Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 220208

Area Forecast Discussion
National Weather Service Buffalo NY
1008 PM EDT SAT MAY 21 2016

Showers associated with a slow moving area of low pressure will
continue to tapering off overnight. Another round of showers will be
possible on Sunday before the low moves off to the east and warm and
dry conditions develop Monday as an upper level ridge moves into the
Great Lakes. This spell of dry and increasingly warm weather is
expected to last through the middle of the coming week before a more
moist and unsettled airmass arrives later in the week.


Showers will continue to diminish in coverage overnight as the mid-
level low weakens and is absorbed into the more powerful circulation
of a developing coastal low currently in the vicinity of the
Delmarva Peninsula. Lingering moisture will likely lead to some low
clouds lingering across the Southern Tier with perhaps an occasional
light shower with generally dry but cloudy conditions elsewhere.
Temperature falls will be limited by the abundant cloud cover with
readings only expected to fall into the upper 40s to lower 50s.

The main upper level trough responsible for this system will drift
across NY while the bulk of the upper level energy dives south
towards VA. While this should shift the bulk of the shower activity
off to our south...with the upper level trough lingering overhead,
another round of showers will certainly be possible. Any scattered
shower activity should be focused from the Southern Tier across the
Finger Lakes to the Western Adirondacks...oriented along the higher
terrain and the upper level trough axis. Elsewhere...look for
generally cloudy skies with some clearing expected across far
western NY late in the day as the upper level trough slowly drifts
eastward and drier air begins to creep into the region. Once again
the clouds will moderate temperatures across the region with highs
ranging from the mid 60s in the Southern Tier to the lower 70s
along the Lake Ontario plains. These readings will still be
slightly warmer than today`s cooler temps as coolest air
associated with the trough will be shifting off to the east.


The persistent trough over New England to the Mid Atlantic state this
weekend will become a cutoff low centered across Virginia on Sunday
night. As upper trough axis and core of the upper low move away from
the region, the cyclonic flow aloft weakens over the Lower Great
Lakes and there will be moderating lapse rates due to warming in the
mid levels, all leading to stabilizing of the atmosphere over our
area. This will encourage a night of fair weather across our region
on Sunday night. Overnight lows will once again be in the middle
to upper 40s.

Beautiful weather can be expected on ridging will nose
northeast from the Upper Great Lakes...extending across southern
Ontario To Quebec. Meanwhile, the closed low will be anchored off
the Mid Atlantic Coast. This will result in a relatively short lived
Rex Block...with our region finding itself within the quadrant of
nicest weather. The resulting sun filled skies will be accompanied
by warmer air 850mb temps of +10C will advect across our
region from the Upper Great Lakes. This will easily support
afternoon temperatures in the mid 70s across the lake plains and
Black River valley with upper 60s to lower 70s well from the lakes
and across higher terrain. These cooler temperatures will be mainly
due to upsloping from northerly winds up to the higher elevations.

The closed upper low will support the development of a coastal low
on Tuesday which will spread a little more cloudiness across the
eastern periphery of the forecast area. The northerly winds will
become more northwesterly, still providing some upslope cooling in
higher elevations, but warmer air across southern Ontario and
western Quebec will will advect into the North Country. 850mb temps
at +10C will still support mid or upper 70s across the North Country
and lake plains with lower 70s across the hills of the Southern
Tier. Low temperatures on Tuesday night will be in the upper 40s to
lower 50s, limited somewhat by the shorter length of night, a mixing
breeze through the night and an increase in dewpoints during the
overnight hours.

Ridging aloft and surface high pressure will be maximized across the
forecast area on Wednesday. This will be the beginning of a
prolonged warm spell as the upper ridge provides widespread
subsidence and mid level temperatures warm with 850mb rising to
+13C. High temperatures on Wednesday will climb to the middle 70s to
lower 80s, and the increase in dewpoints will yield more mild
overnight temperatures with lows Wednesday night in the middle to
upper 50s. As the upper ridge axis approaches the region during
midweek, so will the opportunity for late day and evening
convection. There will be an opportunity for late day through
evening thunderstorms on Wednesday and Wednesday night as a couple
ripples of vorticity move across the upper ridge, from southern
Ontario to the North Country and spreading into western NY during
Wednesday evening and night.


Thursday through Saturday will feature summer-like
weather...complete with increasing humidity and day to day chances
for mainly afternoon showers and thunderstorms.

The overall synoptic pattern will feature a ridge of high pressure
building over the eastern Unites States...this as an upper level low
exits to the east. The main ridge axis will lie across the SE states
and back towards the Central Great Lakes region. At 500 hPa heights
will slowly increase through the long term period...and at 850
hPa...air temperatures will range from +14 to +17c through the

Subtle shortwaves moving through the ridge axis...combined with
increasing instability from building moisture and warmth will
contribute towards afternoon showers and thunderstorms. Hard to
pinpoint which day may feature highest chances for convection...and
thus will have just chance PoPs through the daytime and early
evening hours. If there was a day with slightly less chances for a
shower or thunderstorm it may be Saturday...this as the upper level
ridge axis draws closer to the region...and possibly caps some of
the afternoon convection. Otherwise chances will be place for all
three days...favoring the inland lake breezes over the northern
Niagara Frontier and hilly region east of Lake Erie...and higher
terrain east of Lake Ontario.

The southerly flow will also build the humidity through this period
with uncomfortable levels reached by the end of the week. Dewpoints
will reach to around 60F to the lower 60s. Air temperatures will
likely increase a degree each 500 hPa heights slowly
increase. Afternoon highs will reach into the upper 70s to lower
80s...with the Genesee Valley likely reaching the mid 80s by Friday
and Saturday. There will not be much airflow under the ridge...but a
SW wind will likely develop each day...keeping the City of Buffalo a
few degrees cooler...with the cooling extending out to near the
airport. Along the immediate Lake Ontario shoreline...and then the
western SLV...air temperature will be a few degrees cooler owing to
the still cool eastern Great Lakes.

Overnight lows will drop back into the lower 60s...and with a
similar airmass all three nights expect lows to be similar as


The shower activity will continue to taper off overnight as the main
mid level low weakens and is absorbed by a stronger coastal low
tonight. Nonetheless...lingering moisture enhanced by recent
rainfall should allow for MVFR conditions to linger across the
Southern Tier. Periods of IFR cigs and BR will also be possible
across the higher terrain of the Southern Tier overnight with VFR
conditions hanging on elsewhere.

Another round of showers will be possible Sunday as the parent upper
level trough will remain over the region...however bulk of upper
level energy and hence the main focus for shower activity should
remain well to our SSE across PA and the central Appalachians. Thus
conditions should remain VFR for the bulk of the forecast area on

Sunday Night...VFR with showers ending early.
Monday through Wednesday...VFR.
Thursday...Mainly VFR with a chance of showers and thunderstorms.


A coastal low will develops off the Delmarva Peninsula overnight and
Sunday. Winds will remain light across Lakes Erie and Ontario
through Sunday, with high pressure bringing more light winds through
the first half of next week.





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