Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 301244
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
844 AM EDT TUE AUG 30 2016

.SYNOPSIS...
An area of high pressure will cross the region this morning,
settling over the mid-Atlantic coastline tonight. Expect fair
weather with comfortable levels of humidity to continue through the
day today. A cold front will then cross the region on Wednesday with
some scattered showers and thunderstorms...to be followed by an area
of high pressure that will spell fair weather into the holiday
weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
This early morning, an area of high pressure sits over the Mid-
Atlantic region, providing for a sunny start outside of some
river valley fog across the Southern Tier. A cold front
is well to our west, stretch over Canada and the Upper Great Lakes
region.

For today mostly sunny skies will prevail as this surface high
slides to the coastline. A light southerly wind on the back side of
this area of high pressure will bring warmth, and a touch bit more
of humidity northward, with afternoon highs in the low to mid 80s. A
few clouds will begin to increase, especially northward as this cold
front upstream works its way eastward through the day. A
stable southwest wind off Lake Ontario, and through the SLV, may be
enough delay showers and thunderstorms with the upstream cold front
until the evening hours.

Tonight this cold front will drop across southern Canada and to near
the Eastern Great Lakes Wednesday morning. Moisture pooling ahead of
the front within a marginally unstable atmosphere may bring a few
showers through the overnight, with activity spreading from Southern
Canada and the SLV southward overnight. Towards the NYS/PA line the
overnight period will likely remain dry...being to far away from the
front. Lows overnight will be a bit warmer with the southerly flow,
increased moisture and clouds. Overnight lows will range from the
mid 50s across the Southern Tier to low to mid 60s farther
northward.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
For Wednesday, chances of showers and storms will increase somewhat
as large scale support increases as an upper trough drops across
eastern Ontario. This should induce a stronger downstream
frontogentic response across the area. Western and north central New
York also should become more favorably positioned in right entrance
region of an associated 60-80 knot upper jet streak. Not expecting
severe weather at this time with better shear profiles post-frontal.
Afternoon temperatures should average within a couple degrees of 80.

The focus for precipitation shifts southeast of the area Wednesday
night, but the big story will be period of much cooler and less
humid conditions behind the associated cold front. It should be
noted that while it will be chilly enough aloft to support
instability over the lakes...the short fetch and limited
environmental moisture will greatly reduce any lake response.

On Thursday, a large area of Canadian high pressure will extend
southward across the Upper Great Lakes to the Southern Plains.
This will generate a relatively deep northerly flow of much cooler
air over our forecast area with 850 mb temperatures forecast to drop
to 8-10C. While this will keep instability in place over the Lower
Great Lakes, the overall regime will be relatively dry. Will keep
some clouds in place across the Finger Lakes to account for the
continued northerly upslope flow, otherwise it will be a partly
sunny and cool day with high temperatures generally within a few
degrees of 70.

It will become relatively cool for parts of our forecast area
Thursday night as the center of the expansive surface high will make
its way across the Upper Great Lakes. Favorable radiational cooling
within a fresh Canadian airmass will allow the mercury to drop well
into the 50s away from the lakes, with parts of the Southern Tier
likely experiencing lows in the 40s.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
While the start of this period will feature cool comfortable
weather...it will be more noteworthy to point out the significant
day to day warming trend that will carry us into next week. The
ultimate factor leading to the return to above normal temperatures
will be the development of a strong jet across the Northern Pacific.
This jet will kick out persistent troughiness that will be in place
over British Columbia...a trough that we have not seen in a couple
months and at least partly responsible for the spell of cool
weather at the onset of this period.

In any case...the +120kt H25 jet will help to deamplify and broaden
the west coast trough...which in turn will lead to substantial
height rises downstream across the eastern half of the country.
Meanwhile...expansive high pressure will guarantee rain free weather
through the period. The details...

On Friday...a progressive upper-level trough with high-latitude
Canadian sourced air will pivot across New England. A dry...shallow
cool airmass will build across the region in its wake while a
sprawling surface high will move from the upper Great Lakes Friday
morning to over the forecast area Friday night into Saturday
morning. Despite 850 mb temperatures returning to around +10C Friday
afternoon...the shallow cool airmass will keep a low-level inversion
in place and thus high temperatures will remain in the lower 70s. We
will see much more sunshine however on Friday though...as even drier
air will advect across the region.

Friday night will be the chillest period of the forecast package as
optimal radiational (minus the fresh snowpack) will encourage our
Canadian airmass to support mins in the low to mid 40s across the
majority of the Southern Tier as well as in Lewis County. The
mercury will flirt with the 40s elsewhere away from the lakes.

Temperatures will then recover Saturday into Sunday as the sprawling
high pressure system slides off the New England coast and allows the
airmass to moderate with 850s back into the mid teens C. This will
bring temperatures back into the upper 70s Saturday and low 80s
Sunday and possibly mid 80s by Labor Day. With high pressure
remaining in control this should remain a dry period with fair
weather.

Looking further down the road at the remainder of next week...the
presence of a strong jet across the North Pacific should keep a low
amplitude trough in place over the western conus.  This will favor a
downstream ridge over the eastern seaboard with a persistent
southerly flow over the Lower Great Lakes. The strong zonal
Pacific flow will also help to block any attempt by chilly
Canadian air from making its way south of the border. The result
will be a continuation of above normal temperatures through the
week.

&&

.AVIATION /13Z TUESDAY THROUGH SATURDAY/...
For the 12z TAFS river valley fog through the Southern Tier has
spread across the KJHW terminal and will likely maintain VSBYS less
than 2 miles through 13-14Z, at which time daytime mixing should
erode the fog.

Otherwise VFR flight conditions today with a gentle South to
Southwest breeze. Winds should remain around or less than 10-12
knots today with high pressure nearby, though a few gusts around
15- 18 knots will be possible off the
lakes and across the KBUF and KART airfields.

As this area of high pressure slides eastward today, a cold front
will approach from the Upper Lakes region. This front will bring a
few clouds later today, with the main increase in clouds the last 12
hours of the TAF cycle. Clouds should remain above 3k feet, though a
few showers are possible along the front, especially in the vicinity
and east of Lake Ontario. Will carry a VCSH for now for the KART
TAF.

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

&&

.MARINE...
An area of high pressure over the Eastern Great Lakes this
morning is providing for light winds and near flat wave action on the
lakes. This area of high pressure will slide by to our east today,
and will allow for a light southerly wind to develop, though with
speeds still well below small craft criteria.

A cold front will cross the lakes Wednesday and Wednesday night and
this will kick up the winds and waves a bit Wednesday night and into
Thursday on the lakes...though conditions may remain just below small
craft advisory criteria.

A cool northerly wind will develop Thursday night and this will
likely bring waves above SCA on the Eastern Great Lakes Thursday
night and into Friday. After this, a broad area of high pressure
will anchor over the Great Lakes region during the holiday weekend,
bringing fine boating conditions.

&&

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

&&

$$

SYNOPSIS...THOMAS
NEAR TERM...THOMAS
SHORT TERM...TMA
LONG TERM...RSH
AVIATION...THOMAS
MARINE...THOMAS



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