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000
FXUS61 KBUF 270635
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
235 AM EDT Tue Jun 27 2017

.SYNOPSIS...
Unseasonably cool temperatures with showers and thunderstorms will
continue through today. The upper level disturbances responsible for
the cool and unsettled weather will move east Wednesday with a
return to warmer temperatures by mid-week.

&&

.NEAR TERM /THROUGH TODAY/...
A few broken waves of shower and thunderstorms are showing up on
radar at 2am over Lake Erie and adjacent bordering counties. These
are being driven by a sharp shortwave trough over the west end of
the lake and a pool of cold air aloft creating steep low and mid
level lapse rates. Not much going on with mainly clear skies still
in place for much of central NY.

While we continue to forecast lake effect activity consolidating
into a more organized plume this morning as suggested by some
mesoscale models, latest radar trends leave some question to
whether organized lake effect will in fact occur or if we will
just see several waves of convection down Lake Erie and into
western NY. Given the very efficient nature of lake induced pcpn
(esp rain)...rainfall rates in excess of an inch an hour will
be possible. Localized flooding will not be out of the question
if better organized activity develops.

Off Lake Ontario...the airmass will not be quite as unstable and
will have less fetch to work with...so the lake effect rain showers
are not expected to be as organized nor as heavy. Will keep chc pops
in place for much of the Eastern Lake Ontario region...especially
north of the Tug Hill.

Outside of these waves of convection or a more organized development
of lake effect...it will be partly to mostly cloudy and generally
rainfree. Temperatures will bottom out between the low-mid 50s on
the lake plains to the mid and upper 40s across the Southern Tier
and for sites est of the Tug Hill.

After sunrise...the lake effect rain will weaken and dissipate as
the strong late June heating will break apart the lake driven
convection. Nevertheless...scattered showers and thunderstorms can
be expected as the core of the Lake Huron shortwave will pass
directly across our region. H85 temps in the vcnty of 4c will once
again establish very steep low level lapse rates...so any subtle
boundaries will be able to focus convection that could support
torrential downpours and small hail. Temperatures this afternoon
will only make it into the 60s.

&&

.SHORT TERM /TONIGHT THROUGH THURSDAY/...
Following the upper shortwave, lingering showers will dissipate
off Lake Erie Tuesday Night while those off Lake Ontario will
persist through the night, albeit weakening towards daybreak.
It will be another cool night with lows generally dropping into
the low 50s and interior valleys down into the upper 40s.

Wednesday will begin to transition to a bit of a warmer pattern as
high pressure moves across the Ohio Valley and a west to
southwest flow develops across the region. Expect fair weather
across much of the region with the exception of the north
country where the lingering cyclonic flow aloft will keep more
clouds and the risk of showers through midday. Temperatures,
while somewhat milder reaching into the low 70s will still be
below normal.

On Thursday the first in a series of surface waves will bring the
likelihood of showers and thunderstorms and the threat of locally
heavy rain. Temperatures continue their slow upward trend with highs
Thursday in the mid to upper 70s.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
A series of systems will affect the region from Thursday night
through at least Saturday and possibly Sunday.  As is often the case
during the summer, rainy periods are not expected to last too long
and there will be several-hour periods of dry weather, but not long
enough to keep any particular day complete dry any part of WNY.
Thus expect at least a chance of showers for each 12 hour
period through Sunday.

Thursday night...The first of a series of systems should move
through on Thursday and drop a frontal system across the region
during or by Thursday night. Thus have a likely chance of showers
and possible thunderstorms in the forecast.

Friday...The frontal system should continue into PA with weak
ridging aloft.  This should mean a lower threat for showers overall,
but still non-zero.  The lowest threat should near/N of Lake Ontario
while areas toward the PA border will have a higher threat for
measurable rain.

Friday night and Saturday...The next system will move into the Great
Lakes region and will drag the frontal band back north (warm front)
across the region.  This will be followed by another frontal system
later on Saturday (cold front).

Saturday night and Sunday...Finally the last shortwave associated
with the long wave trough over the east will bottom out over the
Great Lakes region.  Expect a continued threat for showers, with
some lake shadows east of the lakes for Sunday.

Sunday night and Monday...this period should be dry with weak high
pressure moving overhead. This isn`t a guarantee this far out,
but if the timing of the current pattern holds, the natural
progression should be subsidence behind the Sunday system, with
the exception of isolated summer convection on lake breeze
convergent regions by Monday afternoon.

Daily temperatures won`t stray too far off normals for this time of
year, with highs in the mid 70s to near 80 and lows mostly in the
60s.  Humidity levels will vary, with some nights possibly
warranting A/C while in the warm sector, but at this time don`t see
any extreme sultry days or nights for late into the week/weekend.

&&

.AVIATION /07Z TUESDAY THROUGH SATURDAY/...
Overall VFR conditions are expected to prevail through today but not
without some convection/lake effect to contend with. Several waves
of lake enhanced convection will track across Lake Erie and move
over KBUF/KIAG through the morning. Moderate to heavy rain is
certainly possible within any more organized structured band if it
in fact does develop which could produce TEMPO MVFR conditions at
KBUF/KIAG/KJHW through 12z.

After sunrise...the lake enhanced convection will fall apart during
the initial daylight hours. The attention will then turn to more
scattered showers and thunderstorms as the core of a mid level
disturbance will pass over the region. Again...while short lived
MVFR conditons will be possible with any of the storms...VFR
conditons will prevail.

High pressure will build over the region
tonight with any lingering showers during the evening tapering off
with VFR and some clearing developing.

Outlook...

Wednesday...Mainly VFR.
Thursday through Saturday...VFR/MVFR with a chance of showers
and thunderstorms.

&&

.MARINE...
The main concern for this morning is with a few waves of lake-
enhanced showers and thunderstorms that are tracking across Lake
Erie ahead of an upper level disturbance. These could bring some
gusty winds/small hail and possibly waterspouts.

After sunrise...a persistent southwest graident will once again
support gusty winds as high as 30 knots on Lake Erie. A small craft
advisory remains in place for this body of water...and it is
possible that the BUF Harbor and Upper IAG River will once again
have to be added.

Lighter winds will promote sub-advisory wave action on the lakes
from tonight and Wednesday. Winds and waves will again increase
Thursday ahead of the next frontal system pushing toward the eastern
Great Lakes.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Beach Hazards Statement through this evening for NYZ019-085.
MARINE...Small Craft Advisory until midnight EDT tonight for LEZ040-041.

&&

$$

SYNOPSIS...AR/SMITH
NEAR TERM...RSH/SMITH
SHORT TERM...LEVAN
LONG TERM...ZAFF
AVIATION...RSH/SMITH
MARINE...RSH/SMITH