Area Forecast Discussion
Issued by NWS Buffalo, NY

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000
FXUS61 KBUF 232114
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
514 PM EDT Sun Apr 23 2017

.SYNOPSIS...
A sprawling area of high pressure across the Great Lakes will
continue to provide for fair weather through Monday evening. A slow
moving area of low pressure moving up the Eastern Seaboard will
spread showers into New York state Monday night into Tuesday, with
much warmer and drier weather returning by the middle of the week.
Chances of showers and thunderstorms then return late week into the
weekend.

&&

.NEAR TERM /THROUGH MONDAY/...
High pressure extending across the Great Lakes from the central
Mississippi valley to New England has resulted in beautiful spring-
time weather today. This fair weather will persist through tonight
and Monday for much of western and central New York, with just a few
stray clouds sneaking in from the south late in the day Monday.
Clear skies and light winds tonight may once again briefly result in
some patchy fog in the valleys of the Southern Tier around daybreak.

The one area that will see the fine weather subtlety interrupted
will be the North Country. A band of clouds associated with a cold
front is showing up on satellite imagery extending from central
Quebec southwest to just east of Georgian Bay. This band of clouds
will continue to press south to roughly the northern shore of Lake
Ontario by late tonight before stalling out. The cloud shield will
yield partly to mostly cloudy skies in the North Country from late
evening onwards, with clearing not taking place until Monday
afternoon.

Regarding temperatures, with high pressure and light winds promoting
radiational cooling tonight, look for temperatures to easily fall
into the upper 30s to low 40s. Temperatures will feature a gradient
on Monday. Readings will run a few degrees warmer across portions of
the Southern Tier, thanks to increasing 850mb temps and
northeasterly flow. On the other hand, areas along the southern
shore of Lake Ontario, north of the NY Thruway will likely run
several degrees cooler, due to this same northeasterly flow
enhancing the Lake Ontario lake breeze and advecting cooler lake-
modified air inland. Thus, expect highs to range from near 70
degrees near the Pennsylvania border to around 50 near the Lake
Ontario shoreline, with mid-50s to low 60s in the North Country,
where the lingering effects of the cold front will depress
temperatures somewhat.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/...
Monday night should start off dry with the region under the
influence of weak ridging. This ridge will start to break down late
in the night when a weak closed low across the mid-Atlantic nudges a
bit closer to the area. A modest 40kt LLJ will increase the 850mb
flow and transport Atlantic moisture into the area. Model consensus
develops showers along this boundary late Monday night. Showers
should become more widespread Tuesday morning, then diminish as the
as the axis of the LLJ lifts north of the area Tuesday afternoon.
These showers should taper off south of Lake Ontario by late
afternoon, while lingering into Tuesday evening east of Lake
Ontario. Despite likely PoPs in many areas, showers only last a
couple hours so Tuesday will be far from a washout.

Temperatures will be seasonably cool Monday night, with lows mainly
in the lower to mid 40s. Highs Tuesday will generally be in the
upper 50s to lower 60s, with mid 60s across the lake plains west of
Buffalo where downsloping and a partial clearing will help warm
things a bit.

The region will be in between the weakening coastal low and an
approaching trough late Tuesday night through Wednesday night. This
will keep Western New York dry, with mid-level riding supporting
a clearing trend Wednesday afternoon and night.

Despite some differences in guidance, there is little doubt that
temperatures will be above normal Wednesday. Expect highs in the
70s, with a weak southeast flow and associated downsloping bringing
the warmest temperatures to the lake plains. This also will help
limit the inland extent of the lake breeze and keep cooler
afternoon temperatures very close to the lakeshores. Given model
differences the forecast sticks close to model consensus, but does
enhance downslope influences where are likely to be missed by lower
resolution guidance.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
Thursday will likely have a summer feel to the day as a narrow 500
hPa ridge extends northward, between a cut-off low off the SE New
England coastline, and digging trough across the Midwest. Much of
Thursday will be dry, but as this upstream trough, with moisture
pooling ahead of a cold front nears, showers and thunderstorms will
start to blossom through the afternoon and evening hours. Activity
at first will likely be along lake breeze boundaries across WNY,
then as the cold front crosses Thursday night, there will be chances
for storms everywhere. A southerly wind will bring 850 hPa
temperatures spiking towards +15 to +18C across the region and this
should bring a very warm day to the region, with most areas reaching
into the 80s.

It will then turn cooler, and less humid later Thursday night and
into Friday behind the cold front. Some lingering moisture towards
the SE region of the forecast area may allow for an afternoon
showers or thunderstorm, but the bulk of Friday appears to be dry.

Another storm system, with a warm frontal boundary nearing the
region next weekend will bring the next threat of rain. There will
be chances for showers and thunderstorms both days with the frontal
boundary nearby. Temperatures both weekend days will likely average
above seasonal normals.

&&

.AVIATION /21Z SUNDAY THROUGH FRIDAY/...
Widespread unlimited VFR conditions will prevail across much of the
forecast area through Monday, thanks to high pressure sitting over
the Great Lakes. A cold front swinging down out of Canada will stall
just north of Lake Ontario, spreading mid and high clouds across the
North Country tonight, but cigs should remain VFR, perhaps with some
scattered MVFR clouds later tonight. Otherwise, VFR conditions will
prevail.

Outlook...

Monday Night...Mainly VFR with a chance of showers.
Tuesday...Mainly VFR with showers likely.
Wednesday...VFR.
Thursday...VFR/MVFR with a chance of showers and thunderstorms.
Friday...Mainly VFR with a slight chance of showers and
thunderstorms.

&&

.MARINE...
Northeast winds will freshen later tonight on Lake Ontario resulting
in Small Craft Advisories along the south shore for Monday. This
increase in winds and waves is due to a cold front approaching from
the North and the pressure gradient tightening over the lake as a
slow moving surface low moves up the East Coast. Winds and waves on
Lake Erie are not expected to reach advisory levels as the winds are
parallel with the southern lake shore.

Winds will veer to the east Tuesday, as a ridge across the region
becomes re-oriented, shunting most of the wave action to Canadian
waters. By mid-week, conditions on the lakes will become more
tranquil as the pressure gradient relaxes.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...Small Craft Advisory from 5 AM to 8 PM EDT Monday for
         LOZ042>044.

&&

$$

SYNOPSIS...SMITH/WOOD
NEAR TERM...SMITH/WOOD
SHORT TERM...APFFEL
LONG TERM...THOMAS
AVIATION...SMITH/WOOD
MARINE...SMITH/WOOD



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