Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 251051

Area Forecast Discussion
National Weather Service Buffalo NY
651 AM EDT SAT JUN 25 2016

High pressure stretching from the Great Lakes to New England will
continue to drift slowly east today and become centered along the
east coast Sunday. This will provide a dry weekend with abundant
sunshine and very warm temperatures. A cold front will then cross
the region late Sunday night and Monday with scattered showers and
thunderstorms. A secondary cold front will cross the area Tuesday
with a few more showers and much cooler temperatures.


The first few visible satellite images of the morning show clear
skies across the bulk of the area, with just a few small patches of
clouds across the western Southern Tier and Finger Lakes.

Surface high pressure will remain in place from the Great Lakes to
New England today. Strong subsidence and drying associated with the
high will maintain nearly full sunshine in most areas. A few diurnal
cumulus may develop this afternoon across higher terrain well inland
from the stable lake shadows, especially across the Southern Tier
where a modest increase in moisture in the 850-700mb layer will be
found. Some of the NAM based guidance develops isolated convection
across the Southern Tier this afternoon and evening, but this is a
result of unrealistic low level dewpoint pooling in the model,
leading to implausible instability forecasts. With this in mind have
kept a dry forecast regionwide.

The airmass continues to warm day by day, with 850mb temps around
+14C this afternoon supporting highs in the mid to upper 80s at
lower elevations with the dry ground forcing a forecast at or above
the warmest guidance. Local lake breezes will develop and keep areas
within a few miles of Lakes Erie and Ontario cooler.

High pressure will drift to New England tonight. This will keep
mainly clear skies in place. The developing weak southerly return
flow will keep temperatures a little milder than recent nights, with
lows in the mid 60s on the lake plains of western NY, and mid to
upper 50s across the interior Southern Tier and eastern Lake Ontario


Mid-summer conditions will be in place by Sunday as the thermal
ridge axis shifts across the region ahead of the next approaching
cold front for Sunday night into Monday. 850 mb temperatures will
surge to the 90th percentile for this time of year, about +18C,
which will translate to low 90s for most locations. The cooler
exceptions will include the lake shores and the city of Buffalo
where the lake breezes will help moderate temperatures keeping highs
in the 80s. The warmest temperatures, in the mid 90s, will of course
be in the downslope Genesee Valley and northern Finger Lakes
locations, including Rochester. Moisture will also increase ahead of
the approaching front, with dew points near 60F, which will give it
somewhat humid feel, especially in closer proximity to the lakes.

A weak surface low will move through Ontario Sunday night into
Monday morning and will drag a weak cold front across the the
forecast area. Moisture advection and weak frontogensis will act to
produce a broken line of showers that will slowly work across the
region from west to east from Sunday night through Monday morning.
Continued to advertise likely PoPs for this frontal passage. Removed
the mention of thunder overnight as instability continues to look
rather meager and given the overnight timing. As the front continues
eastward into the North Country and central/eastern NY on Monday
thunder chances will increase, however any convection will likely
quickly exit east of the forecast area. Overall rainfall amounts
from this system won`t put much of a dent into our abnormally dry
conditions, with most locations picking up a tenth to a quarter of
an inch or less. Sunday night will be one of the warmest nights of
the forecast period given the breezy, cloudy conditions ahead of and
along the front, lows may struggle to dip into the upper 60s. The
cold air will be rather slow to arrive, and actually the coldest air
holds up until a secondary front arrives Tuesday. Thus 850 mb
temperatures remain in the mid-teens Monday, supporting highs in the

The secondary cold front arrives Tuesday, ushered in by an upper-
level trough and vort max diving across the Great Lakes. By the time
this wave and associated front arrive, the best moisture will have
been shoved into eastern NY and New England by the preceding front.
Thus shower activity with the frontal passage will rather meager,
with mainly spotty instability showers under the upper-level low
across western NY by Tuesday afternoon. The North Country will be a
bit closer to the better moisture source and could pick up some more
robust showers on Tuesday, especially should the EC solution verify
with keeping that moisture a bit farther back to the west than the
GFS. Otherwise, temperatures take a step back to the mid-70s with
the frontal passage.


The coolest air settles over the region by Wednesday, with 850 mb
temps down to about +9/+10C which will bring highs in the low 70s
for most. The EC remains a bit stronger with the forecast upper-
level low and thus lingering instability showers are possible
especially over the higher terrain.

The next sprawling high pressure system arrives mid to late next
week and will bring a slow warming trend and dry weather across the
region to close out the work week.


VFR will prevail for the 12Z TAF cycle. High pressure will remain
centered from the Great Lakes to New England today. Clear skies will
be the rule in most areas, with just a few patches of cumulus across
the Southern Tier and Finger lakes with bases of 5-6k feet. The
diurnal cumulus across the higher terrain will dissipate this
evening with the loss of daytime heating, leaving clear skies


Sunday Night through Monday...VFR/MVFR with a chance of showers and
Tuesday...Mainly VFR with a chance of a few widely scattered showers
and thunderstorms.


High pressure will remain centered from the Great Lakes to New
England today. The light synoptic scale winds and strong
differential heating will allow local lake breezes to develop, with
winds becoming onshore during the afternoon at less than 10 knots
with flat wave action. High pressure builds east to the eastern
seaboard Sunday. This will allow SSW flow to develop across the
lower Great Lakes for Sunday with winds still 10 knots or less and
flat wave action.

A cold front will cross the area Monday with a secondary cold front
on Tuesday. Winds will increase into the 10-15 knot range along and
behind these fronts with waves becoming a little more choppy, but
still well below Small Craft Advisory criteria. A few widely
scattered thunderstorms are possible Monday and Tuesday with locally
higher winds.





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