Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 221422

Area Forecast Discussion
National Weather Service Buffalo NY
1022 AM EDT Wed Mar 22 2017

Behind an arctic front, cold air will flow over the eastern Great
Lakes region today, producing air temperatures that are more like
that of January. Scattered lake effect snow southeast of Lake
Ontario this morning will end as dry air pushes across the lakes.
Air temperatures will then rebound markedly tomorrow and Friday as
much warmer air works its way back into our region...with an
extended period of wet weather set to begin Friday and last right
through early next week.


Regional radars this morning display snow showers waning across the
Southern Tier, while a few flurries and light snow showers fly SE of
Lake Ontario.

For today lake effect snow will peak this morning southeast of the
lakes, as lake parameters very briefly become favorable for snow.
Any additional accumulation will be minor mainly SE of Lake Ontario.

A large area of high pressure over the western Great Lakes
will push much drier air across our region today, ending lake effect
snow, while also encouraging mostly sunny skies. Despite this
sunshine, 850 hPa temperatures in the low negative teens to around -
20C (2 SD below normal) will produce surface temperatures that will
struggle to rebound into the mid 20s this afternoon. Winds will also
become gusty this afternoon as the mixing layer increases. Gusts
upward to 35 mph will be possible. The northwest winds when combined
with the cold temperatures will bring wind chills in the single
digits through much of the day.

Tonight this area of high pressure will cross the central Great
Lakes, reaching WNY late in the night. Winds will decreases this
evening with the setting of the sun, while clear skies allow for
overnight lows to drop back into the teens near the lakes, and low
single digits inland.


The progressive pattern that we have experienced the past week or so
will become somewhat blocked up as we push into the weekend. This
can be a good thing if you are parked under the heart of a ridge...
but if not...then you could be in for an extended period of
unsettled weather. In this particular case...our region will
unfortunately be on the northern fringes of a ridge that will become
pinched between a deep closed low over far eastern Quebec and a slow
moving stacked low over the Upper Mississippi Valley. The lack of
shear found in the lower levels within this synoptic pattern will
then encourage a strengthening surface boundary to become aligned
with the flow...stalling over/near our forecast area in the process.
The result will be a prolonged period of unsettled weather with the
potential for rainfall in excess of an inch and a half. Luckily...
this rain will fall over several days so the risk for any hydro
problems will be minimized. Digging into the details...

This period will start off with one last nice strong
Canadian high pressure will gradually exit to our southeast. This
will support one last nice day across the sun filled
skies and warming temperatures aloft will send temperatures back
towards normal levels. While still a little below will
not be nearly as cold as Wednesday as afternoon temperatures will
climb through the 30s to near 40 over the western counties...while
it will be a little chillier east of Lake Ontario with max temps
close to the freezing mark.

Thursday night...a broad ridge over the Mississippi Valley will push
east to the Ohio Valley and Great Lakes. Ahead of this feature...a
tightening baroclinic zone will become established from Wisconsin
and Lower Michigan to Lake Erie. The associated isentropic lift
along this elevated boundary will generate some showers...with some
of that activity spreading across our far western counties. Any
light pcpn will fall as a mix of light rain or wet snow showers.
Given the strength of the warm advection...temps after midnight will
actually start to rise...climbing back above freezing for counties
near Lake Erie.

Conditions will further deteriorate on the strengthening
baroclinic zone will evolve into a fairly pronounced warm frontal
boundary. This feature will push north across our forecast area
during the course of the day and serve as a focus of lift for the
wealth of moisture being pumped into the region from a 40kt low
level jet. The pcpn could initially start as a bit of wet snow...but
will quickly transition to just rain. The 60 mile wide band of pcpn
will push north during the course of the midday and afternoon...with
the axis of rain aligning with Lake Ontario and the North Country by
late in the day. This means that the Srn Tier will could be far
enough into the warm sector for the bulk of the pcpn to end...or at
the least considerably taper off. Max temperatures on Friday will
range from the low to mid 50s over the Southern Tier to the lower
40s north and east of the Tug Hill.

Friday night...while a mid level ridge will remain pinched in place
over the Lower Great Lakes...the conspicuous sfc frontal boundary
stretched the length of Lake Ontario will slowly be pushed south by
a strong area of high pressure near James Bay. The associated swath
of steadier rain will settle south to the counties lining the south
shore of Lake Ontario with an increasing chance for rain also across
the Finger Lakes and Genesee Valley. Colder air pushing south in the
wake of the slow moving boundary could support some mixed wintry
precipitation after midnight for the Eastern Lake Ontario region.

The pronounced frontal boundary will continue to push south to the
Pennsylvania-Maryland during the day Saturday...while a tight H925-
85 thermal gradient will support fairly strong frontogenetic forcing
over much of our forecast area. This will keep widespread rain over
the western counties...while there could actually be some
improvement over the North Country. Have backed off the pops for
much of Jefferson and Lewis counties while increasing pops to
categorical across the Srn Tier. There will continue to be a fairly
large temperature gradient over the region with daytime highs
ranging from just the upper 30s in the Thousand Islands region
to the low to mid 50s right along the Pennsylvania a border.

As the slow moving stacked low drifts closer to the Lower Great
Lakes saturday night...the boundary will stall and eventually be
pushed back towards the north. This will spread the rain back
towards Lake Ontario...with a wintry mix once again possible over
the North Country.


Unfortunately...there is high confidence that the wet...unsettled
weather will remain in place across western and north central New
York during this period.

The persistent stacked storm system over the mid west will gradually
`open up` and drift across the Lower Great Lakes later Sunday into
Monday. While the baroclinic zone responsible for much of the
previous days pcpn will be shoved out of the region...significant
hgt falls and the introduction of mid level energy will fuel
additional rainfall.

Our region will experience a very brief lull in the inclement
weather Monday night in the wake of what will then be a passing mid
level trough. Will only have chc pops in place for rain and wet snow
showers...although the majority of the night could very well be pcpn

On Tuesday...while the medium range ensembles are not in agreement
as to the strength of the next shortwave...they generally agree that
another disturbance will drop southeast across the Lower Great
Lakes. This will generate a renewed round of shower activity.


For the 12Z TAFS VFR flight conditions are found across the region,
and these conditions should prevail through the TAF cycle for the 5
TAF sites. There may be a little lingering MVFR flight conditions in
snow SE of Lake Ontario this morning, but this activity should
remain just to the east of KROC.

Much drier air will flow in from the northwest today, ending
scattered snow showers and allowing for VFR flight conditions to
prevail. It will become a little breezy, with winds reaching into
the 20 knots range.

Tonight sprawling area of high pressure will reach the region with
lighter winds and VFR flight conditions continuing.


Friday...Deterioration to MVFR/IFR with mixed rain and snow
developing...then changing over to all rain.
Saturday and Sunday...MVFR/IFR with rain likely.


Northwest winds will maintain small craft advisories on the lakes
and lower Niagara River today. High pressure will build towards the
lakes tonight, allowing for winds and waves to subside, with SCA
lingering longest along the SE Lake Ontario shoreline.

This high pressure will then build across the region Thursday while
bringing a return to light winds and negligible waves.


MARINE...Small Craft Advisory until 2 PM EDT this afternoon for LEZ040-
         Small Craft Advisory until 2 PM EDT this afternoon
         for LOZ030.
         Small Craft Advisory until 2 AM EDT Thursday for LOZ043-
         Small Craft Advisory until 5 PM EDT this afternoon for



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