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383
FXUS61 KBUF 181953
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
353 PM EDT Tue Jun 18 2024

.SYNOPSIS...
Hot and humid weather through at least Thursday with apparent
temperatures likely to reach 100F at many locations during the
afternoon hours today through Thursday. There will also be
showers and thunderstorms at times, especially during the
afternoon and early evening hours.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
Remnant clouds from convection earlier today will move across
the Eastern Lake Ontario region. This will slow rises in
temperatures some there, as it did for areas to the west when it
moved through. Since showers and storms moved through,
temperatures haven risen steadily in Western NY, with highs on
track to reach the upper 80s to lower 90s today. Heat index
values are still on track to reach into the mid 90s to lower
100s this afternoon, making very dangerously hot and humid
conditions. Heat advisories remain in place for the entire
forecast area.

The departing wave also impacted convection today, with the
slightly slower warming leading to a later onset of instability
convection this afternoon. Still impressive CAPE values over
2000 J/Kg early this afternoon, with the most unstable
conditions across the Western Southern Tier which was not
impacted the convective wave this morning. Radar trends show
thunderstorms developing to our south and west, and expanding cumulus
fields suggest its only a matter of time before storms develop
there mid to late afternoon. Noted the HRRR is too low in its
dew points, which is likely causing it to be too slow with is
convective initiation. Overall there is low forecast confidence
in exact timing and location of storm development.

The 12Z Buffalo sounding showed precipitable water values of
1.77 inches, and any storms that develop today will have the
potential to produce torrential downpours. Also, winds aloft are
weak, with upstream radar trends showing a potential for
backbuilding. As a result there is a marginal risk for flash
flooding, mainly across the Western Southern Tier and Upper
Genesee Valley even if overall coverage is scattered. The
severe weather risk appears limited due to the weak wind
profiles and the departure of the convective shortwave. However,
the severe weather risk is non- zero since disorganized pulse
convection can still produce damaging winds.

Any afternoon and evening convection will diminish overnight
tonight, other than perhaps a stray shower or storm. There will
be little reprieve from the muggy conditions with low
temperatures in the lower to mid 70s, with some upper 60s across
the Southern tier and North Country.

Wednesday will likely be the hottest day of this heat wave for
most areas. 850mb temperatures will continue to hover around
+20C, supporting another day with highs in the upper 80s to mid
90s. In addition, dew points will be slightly higher in the
lower 70s at most locations, leading to heat index values to top
out in the lower 100s at many locations. The lower Genesee
Valley and city of Rochester will be close to heat warning
criteria (105).

The region will remain within an upper level ridge, with a weak
flow aloft. Instability thunderstorms are possible during the
afternoon hours, especially along and inland of lake breezes.
PWAT values will remain high, with slow storm motion again
presenting a risk for localized flash flooding where storms
develop.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/...
-- Changed Discussion --
...Heat Advisory in Effect for the Entire Area as Dangerous Heat
Builds Through Thursday...

Well above normal temperatures and dangerous heat index values will
continue through Thursday. Temperatures & dewpoints drop a few
degrees for Friday and into the weekend, but humid conditions
overall will linger. With the warm and humid conditions, the
potential for showers/thunderstorms will continue through the
weekend.

Wednesday night into Thursday, an approaching weak cold front along
with a flattening trough to the north will continue the potential
for showers and thunderstorms across the region. The loss of daytime
heating Wednesday night will help diminish some shower/storm
coverage. The potential for scattered showers and storms will
continue into the morning on Thursday before becoming better
organized along lake breeze boundaries in the afternoon and as a
weak cold front drops southeast across the area. There is a
`Marginal Risk` from the SPC for the entire area as plenty of
instability will be in place for storms to develop, but shear values
will be relatively low. Temperatures remain hot and humid for
Thursday ahead of the weak front, highs will return to the upper 80s
to mid 90s. Combined with high dewpoint values, index readings into
the mid 90s to around 100.

