Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 240220

Area Forecast Discussion
National Weather Service Buffalo NY
1020 PM EDT Thu Mar 23 2017

High pressure ridged across the lower Great Lakes will continue fair
weather through late evening. A warm front will then bring a period
of rain to western New York with some mixed wintry precipitation
from the interior Southern Tier to the eastern Lake Ontario region
late tonight into Friday morning. Expect much warmer temperatures on
Friday afternoon behind the front. The front will stall across the
region this weekend, with several disturbances moving along the
front and bringing periods of rain over the weekend and into the
first half of next week.


High pressure will continue to drift east off the Mid Atlantic coast
through the overnight, with a ridge extending northward into New
England. Subsidence associated with the ridge will gradually fade
with mid/high clouds increasing from northwest to southeast.

Surface ridging will keep us dry through much if not all of tonight
with mainly increasing and lowering clouds. Temperatures will bottom
out around midnight in the upper 20s to low 30s across western New
York with lower 20s across central New York and even some upper
teens east of Lake Ontario. After midnight, increasing southerly
flow will help temperatures begin a slow climb ahead of a warm front
lifting across the Ohio Valley. Models show an axis of 925-700mb
moisture being lifted ahead of the warm front and on the nose of a
40-50kt jet. Precipitation will quickly overspread western NY
between 10-12z where surface temperatures will be very critical for
p-type at the ground. Using a warm layer tool which produces a p-
type based on a warm layer aloft and looking at surface
temperatures, have included some freezing rain across the interior
southern Tier into the western Finger Lakes for a few hours before
changing quickly over to plain rain as surface temps rise above
freezing. Have issued a Winter Weather Advisory to cover the areas
most likely to see a trace to a few hundredths of an inch of ice.
There may be some sleet as well but the more dominant p-type will be
freezing rain. This idea matches very well to ensemble guidance from
the SSEO/NCAR/SREF. The lake plains of western NY and Chautauqua
County should have surface temps above freezing when the rain
arrives including Jamestown to Buffalo to Rochester. Total liquid
QPF will run around a quarter of an inch.

As the warm front approaches then crosses western NY on Friday,
expect precipitation to begin to overspread the eastern Lake Ontario
region around Sunrise where temperature profiles support a very
brief period of snow changing to sleet and freezing rain before
switching to plain rain around Noon. Less than an inch of snow is
expected along with a few hundredths of an inch of ice which also
lead to a Winter Weather Advisory. Total liquid QPF after the mixed
precip here will run a quarter to a third of an inch.

As the warm front shifts across western NY, expect rain to
taper off to a chance of some more spotty showers by noon with a
possibility that much of the region south of the front may become
mainly dry during the afternoon. Temperatures will warm nicely into
the 50s across western NY behind the front with 40s for highs east
of Lake Ontario where the front may stall leaving rain in the
forecast through the day.


By Friday night a sharp frontal boundary will be in place
across the Great Lakes from southern WI to northern New England
as broad southerly return flow around high pressure stationed
off the Eastern Seaboard and a large, vertically stacked low
over the southern Plains encounters an anticyclonic flow of cold
and dry air moving down from the north out of Canada. A broad
swath of precipitation will be in place along this front Friday
night thanks to aforementioned convergence and frontogenetic
forcing along and north of the boundary. Latest model consensus
places the axis of this precipitation primarily north of the
Thruway, with the bulk of the precip falling across Ontario and
the North Country. Precip type should remain all rain, as
virtually all of the forecast area should stay on the warm side
of the frontal boundary, with lows ranging from near 50 along
the PA border to the mid 30s in the St. Lawrence valley.

The frontal boundary will shift south across the forecast area on
Saturday as the high over Canada shifts position eastward across
James Bay. A low-level northeasterly flow of colder air will ooze
back into the forecast area from the northeast during the
day...depressing temperatures across the area, with highs barely
budging from overnight readings. Temps should only top out in the
mid 50s along the PA border, with low 40s across the Buffalo-
Rochester metros, and upper 30s in the St. Lawrence valley. Precip
should taper off in intensity/coverage as we move through Saturday,
as upper level forcing diminishes with the departure of an upper
level jet max over eastern Ontario/Quebec.

