Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Buffalo New York
416 am EDT Monday Sep 22 2014
our region will experience much cooler weather today in the wake of
a strong cold front...with high temperatures likely remaining
confined to only the lower to middle 50s. Expansive high pressure will
then build across the area on Tuesday and remain overhead through
the upcoming weekend. This will provide western and north central
New York with an extended period of fine early Fall weather...along
with temperatures warming to above normal by midweek.
Near term /through tonight/...
as of this writing...western and north central New York is awash in
widespread low clouds...along with some lingering spotty drizzle...
sprinkles...and light showers. This is all courtesy of a
northwesterly upslope flow of much cooler air and fairly plentiful
low level moisture...which is being further enhanced as it crosses
the relatively warmer waters of lakes Erie and Ontario.
As we progress through today and tonight...the axis of deep upper
level troughing will lift northeastward from the north country to
the Canadian Maritimes today...before pulling further away from our
region tonight. At the same time...burgeoning high pressure and
drier air currently centered over the lower Missouri Valley will
gradually build eastward...with the axis of this ridge settling
across the Ohio Valley tonight.
While all of this will lead to an improvement in our weather...this
process will only be very gradual thanks to the combination of the
aforementioned upslope flow...as well as lake influences due to the
cool airmass that will be place aloft. Together...these will keep
skies mostly cloudy across our region through the vast majority of
today...with any partial clearing largely holding off until this
evening. In addition...any spotty lingering light precipitation will also
only gradually diminish...ending first across the lower elevations
by midday/early this afternoon...and last across the higher terrain
of the north country by late this afternoon.
Later on tonight...some middle level cloudiness will gradually increase
from north to south as a weak cold front presses in our direction
from central Ontario and Quebec...however conditions should
otherwise remain dry with a little patchy valley fog forming
across the western southern tier.
With respect to temperatures...850 mb readings will dip to within a couple
degrees either side of zero celsius by early this afternoon. Coupled
with the persistent cloud cover...this will result in surface temperatures
likely getting no higher than the lower to middle 50s today...and these
will feel even cooler owing to a continued fresh northwesterly
breeze. Following this...lows tonight will fall into the lower to
middle 40s...with perhaps a few upper 30s sprinkled in across the
deepest interior southern tier valleys.
Short term /Tuesday through Thursday night/...
a commanding...broad based ridge will be found across the entire
Continental U.S. During this period...effectively placing a protective dome of
dry fair weather over the country. While this staunch fair weather
giant will initially span from coast to coast...a train of
shortwaves racing across the North Pacific will feed into and deepen
a longwave trough off the Pacific northwest. This will buckle the
flow a bit and promote amplification of the already impressive
downstream ridge...so that by late week...profound height departures
will be found just to the north of the Great Lakes.
The result of all of this will be a prolonged period of dry weather
for our region with a gradual day to day warming trend that will
send our temperatures to above normal levels. There will not be a
lot of details to cover within this unusual synoptic pattern...but
lets try to break this down a bit on a day to day basis.
As we open this stretch on Tuesday...a moisture starved cold front
over Quebec will sweep southwards across the St Lawrence Valley and
New England states. While an isolated shower cannot be ruled out
across the north country (jeff/Lewis co's) Tuesday afternoon...feel
that the bulk of any showers will be further east across the
Adirondacks. Will carry slight chance probability of precipitation north and east of the tug...
otherwise dry weather will prevail over our forecast area as
expansive high pressure centered over the Ohio Valley will build
northeast across the Saint Lawrence valley in the wake of the front.
Tuesday will also be a noticeably milder day than its predecessor as
an already on going warm advection pattern will send 850 mb temperatures to
around 8c...up from zero c just 24 hours prior. This process will
likely generate a fair amount of Alto-cumulus as well. In any case...we
should be able to experience at least partial sunshine with the
higher 850 mb temperatures supporting maximum temperatures in the middle to upper 60s f for
The Heart of the strong surface high will drift across New England
Tuesday night....then will become anchored in the vicinity of Nova
Scotia on Wednesday. How strong will the surface high be? Forecast mslp
values of 1036-37mb will translate to levels that are only
experienced in that area/at that time of year to a once in 30 year
return interval. In any case...this will put the brakes on the warm
advection. 850 mb temperatures will be held around 10c...so after a night of
widespread lows in the 40s (away from the lakes)...we can anticipate
Wednesday afternoon highs close to 70 along with a fair amount of
On Thursday...a weakness in the height field over the Middle Atlantic
States will be blocked from advancing northwards by ridging over the
Great Lakes while at the surface strong high pressure will extend from
the Great Lakes from just south of Nova Scotia. The associated
subsidence from the latter and amount of dry air in place will once
again promote prtly/mostly sunny skies with a generous covering of
maximum temperatures in the lower 70s. In fact...the warmer valleys could reach
Long term /Friday through Sunday/...
you will not find the medium range guidance in much better agreement
than you will during this period as both the European model (ecmwf) and GFS based
ensembles continue to be in lock step agreement of depicting a very
robust...domineering 500 mb ridge over the the eastern half of North
America. The Heart of the 588dm ridge will be centered over the
Great Lakes region with 2-3 Standard height departures found across a large
portion of eastern Canada. Another way to spin the numbers for this
feature is that the strength of this ridge has a return (occurrence)
interval (for this time of year) of roughly once in a >30 year
period. This upper level pattern will support a subsidence crushing
area of high pressure that will encompass the Great Lakes region and
virtually guarantee dry weather.
Meanwhile...850 mb temperatures will range from around 10c on Friday to
between 12 and 14c for both days of the weekend. This will result in
above normal temperatures for our forecast area with daytime highs
in the 70s and overnight lows mainly in the 50s. These values will
be some 5 to 10 degree f above normal late sept values.
Aviation /08z Monday through Friday/...
in the wake of a strong cold front...a northwesterly to northerly
upslope flow of colder air has overspread the region. In concert
with an increase in wraparound low level moisture and contributions
from the lakes...this has resulted in the development of widespread
lower-end MVFR conditions...with areas of IFR found across the
higher terrain. These general conditions will continue through the
rest of the night and much of this morning...with much more
spotty/brief localized IFR possibly affecting some of our lower
elevations as well.
From late this morning on through this evening...high pressure and
drier air will gradually build into the region. In concert with
diurnal influences...this will result in the IFR/low MVFR ceilings first
lifting to high MVFR/low VFR...before scattering out late this
afternoon and this evening.
Once these dissipate...general VFR conditions should tend to prevail
through the remainder of tonight...though there will be some
increase in middle level clouds overnight as a weak cold frontal
boundary over central Ontario/Quebec pushes in our direction. The
one exception to all this will be across the southern tier...where
some localized IFR in patchy valley fog may develop overnight.
Tuesday through Friday...VFR...except for localized IFR in southern
tier valley fog each overnight/early morning.
fresh northwesterlies and associated cold advection will result in
advisory-level winds and waves persisting along the South Shore of
lakes Erie through this morning...and through the bulk of tonight
along much of the South Shore of Lake Ontario.
After that...expansive high pressure will settle across the lower
Great Lakes on Tuesday...then will linger in place right through
next weekend. This will result in an extended period of tranquil
Marine...Small Craft Advisory until 11 am EDT this morning for lez040-
Small Craft Advisory until 11 am EDT this morning for
Small Craft Advisory until 6 am EDT Tuesday for loz043>045.
Small Craft Advisory until 11 PM EDT this evening for