Thursday night and Friday, the frontal boundary stalls over the
forecast area and will continue to provide the opportunity for
showers and thunderstorms with the best chance for showers toward
the NY/PA line. High temperatures on Friday will cool a few degrees
down to the mid 80s to low 90s, on the northern side of the frontal
boundary. If the front stalls farther north, then temperatures will
be a bit warmer.

Friday night, the front stalled over the area will start to slowly
push north as a warm front late in the night and into the early
morning on Saturday. There should be a break in the shower/storm
activity, especially with the lack of diurnal processes.
Showers/storms potential will increase around/after daybreak
Saturday morning as the front starts moving north and a ribbon of
vorticity and area of increased moisture pushes toward and across the
region. As of now, the best chance for showers early Saturday
morning looks like it should be over the North Country. Certainly
can`t rule out a shower or storm for the rest of the area as the
warm sector of a sfc low tracking north of the region moves back
into the area.
-- End Changed Discussion --

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
-- Changed Discussion --
The warm sector of a sfc low crossing the Great Lakes will be in
place for Saturday and Sunday continuing the potential for
showers/storms across the entire area. Temperatures will be a few
degrees warmer than Friday, but not as warm as the current mid-week
temperatures.

The cold front associated with the sfc low passing to the north will
cross the area on Sunday evening and into the night, causing more
organized showers/storms to move through the area. A potent
shortwave trough tracking across the area behind the passing front
will continue the shower potential for Monday.

Increased ridging and an incoming sfc high will result in drier
conditions for Monday night through the rest of the period.

Temperatures will be well above normal for the weekend with highs in
the mid 80s to low 90s. Temperatures cool behind the passing cold
front to the mid 70s to low 80s for Monday before warming again for
Tuesday back to the low to upper 80s.
-- End Changed Discussion --

&&

.AVIATION /20Z TUESDAY THROUGH SUNDAY/...
Mainly VFR flight conditions for the 18Z TAF cycle. Scattered
thunderstorms will develop this afternoon, and these may briefly
result in heavy rain and IFR or lower conditions at times.
Greatest risk for this is at KJHW. Storms will weaken and
decrease in coverage tonight.

Chances for thunderstorms increase again Wednesday afternoon due
to daytime instability. Without a large scale trigger for the
convection, it should be scattered with best chances in the
Western Southern Tier and Upper Genesee Valley.

Outlook...

Wednesday night through Saturday...Mainly VFR, but a chance for
afternoon and evening thunderstorms inland from the lakes.

Sunday...VFR/MVFR. A chance of thunderstorms.

&&

.MARINE...
High pressure will be near the eastern Great Lakes through much of
this week, offering light winds, generally 15 knots or less on the
lakes. Locally higher winds and waves are possible in scattered
periodic thunderstorms.

&&

.CLIMATE...
A prolonged period of heat is expected for our region this week.
Below are record high temperatures for our three main climate
sites:

...Buffalo...

...Date.....Record Maximum (F)...Record warm Minimum (F)...

...June 18........95/1994............73/2006
...June 19........90/2001............73/1919
...June 20........92/1995............73/2012


...Rochester...

...Date.....Record Maximum (F)...Record warm Minimum (F)...

...June 18........97/1957............72/2018
...June 19........95/2001............72/1919
...June 20........95/1953............72/1923


...Watertown...

...Date.....Record Maximum (F)...Record warm Minimum (F)...

...June 18........91/1957............70/1992
...June 19........91/2007............70/1949
...June 20........90/1971............71/2012

Temperature records for Buffalo and Rochester date back to 1871.
Temperature records for Watertown date back to 1949.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Heat Advisory until 8 PM EDT Thursday for NYZ001>008-010>014-
     019>021-085.
MARINE...None.

&&

$$

SYNOPSIS...Apffel
NEAR TERM...Apffel
SHORT TERM...SW
LONG TERM...SW
AVIATION...Apffel
MARINE...Apffel/TMA
CLIMATE...Thomas/TMA