Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 280600
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
200 AM EDT WED SEP 28 2016

.SYNOPSIS...
A brief period of dry weather will encompass the region today as an
upper level low drops southward across the Central Great Lakes and
Ohio Valley regions. This upper level low will bring moisture and
rain showers back to the region along and south of Lake Ontario this
evening and through the night. Unsettled weather will then remain
over the Eastern Great Lakes through the remainder of the week.

&&

.NEAR TERM /THROUGH TODAY/...
Regional radars display lake effect rain showers now dissipated,
with just a few isolated showers/sprinkles over Lake Ontario. An
area of alto-stratus clouds remains over a portion of WNY, but this
is eroding from south to north. These clouds should diminish in
coverage area as they erode/lift northward through the remainder of
the night.

Otherwise, most of forecast area will see clear skies this
overnight. Expect lows in the upper 40s to lower 50s across the lake
plains, with low to mid 40s in some of the cooler Southern Tier
valleys and Lewis County. The radiational cooling will allow for
some limited river valley fog in the typical areas of the Southern
Tier late tonight and early Wednesday.

A dry day is in store for all on Wednesday as the upper-level low
settles over northern Indiana. Initially limited moisture and
forcing staying clear of our area will allow for a dry day, however
as Atlantic sourced air is pulled northwestward by the low, we will
see increasing cloud cover from south to north across the region.
Temperatures will also moderate with the developing easterly flow
from the Atlantic, as 850 mb temperatures climb to near +10C. This
will result in a pleasant day, with high temperatures mainly in the
low 70s. Bottom line, Wednesday will be a great day to get any
outside work done before a long stretch of unsettled weather through
the end of the work week (more on that below).

&&

.SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/...
An upper level low will meander from Indiana down into Kentucky and
back into Indiana during this period as it encounters a stout
blocking ridge over the Western Atlantic. This will result in mild
and showery weather across much of Western and North-Central New
York for the latter half of the week as the area comes under the
influence of a easterly conveyor belt of maritime air advecting in
off the Atlantic around the northeastern flank of the broad low to
our southwest over the upper Ohio valley.

Shower chances will gradually increase as we move from Wednesday
evening into Wednesday night as east-southeast flow begins to become
better aligned across the Mid-Atlantic states. The easterly surface
flow down the axis of Lake Ontario combined with relatively cool
temperatures aloft, around +9C, should yield a decent lake response,
producing considerable rainfall across the Golden Horseshoe in
Ontario province, however lake effect showers should largely spare
the New York side of the border, though showers may begin to affect
areas along the Lake Ontario shoreline as we move into Thursday
morning and flow begins to back to the northeast. Temperatures
overnight will reflect the mild airmass advecting into the region
and increasing cloud cloud cover, with temperatures only falling
into the mid to upper 50s.

The period of most significant rainfall across the forecast area
will likely be on Thursday, when the core of the easterly low level
jet arrives over the area, representing the maximum of the moisture
advection and isentropic lift across the region. Expect widespread
rain showers with periods of moderate rainfall, with general
rainfall around a half inch to an inch, with localized heavier
amounts. Lowest pops and QPF will be found across the North Country,
where the northeasterly flow will limit moisture advection. Higher
amounts will be found in the Niagara Frontier near the Lake Ontario
shoreline, where lake enhancement will come into play.

While the heaviest rains are expected on Thursday, when
southeasterly flow across the area will be maximized, the persistent
proximity of the low and general southeasterly orientation of flow
across the area will keep showers in play through the end of the
week. Regarding temperatures, expect readings to remain within a
couple of degrees of climatology during the day, with highs in the
mid to upper 60s, while overnight readings will remain above
average thanks to the abundant cloud cover, with lows in the 50s.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
The upper level closed low centered over the Ohio Valley early
Saturday morning is forecast by 12z medium range models to lift
north and east across the eastern Great Lakes on Sunday. This low
will then get picked up by a sharp trough diving across Quebec on
Monday and shift off the coast of Nova Scotia by Tuesday. The
movement of this closed low will be due to a deep trough forecast to
dig into the west coast. This pattern all breaks down into a rather
showery day across the forecast area on Saturday, especially across
western New York with chances of showers also included Sunday and
Monday as the upper low passed near or across New York. Monday night
into Tuesday guidance shows ridging will build over the forecast
area ahead of the approaching sharp western trough. The ridging
should provide dry weather.

Have bumped POPs across western New York to the likely range on
Saturday as both GFS and EC models show a spoke of vorticity
providing lift while cyclonically shifting across the region where a
east to west feed of Atlantic moisture will be in place to support
the higher probability of rain showers. Further east have featured
high chance pops with the lift from the vort lobe being a little
weaker further from the center of the low. As mentioned above chance
POPs have been included Saturday night through Monday for now but
expect that as confidence builds in timing and location of more vort
maxes increases POPs for at least a few hours on Sunday and Monday
may need to be raised.

In terms of temperatures expect seasonal highs in the mid to upper
60s and lows in the upper 40s to low 50s as the polar jet will be
displaced well to our north keeping any cold airmasses from surging
south across the border.

&&

.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
VFR flight conditions at 06Z are found across the TAF region, and
these conditions should prevail through the TAF cycle. There is
possibility of valley fog across interior Southern Tier, but a drier
boundary layer near KJHW should preclude fog from forming near the
airfield.

Today and this evening clouds will slowly increase and lower from
south to north as an upper level low drops slowly southward towards
the Ohio Valley. This feature will bring Atlantic moisture
northward, such that a few rain showers may near KJHW and the
western Southern Tier by late this afternoon. This activity will
increase in coverage area through the night, though largely
remaining scattered in nature through 06Z. After 06Z a deeper plume
of moisture from the Atlantic will make showers south of Lake
Ontario more numerous.

Winds will be light and from a south to southeast direction today.
Tonight winds will back around to the east, and increase in speed
to 10 to 15 knots as the upper level low drops farther southward.

Outlook...

Thursday through Friday...Areas of MVFR/IFR with periods of showers.
Saturday and Sunday...VFR/MVFR with scattered showers.

&&

.MARINE...
Will drop the small craft advisory on Lake Erie as both winds and
waves have dropped below criteria.

After a brief respite overnight and Wednesday morning...a brisk
easterly flow will develop across the Lower Lakes region between
later Wednesday and Thursday morning...then will persist through the
end of the work week. This will likely require the issuance of
another round of small craft advisories starting Wednesday evening.
Chance for waterspouts will return Wednesday night on both Lakes
Erie and Ontario.

&&

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

&&

$$

SYNOPSIS...THOMAS
NEAR TERM...CHURCH/HITCHCOCK/THOMAS
SHORT TERM...WOOD
LONG TERM...SMITH
AVIATION...THOMAS
MARINE...CHURCH/HITCHCOCK/THOMAS



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