Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Buffalo New York
730 PM EDT Wednesday Jul 23 2014
a cold front will continue to move to the southeast this evening and
allow cooler and drier high pressure to build across the region
tonight. The high pressure area will remain across the region
through the rest of the work week with cooler temperatures
initially...then a warming trend into the weekend. The next round of
rain will hold off until Saturday evening.
Near term /through Thursday/...
cold front will continue to push southeast of our region through
the evening hours. By 730 PM...the last of the showers are just
about to exit Lewis County...with the remainder of the overnight
period expected to be rain-free.
Surface high pressure centered across the upper Midwest will
build across the eastern Great Lakes and over New York state tonight.
This will bring a cooler and drier airmass to the region for the
next few days. Expect clouds to linger this evening...and probably
longer across the southern tier. This should limit fog formation
to some extent...however breaks in the clouds late tonight should
allow for patchy fog to develop...especially with the help of some
upsloping in the northerly flow. Overnight low temperatures will
range from the lower to middle 50s east of Lake Ontario to the upper
50s to lower 60s across western New York.
With a cooler and drier northerly wind on Thursday...expect a
sunnier day with high temperatures only in the upper 60s to lower 70s.
There will be more cloudiness across the hills of the southern tier
with the upslope component and afternoon instability.
Short term /Thursday night through Saturday night/...
high pressure will shift just south of New York on its way to the
East Coast through this period. A dry northerly flow and subsidence
aloft will for the most part bring pleasant weather with comfortable
temperatures into the weekend. Clear skies and light winds Thursday
night will allow for southern tier River Valley fog overnight
otherwise mainly clear skies. On Friday plenty of sunshine will be
in place with some scattered fair weather clouds developing as model
soundings suggest a thin nearly saturated layer near 5kft. Friday
night expect southern tier valley fog to redevelop with high clouds
working across the state overnight ahead of a leading middle-level
shortwave and surface low moving across the central Great Lakes.
On Saturday models show this middle-level shortwave trough will shift
across the lower Great Lakes. This will thickens and lower the high
cloud deck with chances of showers arriving across wny by the
afternoon. Saturday night shower chances increase and extend into
cny. High temperatures on Friday and Saturday will run near average
but the drier airmass will allow for temperatures on Thursday and
Friday nights to dip below average. The coolest temperatures which will dip
into the 40s will be found across the interior southern tier
Thursday night. As the high shifts over the East Coast a southerly
flow will boost dewpoints into the 60s Saturday and Saturday night
so much more milder overnight temperatures will then be found.
Long term /Sunday through Wednesday/...
an unsettled pattern will develop and persist into next week as a
significant upper low amplifies a broad 500mb trough across the
eastern states. This will bring an increasing threat of some showers
and occasional thunderstorms with temperatures lowering below
average. Sunday and Monday have the best potential for showers and
thunderstorms as the Great Lakes upper low opens to a sharp
shortwave trough as it phases with a 500mb low over Quebec. The
shortwave trough will pass across the lower Great Lakes over an
increasingly moist and unstable airmass brought on by southwest
surface winds. Have therefore increased probability of precipitation to likely on Sunday and
Monday. Cooling temperatures aloft brought on by -2sd 500mb heights
will bring increasingly cooler temperatures Sunday and Monday. Highs
Sunday will top out around average while mondays highs will run 5 or
more degrees below average.
The 500mb trough and associated heights bottom out on Tuesday and
Wednesday at -3sd over the Ohio Valley. While most of the time will
remain cool and dry the instability brought on by the lower heights
and colder air aloft will be enough to keep a chance of diurnal
showers on Tuesday and Wednesday. High temperatures on Tuesday will
be the coolest of the next 7 days topping out in the upper 60s to
low 70s or 10 degrees below average. Wednesday will also feature
below normal temperatures topping out in the low to middle 70s. A Pacific
sourced airmass will keep dewpoints in the 50s so overnight temperatures
will only run a few degrees below average.
Aviation /00z Thursday through Monday/...
a cold front will continue to push southeast of the region this evening.
Expect a mix of VFR/MVFR ceilings as a secondary wave of moisture
moves across the region. The best chance for lower ceilings and fog will
be at jhw where there is some upsloping. Expect some diurnal
cumulus to develop on Thursday...but these should generally be
above 3k feet and in the VFR category. Skies will then clear out
with the exit of a shortwave late afternoon.
Thursday night through Saturday...mainly VFR...except for
IFR/MVFR in patchy southern tier valley fog later each night/early
Sunday and Monday...VFR/MVFR scattered showers/thunderstorms.
northwest winds will briefly increase to 10 to 20 knots behind the
cold front...which will build waves just shy of small craft
criteria on the south shores of Lake Ontario. After this...northerly
winds will diminish with waves subsiding to 2 feet or less. Winds
and waves will settle back to more benign conditions overnight and
for the next few days as the pressure gradient relaxes with high
pressure building in across the eastern Great Lakes.