Area Forecast Discussion
Issued by NWS Buffalo, NY

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000
FXUS61 KBUF 280252
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
1052 PM EDT Thu Jul 27 2017

.SYNOPSIS...
A weak cool front will push across the region early tonight. Notably
less humid conditions will follow for the next several days...as
expansive high pressure will build across the Upper Great Lakes.
While our forecast area will be able to enjoy fine weather through
the weekend...an unusually well organized mid summer storm system
will dump excessive rains over parts of Pennsylvania and the mid
Atlantic region.

&&

.NEAR TERM /THROUGH FRIDAY/...
A weak cool front will push south across our forecast area tonight.
While there may be a few showers or even an isolated thunderstorm
during the passage of this feature...the bulk of the night will just
be partly cloudy. There will be some localized areas where stratus
will develop late tonight though...as a northerly upslope flow of
cooler air will be found near the Tug Hill and across parts of the
Finger Lakes and lower Genesee Valley.

On Friday...the frontal boundary will be stalled in the vcnty of the
Mason Dixon line while expansive high pressure will build across the
Upper Great Lakes. This will set up a northeast flow of relatively
cool air over our region so that most areas will only experience
afternoon temperatures in the lower 70s. While skies will be mostly
sunny across the North Country...clouds will become more prevalent
south of Lake Ontario and particularly across the Southern Tier
where low level moisture from the Mid Atlantic storm system will
become trapped under a fairly strong subsidence inversion.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
An upper level trough near Northern MN should have closed off and be
somewhere near Eastern OH/Western PA Friday Night into Saturday.
This scenario paints a rather dreary picture for areas south of NYS,
but results in weak subsidence overhead.  Surface high pressure
underneath a longwave ridge upstream should therefore be the
dominant feature for the weekend. The ridge will remain just
upstream, with NE flow over the region through the weekend.

The result should be dry weather for the entire region.  The only
concern would be along the PA border/Southern Tier, where some
moisture could sneak north across the border if the low ends up a
little north of most models.  Otherwise, the main impact will be
mostly opaque high cirrus over the region mainly on Saturday. Sunday
looks better for sunshine and resulting higher temperatures closer
to normal - near upper 70s to near 80, while Saturday`s highs will
be ~5F lower.  Overnight, there may be some patchy valley fog Friday
night and Saturday night, but high clouds should prevent strong
radiational cooling. Clearing skies Sunday night may result in
typical inland river valley fog.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
A slow moving low over the mid-Atlantic will make its exodus along
the New England coastline through mid next week. Meanwhile, a bubble
of high pressure will build in from the upper Great Lakes keeping a
supply of seasonable and mainly dry air into the region early in the
week. By mid-week slowly increasing humidity with a weak frontal
passage from a shortwave passing to our north will spark some
scattered showers and thunderstorms. Temperatures will be mainly
seasonable through the period, although will peak on Wednesday with
highs just above normal in the low to mid 80s. Temperatures will
return to normal by Thursday behind a weak frontal passage. Lows
will be near normal in the upper 50s to mid 60s.

&&

.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
A weak cool front will slip through western and north central New
York tonight...with a few widely separated showers or thunderstorms
marking its passage. Otherwise...VFR conditons will be in place
regionwide through at least 06z. Late tonight...a moist northerly
upslope flow late tonight may generate some MVFR level
stratus/strato-cu across the Finger Lakes... while fog could reduce
vsbys to 1-3SM across the Southern Tier.

On Friday...the frontal boundary will stall in the vicinity of the
Mason-Dixon line while expansive high pressure will build across the
Upper Great lakes. This scenario will support fair dry weather
across our region...although some MVFR cigs could be present across
the Southern Tier and Finger Lakes to start the day.

Outlook...

Friday night through Monday...VFR with only the chance for late
night IFR/MVFR vsbys across the Southern Tier.
Tuesday...Mainly VFR. A slight chance of showers and thunderstorms.

&&

.MARINE...
A cold front will drop across the eastern Great Lakes this evening.
Westerly winds ahead of the front will veer to north to
northeasterly this evening and remain at this direction through
Saturday morning. These winds will increase to around 20 knots late
tonight into Friday morning and again Friday night, while producing
waves of 3 to 5 feet for the Lake Ontario nearshore waters west of
Mexico Bay. This will yield a series of small craft advisories.

Winds appear to have enough of an easterly component near the
Niagara River such that a SCA will not be needed here.

On Lake Erie...winds will yield the highest waves on the western
waters of the lake...with waves less than four feet from the state
line northward.

Later Saturday and then through the weekend high pressure over the
Eastern Great Lakes will bring fine boating conditions continuing
through the weekend as high pressure slowly passes by.

&&

.TIDES/COASTAL FLOODING...
An intensifying storm system over the Middle Atlantic states
Friday-Saturday will combine with high pressure over the Upper
Great Lakes to produce a prolonged period of fresh
northeasterlies on Lake Ontario from late tonight through
Friday. While winds and waves may temporarily subside late
Friday...winds are forecast to become northerly and increase
during the first half of Friday night. The risk remains that
waves could build to levels that may produce additional erosion
and flooding along much of the south shore of the lake. A
lakeshore flood watch continues from Niagara county to Wayne
county to cover this heightened risk.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Lakeshore Flood Watch from 7 AM EDT Friday through late Friday
     night for NYZ001>004.
MARINE...Small Craft Advisory from 5 AM Friday to 6 PM EDT Saturday for
         LOZ042-043.
         Small Craft Advisory from 5 AM to 6 PM EDT Friday for
         LOZ044.

&&

$$

SYNOPSIS...RSH
NEAR TERM...RSH/THOMAS
SHORT TERM...ZAFF
LONG TERM...CHURCH
AVIATION...RSH
MARINE...RSH/THOMAS
TIDES/COASTAL FLOODING...RSH/THOMAS



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