The arrival of shallow cooler air from the northeast will once again
present precip type issues Saturday night into Sunday morning, as
temperatures fall below freezing across the North Country, bringing
back a potential for freezing rain from the Tug Hill north to the
St. Lawrence River. Precip should stay as rain elsewhere though, as
temperatures should range from the mid 40s along the PA border to
the mid 30s along Lake Ontario. With upper level ridging amplifying
across the area, precipitation should taper off to showers
overnight, before precipitation ramps up again Sunday into Sunday
night, as the upper level low that will be drifting across the
Midwest during the first half of the weekend approaches the Great
Lakes. Strengthening southerly flow with the approach of this
feature and its attendant surface low will shove the cold front back
to the north, with highs running from the 50s in Western NY to the
low 40s in the North Country. Lows Sunday night will run in the 40s,
meaning that precip should once again fall entirely as rain.

Regarding flooding concerns, while warming temperatures will
accelerate melting of remaining snowpack across the forecast area,
the axis of heaviest rainfall Friday night should fall primarily
across Canada. There will be enough of a break in the steady
rainfall Saturday/Saturday night to allow for some recovery in
stream levels before the next round of rain arrives Sunday.  All
told, current MMEFS hydro ensemble guidance suggest that area
streams may rise to action stage, but no flooding is currently


A stalled frontal boundary will remain near or over the forecast
area through mid next week. Several rounds of showers are possible
through this period as various disturbances ride along the boundary.
Temperatures will remain variable, as the front ripples through the
region, with generally more mild to above normal temperatures for
locations south of Lake Ontario, while locations east of the Lake
and along the Saint Lawrence valley will likely remain cooler as
colder air on the north side of the front flows into the region from
a strong Canadian high pressure system. By Tuesday, global models
are in better agreement that a strong trough will track along the
boundary, sending warmer air northward all the way through the Saint
Lawrence valley and bringing an organized widespread rain event.

Finally by mid-week, mid-range models show some hope for a drier
stretch of weather a large scale ridge finally builds in across the
Great Lakes. However, this would also bring in some slightly below
normal temperatures.


High pressure drifting away from the region will continue dry/fair
weather through most of tonight with increasing high clouds this
evening yielding to a lowering mid level deck overnight.

A warm front will move from southwest to northeast across the area
on Friday. Precipitation will overspread western NY quickly from 10Z-
12Z, then reach east of Lake Ontario shortly after 12Z as warm
advection increases ahead of the warm front. Most of the
precipitation will fall in the form of rain as temperatures warm
quickly above freezing, but there may be a brief 1-2 hour period of
freezing rain from the colder sheltered valleys of the interior
Southern Tier through the Finger Lakes and Central NY. East of Lake
Ontario precip may start as a very brief period of snow and sleet,
before briefly changing to freezing rain, and then rain by midday.
VSBY may drop to MVFR in the steadier precipitation with the warm

CIGS will drop to MVFR as the warm front and steadier precip move
through the region Friday morning. The lake plains should then
improve back to VFR briefly, with the low levels drying in SSW
downslope winds. CIGS will then deteriorate to MVFR again later in
the afternoon as the low levels saturate and downslope winds
diminish. Expect the higher terrain to remain MVFR Friday morning,
then deteriorate further to IFR in the afternoon.

Low level wind shear will become widespread later tonight through
Friday as the warm front stalls nearby and a low level jet crosses
the area.


Friday night through Tuesday...MVFR/IFR cigs with rain likely at


High pressure ridged across the lower Great Lakes will maintain
light winds and negligible waves through most of tonight.

South to Southwest winds will increase Friday as a warm front lifts
into the eastern Great Lakes. Winds will approach small craft
criteria across eastern portions of Lake Erie and northeast Lake
Ontario but waves look to remain just below 4 feet. After this, a
warm frontal boundary will stall across the region, with a
northeasterly flow likely on Lake Ontario and variable winds on Lake
Erie. This may require small craft headlines on Lake Ontario at
times this weekend.


NY...Winter Weather Advisory from 6 AM to noon EDT Friday for
     Winter Weather Advisory from 5 AM to 11 AM EDT Friday for



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