496
FXUS61 KBUF 160714
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
314 AM EDT Fri Aug 16 2024

.SYNOPSIS...
High pressure draped across central and eastern New York will slowly
drift east to New England today. This will keep fair weather in
place through most of today...with just a chance of showers and
thunderstorms reaching far western New York later in the day. A
large...slow moving storm system will then track across the region
and bring periodic rounds of showers and scattered thunderstorms
tonight through Monday...with locally heavy rainfall and a few
stronger storms possible over the weekend. Otherwise temperatures
will remain near to above normal through the weekend...before
falling below normal early next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Today surface high pressure across central and eastern New York will
drift out across New England...while a vertically stacked and
increasingly expansive storm system slowly makes its way across the
Upper Great Lakes. Out ahead of this system broad upper level
ridging will crest across our region this morning...before sliding
east into eastern New York/western New England during the afternoon.
The combination of lingering plentiful dry air and subsidence
attendant to the upper level ridge should help to keep our region
dry through the midday to early afternoon hours...with just a
general west to east increase in mid and high cloud cover that will
be most pronounced west of the Genesee Valley. As the upper ridge
axis slides further east during the afternoon...increasing moisture
out ahead of the approaching low will result in mid and high cloud
cover continuing to increase and lower from west to east. Coupled
with daytime heating and the arrival of some weak lift on the
eastern periphery of the low...this may allow for some scattered
showers and thunderstorms to develop across far western New York
during the late afternoon and early evening hours...though coverage
should remain on the limited side through 22/23z. With respect to
temperatures...the warm airmass out ahead of the low and a modest
south to southeasterly low level flow will allow for another warm
day...with highs ranging from the upper 70s to mid 80s across far
western New York to the mid to upper 80s across much of the Finger
Lakes and eastern Lake Ontario region...where more sunshine is
expected.

Tonight the center of the large storm system will make its way into
northern Lower Michigan...and in the process will push its attendant
warm front into our region...with this latter feature roughly making
it to about the south shore of Lake Ontario by 12z Saturday. This
boundary will be accompanied by a surge of GOMEX-based moisture
attendant to a 30+ knot low southerly level jet that will push
precipitable water values up into the 1.5-2 inch range. At the same
time...isentropic upglide out ahead of the warm front...convergence
at the nose of the low level jet...and a broadly diffluent flow
regime aloft will all combine to lift this deepening moisture
field...thereby leading to a round of showers and scattered
thunderstorms that will work across the area from west to east
through the course of the night. Given the quality of the forcing
and moisture that looks to be in place have raised PoPs into the
categorical range... with most of western New York likely to pick up
basin-average rainfall amounts of a quarter to a half inch before
the warm frontal pcpn begins to wind down across far WNY late in the
night. Owing to the above...also cannot completely rule out some
locally heavier rainfall/limited flooding risk...as reflected by the
Marginal Risk across western New York in WPC`s Day 1 Excessive
Rainfall Outlook. Otherwise it will be a notably warmer and more
humid night...with lows ranging from the low-mid 60s east of Lake
Ontario to the mid 60s to lower 70s elsewhere...and surface
dewpoints rising into the lower to mid 60s.

&&

.SHORT TERM /SATURDAY THROUGH MONDAY/...
The longwave pattern across the CONUS will amplify over the weekend,
with a strong ridge building over the Rockies and High Plains,
forcing a deep longwave trough to carve out over the eastern third
of the nation. A mid level closed low found within the deepening
longwave trough will meander very slowly east across the central
Great Lakes Saturday through Sunday before finally reaching the
eastern Great Lakes Monday. A weak surface low will remain
vertically stacked beneath this mid level feature through the
period. PWAT values will run in the 1.5" to 1.75" range much of the
time, with persistent forcing and moisture bringing an extended
period of unsettled weather Saturday through Monday.

Saturday, the initial push of moisture transport and convergence
near the nose of a 35+ knot low level jet will provide the focus for
an organized area of showers moving from the Genesee Valley and
Finger Lakes early in the morning into the eastern Lake Ontario
region through the day. Emerging consensus of operational guidance
suggests a lull in rain chances across Western NY for a time
Saturday behind this initial wave of showers. DPVA and height falls
will continue to spread east out of the Central Great Lakes Saturday
afternoon, combining with ample moisture and diurnal instability to
bring increasing coverage of showers and a few thunderstorms again
in the afternoon and evening.

