Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 241516

Area Forecast Discussion
National Weather Service Buffalo NY
1016 AM EST Fri Feb 24 2017

Unseasonable warmth will continue through Saturday morning. Through
this morning, a warm front will bring widespread showers and some
scattered thunder. A strong cold front will cross the region
Saturday, and may be accompanied by thunderstorms with gusty winds,
followed by windy conditions Saturday afternoon and evening. A quick
shot of colder air Sunday may bring some lake effect snows east of
the lakes.


A large low pressure system tracking through the central CONUS
toward the Great Lakes today will force a surface warm front
northward across the region today and tonight. The front is
partway through the Southern Tier at 14Z with southerly winds
and clearing skies allowing for rapidly warming conditions.
Temperatures have already passed the 60F to the south. Winds
closer to the Buffalo Metro region, currently easterly, should
come around to the S/SSW based on the 12Z sounding showing all
but the lowest winds out of the SW. The strongest part of the
inversion is about 2000` thick, but surface obs near 1000` to
the south have already mixed out. A recent 14Z AMDAR sounding
shows warming throughout the inversion layer, but not quite as
warm as 1hr forecast RAP data. However, this is within a tight
and mobile temperature gradient so comparisons are not useful.
Will increase temperatures a few degrees toward the Lake Ontario
shoreline, but will maintain the huge 30+F gradient between the
lakeshore and a few miles inland,

From a precipitation standpoint, the main area of rain
accompanying the warm front continues to move to the NE...and
will be out of the Genesee Valley well before noon, then out of
the Eastern Lake Ontario region later this afternoon.

As noted earlier, locations south of the NYS Thruway should
become solidly established in the warm sector, particularly with
sunshine breaking out in the afternoon. High temperatures will
likely soar in these locations, with downslope southerly winds,
and an airmass near all time record warmth for the month of
February. GFS and EC forecast 925 mb temperatures range from +15
to +17C by 00Z; per the SPC sounding climatology at KBUF (back
to 1948) the warmest 925mb temperatures ever recorded in
February was +16.6C. With this in mind, locations south of the
Thruway could easily challenge their all-time warmest February
high temperatures. The warmest ever recorded at KBUF in February
was 71 degrees on 02/26/2000, the current forecast for today
has now at 72 degrees at KBUF as clearing continues to rapidly
approach the region. HOWEVER, the main potential for failure to
reach the record at KBUF will be if the warm frontal boundary
becomes hung up several miles farther south, taking longer for
us to get into the warm sector. The warmest readings in the
forecast area will be in the Genesee Valley and northern Finger
Lakes as is typical with southerly downslope winds, but high
temperatures will likely easily top out in the mid 70s, with a
forecast high of 75 degrees in Dansville.

The North Country will be very slow to warm up today, as the warm
frontal boundary gets hung up southern Lake Ontario for much of the
day. However by this evening, with a weakening lake breeze and large
synoptic push ahead of the approaching low pressure system, the
boundary will lift northward well into Canada tonight. Expect
locations in along the Saint Lawrence Valley to be locked into the
cool side of the front with a northeast wind all day today. This
will keep cloud cover and some patchy fog in place, along with high
temperatures struggling to get out of the 30s to low 40s. Then
overnight tonight, temperatures will rise well into the 50s as the
front moves northward. Thus temperatures in much of Jefferson county
will rise all night, peaking in the mid to upper 50s by Saturday

Tonight, expect an extremely mild and fair weather night across the
region, with temperatures remaining in the 60s (about 40 degrees
above normal low temperatures for this time of year!) across western
NY and the mid to upper 50s in the North Country. We will be solidly
in the warm sector ahead of the approaching low pressure system, so
dont expect any precipitation for much of the overnight period.
Toward daybreak Saturday the cold front will approach western NY,
complete with strong showers and scattered thunderstorms capable of
producing strong gusty winds, but more on that below.


