Area Forecast Discussion
Issued by NWS Buffalo, NY

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000
FXUS61 KBUF 211842
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
142 PM EST Wed Feb 21 2018

.SYNOPSIS...
In the wake of a strong cold front lingering light rain will
steadily diminish this afternoon...while much cooler air finishes
overspreading our region. A weak system passing by to our south
will then bring some limited mixed precipitation...then an
accumulating snowfall to the Southern Tier and interior portions
of the Finger Lakes later tonight and Thursday. Yet another low
pressure system will then bring another round of mainly rain to
our area on Friday. Otherwise...temperatures will still remain
near to above normal through the end of the week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of early afternoon the cold front has completely cleared the
area...with most areas (aside from far southeastern sections) having
already seen temperatures drop into the upper 30s and lower 40s.
Expect those areas still experiencing warmer readings to see the
same within the next couple of hours...with fairly steady or slowly
falling temps then expected for the balance of the day. With respect
to precipitation...the previously large area of rain behind the front
is in the process of disintegrating into some remnant patchy light
rain...and this trend will also continue through the balance of the
day with the precip pretty much tapering off by sunset.

The surface high will shift north of the Great Lakes tonight keeping
 most of the night dry. Guidance then shows a wave of low pressure
and associated moisture lifting across the Ohio Valley. There is an
increasing risk that some freezing rain could extend into the
western Southern Tier late tonight. Surface temps will be below
freezing when precip likely arrives along with a warm nose aloft
supporting a p-type of freezing rain. This is supported by
00z GFS BUFKIT profiles for Jamestown and Whitesville and the
00z SPC HREF. Pops are only into the likely probability owing to
some timing refinement needed with newer model runs. Will hold
off on Winter Weather Advisory along with surrounding forecast
offices until confidence on timing increases. Will include this
risk in the Hazardous Weather Outlook.

&&

.SHORT TERM /THURSDAY THROUGH SATURDAY NIGHT/...
The prevailing flow aloft Thursday night through Saturday night will
feature a SW-NE oriented jet stream generally stretching from the
Desert Southwest into the Central Great Lakes region.  The result at
the surface will be a number of relatively weak troughs/lows.

The first feature will already be east of the region by Thursday
night while surface high pressure moves from the Northern Great
Lakes region east across Southern Ontario and Quebec.  This will
result in a temporary break in any precipitation across Western and
Central NY for Thursday night with weak subsidence in place.

The break will be short-lived however as another feature moves in.
Although the surface pattern looks relatively weak, moisture will
will be tapped from the Gulf of Mexico, with the potential for
another decent precipitation event at least toward the NY/PA line.
Although the details will likely change, overall it looks like some
areas could briefly start out with snow or a very brief period of
freezing precipitation before quickly changing over to rain on
Friday.

Another surface high pressure system follows with a dry period
expected for most of Friday night and Saturday.  A more significant
synoptic low should have developed by this time over the plains.
This low, a result of the upper level disturbance currently moving
down the BC coast, should deepen as it moves toward the Northern
Great Lakes Saturday night.  The result will be increasing chances
for rain, with widespread rain expected Saturday night.

&&

.LONG TERM /SUNDAY THROUGH TUESDAY/...
An active weather pattern will continue this weekend with mild
temperatures and chances for precipitation. The large scale weather
pattern will remain relatively unchanged with a stubborn ridge over
the southeast CONUS and large scale troughing over the intermountain
west. This pattern will continue to supply above normal temperatures
and increased precipitation chances with the flow of Gulf of Mexico
moisture wide open.

In particular, a low pressure system will eject from the four
corners region Saturday across the Great Lakes by Sunday. The result
should be a chance of widespread rainfall Sunday ahead of the
approaching low pressure system. As the low passes by to our
northwest, expect decent southwest winds to pick up behind in the
cold advection behind the front. Models vary on the strength of the
surface low, but there at least low potential for a high wind event
if surface low deepens sufficiently.

Quiet and drier weather returns Monday with surface high pressure
building over the Ohio Valley. Otherwise, highs will remain above
climo (+5F - +10F) with the daytime highs in the mid and upper 40s
likely for most locations. Sunday will likely be the warmest day, so
long as we briefly break into the warm sector, with at least 50s
possible.

&&

.AVIATION /19Z WEDNESDAY THROUGH MONDAY/...
For the balance of the day...lingering areas of light rain in the
wake of a cold front will continue to break down and taper off as
high pressure and drier air begins building into the region...with
the rain expected to pretty much come to an end before sunset.
Concurrent with this...predominantly IFR to MVFR flight conditions
will improve back to MVFR and then VFR through late afternoon and
early this evening...with this improvement arriving across the
lake plains first...and the higher terrain of the Southern Tier/
North Country last.

After that...high pressure will build eastward across Great Lakes
and into Southern Quebec tonight through Thursday...while a wave
of low pressure passes by to our south across the Ohio Valley and
Virginias. After a period of widespread VFR conditions this evening...
this latter system will bring a brief wintry mix of precipitation
to the Southern Tier overnight and early Thursday...followed by an
accumulating snowfall to areas south of KBUF/KROC during Thursday...
with all of this accompanied by another round of IFR to MVFR conditions
in the aforementioned areas. To the north of the steadier precip...
there will just be a chance of a little spotty light rain or snow
during the day Thursday...with VFR conditions continuing to prevail.

Outlook...
Thursday night...VFR/MVFR with a chance of snow or rain.
Friday...Deterioration to MVFR with rain developing...with a very
brief wintry mix possible at the onset.
Saturday and Sunday...VFR/MVFR with additional periods of rain
developing...which may be mixed with a little snow across the
North Country.
Monday...Mainly VFR.

&&

.MARINE...
A cold front will cross our region from northwest to southeast this
morning. In its wake, a brisk westerly to northwesterly flow will
set up across Lake Ontario late morning and afternoon before
diminishing tonight. This will bring a round of advisory-worthy
conditions to areas along the southeast shore of Lake Ontario into
tonight. High pressure building over the eastern Great Lakes
overnight into Friday should bring a return to light winds and lower
waves. A weak low pressure will cross our region Friday but without
any advisory level conditions.

&&

.HYDROLOGY...
RFC forecasts (and the risk of flooding) continue to trend downward
across the Eastern Lake Ontario Region as of this writing...with now
only the Watertown forecast point forecast to reach action stage.
Probably the biggest reason for this so far has been the still-
incomplete melting of the snowpack across this region...with reports
from early this morning still suggesting the presence of a foot to a
foot and a half of snow across the higher terrain. This has likely
helped to hold back runoff contributions from snowmelt at least
somewhat...with the window for rapid snowmelt also now quickly
closing as a sharp cold frontal boundary nears the area.

For now...have left the Flood Watch intact given the still-elevated
flows expected...as well as a lingering risk for ice jams and related
flooding along area waterways until temperatures drop off this afternoon
and evening.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Flood Watch until 7 PM EST this evening for NYZ006>008.
MARINE...Small Craft Advisory until 1 AM EST Thursday for LOZ043-044.

&&

$$

SYNOPSIS...JJR
NEAR TERM...JJR/SMITH
SHORT TERM...ZAFF
LONG TERM...CHURCH
AVIATION...JJR
MARINE...SMITH
HYDROLOGY...JJR


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