling to near
the dewpoints under light winds. All fog should dissipate by middle
morning with the daytime mixing and increased cirrus limiting
Clouds will thicken over our region this morning 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 near 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 /08z Tuesday through Saturday/...
at 06z southern tier valley fog has brought LIFR visibilities across the
valleys...including the kjhw terminal. Elsewhere mainly VFR with
some patches of MVFR visibilities in fog.
Clouds will thicken through the late overnight with scattered
showers reaching far western New York around noontime. Greatest
chances for showers will be across the southern tier. Otherwise
mainly VFR ceilings will be the rule through the daylight hours.
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
Across the north country VFR flight conditions should prevail through
the taf cycle.
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.