Area Forecast Discussion
Issued by NWS Buffalo, NY

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000
FXUS61 KBUF 190650
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
250 AM EDT Mon Aug 19 2019

.SYNOPSIS...
Warm and muggy conditions will remain over the region through the
middle of the week. A weak high pressure ridge will provide mainly
dry weather outside of a few widely scattered showers and
thunderstorms today and Tuesday. A strong cold front that will pass
through the region late Wednesday will then introduce a cooler and
notably more comfortable airmass to our region for the second half
of the week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
A well defined shortwave over Lake Erie will move eastward across
our region during the early morning hours. There is a solid line of
showers with embedded thunderstorms just ahead of this shortwave,
and this line will continue gradually weaken as instability wanes.
This line move across the Genesee Valley between 3-5 a.m. before
reaching the eastern Lake Ontario region just before daybreak.

A weak cold front associated with this shortwave will gradually push
across our forecast area through this morning. The passage of the
front will be too early to take advantage of daytime heating.
Although a stray shower or thunderstorm cannot completely be ruled
out today, the vast majority of the day will be dry. It will also be
slightly less humid today, with dew points falling into the mid 60s
by this afternoon. Highs will be in the lower 80s.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY NIGHT/...
This period will feature a mainly dry and warm, but less humid day
on Tuesday, followed by showers and thunderstorms on Wednesday into
Wednesday evening as a strong cold front plows across the area.

Monday night into Tuesday will be mainly dry as a push of somewhat
drier air works in behind a weak, stalled out frontal boundary lying
across northern PA. With no discernible shortwaves moving over the
area, there will just a slight chance for a few showers toward the
PA line closest to the boundary. Dew points will drop off some
across the entire area, bringing some relief to the mugginess,
especially east of Lake Ontario where dewpoints could fall into the
upper 50s. Temperatures Monday night will be some ten degrees cooler
than the previous night, with lows in the upper 50s to lower 60s.
Highs on Tuesday will be mainly in the upper 70s to lower 80s,
however will a drier `feel` to the air.

Tuesday night, the frontal boundary over PA will start to make a
move back to the north as a weak warm front, while an upper level
shortwave approaches the Lower Great Lakes. While the night may
start out dry, deeper moisture to our south will make a push back to
the north ahead of the now northward advancing warm front. This will
increase the chance of some showers/isolated storms from south to
north across the area, especially during the second half of the
night due to added lift associated with the approaching shortwave.
Humidity levels will be a bit higher, as will overnight temperatures
as compared to Monday night, with lows mainly in the mid 60s. The
exception will be across the northcountry, where lows will bottom
out in the upper 50s to lower 60s.

A cold front will be poised to plow across the region later
Wednesday into early part of Wednesday night. A warm, humid airmass
will be found out ahead of the approaching cold front. As the upper
level trough sharpens just to the west over the central Great Lakes,
enhanced lift provided by this feature within an already unstable
environment will promote widespread showers and thunderstorms
Wednesday afternoon/early evening with the pre-frontal trough out
ahead of the main cold front. The main cold front will then plow
across the region later Wednesday evening into the early overnight,
with possibly another round of general showers and storms. Storms
Wednesday afternoon into the early evening hours could become strong
with both gusty winds and hail possible. Mid level lapse rates will
increase with height falls aloft, bulk wind shear values upwards of
35 to 40 knots and CAPE deepening through the mid levels on forecast
soundings will support these stronger storms.

Temperatures on Wednesday will be similar to Tuesday, however dew
points pushing back into the upper 60s to near 70 will make it feel
more uncomfortable outside. Cooler, less humid air will pour in
behind the cold front Wednesday night. Lows will generally be in the
upper 50s to lower 60s, with some mid 50s across the higher terrain
east of Lake Ontario.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
In the wake of a strong cold front...a much cooler and drier airmass
will continue to overspread our region Thursday and Thursday night...
with 850 mb temperatures falling to within a couple degrees either
side of +7C. The combination of lingering secondary surface troughing
and a digging upper level trough could lead to a few more isolated
to widely scattered showers on Thursday...with the cooler airmass
and loss of diurnal influences then potentially supporting a weak lake
response east and southeast of Lake Ontario Thursday night into early
Friday...with this limited by the rather dry nature of the airmass.
Otherwise...the Thursday-Friday time frame will be dry and notably
cooler as expansive surface-based ridging slowly builds southeastward
across the Great Lakes. Expect highs to mostly be in the lower half of
the 70s both days...though some of the higher terrain may see readings
confined to the upper 60s. Meanwhile lows will be mainly in the 50s...
with some upper 40s possible across interior portions of the Southern
Tier and North Country.

After that...the axis of the aforementioned surface ridge will crest
across our region on Saturday...then will drift to the Atlantic
coastline on Sunday. This will provide our region with continued
fair dry weather both days...with diurnal airmass modification
and eventually warm air advection allowing highs to climb back into
the mid to upper 70s on Saturday...and to the upper 70s to lower 80s
on Sunday.

&&

.AVIATION /07Z MONDAY THROUGH FRIDAY/...
A line of showers and thunderstorms will continue to weaken as it
moves east across the KROC and KART terminals. Rain will only last
an hour or so, but there will be lingering low moisture which is
likely to bring a period of MVFR cloud cover to some spots which
will linger through the morning hours.

Otherwise, today will be mainly dry, with widely scattered showers
and mainly VFR flight conditions by this afternoon. High pressure
will build into the region tonight with VFR conditions. The only
exception is that patchy fog will develop across the western
Southern Tier which may result in IFR conditions at KJHW.

Outlook...

Tuesday...VFR...with a chance of showers and thunderstorms
across the Southern Tier
Wednesday...Thunderstorms likely that could impact operations.
Thursday and friday...Mainly VFR.

&&

.MARINE...
West winds will briefly run 15 to 20 knots early this morning behind
a line of thunderstorms, but this increase in winds will be
temporary. It still will produce choppy conditions, and waves will
build to 3 feet but still remain below small craft criteria.

Looking further out into the middle of next week...a cold front
will cross the region on Wednesday along with more showers and
thunderstorms. In its wake...increasingly brisk northwesterly
winds will bring an increase in wave action and could eventually
require the issuance of Small Craft Advisories for Wednesday night
and Thursday.

&&

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

&&

$$

SYNOPSIS...Apffel/RSH
NEAR TERM...Apffel
SHORT TERM...JM
LONG TERM...JJR
AVIATION...Apffel
MARINE...Apffel/Hitchcock/RSH


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