Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 201128

Area Forecast Discussion
National Weather Service Buffalo NY
628 AM EST Mon Feb 20 2017

High pressure will provide our region with fair weather through
Tuesday morning. Then a weak front will then cross the area later
Tuesday and Tuesday night with a period of showers. Mainly dry
weather will then return for Wednesday and Thursday before low
pressure moves into the Great Lakes Friday with the next period of
rain. Temperatures will remain well above average through the week
before colder air arrives next weekend.


A weak backdoor cold front will wash out just to our south
through this morning. Cloud cover with this front has been very
limited, with patchy cloud cover centered across Livingston and
Ontario counties early this morning. An elongated ridge of high
pressure extending from Hudson Bay all the way to the
Southeastern U.S. states will gradually slide east and build
across our region through tonight. This will result in dry
weather throughout the period with clear skies for much of the
day. High clouds will spread in advance of an approaching
shortwave late this afternoon and tonight, but any precipitation
with this shortwave will remain well to our north and west.

Temperatures today will be cooler than they have been, but
still above normal for this time of year. The forecast will
hedge slightly warmer than consensus guidance, given the recent
cold bias of this guidance, but forecast soundings show that
the air aloft is not nearly as warm as the past two days with
previous errors in model guidance largely stemming from an
erroneous cold layer near the surface. Expect highs today to
range from the mid to upper 40s west of Rochester, cooling to
the mid 30s east of Lake Ontario. The departing high will allow
for more radiational cooling East of Lake Ontario tonight where
temperatures should fall into the teens. An increasing
southerly flow late in the night will inhibit cooling across
western portions of the cwa.


Tuesday an upper level shortwave will impinge upon an upper level
ridge of high pressure, with the shortwave aiding in pushing a weak
cold front across the Eastern Great Lakes region. There are still
some model timing inconsistencies, but the overall consensus is to
bring a line of showers into the CWA Tuesday afternoon, with
activity carrying eastward across the region Tuesday afternoon and
evening. The strong ridge ahead of the weak cold front increases the
confidence that Tuesday morning should be most if not completely

As the shortwave pushes eastward and lifts over the ridge of high
pressure it will weaken some. Expect precipitation to wane farther
inland, where both the weakening shortwave and lift aloft along with
less additional lake moisture will leave PoPs at just likely range,
while closer to the lakes categorical PoPs will remain in play.

There will be neutral to warm air advection behind the front Tuesday
night and into Wednesday. Lingering low level moisture will likely
bring a period of low clouds and fog to the region, especially over
SW NYS, and east of Lake Ontario where a snowpack remains.

A low level inversion Wednesday morning may remain low clouds
through the day, but as winds become southwesterly, and increase
through the day clouds will break for some afternoon sunshine.

Weak high pressure following the cold front should bring fair
weather Wednesday and Wednesday night to our area.

Temperatures Tuesday ahead of the weak cold front will climb into
the 50s across WNY, with mid to upper 40s east of Lake Ontario. The
little cold air behind the cold front Wednesday will again continue
the above normal temperatures, with highs pushing into the 50s,
possibly reaching the lower 60s across the Genesee Valley.


During this period a blocked flow will persist across the northern
hemisphere...with a Rex Block remaining anchored between Alaska and
the Hawaiian Islands. Across the CONUS...this will favor large-scale
troughing across the western half of the country and broad/flat
downstream ridging over the east...which for our region will translate
into temperatures remaining above typical late winter averages. While
the overall pattern may break down a little early on with the trough
temporarily broadening across the country and consequently leading to
an incursion of seasonably colder air into our region next weekend...
this should be short lived as the various guidance packages still
suggest that the mean trough will become re-established over the west
by the end of next weekend or early next week.

In terms of the day to day weather...the upper level pattern described
above will be very conducive for `cutter` type storms to make their
way from the high plains to the Upper Great Lakes. This storm track
will keep the storm systems to our west...further enhancing the mild
weather with periodic injections of warmth from the GOMEX. During the
extended portion of the forecast...this will be the case Friday and
Friday night when a sub 990mb low will direct some late winter sub
tropical warmth (H85 temps 10 to 12c) across the Lower Great Lakes.
Following the passage of this low and its trailing cold front sometime
on Saturday...the aforementioned colder air will then filter across
our region through the remainder of the weekend...resulting in our
temperatures pulling back closer to normal...but still remaining a
bit above average overall.

With respect to precipitation potential...the cutter system referenced
above should bring general shower chances to our region Friday right
through Saturday...with these appearing most likely to peak sometime
during Friday night...when PoPs have been bumped up to the low likely
range. After that...drier weather should return for the rest of the
period...with any potential lake response east of the lakes likely
remaining greatly limited in scope by the dryness and marginally cold
nature of the incoming colder airmass.


There are patchy MVFR clouds across the Genesee Valley this
morning, but these are unlikely to impact any TAF sites.
Otherwise, high pressure will build across the area with
widespread VFR conditions throughout today and tonight.


Tuesday and Tuesday night...Showers likely with areas of MVFR.
Wednesday and Thursday...Mainly VFR.
Friday...Showers likely with areas of MVFR.


There will be a modest northeast flow today which will create
choppy conditions along the south shores of Lake Ontario, but
winds and waves should remain small craft advisory criteria. While
winds will gradually freshen with a continued veering flow
tonight, the flow will be offshore and this will limit the risk
for small craft advisory conditions. The lower lakes will be
between systems on Wednesday, with a light southwesterly flow





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