Saturday night through Sunday, ongoing height falls and numerous
convectively augmented vorticity maxima propagating through the
longwave trough will continue to bring periodic enhanced ascent,
supporting numerous rounds of showers and a few thunderstorms.
Sunday night through Monday, the closed low will gradually deamplify
into an open wave, but ongoing forcing and deep moisture will still
support occasional showers through the start of the work week.
Thunder chances will gradually wane from northwest to southeast as
better instability moves to the east coast.

Potential Hazards...

SPC has much of the area in a Marginal Risk for severe thunderstorms
both Saturday and Sunday. Flow will be relatively weak through the
period with low end shear values for more organized modes of
convection. Some diurnal instability will develop both days,
although poor mid level lapse rates will limit updraft strength.
Expect an isolated risk of damaging winds with any organized multi-
cell clusters, with the risk peaking in the afternoon and early
evening each day.

The persistent moisture and forcing also suggests a potential for
localized heavy rainfall and an isolated flash flood risk later
Saturday through Sunday night, particularly in areas where
convection repeats. WPC has a Marginal Risk of excessive rainfall
Saturday through Sunday.

&&

.LONG TERM /MONDAY NIGHT THROUGH THURSDAY/...
Monday night through Tuesday the trough axis will finally move just
east of our longitude, with the plume of deep moisture on the
eastern flank of the trough drifting to the east coast. Surface high
pressure will build into the upper Great Lakes Tuesday, then expand
south and east to cover the entirety of the Great Lakes, Ohio
Valley, and Northeast Wednesday through Thursday.

A few showers may linger into Monday night, particularly in Central
NY and the eastern Lake Ontario region. Thereafter, dry weather will
prevail from Tuesday through the end of next week. The airmass is
quite cool initially, with highs Tuesday only around 70 for lower
elevations and 60s for higher terrain. The airmass will then
gradually modify through the rest of the week. Nights will be cool
with high pressure and a cool airmass overhead. This will translate
into 50s close to the lakes and 40s inland each night from Monday
night through the end of next week.

&&

.AVIATION /07Z FRIDAY THROUGH TUESDAY/...
Through daybreak expect fair dry weather to continue...with just
some increase in high clouds across far western New York. Flight
conditions will be VFR...save for localized reductions in patchy fog
within the Southern Tier river valleys and east of Lake Ontario.

During the course of today...high pressure will slide off to our
east...while the next storm system drops across the Upper Great
Lakes and spreads increasing mid and high clouds across our area
from west to east. Later this afternoon and early this evening the
above system will get close enough to our area to potentially
trigger a few scattered showers and thunderstorms across far western
New York...with dry VFR weather otherwise prevailing.

Our weather will then trend steadily downhill tonight as the center
of the aforementioned low makes its way across northern Lower
Michigan and pushes its attendant warm front into our region...with
this feature making it to about the south shore of Lake Ontario by
the end of the TAF period. This will result in a round of fairly
widespread showers and scattered thunderstorms making its way across
our region from west to east...with flight conditions lowering to
lower-end VFR/MVFR across the lower elevations and MVFR/IFR across
the higher terrain as the atmosphere moistens.

Outlook...

Saturday and Sunday...Occasional rounds of showers and scattered
thunderstorms with associated reductions to IFR/MVFR...and MVFR/VFR
otherwise.
Monday...MVFR/IFR ceilings with showers likely and a chance of
thunderstorms.
Tuesday...Improvement to VFR.

&&

.MARINE...
A modest southeasterly to southerly flow will develop today as a
warm front approaches the region...however wind speeds should remain
less than 15 knots. As the warm front pushes into our region...
southeasterlies may then briefly freshen to 15 to 20 knots across
central and eastern portions of Lake Ontario later tonight and
Saturday morning...however the offshore nature of the flow will
direct the bulk of the greater wave action across Canadian waters.
Following the warm frontal passage a general south to southwest flow
will then prevail over the weekend...though winds should again
generally remain below 15 knots.

Of greater concern to marine interests will be the potential for
scattered thunderstorms with locally higher winds and waves...
beginning this afternoon across Lake Erie and western Lake
Ontario...then spreading east across the rest of the region over the
weekend.

&&

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

&&

$$

SYNOPSIS...JJR
NEAR TERM...JJR
SHORT TERM...Hitchcock
LONG TERM...Hitchcock
AVIATION...JJR
MARINE...JJR