Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 210851

Area Forecast Discussion
National Weather Service Buffalo NY
451 AM EDT Wed Jun 21 2017

Weak high pressure will build into our region today bringing a
return to mainly dry conditions through tonight. Broad low pressure
will then slide east across central and eastern Canada Thursday and
Friday...while bringing a return to increasingly unsettled weather
to close out the work week. A trough shifting over the Great Lakes
in the wake of the low pressure will continue a threat for unsettled
weather through the weekend.


The main band of showers has shifted into eastern/southern NY early
this morning with only a few trailing isolated showers shifting
across the western Southern Tier and eastern Lake Ontario regions.
A slow clearing trend to sky cover is building across western NY
behind the rain showers as drier air shifts into our region. Expect
this clearing trend to continue to spread west to east across the
Finger Lakes behind the departing surface trough. Temperatures will
start the day in the mid to upper 50s with areas along the immediate
lakeshores closer to 60.

The weather for the summer solstice will be very comfortable with
mainly dry conditions expected. This is courtesy of weak surface high
pressure slowly building east across our region from the upper Great
Lakes. Daytime mixing should support some fair weather cumulus
clouds developing away from stable lake breezes. The exception to
the dry weather is across the Saint Lawrence Valley and far North
Country where lingering moisture and upslope flow along with a
closer proximity to the eastward shifting trough axis may produce a
few afternoon showers. Have also left a slight chance of a shower
along a lake breeze convergence boundaries which near-term guidance
such as the HRRR indicates will set up near the Niagara and Erie
county border. Otherwise, expect very comfortable temperatures and
humidity levels thanks to cooler air aloft within the trough. Highs
are expected to top out in the lower to mid 70s with dewpoints in
the 50s. Winds will be 5-15 mph from the west.

The center of high pressure will shift along the NY/PA border
tonight. Any leftover cumulus in the evening will dissipate around
sunset with mainly clear skies expected overnight. The airmass will
remain dry with light winds supporting good radiational cooling.
Expect lows to dip into the mid 50s on the lake plains and upper 40s
to around 50 in the cooler Southern Tier valleys and Tug Hill. There
may also be some Southern Tier river valley fog developing during
the second half of the night.


High pressure over the area early Thursday will be quickly replaced
as dynamics associated with the next system begin to manifest over
the Great Lakes. While the early morning hours should be dry,
scattered convection is expected to develop by midday or early
afternoon in western New York along the nose of the low level jet
and surface warm front as a surge of higher theta-e air presses into
the area. Poor lapse rates preclude any severe concern, although a
few rumbles of thunder cannot be ruled out. The surge of warmth and
moisture will favor substantially more humid conditions on Thursday.
Expect highs around 80 in most areas and mid 70s North Country.

Scattered showers and isolated thunderstorms will continue through
early Thursday night as the warm front crosses the region. Coverage
should take on an uptick after midnight coincident with resurgence
of a nocturnal low-level jet. Persistent warm air advection and
cloud cover will keep temperatures on the mild side, with lows in
the mid 60s on the lake plains and lower 60s interior Southern Tier
and North Country.

Additional showers and scattered thunderstorms will continue Friday
as the area resides well within the warm sector ahead of approaching
cold front. Will have to watch for the potential for stronger storms
due to moderate instability and vertical wind shear. Highs on Friday
are expected to be in the upper 70s to lower 80s.

The cold front will move across the area Friday night, with showers
and scattered thunderstorms ending from west to east with the cold
frontal passage. Fairly strong cold advection after midnight and the
arrival of a drier airmass will allow lows to drop to the upper 50s
to lower 60s in most areas by daybreak Saturday. On Saturday
subsidence in the wake of the cold front and mid level shortwave
should bring a mainly dry day with mid level drying supporting
increasing amounts of sun. A cooler airmass builds into the region
again, with highs in the mid 70s at lower elevations and around 70
on the hills.


Long range models are in good agreement on a overall broad troughing
pattern over the Hudson Bay through the weekend and into early next
week. The forecast area will be located on the southern periphery of
this broad low, and generally embedded within the west-southwesterly
flow aloft initially. This will allow for several fast-moving
Pacific sourced shortwaves embedded with the flow to cross near the
region. The day-to-day temperature trend will be generally cooler
through the weekend and into the start of next week as the trough
axis nears and crosses the region. Scattered showers and
thunderstorms are likely at times with the wave passages, with ample
dry time in-between.

Overall the weekend will be mainly dry with shower and thunderstorm
changes increasing through the day Sunday into Sunday night as a
cold front moves across the region. Cooler drier air will filter
into the region for the start of the work week behind a cold front
passage Sunday night. Latest model runs have trended cooler yet with
a more amplified trough for the beginning of next week. High
temperatures may well stay in the 60s Monday into Tuesday.


The band of showers has pushing east into eastern/southern NY near
09z. Outside of the low risk of an isolated shower, mainly VFR
conditions are in place across the region. Some limited MVFR cigs
are found lingering at KART and IFR Vis in development of fog due to
wet ground is showing up at KJHW. Mainly clear skies working across
the Niagara Frontier will continue to spread east with most areas
seeing clearing toward daybreak.

After sunrise, VFR should be widespread with clearing skies as high
pressure builds over the lower Great Lakes. Expect diurnally driven
cumulus to develop during the late morning/early afternoon, with VFR
bases around 5k feet. A widely scattered shower cannot be ruled
out near ART which will be closest to a departing upper level
trough. VFR is expected under clear skies tonight although some
Southern Tier River Valley fog may develop after 22/06.

Thursday...Mainly VFR with a chance of showers and
Friday...VFR/MVFR with showers and thunderstorms likely.
Saturday...Mainly VFR.
Sunday...Mainly VFR with a chance of showers.


High pressure will cross the Lower Great lakes through today and
tonight. This will result in light to occasionally moderate winds
with waves 1-3 feet through midday, then diminishing winds and waves
will follow this afternoon and tonight.

Light winds and waves will continue on Thursday then increase again
Thursday night and Friday as a storm system passes across the
Central Great Lakes with its associated warm/cold fronts cross the
eastern Great Lakes. Expect conditions to be just below Advisory
criteria through Friday and Saturday.





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