Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 181431

Area Forecast Discussion
National Weather Service Buffalo NY
1031 AM EDT Wed Jul 18 2018

High pressure over the Upper Great Lakes will gradually settle
across our region through Thursday...before sliding off the New
England coast on Friday. This will result in dry and comfortable
weather prevailing through Thursday...before a return southerly
flow around the departing high brings increasing heat and humidity
back into our region on Friday. A slow-moving low pressure system
will then bring a gradual return to more unsettled weather over
the weekend.


During this period sprawling high pressure will slowly settle from
the Upper Great Lakes to New York State. Plentiful dry air and
subsidence attendant to the high will provide our region with fair
and dry weather...with morning stratocumulus/diurnal fair
weather cumulus over western New York today giving way to
largely clear skies by tonight. With respect to
temperatures...850 mb readings of +8C to +11C will support
widespread highs in the lower to mid 70s today...with excellent
conditions for radiational cooling then allowing tonight`s lows
to settle into the lower to mid 50s across the lake plains...and
into the mid to upper 40s across interior portions of the
Southern Tier and North Country. The latter should allow for the
formation of valley fog across the Southern Tier
overnight...with some additional areas of fog also possible near
water bodies east of Lake Ontario.


Thursday will start cool, but within a dry lower atmosphere we will
quickly warm into the mid 70s to lower 80s under full sunshine as
surface high pressure crosses our region. Winds will remain light.

Thursday night the surface high will begin to slip to our east and a
light southerly flow on the back side of this high pressure will
keep overnight lows several degrees warmer than the previous night.
Lows will range from the lower 50s across the inland So. Tier and
inland eastern Lake Ontario the mid and upper 50s across
the Genesee Valley and Niagara Frontier.

Friday will continue to remain dry with high pressure over New
England continuing to influence our weather. Skies will start the
day mostly sunny, however models are showing a thin plume of
moisture advecting northward up the western spine of the
Appalachians and to WNY. Strato-Cumulus may begin to fill the sky
across the So. Tier and Niagara Frontier through the day. Highs
Friday with a southerly flow will be well into the 80s, and possibly
lower 90s across the Lake Plain and Genesee Valley. Dewpoints will
still be in the upper 50s to around 60...with just a touch of
stickiness to the air Friday afternoon.

Friday night a closed upper level low will spiral across the Western
Great Lakes, and begin to pull deeper moisture northward across WNY.
There will be a sharp cut off to the moisture, with areas west of
the Genesee Valley likely to be partly to mostly cloudy, with a risk
for a shower, while areas east...and especially east of Lake Ontario
remaining clear. Temperatures like-wise will be cooler to the east
where clear skies will allow for overnight lows in the upper 50s to
mid 60s, while areas to the west, and especially the Niagara
Frontier remain in the mid 60s to lower 70s with mostly cloudy

Saturday the upper level low will only move eastward to about the
Central Great Lakes region. Moisture will continue to build across
our region, with an easterly flow from the Atlantic beginning to
bring additional moisture in from the southeast. Chances for shower
will increase across WNY, though PoPs will remain in the chance range
as activity does not look to be widespread. Areas east of Lake
Ontario may remain dry through the day as deeper moisture does not
arrive until Saturday night. The additional cloud cover will bring
highs a few degrees cooler than Friday across WNY, though some
sunshine east of Lake Ontario could bring highs into the upper 80s
through the Saint Lawrence Valley.


A closed upper level low will drop through the Ohio Valley early
this period, which when coupled with an increase of moisture from a
subtropical wave off the Atlantic coastline will bring chances for
showers and thunderstorms through the remainder of the weekend.
Deeper Atlantic moisture may remain across our eastern zones, though
moisture associated with the upper level low will also feed into
showers across western zones. Will continue to use chance pops until
the finer details on how the closed low interacts with the increase
in subtropical moisture plays out. Cloudy skies may bring slightly
below normal afternoon temperatures, with highs Sunday under the
closed low likely to remain in the 70s.

The closed low will weaken and become an open wave over the Ohio
Valley and Northeast Monday and Monday night. Tuesday an upper level
trough will remain across the Great Lakes, and both Monday and
Tuesday showers and thunderstorms will be possible with the greatest
chance in the afternoon and early evening. Temperatures Monday and
Tuesday will likely be seasonal, with highs in the mid 70s to lower
80s. Overnight lows both nights will drop back into the 60s.


Any limited MVFR conditions in patchy light fog/stratocumulus across
the Southern Tier this morning will give way to a return to VFR
conditions areawide this high pressure builds
into the region and forces any scattered cloud cover to
dissipate. The high will then settle directly overhead tonight
with mainly VFR conditions continuing... with just some IFR fog
developing overnight near rivers and other bodies of water in
the Southern Tier and North Country.

Thursday and Friday...VFR.
Saturday...Mainly VFR...with just a chance of showers and
thunderstorms/attendant MVFR across far western New York.
Sunday...VFR/MVFR with a chance of showers and thunderstorms.


A brisk northerly to northeasterly flow across Lake Ontario has
diminished, allowing the Small Craft Headlines to be dropped on
this issuance.

Otherwise, expect fine boating conditions with light to modest
winds and minimal waves are expected through Friday as high
pressure moves across the waters and to the New England
coastline. More unsettled weather will then gradually return
over the weekend as a slow- moving low pressure system makes its
way eastward across the Great Lakes.





LONG TERM...Thomas
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