Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 230144

Area Forecast Discussion
National Weather Service Buffalo NY
944 PM EDT THU SEP 22 2016

A frontal boundary across the province of Ontario will slide
southeastward overnight, crossing the region through the day Friday.
Shower chances will increase with the frontal passage, which will be
followed by cooler, drier and more seasonable air for the weekend as
high pressure builds in again.


A shortwave will track across Ontario and into Quebec overnight
which will push a cold front slowly southward Lake Ontario early
Friday morning. An initial round of showers will exit into the St
Lawrence Valley late this evening, resulting in mainly dry weather
for the majority of the cwa. Chances for showers will increase
across the Eastern Lake Ontario region late tonight as the
frontal boundary gets closer. Model guidance has struggled with
this a bit, especially with the initial round of showers which
appears to be associated with a wave of warm air advection in the
mid-levels. Expect another wave which is across Eastern Michigan
to arrive late tonight, but some high resolution guidance appears
overdone with this when compared to radar. Temperatures tonight
will remain mild (upper 50s to mid 60s) as we stay on the warm
side of the surface frontal boundary and with increasing cloud

On Friday, the front will sag southward across the region with
the bulk of the rain showers trailing the frontal passage. Based
on a faster 18Z model consensus, the forecast speeds up the timing
of the front, and ends precipitation a bit earlier. Coverage will
be most widespread across the North Country early Friday morning
as the best plume of moisture combines with upslope flow behind
the frontal passage. Otherwise, less impressive moisture and
weaker forcing behind the frontal passage south of Lake Ontario,
including western NY, should leave shower coverage much spottier
and have have maintained chance PoPs (30-50%). The cold air
advection behind the morning cold frontal passage and lowering
cloud cover behind the front will keep temperatures from rising
much during the day Friday. High will range from the mid 60s in
the North Country to the mid 70s in the Southern Tier. These
should come early in the day, with much of the day cloudy and
notably cooler than the past several days.


Post frontal conditions developing at the start of the short term
period, with northerly flow, cold air advection, and drying in the
mid and upper levels. The upper level pattern looks to be a nearly
blocked Omega pattern, with a sharp ridge along the Mississippi
River, which separates a closed low over the Canadian maritimes from
a low lifting northeast through the intermountain west. There could
still be some leftover showers across the Southern Tier counties
during Friday evening with lingering moisture.

An expansive canadian high will build southeast across the Lower
Great Lakes on Saturday. This will promote continued drying with
abundant sunshine for most areas...while leftover cloud cover from
the Friday nights orographic lifting could limit the amount of
sunshine into the first part of the afternoon. Despite the partly
to mostly sunny skies, cold air advection will bring 850 mb
temperatures down into the single digits C and only support high
temperatures in the lower to mid 60s, perhaps only 50s over the
higher terrain east of Lake Ontario.

The high becomes centered over the region Saturday night. Light winds
and generally clear skies will combine with the associated Canadian
airmass to allow temperatures to drop off into the mid 30s to lower
40s...with patchy frost a possibility in the normally colder parts
of the Southern Tier and Eastern Lake Ontario region.

Sunday should be very comparable to Saturday as the large surface
high will remained extended across our forecast area. Plenty of
sunshine will accompany seasonable temperatures as afternoon mercury
readings will once again be in the 60s. It should be a great day to
get out and enjoy some early Fall foliage.


Significant differences between the ECMWF and GFS based ensembles
remain, thus will tweak continuity and rely on blended guidance
for Day 7.

Run to run continuity has been poor for Days 4 to 7 over the past
couple of days, particularly with the current 12Z GFS depicting a
strongly progressive deep, closed low moving from the Upper Midwest
on Tuesday to the middle Appalachians on Friday. ECMWF also seems to
be too quick with the breakdown of the eastern ridge and progression
of the upper Midwest trough to the Mid Atlantic by Thursday, but as
an open wave rather than as a deepening closed low.  While there is
still good fairly high confidence that dry weather will persist
through Monday, the remainder of this forecast period offers little
confidence given the wide range of model solutions through the end
of the week.

As the region will be under the influence of inter-trough ridging,
high temperatures will average a few degrees above normal.


A frontal boundary will slowly drop toward the region tonight, but
most of the showers associated with this will stay to the north,
only impacting the ART terminal tonight. These showers are
unlikely to produce any restrictions below VFR.

On Friday on the cold front will slide south across the region
with showers which will be most widespread east of Lake Ontario.
The moist northeast flow behind the front will produce low
stratus, probably in the IFR or MVFR category. This is a
climatologically favored flow to produce IFR conditions, and with
BUFKIT soundings supporting this most TAFS carry a period of IFR
conditions Friday morning. Conditions should improve late Friday
as drier air builds in behind the front which will raise cloud


Friday night...MVFR improving to VFR.
Saturday through for some patchy overnight/
early morning valley fog across the Southern Tier.
Tuesday...VFR...with a chance of showers.


A cold front will cross the region late tonight and Friday...with a
stiffening northeasterly flow of much cooler air in its wake. This
will result in SCA conditions along the Southeast shores of Lake
Ontario where winds will be the strongest. Conditions will also
approach SCA criteria across Western Lake Ontario, and portions
of Lake Erie near Ripley. Winds should drop off a bit Friday night
and Saturday, but still will be close to SCA criteria.

High pressure will then build in for the weekend bringing a
return to fine boating conditions, especially by Sunday.


MARINE...Small Craft Advisory from 8 AM to 6 PM EDT Friday for LOZ043-



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