Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 211750
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
1250 PM EST Tue Feb 21 2017

.SYNOPSIS...
A weak frontal boundary will push across our region this evening
with some shower activity...then fair weather will return for
Wednesday and Thursday. Temperatures will remain well above normal
through the end of the work week...particularly on Friday when parts
of the region will flirt with 70 degrees. A strong cold front will
cross the area late Friday night with notably colder weather
returning for much of the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
High pressure over New England at midday will continue to push away
to the east during the course of the afternoon...while a weak
frontal boundary will approach from the Upper Great Lakes. A mild
southerly flow ahead of the front will boost H85 temps to around
8c...so despite our cloud cover...this will support max temps of at
least the mid to upper 50s across many of the western counties. It
will be cooler east of Lake Ontario where readings will remain in
the 40s.

Speaking of cloud cover...satellite imagery shows a wealth of mid
and upper level moisture streaming across the Lower Great Lakes. The
AMSU blended total pcpn product shows a plume of 1" inch PWAT values
streaming northward from the GOMEX. This narrow...but moisture rich
band will accompany the aforementioned frontal boundary late this
afternoon and evening.

While the dynamics will not be overly impressive with the frontal
passage early tonight...the rich moisture source will help to
promote fairly widespread showers. The showers will make their way
across the far western counties after 21z (4pm)...with the main band
crossing the region early this evening. Most of the rain will fall
before midnight...with basin average QPF in the vcnty of a tenth of
an inch.

Temperatures tonight will remain well above freezing...with mins
ranging from the mid-upper 30s to the mid 40s over the west.

&&

.SHORT TERM /WEDNESDAY THROUGH FRIDAY NIGHT/...
Flat ridging follows in the wake of the front for Wednesday. This
should allow for dry weather, with at least partial sunshine
developing by afternoon. Little change in airmass will result from
the front, and have continued with temperatures well above
climatology. Afternoon highs of 60 to 65 are expected for the
western counties, with cooler temperatures east of Lake Ontario
where highs will be closer to 50.

By Wednesday night, a southwesterly low level flow will develop as
low pressure moves well to the north and west of region. This will
begin to induce some isentropic lift and a slow increase in
moisture. This may be enough to touch off a few light rain showers
late Wednesday night. Temperatures will remain quite mild,
especially in the west with lows in the mid 40s to near 50, with
areas east of Lake Ontario possible sneaking down into the upper 30s.

On Thursday, there are some hints that a weak cool front could sink
south of the Canadian border with the possibility for scattered
showers, but there is a lot of disagreement in guidance. Based on
the mid level ridging expected to be over our region, siding with
the warmer and somewhat dryer scenario, although have maintain a low
chance for some showers. It will be another mild day with most high
temperatures well in the 50s to the lower 60s. This will especially
be the case over the Finger Lakes and Genesee Valley.

Jet energy digging south along the West Coast will deepen the
existing trough as it translates across the Rockies. Strong
cyclogenesis will result. A deepening surface low will track into
the upper Midwest Friday morning before drifting into the western
Great Lakes by Friday night. Weakly coupled jet structure will
emerge as longwave pattern amplifies, dominated by the southern jet,
allowing isentropic ascent to ramp up. Baroclinic zone will lift
back north across the forecast area bringing the likelihood of
showers to the area Friday. Consensus is essentially set on a warm
surface low track to the west of the area, with afternoon
temperatures likely to warm into the 60s within the warm sector
across western New York, but probably remaining in the 50s north of
the boundary across central New York. Confidence in Friday afternoon
high temperatures remains low at this point, as this is greatly
dependent on how far north the surface warm can progress. If skies
were to clear enough to allow for prolonged afternoon sunshine these
temperatures may not be nearly warm enough, with lower 70 degree
readings not out of the question. It is worth noting that the
potential exists for a run at the all-time February high
temperature at Buffalo of 71F/2000.

Friday night...the still deepening cyclone will track to Lake Huron
while its strong cold front will plow across southern Ontario to to
the Niagara River. Strong southerly winds ahead of the front will
keep very mild conditions in place across all of the forecast
area...with some sites form the Genesee Valley eastward probably
not falling below 50 for an overnight low. Any showers that will be
found over the region early in the night will become more common as
the front approaches...especially over the far western counties.

This should set the stage for a windy day on Saturday.

&&

.LONG TERM /SATURDAY THROUGH MONDAY/...
It will certainly be notably colder during this period as
temperatures will return to more seasonable levels. The change back
to winter will include some snow showers...especially in the
snowbelts east of the lakes where mesoscale processes (ie. lake
effect) will contribute to potentially significant accumulations.

As so often happens here during the cold season...the passage a deep
surface low to our west and north will mark the change in the
overall pattern across the country. Rather than having a trough in
the west and ridging in the east...a broad trough full of Canadian
air will dominate the Great Lakes region. Unfortunately...these
pattern changes are also usually marked by significant/damaging
weather events. This case may be no different.

When we open this period Saturday morning...a strengthening sub
990mb low will be pushing northeast from Lake Huron while its
powerful cold front will be bulldozing across western and north
central New York. The accompanying rain showers will be accompanied
by winds of at least 25 to 40 mph with the frontal passage...then
after a couple hours where winds will subside a bit...winds will
ramp back up...possibly as high as 50 mph. The storm track...
negative tilt to the supporting mid level trough...and suggested
subsidence all favor at least advisory criteria winds. The only
thing missing is a significant low level jet. Stay tuned.

Strong cold advection on the backside of the exiting cyclone will
send H85 temps to as low as -15c Saturday afternoon into MOnday.
This will be more than cold enough to promote lake effect snow
showers east of both lakes..with significant accumulations possible
east of Lake Ontario where an upstream connection and full fetch
will be likely. Outside of the lake effect areas...Sunday and Monday
will feature partly to mostly cloudy skies and scattered light snow
showers.

After temperatures fall from 50 Saturday morning in the wake of the
front...max temps will be in the mid 30s on Sunday and close to 40
for most areas on Monday. Mins through the period will be in the
20s.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
VFR conditions will be in place through the afternoon...although the
cirrus and alto-cu will gradually lower to strato-cu by this evening.
Lowering cigs will eventually lead to MVFR conditions this
evening... with most areas experiencing MVFR cigs through the night.
Parts of the Srn Tier and Finger Lakes region will have IFR cigs
late tonight and early Wednesday.

On Wednesday...the relatively low cigs will linger through a
good part of the morning in most areas before rising to VFR
levels.

Outlook...

Thursday...Mainly VFR.
Friday and Saturday...Periods of rain showers with MVFR and
local IFR. Windy on Saturday.
Sunday...Mainly VFR but IFR to MVFR in lake effect snow
southeast of both lakes.

&&

.MARINE...
Light easterly winds on the lakes today will gradually veer to
southerly through the day. Winds will pick up some, but the
strongest winds may remain over the central waters and towards
Canada, and thus will not issue any small craft advisories as winds
should largely remain 15 knots or less.

A weak cold front will cross the lakes this evening, though with
very little cold air behind this feature waves and winds will have
little response.

Winds and waves should then remain below SCA thresholds, until an
easterly flow picks up on Lake Ontario Friday ahead of the next, and
more potent storm system.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...None.

&&

$$

SYNOPSIS...RSH
NEAR TERM...RSH
SHORT TERM...TMA
LONG TERM...RSH
AVIATION...RSH
MARINE...THOMAS



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