Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 211816

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

A strong cold front will finish crossing the region this morning.
The front will be followed by several hours worth of rain...along
with falling temperatures for the remainder of the day. A weak
system passing by to our south will then bring the chance for some
mixed precipitation to portions of the region late tonight and
Thursday...with yet another low pressure system then bringing
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.


As of 1445Z...regional surface analysis suggests that the main cold
front is draped from eastern Lake Ontario southwestward across the
Finger Lakes into interior portions of the Southern Tier. This
boundary will finish its passage across the remainder of the area
by late morning/midday. Behind it...our brief run of springlike
weather will give way to a 3-6 hour long period of rain along with
sharply falling temperatures through the remainder of the day...
with readings dropping into the upper 30s to lower 40s areawide
by mid to late afternoon. Expect the bulk of the rain to occur
between now and early to mid afternoon...with the precip then quickly
tapering off from northwest to southeast through the balance of the
day as high pressure and drier air begins building in from the
Upper Mississippi Valley and Upper Great Lakes.

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.


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

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.


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


A strong cold front will finish crossing the region by late
morning/midday. In the wake of the front...a rough 3-6 hour
long period of light to moderate rain can be expected with
VFR flight conditions lowering to IFR to MVFR areawide.

Expect the bulk of the rain to come between now and early to
mid afternoon...with the precipitation then quickly tapering off
from northwest to southeast as high pressure and drier air
begins building into the region...with flight conditions also
improving back to MVFR and then VFR through early this evening.

After that...general VFR conditions are expected to continue
through most of the rest of the night...with a little mixed
precipitation/MVFR conditions becoming possible across the
Southern Tier late.


Thursday...MVFR with mixed precipitation likely across the
Southern Tier and Finger Lakes...and VFR/MVFR with a chance of
rain and snow elsewhere.
Friday...VFR/MVFR with some rain developing.
Saturday and Sunday...VFR/MVFR with scattered to numerous rain
and snow showers.


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.


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 well as a lingering risk for ice jams and related
flooding along area waterways until temperatures drop off this afternoon
and evening.


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



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