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356
FXUS61 KBUF 191052
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
652 AM EDT Sun Aug 19 2018

.SYNOPSIS...
High pressure will provide dry weather with comfortable humidity and
seasonal temperatures through Monday. An unseasonably deep low
pressure system is forecast to shift west then north of New York
through Tuesday. This storm will bring widespread showers and
chances for thunderstorms with heavy rainfall possible. A few
showers may linger into Wednesday before another area of high
pressure brings a return of fair weather Thursday and Friday.

&&

.NEAR TERM /THROUGH TONIGHT/...
Satellite imagery this morning shows some patches of low clouds
across portions of western NY with more widespread low cloud cover
over the Finger Lakes into CNY. Clear skies are in place east of
Lake Ontario. Some thin high level smoke is also likely lingering
but is not being picked up by IR imagery. High pressure is centered
over central Quebec with a surface ridge extending southwest into
into the lower Great Lakes. This ridging is providing for rain-free
conditons with light winds. River valley fog across the western
Southern Tier will dissipate through the morning hours.

It will be less humid today under northeast flow with dewpoints
running within a few degrees either side of 60F and comfortable air
temperatures topping out in the mid 70s to lower 80s. Outside of
some lingering morning stratus then diurnal cumulus developing
inland from the lakes, some high level smoke from western wildfires
may again be observed across our area as suggested by the HRRR
Vertically integrated smoke model.

Tonight, the center of high pressure shifts over Newfoundland with
fair weather continuing. Look for mainly clear skies for most with
some low stratus possibly limited to the interior western Southern
Tier. River valley fog is expected to again develop with just light
southeast winds. Lows will again dip to within a few degrees of 60.

&&

.SHORT TERM /MONDAY THROUGH WEDNESDAY NIGHT/...
Monday surface high pressure over New England will continue to
influence our region with fair weather, mostly sunny skies and
temperatures rising into the upper 70s and lower 80s.

The weather pattern will turn more active Monday night through
Wednesday as a season strong storm system, and impacts along its
associated warm and cold fronts pass through our region.

Monday night an upper level low will be spiraling towards the
Central Great Lakes from the mid Mississippi Valley. This feature
will bring a surface low to near southern Lake Michigan, with a warm
front extending eastwards towards WNY. Rain showers developing
within instability aloft will be possible near Lake Erie and inland
across the Niagara Frontier and So. Tier after midnight...with rain
becoming likely across Chautauqua county by the start of Tuesday.

Showers and a few thunderstorms will expand across our region
through the day Tuesday as another shortwave dipping southward from
Canada produces height falls aloft, deepens the surface low and
enhances low level convergence. Aiding in lift will be the right
entrance region to a 110 knot 250 hPa jet whose axis will be
oriented northeastward across southern Ontario and Quebec. Morning
clouds and rain showers will limit the amount of daytime
destabilization, though with the surface low now deepening as it
passes by to our NW, it will enhance the low level wind field such
that there may be a risk for severe thunderstorms later in the day
Tuesday. This will most likely be well south of the warm front, and
ahead of an inbound cold front...across the Ohio Valley and towards
the western So. Tier...which is presently outlined in a Slight Risk
for Severe Storms by SPC. Of concern also will be heavy rain, with
PWATS again nearing 2 inches. The increase in low level winds will
keep storms moving, but any training of storms over the same region
could bring an isolated flood threat.

A surface cold front will cross our region Tuesday night with
additional showers...though very little instability aloft will limit
thunder chances. Another jet aloft, this across the Ohio
Valley...whose left exit region will be near our region will again
bring additional synoptic lift to aid in precipitation formation.

Behind the front 850 hPa temperatures will lower into the single
digits Celsius across much of the region by the end of Wednesday.
The axis of an upper level trough will pass across the region
Wednesday, maintaining chances for scattered showers. The cooling
aloft will also bring a response from the lakes, with lake enhanced
showers downwind of the lakes. Bountiful clouds through the day
Wednesday combined with the pool of cold air aloft will make this a
cool day, with highs in the upper 60s to lower 70s...which is 5 to 8
degrees below normal. Drier air building towards the region
Wednesday night combined with the pool of cold air aloft being
displaced to the east will end much of the showers...though a slight
chance for a few lake effect sprinkles or light rain showers will
continue.

&&

.LONG TERM /THURSDAY THROUGH SATURDAY/...
This period will feature a return to pleasant weather as high
pressure ridging aloft builds towards the Eastern Great Lakes behind
a recently departed mid level trough of low pressure.

Thursday will start cool with a few nuisance lake effect clouds, and
possible sprinkles/light showers starting the day. The building
ridge will bring day to day increasing warmth, with highs in the mid
70s Thursday topping out in the mid 80s by Saturday. Humidity will
remain comfortable through the period, and it will not be until
Saturday, ahead of another storm system that some stickiness returns
with dewpoints rising into the lower 60s. A few showers will be
possible later in the day Saturday as another shortwave rides
through the Central Great Lakes and towards James Bay.

&&

.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
VFR ceilings with patches of lower level stratus are showing up
across portions of western NY and the Finger Lakes region. VFR is
expected to continue this morning at most terminals. Saturated
ground from recent rainfall and calm to light winds has led to
patches of fog and low stratus mainly in the western Southern Tier
river valleys including some IFR at KJHW.

Surface ridging from high pressure over eastern Canada will continue
to provide fair weather through today and into tonight. Some VFR
level diurnal cumulus is likely inland from the lakes while high
level smoke will likely linger from western wildfires. Some river
valley fog may again develop across the western Southern Tier late
tonight possibly impacting KJHW.

Outlook...

Monday...VFR.
Tuesday...MVFR. Showers and thunderstorms likely.
Wednesday and Thursday...Mainly VFR. A chance of showers.

&&

.MARINE...
High pressure will continue to provide for fine boating conditions
on the lakes today and Monday. On Tuesday a unseasonably deep
surface low is forecast to track north across the central Great
Lakes with southerly winds picking up on the eastern Great Lakes.
There is a chance of advisory level winds and waves but the
southerly direction should direct the worst into Canadian waters.

A sharp cold front is forecast to cross the lower Great Lakes
Tuesday night which will bring westerly winds and higher waves.
Small craft advisories are most likely on Wednesday for the eastern
end of Lake Ontario. High pressure will return for the end of the
week with a return of fair conditons.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...None.

&&

$$

SYNOPSIS...Smith
NEAR TERM...Smith
SHORT TERM...Thomas
LONG TERM...Thomas
AVIATION...Smith
MARINE...Smith