Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 282049
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
449 PM EDT SUN AUG 28 2016

.SYNOPSIS...
A weak cold front will slide across the region this evening while
triggering some scattered showers and thunderstorms. High pressure
will then build into the region Monday and Tuesday along with a
return to fair weather...before another cold front passes through
the region Wednesday and ushers in a significantly cooler air mass
for the end of the week.

&&

.NEAR TERM /THROUGH MONDAY/...
As of 2045z...visible satellite imagery continues to show
pronounced lake shadows to the northeast of both lakes. Along the
southern fringes of the lake shadows...both radar and satellite
imagery are now showing a developing line of enhanced cumulus/
scattered convection extending from interior portions of the
Southern Tier into the Finger Lakes... while additional scattered
convection continues to trek eastward along the lake breeze
convergence zone north of Buffalo.

Through early this evening...expect scattered convection to
continue to develop and move eastward along the aforementioned
lake breeze boundaries... with the activity probably filling in at
least a little bit more across the Southern Tier/Finger Lakes as
it takes advantage of a very warm/humid airmass featuring mixed
layer CAPEs in excess of 1500 J/kg. All of this will then end from
west to east during the balance of the evening with the passage of
a weak cool front (presently draped across the Niagara Peninsula)
and diminishing heating. Given PWAT values near 1.75"...there will
be at least some continued potential for locally heavy rainfall
within any storms...while modest bulk shear values of 25-30 kts
will also keep the potential for an isolated strong/severe storm
or two in place... as has already occurred across Niagara County.

Behind the cold front...trapped low moisture may result in some
clouds or fog tonight, with otherwise clearing skies. Low
temperatures tonight will be in the lower to middle 60s.

Monday should be a pleasant day with high pressure centered across
the Great Lakes region. Lingering cloud cover in the morning
should give way to sunny afternoon skies. Temperatures will be
cooler, but still a bit above normal with highs right around the
80 degree mark.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
Monday night a surface high pressure system will settle across the
forecast area with a cooler and drier airmass (850 mb temps around
+12) and light winds. Optimal radiational cooling conditions will
allow for low temperatures to fall into the low 50s in Southern Tier
valley and inland North Country locations, with upper 50s common
across the lake plains.

Tuesday will feature tranquil and comfortable conditions as the
surface high weakens and slides off the northeast coast. Mostly
sunny conditions will prevail on Tuesday as 850 mb temperatures
increase to around +16C in the southerly return flow ahead of the
next approaching wave. This will result in high temperatures back
into the mid 80s, but with a very dry airmass in place (afternoon
dew points in the low 50s) should be fairly comfortable.

The pattern turns more interesting by Wednesday as downstream
development of a highly amplified pattern across the western CONUS
allows a surge of high-latitude, Canadian sourced air to dive from
the Hudson bay region toward the northeast CONUS. Global models
continue to be slightly faster with the progression of this airmass,
with the initial cold frontal boundary pushing across the forecast
area Wednesday morning. This boundary will have the best chance to
spark off some showers with perhaps a rumble of thunder, but will be
ill-timed diurnally to produce much strong convection. The true
colder air looks to arrive with a secondary cold front later
Wednesday, but with the better moisture already pushed southeast of
the forecast area from the primary front, this secondary front
should a mostly dry passage. 850 mb temperatures will fall from
around +14 to +16C on Wednesday to about +8C on Thursday afternoon,
making for high temperatures only in the upper 60s to low 70s. As a
consequence of these much cooler temperatures, this should generate
some lake cloudiness lake sfc to 850 temperatures differences exceed
13C. Minor amounts of low-level synoptic moisture on Thursday should
make for a fairly cloudy day southeast of the lakes, however
moisture is limited enough that only some isolated sprinkles or
showers may manifest.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
Labor day weekend will be the tail of two halves. The start of the
weekend will feature below normal temperatures, while the second
half will feature temperatures return to above normal temperatures.
However the far majority of the weekend should feature dry and fair
weather.

Picking up Friday, a progressive upper-level trough with high-
latitude Canadian sourced air will be pivoting through New England.
A dry and shallow cool airmass will build across the region as a
sprawling surface high moves 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 upper 60s to
low 70s. We will see much more sunshine however on Friday as much
drier air builds in a lowering inversion heights will cancel out the
lake effect cloudiness from the prior day. Low temperatures will be
quite cool Friday morning and Saturday morning, however Saturday
morning looks the coolest as the surface high settles overhead and
allow for optimal radiational cooling. This will result in upper 40s
to lower 50s, with interior valleys and rural locations seeing some
low to mid 40s on Saturday morning.

Temperatures will 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.

&&

.AVIATION /21Z SUNDAY THROUGH FRIDAY/...
Through early this evening...expect scattered showers and
thunderstorms to continue along and inland from lake breeze
boundaries...before ending with the passage of a weak cool
front and diminishing heating. These may produce localized IFR
conditions, but the scattered areal coverage and moderate storm
motion should limit this impact.

A weak cold front will move through this evening. This may produce
some patchy MVFR cigs and fog along and just behind the boundary.
The best chance for IFR conditions is at JHW, where fog and low
cigs are likely late tonight. Pinning down the timing and location
of this is tricky elsewhere, with variable conditions likely
until drier air builds in later tonight.

High pressure will build in Monday, with widespread VFR conditions
developing regionwide.

Outlook...
Monday night and Tuesday...VFR.
Tuesday night and Wednesday...Mainly VFR with a chance of showers
and thunderstorms.
Thursday and Friday...VFR.

&&

.MARINE...
A weak cold front will cross the lakes this evening, followed by
high pressure Monday and Tuesday. This will result in relatively
light winds with no headlines expected during this time. A more
significant front on Wednesday will increase winds, especially
behind it when cold air advection aids mixing late in the week.

&&

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

&&

$$

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


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