Area Forecast Discussion
Issued by NWS Buffalo, NY

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374
FXUS61 KBUF 281324
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
924 AM EDT SUN AUG 28 2016

.SYNOPSIS...
As high pressure moves to the east of the region, warm and more humid
air will overspread the area. Low pressure across eastern Canada
will draw a cold front over the northeastern states today, and this
will produce showers and thunderstorms into the evening, especially
across Central New York. The next round of fair weather will then
move in for Monday and Tuesday when high pressure builds in from the
Upper Great Lakes.

&&

.NEAR TERM /THROUGH MONDAY/...
The return flow around high pressure across northern New England
will advect warm and moist air into the region. The 12Z Buffalo
sounding already has a PWAT of 1.6 inches, with some increase in
this likely as dew points rise to near 70. This will result in a
hot and muggy day with highs in the mid 80s to around 90.

Through mid-morning IR Satellite and radar loops show some
showers and clouds along a mid-level wave which is across Central
New York extending into the North Country. Otherwise, it is mostly
dry with a fair amount of sunshine in many areas. Daytime heating
will increase instability, however there appears to be little to
focus this. The most likely trigger will be a weak pre- frontal
trough which is forecast to slowly slide to the east this
afternoon. A consensus of mesoscale guidance has trended
considerably drier with this and although this should produce some
showers and thunderstorms the coverage is expected to be a bit
more scattered in nature.

Although mesoscale guidance varies a bit, there appears to be two
areas which are more likely to get showers and thunderstorms this
afternoon. The first areas along and east of the Genesee River
where the timing of the pre-frontal trough passage is most
favorable. The second is across northern portions of the Niagara
Frontier, north of the lake breeze off Lake Erie. Elsewhere, there
still is a risk of thunderstorms, but generally of the scattered
variety.

The risk for severe weather appears low given the sparse coverage
in our area and the modestly supportive wind profiles with 700 mb
winds up to 30 kts providing only limited shear. This said, this
is ample to produce a few bowing line segments across Central New
York which is in line with the latest SPC marginal risk.
Thunderstorms will also produce locally heavy rainfall, but should
be progressive enough to limit the risk for flash flooding.

A cold front will drop across the region this evening, with
perhaps a stray shower or thunderstorm before drier air builds in
behind the boundary. Low temperatures tonight will be in the lower
to middle 60s.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
Monday will feature building high pressure as the shortwave trough
tracks into New England. Subsidence and influx of drier air will
dissipate morning cloudiness from northwest to southeast.
Temperatures will be a little cooler under lower heights and 850 mb
temperatures cooling to around 13C, supporting highs in the upper
70s to lower 80s.

High pressure will continue to build across the region Monday night
and Tuesday leaving dry conditions and mostly clear skies. Monday
night will feature optimal radiational cooling with a dry airmass,
and light winds allowing temperatures to fall into the 50s for most
locations, except near the lake shores and urban locations. Tuesday
will see a warming trend as high pressure slights to slide east and
the airmass modifies with 850 mb temperatures to +17C, resulting in
high temperatures back into the lower to mid 80s.

The upper level pattern across the CONUS starts to become more
interesting into Wednesday as a large Pacific trough craves out
across the western US which helps with downstream development of a
large ridge across the central plains. During the day Wednesday,
this will open the door for Canadian sourced airmass to dive from
the Hudson Bay region toward the northeast US. This airmass will be
on our doorstep by the second half of the day Wednesday. A warm,
humid and unstable airmass will be in place ahead of this front
across our region for the first half of Wednesday, and thus we
should see at least some scattered convection across the region
ahead of the frontal passage. However, with models trending quicker
on the arrival of the front, there may not be enough time
destabilize ahead of the frontal passage on Wednesday to develop
stronger thunderstorms across western NY.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/...
An upper level trough axis will dig across Northern New England
through Friday. This will set up a persistent northwesterly flow
with cold air advection during this time. Model guidance is in
good agreement, with the 12Z GGEM/ECMWF/GFS all showing a similar
pattern. As such, model consensus will serve as a good starting
point, however some adjustments are still needed.

GFS BUFKIT shows moisture trapped beneath an inversion at about 5k
ft south of the lakes. Although deep layer mean RH largely misses
this, consensus 850 mb forecast to drop to +3C should support
some lake effect clouds during during the Wednesday through Friday
night period. Moisture is shallow and the flow is mostly
perpendicular to the lakes which will make lake effect rain
showers unlikely. However, because of this consensus guidance is
likely too warm for high temperatures on Thursday and Friday.
Daytime highs will be cooler than they have been for some time,
with many areas struggling to reach 70 on Friday.

For Friday night and Saturday, high pressure is forecast to build
across the region with dry and pleasant weather going into the
weekend. Good radiational cooling will result in chilly overnight
temperatures Friday night, followed by seasonable temperatures for
Saturday.

&&

.AVIATION /13Z SUNDAY THROUGH THURSDAY/...
VFR conditions will prevail for most of this TAF cycle. There
will be a grater chance of showers and thunderstorms across the
forecast area, excepting the North Country, mainly after 15Z. Some
heavy showers of stronger thunderstorms may limit visibility to
IFR category, but it should be of short duration as mean boundary
layer winds moves storms along at 25-30kt. Weak cold front moves
through later tonight with a wind shift to northwesterly direction
after 03Z.

Outlook...
Sunday night...Mainly VFR with some leftover evening showers and
thunderstorms.
Monday and Tuesday...VFR.
Tuesday night and Wednesday...Mainly VFR with a chance of showers and
thunderstorms.
Thursday...VFR.

&&

.MARINE...
Southwest winds will pick up a bit ahead of an approaching cold
front, but should remain about 10 knots or less. Winds will
become northwesterly later tonight as the cold front passes and
the next Canadian surface high builds across the region.

&&

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

&&

$$

SYNOPSIS...WCH
NEAR TERM...APFFEL/WCH
SHORT TERM...CHURCH/TMA
LONG TERM...APFFEL
AVIATION...WCH
MARINE...WCH



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