On Saturday a sharp mid level trough will move east across the Great
Lakes, taking on a negative tilt with time. At the surface, a
deepening surface low will track northeast across the central Great
Lakes, reaching western Quebec by late in the day. A trailing
surface cold front will cross the area from west to east during the
morning and early afternoon.

Large scale forcing will be strong, with strong DPVA ahead of the
negatively tilted mid level trough and a coupled jet structure aloft
providing strong divergence in the upper levels. Low level
convergence will be strong along the advancing cold front, with
moisture transport further enhanced by a 50 knot low level jet. PWAT
values will exceed 1 inch just ahead of the front, which is 3
standard deviations above normal for late February. The high quality
dynamics and moisture coming together will support a band of
moderate to heavy rainfall along the advancing front, which will
last for a few hours at any given location.

There will be some instability available along the front as well,
with Lifted Index of around -1C and modest SBCAPE of up to 200J/kg.
This will support a chance of a few scattered thunderstorms along
the cold front, embedded within a band of heavy showers. The band of
heavy showers and scattered storms will likely produce gusty winds
as they move east across the area, along with heavy downpours. If a
focused line of frontally forced convection is able to develop
spotty damaging winds cannot be ruled out, and SPC has maintained a
marginal risk for a portion of the area.

Behind the cold front, a secondary period of stronger winds will
develop as strong cold advection develops from late morning through
the afternoon and evening. The track of the surface low is very
favorable climatologically, to the north and west of the area. The
low is not particularly deep to support a true high wind event
however. Strong pressure rises and implied subsidence behind the
cold front will support downward transfer of stronger winds aloft.
Subsidence and mixing of winds from aloft will be further enhanced
by a decent tropopause fold, with the 1.5 PVU surface decending to
around 600mb.

Model guidance is still not in very good agreement with respect to
how much wind will be available aloft to mix down. The GFS remains 5-
10 knots stronger than the NAM with mean wind in the 2-5 thousand
foot layer. If the GFS verifies, gusts would likely approach warning
criteria northeast of Lake Erie, while the NAM would suggest a low
end advisory. Given the model differences, we will take a middle
ground between the NAM and GFS and go with a solid wind advisory for
the Niagara Frontier and Chautauqua County from late Saturday
morning through Saturday evening. If the stronger guidance ends up
verifying, an upgrade to a high wind warning may be required for
portions of the advisory area, but there is not enough confidence to
go that route yet. Further complicating the situation, the thawed
and muddy ground conditions may facilitate more tree damage than
normal for the expected wind gust speeds.

Saturday night and Sunday the deep low will exit to the northeast
across Quebec. A period of wrap around moisture and ascent with the
passage of the mid level trough will produce a few scattered snow
showers Saturday night. The airmass will also become cold enough to
support a modest lake response east of the lakes, with lake induced
equilibrium levels rising to around 8K feet briefly. East of Lake
Erie expect lake effect snow showers to peak from late evening
through the early overnight Saturday night across the western
Southern Tier and portions of southern Erie and western Wyoming
counties, with snow showers then weakening by Sunday morning and
ending by Sunday afternoon. Expect total amounts of 2-3 inches
across the higher terrain east of Lake Erie. East of Lake Ontario,
expect snow showers to peak later Saturday night and Sunday morning
across the Tug Hill and portions of Oswego County, with lake effect
then weakening in the afternoon. Expect total accumulations of 2-5
inches east of Lake Ontario, with the higher amounts restricted to
the Tug Hill Plateau.


The main feature to contend during this period will be yet another
Colorado Low cutting across the Great Lakes around the middle of
next week.

The overall pattern during this time frame will be quite a broad low amplitude trough over the country will
give way to a progressive longwave trough that will start over the
western states. Significant cutter storms typically mark the change
in the overlying pattern...and this time period will feature such a
storm. The details...

Sunday night and Monday, a weak mid level trough and associated
surface low will track from the northern Great Lakes east across
Quebec, with a trailing weak trough brushing by the Lower Great
Lakes. The combination of weak synoptic scale forcing and very
limited lake enhancement may produce a few snow showers east and
northeast of the lakes Sunday night and Monday morning, with any
leftover precip changing mainly to a few rain showers by Monday
afternoon as the boundary layer warms.

