Forecast Discussion

Forecast Discussion for BUF NWS Office
FXUS61 KBUF 202029

Area Forecast Discussion
National Weather Service Buffalo NY
429 PM EDT Fri Sep 20 2019

Expansive high pressure will continue to provide us with an
overall pleasant late summer weather stretch through Sunday,
allowing temperatures to climb well above normal. The next
chance of widespread rain will not arrive until Sunday night
and Monday as a cold front moves through the eastern Great


A surface high pressure ridge that extends northward from the
Piedmont toward western New York remains in control of our
weather at this time. Under this ridge, subsidence has precluded
even fair weather cumulus formation today, and cirrus is having
increasing difficulty traversing the apex of the ridge. The end
result is a continuation of the glorious late summer/early fall
conditions we have seen all week.

With the ridge remaining in place through the night, clear skies
remain, and wind under the overnight inversions drops off again.
This will yield valley fog in the Southern Tier yet again as the
warm water temperatures manifest as fog in the isolated valleys.
Elsewhere, modest increases in dewpoints will keep temperatures
up a few degrees tonight relative to the last few nights,
however sleeping weather still looks comfortable.

Increased southwesterly flow looks to start to edge into the
western half of the area on Saturday after morning inversions
break. This will finally allow dewpoints to start to jump.
Summarily, cumulus development looks to be a far better bet
tomorrow, especially along the Lake Erie lake breeze interface
in western New York. In fact, enough instability may be
generated here to develop a few showers or even a thunderstorm
that would move inland during the late afternoon hours. PoPs for
this possibility have been increased, however the vast majority
of areas should remain dry yet again.

By Saturday night, inversions will again form even with a more
sultry boundary layer. This will cut off chances of rain,
however the higher dewpoints and warmer temperatures will remain
through the night on increased southwesterly flow relative to
recent nights.


The current pattern features a sprawling high amplitude longwave
ridge over the eastern half of the country, while an upstream trough
spins over the northern Rockies.  There`s another system over the
Canadian Rockies that will drop into this trough over the weekend.

The axis of the ridge should be along the East Coast Sunday, while
the upstream trough(s) move into the Northern Plains.  In between, a
slowly strengthening jet will stretch from the Four Corners region
NE to the Northern Great Lakes, while a surface frontal system
that`s been forecast for days forms underneath it. This boundary
will be tied to a relatively weak surface low somewhere over Central
Ontario Province.

The pseudo-parallel flow along the front will result in a slow
moving system, so it will take some time before a highly
confident period of measurable rain moves in. Earlier forecast
model runs were focused on Sunday night, but it`s increasingly
looking like rain may hold off until later, maybe into, or well
into Monday morning for WNY, and later in the day for central
NY. That is, confidence is high for measurable rain, given
abundant atmospheric moisture content, but confidence in
start/duration/end timing isn`t quite as high.

Winds and temps...Sunday should get a little breezy (SW flow) when
compared to the long stretch of near perfect conditions.  Dewpoints
will also be higher (mid 60F range), making Sunday feel more like
mid-August rather than mid September.  Highs during the afternoon
should fairly impressive, with readings in the lower to mid 80s
across much of WNY, but these forecast values are still below record
highs. Meanwhile, behind the front, Monday`s highs will be ~10F
lower. Also, a stronger (WSW) wind field however is expected on the
back side of the front on Monday.  Some gusts may approach wind
advisory criteria if precipitation moves east quickly enough
followed by adequate mixing.

Monday night, with above noted low confidence timing considerations,
the front is still expected to move east by Monday night.  Precip
may still be ongoing or waning east of Lake Ontario, but should be
completely east of the region by Tuesday AM.


A sharp mid level trough and surface low will exit off the New
England coast Tuesday. Wrap around moisture and lingering ascent
from the departing mid level trough may support a few showers
through the first half of the day east of Lake Ontario, with dry
weather across Western NY. Wrap around and diurnally driven cloud
cover will be most prevalent east of Lake Ontario, with clearing
skies by evening as deeper moisture moves east of the area.

High pressure will build into the Ohio Valley and eastern Great
Lakes Tuesday night before moving to the east coast Wednesday. This
will provide a return to dry weather for our region. A cold front
will then sweep east across the eastern Great Lakes late Wednesday
night or Thursday. The GFS is faster than the ECMWF by about 6
hours. The slower ECMWF timing is preferred with the best rain
chances during the day Thursday. High pressure is then forecast to
build into the eastern Great Lakes Friday, with a return to dry

The coolest day will be Tuesday as a pool of cold air aloft moves
across the eastern Great Lakes. Expect highs in the upper 60s at
lower elevations, and lower 60s across higher terrain. Temperatures
will then warm into the 70s for the rest of the week. Lows will
generally be in the 50s, with some 40s in the cooler Southern Tier
valleys and east of Lake Ontario.


High pressure remains in control with VFR conditions everywhere
through the period. The lone exception will be the valleys
around and to the east of KJHW, where overnight fog will develop
and become locally IFR. This will burn off by about 14z
tomorrow, returning all areas to VFR.


Tonight through Sunday...Mainly VFR, with localized IFR in Southern
Tier valley fog possible each night/early morning.
Sunday night and Monday...Areas of MVFR with showers likely.
Tuesday...MVFR/VFR with scattered showers.


High pressure will provide our region with light winds and minimal
wave action through Saturday night.

A low pressure system will develop across northern Ontario Province
this weekend, with southwest winds increasing to at least 15 to 20
knots by Sunday.





LONG TERM...Hitchcock

NWS BUF Office Area Forecast Discussion