Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 230737

Area Forecast Discussion
National Weather Service Buffalo NY
337 AM EDT Mon Apr 23 2018

High pressure will slowly drift off the southern New England coast
today and continue to provide sunshine and much warmer temperatures.
Low pressure moving from the Ohio Valley to New England will then
bring occasional rain showers to the region from late Tuesday
through Wednesday. Dry and cooler weather will return by late in the
week as high pressure builds into the Ohio Valley and eastern Great


Surface high pressure will drift off the southern New England coast
today, allowing for more robust boundary layer warm advection to
develop. This will boost 850mb temps to around +5C in the west and
+3C east of Lake Ontario by 18Z Monday. Sunshine and deep mixing
aided by southeasterly downslope flow will boost temperatures into
the lower 70s on the lake plains and warmer valleys this afternoon,
with mid 60s on the higher hills and east of Lake Ontario. It should
be noted that at this time of year, prior to green-up, high
temperatures often over-achieve on sunny, dry days given the lack of
transpiration from actively growing foliage and grass. With this in
mind, went at or above the warmest available guidance.

The southeasterly surface flow will be strong enough to prevent lake
breezes in most areas with a few exceptions. Winds will likely turn
ENE along the south shore of Lake Ontario from near Braddock Bay to
Youngstown this afternoon, keeping the immediate lakeshore cooler.
A lake breeze will also develop in Jefferson County this afternoon,
keeping the lakeshore cooler there. Strong subsidence and dry air
will keep nearly full sunshine in place today, with just some
passing very thin cirrus at times.

Broad southerly warm advection will remain in place tonight. This
will allow for a gradual increase in mid/high clouds from southwest
to northeast overnight. Any showers will remain south and west of
the area through 12Z Tuesday. The southerly breeze will also keep
temperatures milder than recent nights, with lows in the mid to
upper 40s for the lake plains and downslope areas. 30s will be
relegated to a few cool sheltered valleys in the Southern Tier and
Lewis County where surface winds are more likely to decouple.


A cooler and wetter stretch of weather is in store for the middle of
the week. Tuesday through Thursday a cutoff low, currently over the
deep south, will drift northeastward through the Tennessee Valley to
off the mid-Atlantic coast, while phasing with a robust northern
stream wave that is currently in northern Alberta. The phasing of
these systems will result in a deepening surface low tracking from
the Carolinas Tuesday to New England by Wednesday night, with an
inverted surface trough extended northward toward Lake Ontario by

Tuesday will still be mainly dry as we remain under the influence of
the surface high sliding off the New England coast to start the day.
However, cloud cover will increase from south to north through the
day, along with increasing chances for some scattered rain showers
across western NY by late Tuesday as Atlantic moisture is advected
northwestward by the anomalous easterlies ahead of the low in the
deep south. Little airmass change will occur on Tuesday, with just
more cloud cover and a bit more moisture than Monday, thus high
temperatures will still be largely in the low to mid 60s. The
warmest temperatures on Tuesday will likely be across the North
Country away from the better moisture advection and last to see the
increasing cloud cover. Highs near Fort Drum will likely push the
upper 60s.

Rain chances will increase through Tuesday night, and especially
into Wednesday, as the northern stream wave moves in from the west
and phases with the low exiting the south. The inverted surface
trough extending northwestward from the surface low moving up the
coast, along with the upper-level wave pivoting near to just south
of the forecast area will help focus a period of fairly widespread
rain across the region. Forecast models continue to struggle a bit
with the complex merger of the system, with the GFS remaining of the
faster more progressive side of the global model consensus. Given
the consensus between the EC/GEM/NAM of a stronger and thus slower
merger, have aired toward the higher side of precipitation totals
(two thirds of an inch up to an inch through Wednesday night), and
toward rain showers lingering Wednesday night and into Thursday with
the wrap around moisture in the northwest, upslope flow. Rain
showers will taper off late Thursday from west to east. Wednesday
and Thursday will also run a bit cooler with the upper-level low
passing overhead along with cloudy and wet conditions keeping
daytime highs in the 50s. Overnight lows will remain the mid 30s to
low 40s.


Behind the departing mid-week storm system, overall troughing will
remain in place across the northeast into the weekend. While this
will dictate an overall cooler pattern with chances for rain shower
showers, we will see a brief break of pleasant weather Friday as a
shortwave ridge builds across the forecast area. This will allow for
mainly dry conditions Friday with high temperatures in the upper
50s, if not pushing the 60 degree mark for many location. Behind
this shortwave ridge, another sharp wave dives in from the upper
Great Lakes to the forecast area Friday night into Saturday. This
will bring more rain shower chances to start the weekend along with
cooler temperatures back into the low to mid 50s for Saturday and
Sunday in its wake.


VFR will prevail today and tonight as high pressure drifts slowly
east off the southern New England coast. Just a few thin wisps of
high cirrus will cross the region today, with a gradual increase in
mid and high clouds from southwest to northeast later tonight.


Tuesday...VFR with a chance of afternoon showers.
Tuesday night and Wednesday...Areas of MVFR/IFR with occasional
Thursday...MVFR improving to VFR with a chance of showers.


High pressure will drift slowly east off the southern New England
coast today and tonight. This will continue to provide light winds
in most areas today, although easterly winds will increase locally
at the west end of Lake Ontario this afternoon with choppy
conditions west of Rochester. Otherwise fairly light winds will
continue tonight through the middle of the week as weak low pressure
moves from the Ohio Valley to southern New England.


High pressure will drift slowly off the southern New England coast
today. This will keep a warm and very dry airmass in place across
Western and North Central New York. Minimum Relative Humidity will
drop to around 20 percent in Western New York, and 15 percent east
of Lake Ontario this afternoon. Winds will generally range from 10
to 15 mph today, with the strongest winds on the ridges of the
western Southern Tier and western Finger Lakes. Low pressure will
then move from the Ohio Valley Tuesday to near Long Island on
Wednesday. The dry airmass Tuesday morning will give way to
increasing humidity later Tuesday afternoon and evening. A few light
showers will develop Tuesday afternoon, followed by widespread
wetting rainfall Tuesday night and Wednesday.





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