Scientific Forecaster Discussion
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Area forecast discussion
National Weather Service Buffalo New York
803 PM EDT Thu Aug 22 2019
a comfortably cool and dry weather pattern will be over western and
central New York right through the weekend. There may be some
typical inland valley fog during the overnight and early morning
hours. The next chance of rain along with warmer weather won't
return until next Tuesday or Wednesday.
Near term /through Friday/...
a relatively amplified upper level pattern is in place over much of
eastern Canada southward into the Great Lakes region. In
particular, a large upper level ridge is over the plains (poised to
give US a prolonged dry weather pattern later this weekend) while a
low spins over Quebec. A SW-NE oriented jet aloft shapes the base of
the low, with a parallel and hence slow moving surface front
stretching from the Ohio Valley through northern PA and into eastern
New York/northern New England. The showers that were sneaking into our
area along this boundary have dissipated as they moved into the
interior southern tier of New York, and clear skies have filled
into the majority of our area in their wake.
For this evening, the resulting flow over New York from the above noted
upper level pattern will be a refreshingly dry and cool Canadian
sourced airmass from the southern end of the upper level low. The
coldest air aloft (that will affect our region) is roughly co-
located with a dry shortwave trough, easily identified in water
vapor imagery over WI/northern Great Lakes. This will move across
our region on Friday. After some valley fog from left over low
level moisture, expect some brief Friday morning sunshine, followed
by fairly rapid upslope induced inland stratocumulus, with available
low level moisture trapped below ~5000' as depicted with a classic
inverted-v sounding. This should clear out some with afternoon
mixing - areas closest to the lakeshores first, then progressively
inland toward the southern tier by late afternoon.
Short term /Friday night through Monday night/...
one word can be used to characterize the weather during this
period...spectacular! The undeniably nice weather will be supported
by a progressive ridge that will move from the upper Mississippi
Valley across the Great Lakes region to the Canadian Maritimes. The
ridge will become part of a short lived Rex block that will also
include an impotent...moisture starved cut off mid/upper level low
that will stay to our south and east. Meanwhile at the surface...
expansive high pressure will slowly cross eastern Canada.
As for some day to day details...it will be quite cool across the
forecast area Friday night with most areas experiencing mins in the low
to mid 50s. For the folks across the western southern tier and in parts
of the north country...it will be feel downright chilly with
temperatures falling well into the 40s. The early fall-like conditions
will be accompanied by generally starlit skies and light winds...as
high pressure will be centered over the upper Great Lakes. The only
potential fly in the ointment to the otherwise clear skies will be the
passage of a longwave trough axis that could include some patchy mid
level clouds. For what its Worth...it will be a vortex within this
southward moving mid level trough that will eventually become cut off
and prove to be the southern component to the aforementioned Rex block.
On Saturday...the large surface high will pass by to our north across
the Ontario-Quebec provincial border. The resulting northeast flow of
dry 'continental polar' air will keep humidity levels quite low...but
it will also support 850 mb temps in the upper single digits c. This will
translate into afternoon temperatures that will straddle 70 deg f...
well below normal readings for late August. The autumn like airmass
will be tempered though by full sunshine...so this will allow for a
refreshing day for outdoor activities.
As the surface high drifts across the St Lawrence Valley Saturday
night...it will be just as cool as the previous night under clear skies
and light winds.
The second half of the weekend may prove to be even nicer (if that is
possible)...as the return flow around the exiting high pressure over
the Canadian Maritimes will encourage a little stronger warm advection.
850 mb temps on Sunday will climb back above 10c...so afternoon
temperatures may actually be a little more comfortable for some...
returning to the mid 70s across the valleys and lake plains. Otherwise
we can anticipate sun filled skies and generally ideal weather for
The large surface high...which will be anchored in the vcnty of the
Canadian Maritimes Sunday night...will reach back across New England to
the lower Great Lakes through Monday night. This will maintain fair dry
weather over our forecast area with temperatures slowly climb back to
above normal levels. High temperatures Monday will generally be in the
mid to upper 70s.
Long term /Tuesday through Thursday/...
there is high confidence that temperatures will average above normal
during this period...as a broad longwave trough will slowly carve
across the center of the continent. Warmer and more humid air will
funnel to the northeast across the lower Great Lakes in advance of the
trough with 850 mb temperatures generally in the mid teens c. This will
easily support Mercury readings of at least the lower 80s in the
valleys and across the lake plains each afternoon...while overnight
lows will be in the 60s. These values will be a solid 5 degrees above
In regards to precipitation...a warm front is forecast to push to the
north across the region late Monday night or Tuesday. While this could
generate scattered showers and thunderstorms...a higher chance for
precipitation will come Tuesday night into Wednesday when the
associated cold front will slowly cross the region. Given the lack of
strong continuity and model to model consistency...will refrain from
going higher than chc pops.
High pressure is then forecast to build across the region later
Wednesday into Thursday. This will encourage the return of fair
weather along with more comfortable humidity levels.
Aviation /00z Friday through Tuesday/...
the vast majority of the cloud cover has cleared the area and
shower activity has moved out with it. Just some scattered
clouds remain over western New York, and those will fade. Light
winds will promote valley fog around jhw overnight, which will
dissipate after sunrise. Cold air aloft will promote efficient
cumulus development on Friday, however the majority of it should
Friday through Monday...mainly VFR with nothing more than southern
tier valley fog producing local IFR conditions each late night and
Tuesday...MVFR possible with showers and thunderstorms.
near Small Craft Advisory conditions will continue to weaken overnight. Another
round north-northeast winds could result in another period of
choppy conditions late Friday night into Saturday on Lake
Ontario, but again it looks like conditions stay below Small
Craft Advisory criteria. Winds and waves will diminish later
Saturday afternoon into Sunday.