Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 242108

Area Forecast Discussion
National Weather Service Buffalo NY
508 PM EDT Fri Mar 24 2017

A slow moving frontal boundary draped across the region will slip
back south of the area tonight and Saturday...before slowly lifting
back north across the region as a warm front Sunday and Monday.
Several disturbances sliding along this boundary will bring frequent
bouts of precipitation through the weekend and early next week...
with cooler temperatures prevailing north of the boundary and
milder temperatures found to its south.


As of late afternoon...regional surface obs show that the surface
warm front extends from Lake Ontario southeastward across the
eastern Finger Lakes...with area radars indicating that its
associated elongated swath of precip has pushed north into the
Saint Lawrence Valley. To the north of the front temperatures
remain locked in the mid 30s to lower 40s across the North Country...
while to its south readings have soared into the 60s from roughly
the Genesee Valley westward...with KDSV the warm spot (68 degrees)
as of this writing.

Latest models continuing to insist that the frontal boundary
will stall by this evening, then head back south across the
region tonight. By Saturday morning expect the boundary to
extend roughly from Dunkirk to Dansville. This will result in a
tight thermal gradient across the area, with temperatures near
or just below freezing across the North Country to near 50
degrees close to the Pennsylvania border. Rain will likely
redevelop across the area ahead of the southward moving boundary
by late evening then persist through the remainder of the night
and through much of the day Saturday as the boundary remains
stalled across the region. This pattern is also likely to result
in at least some patchy fog along and north of the boundary.
Temperatures may cool enough for precipitation to change back to
snow or sleet across the North Country late tonight and Saturday


An unsettled pattern will continue this period as a frontal boundary
oscillates across the Lower Great Lakes.

Saturday night the frontal boundary will sag southward, stalling
across the Southern Tier as a strong Canadian high pressure system
moves into Quebec. This will bring a break in rain showers overnight
to the North Country and locations south of Lake Ontario, except for
the far Southern Tier. Temperatures will fall into the 30s north of
the front and even the mid 20s along the Saint Lawrence Valley where
strong northeast flow from the Canadian high becomes established.
The far corner of the Southern Tier will remain in the mid to upper
40s with scattered rain showers.

For Sunday through Sunday night, the strong low pressure system
currently seen on WV imagery churning over the central plains will
eject northeastward across the Great Lakes and the forecast area as
it starts to get picked up by the mean mid-latitude flow. In the
process, this will bring plentiful Gulf of Mexico moisture advection
and warm air advection sending the warm front northward. This push
of the frontal boundary will be accompanied by scattered rain
showers in the morning across Western NY. As the warm front
progresses northward on Sunday, expect to see a sharp rise in
temperatures across western NY from the 30s in the morning to the
upper 50s to low 60s by mid-day and early afternoon, especially if
there is a well defined break in the precipitation and possibly the
cloud cover. For the North Country, the surface temperatures in the
20s to low 30s in the morning may prove troublesome, as showers
along the front move northward, there could be a period of freezing
rain at the onset of precipitation before surface temperatures rise
into the 40s for the afternoon. The best chance of widespread
rainfall then come Sunday night with the mild, moist airmass in
place ahead of the approaching cold front and vorticity advection
with the parent upper level low. QPF amounts for Sunday and Sunday
night are only expected to add up to a quarter to a third of an
inch, with some locally higher pockets up to a half inch possible.
Temperatures overnight will be very mild, with many locations across
western NY in the upper 40s to around 50, with low 40s in the North

By Monday, a mild airmass will be left in the wake of the largely
cut-off low pressure system exiting to our east along with height
rises. This will result in lingering partly to mostly cloudy skies,
but rain showers tapering off from west to east, and becoming more
widely scattered by the afternoon. In fact, much of western NY will
likely see plenty of dry time by Monday afternoon. High temperatures
will top out in the mid 50s to low 60s across western NY, warmest in
the typical downslope regions of the Genesee Valley and northern
Finger Lakes. The North Country will remain somewhat cooler, in the
mid to upper 40s. Scattered shower chances will remain in place
Monday night as another wave is set to track just to our south.
Temperatures will remain mild overnight, in the 40s for most


The lengthy unsettled period will last into Tuesday as the stalled
complex frontal zone remains nearby. Both the GFS and ECMWF based
guidance suggest one more wave moving along the frontal zone and
passing to our north on Tuesday, producing another round of showers.
Temperatures will remain mild given the northerly low track, with
highs at least into the 50s and possibly into the 60s for the
southern half of the area.

Tuesday night and Wednesday a mid level trough will amplify across
Quebec and finally drive the frontal zone well south of our area,
with moisture and showers diminishing from northwest to southeast.
Cold advection associated with the trough will knock temperatures
back a few notches, with highs in the 40s Tuesday.

A slow warming trend should then ensue for the second half of next
week as the trough over Quebec moves offshore of the Canadian
Maritimes and height rises/weak warm advection overspread the
eastern Great Lakes. Model guidance diverges by next Friday with
respect to the track of the next system. The GFS keeps most of the
energy and deeper moisture suppressed well to the south across the
Ohio Valley and southeast States, while the ECMWF takes a much more
northerly track through the Great Lakes and would be a warmer and
wetter solution. Given the time range and inherent uncertainty, have
just included chance POPS for now.


Expect most TAF sites to remain VFR into early this evening. After
that time...a stalled out frontal boundary draped across Lake Ontario
and the eastern Finger Lakes will slowly drop back southward...with
rain also redeveloping along the boundary over time. As the boundary
slides southward...winds will also shift to the north and northeast...
which in turn will allow IFR or lower conditions in lower stratus
and fog.

During Saturday...expect general IFR/LIFR conditions and rain/drizzle
to continue.

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


A frontal boundary draped across Lake Ontario will slip back southward
tonight and Saturday...with a northeasterly flow developing across the
Lower Lakes region. This will especially be the case on Lake Ontario...
where small craft advisories will likely become necessary later on in
the weekend.





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