350
FXUS61 KBUF 182002
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
402 PM EDT Sun Aug 18 2024

.SYNOPSIS...
A slow moving area of low pressure will continue to bring unsettled
and eventually cooler weather through Monday, with several more
rounds of showers and scattered thunderstorms. A few storms may
contain localized heavy downpours and gusty winds, mainly through
this evening from the Genesee Valley into Central NY and the eastern
Lake Ontario region. Cool and drier weather will return Tuesday,
with expansive high pressure then bringing dry weather and a day to
day warming trend later in the week.

&&

.NEAR TERM /THROUGH MONDAY/...
Vertically stacked low pressure across the Eastern Great Lakes will
gradually open up and shift into New England through Monday. Some
breaks of sunshine late this afternoon has allowed for CAPEs to
build to 1000 to 1500 J/Kg, with a generally weak flow aloft.
The combination of instability and approaching trough has
sparked some convection, with radar showing scattered to
numerous showers early this afternoon. The exception is
northeast of Lake Erie in the Buffalo area where the southwest
flow is helping shadow the area.

For the remainder of this afternoon and early evening there`s a risk
of locally heavy rainfall. Consensus of latest mesoscale guidance
suggests the greatest risk is east of Lake Ontario, but locally
heavy downpours cannot be ruled out elsewhere due to the slow storm
motion. Not much wind shear, but ample instability to support a few
strong to severe storms with gusty winds from the Genesee River
valley east. Here is where the most of limited wind shear is in
place, with 700 mb winds about 30 knots.

Tonight, the diurnally driven storms along the pre-frontal trough
will continue to move east and weaken during the evening. Meanwhile,
showers and scattered thunderstorms may also develop this evening as
the cold front moves into Western NY and then across the area. An
axis of deformation and frontogenesis on the cold side of the
boundary will move from southern Ontario southeastward across the
eastern Great Lakes overnight, supporting additional rounds of
showers and possibly some embedded thunder. Low stratus will expand
across the region overnight, and some of this may begin to intersect
the higher terrain with areas of fog developing across higher
terrain.

Showers will linger Monday as the upper low slowly lifts out. Expect
it to be a cloudy day, with the cool air aloft resulting in lake
induced stratus which tends to linger. Hedge forecast on the cloudy
and cool side of model blends given the synoptic set up. Monday will
be much cooler with daytime highs only topping out in the lower to
mid 60s.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/...
An upper level low will linger near our region this period, with its
associated cool pool granting a fallish feel to our airmass. Highs
Tuesday will be 10 to 15 degrees below normal, and Wednesday will
fair just slightly warmer. Both days will feature a wealth of
clouds. Synoptic showers will end early Monday night with deeper
moisture shifting eastward, but a lobe of moisture rotating around
this cool upper level low will lend to the formation of lake clouds
and even a few showers/sprinkles Tuesday night and Wednesday south
of Lake Ontario. A few upslope showers are possible east of Lake
Ontario as well. Some clearing Wednesday night, but still enough
moisture lingering in close proximity to this upper level low that
we probably will not completely clear out. This will make for a
tricky forecast for overnight lows both Tuesday night and Wednesday
night as if we clear, or get enough of a clearing break temperatures
could plummet down into the mid 40s inland/mid 50s closer to the
lakes. However if clouds remain thick then the forecasted lows may
end up too cold.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
The nearly vertically stacked low will begrudgingly drifts northeast
across New England on Thursday. Lingering effects from this trough
`may` induce a few shower, specifically focused across the North
Country. Even so...this is low end chances (< 20%) with most locales
seeing dry weather across the forecast area.

After that...the stubborn trough exits and high pressure will
`likely` take over the remainder of week. We will also see a day to
day warming trend with overall spectacular weather. The next chance
of any precipitation `may` potentially come over the weekend. That
said...guidance is all over the board and have low confidence at
this point to carry no more than slight chance PoPs (< 20%).

Overall...a return to near normal temperatures will occur to a
little above in some spots over the weekend.

&&

.AVIATION /20Z SUNDAY THROUGH FRIDAY/...
There`s a risk of showers and thunderstorms through 00Z, especially
from KROC to KART which has a stronger flow ahead of the approaching
closed low. Smaller risk at KBUF/KIAG until very late this
afternoon into the evening due to lake shadowing, but showers
and storms will move across these sites with the cold front
around 00Z. Outside of showers and storms, mainly VFR flight
conditions.

Tonight a cold front will move across the area, and this will bring
showers and much lower CIGS. Moderate to high confidence that
this will drop CIGS to IFR at TAF sites tonight, with lower
confidence in VSBY due to a risk of IFR or lower VSBY if clouds
drop all the way to the surface, especially across the hilltops.

Slowly improving conditions on Monday, with mainly IFR CIGS
during the morning likely to lift to MVFR across lower terrain
during the afternoon. Showers taper off from west to east during
the afternoon.

Outlook...

Monday night...Areas of MVFR or lower. A chance of showers early,
and lingering stratus.

Tuesday...Improvement to VFR.

Wednesday through Friday...VFR. River valley fog with local IFR
across the Southern Tier each late night and early morning.

&&

.MARINE...
Issued small craft headlines for Lake Erie, due to the increase in
southwest winds early this afternoon. Marginal, but winds should
stay elevated 3 to 5 hours which will be just enough to build waves
to 4 or 5 feet.

A cold front will move southeast across the lower Great Lakes
tonight. Winds will become north and increase behind the cold front
late tonight and Monday. This will support a round of solid Small
Craft Advisory conditions on Lake Ontario, with a chance of lower
end Small Craft Advisory conditions on Lake Erie as well. The
elevated north winds will continue through Monday night and Tuesday
morning before gradually diminishing through midweek.

There will also be a risk for waterspouts through Monday morning.
There were multiple waterspouts on central Lake Erie this morning,
so there`s a risk for more - especially on any boundaries which move
across the Lake during this time.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...Small Craft Advisory until 11 PM EDT this evening for LEZ040-
         041.

&&

$$

SYNOPSIS...Apffel/Hitchcock
NEAR TERM...Apffel/Hitchcock
SHORT TERM...Thomas
LONG TERM...AR
AVIATION...Apffel
MARINE...Apffel