Significant cyclogenesis will begin across the central High Plains
late Monday and Monday night. For what its worth...the operational
ECMWF again looks to be most realistic with this whole
have leaned more heavily with this guidance package.

The newly formed storm system will track across the Plains to near
Chicago on Tuesday...while its associated far reaching warm frontal
boundary will approach our region. This could lead to some light
rain or snow for our region...which will transition to all rain and
increase in coverage and intensity Tuesday night and Wednesday as
the parent low is forecast through the Lower Great Lakes.

In the wake of this system...there will be the risk for gusty winds
Wednesday night and Thursday...although guidance is not quite as
impressive looking with it than it was in earlier runs. There is
also markedly more spread in the various ensemble solutions.

Following this storm system, model guidance continues to support a
return to winter for Thursday through the following weekend with
temperatures returning to at or below normal, and a series of
clipper systems bringing several opportunities for snow and lake
effect snow.


The back edge of showers will continue NE and cross the Eastern
Lake Ontario region this afternoon. Improving conditions to
VFR should be expected away from the Lake Ontario shoreline.
Along the shoreline, a warm front will get hung up with variable
CIG conditions expected. IAG/ROC will be very close to this
boundary, and will see the most persistent MVFR conditions. KART
will remain on the cool side of the boundary with persistent
MVFR as well.

Tonight conditions will lower to MVFR across the area with
increasing moisture ahead of an approaching strong cold front
boundary for Saturday morning.


Saturday...Periods SHRA with MVFR and local IFR, then windy.
Sunday...VFR but IFR to MVFR in lake effect snow SE of both lakes.
Monday...VFR, possible MVFR...depending on low location with a
chance of rain and snow showers.
Tuesday...Chance of rain with MVFR/IFR possible.


A warm front will lift north across the eastern Great Lakes through
today with rain showers and isolated thunderstorms but winds and
waves are not expected to build until late Friday night and Saturday
when a powerful cold front will cross the Lower Great Lakes from
west to east. Strong, possibly gale force winds will be found in the
wake of the front Saturday and Saturday night.


There is a potential for flooding across the Eastern Lake
Ontario Region starting late Friday night and lasting into
early next week.

While the snow pack has largely melted across Western New York,
a significant snow pack remains east of Lake Ontario, including
the Black River basin. Snow water equivalent values are about
130% of normal, with this snow pack expected to become
increasingly ripe through the end of the week due to the warm

On Saturday, a strong system will pass to our north with
a prolonged period of warm (50+ degree) temperatures expected
late Friday through Saturday until the passage of a cold front
drops temperatures below freezing Saturday night. This will be
combine with gusty winds and high dewpoints to rapidly melt a
significant portion of the snow pack in place. This system will
also bring a period of rain Saturday, with amounts expected to
average around an inch.

This may result in multiple issues east of Lake Ontario. First,
the combination of snowmelt and rain may cause areal flooding on
small, faster responding creeks and rivers starting late
Saturday. Some ice jams are also possible. After this, runoff
will cause the Black River and its tributaries that drain the
Tug Hill Plateau and the western Adirondacks to respond
Saturday night and Sunday and lasting into next week. MMEFS
ensembles show a low probability for flooding at McKeever and
Boonville, but chances may be higher than indicated if surface
temperatures exceed the model consensus. The risk is greater for
the Watertown forecast point, extending upstream to Lyons Falls
with extensive snow pack contributing to the runoff for the
entire basin. Flooding is also possible on the Salmon River and
other rivers in northern Oswego County that drain the western
slopes of the Tug Hill. With this in mind, a flood watch has
been issued for Oswego, Jefferson, and Lewis counties from
Friday night through Sunday.


NY...Flood Watch from 7 PM EST this evening through Sunday evening
     for NYZ006>008.
     Wind Advisory from 10 AM to 10 PM EST Saturday for NYZ001-002-



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