166
FXUS61 KBUF 182120
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
520 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/...
While the airmass over our region is QUITE unstable...there is a
weak cap in place arnd H7 that has prevented any of the Cu from
really becoming enhanced. Part of this is due to the fact that our
convective temps of 92-93F have just been reached...as they were 3-4
hours delayed from the morning convection/cloud cover. VSBY imagery
is now showing some Cu trying to become enhanced over the far western
counties...but as mentioned...a cap arnd H7 and synoptic subsidence
under the mid level ridge is preventing much from happening.

We will have to watch a subtle wave moving out of northeast Ohio/
Northwest Pennsylvania though...as this could be enough to allow for
some of the Cu to finally break through the cap to develop into
thunderstorms. As we are all too aware by this point...our airmass
is sub tropical in nature with Tds in the vcnty of 70-74F. This
soupy airmass...combined with very short MBE vectors...will elevate
the risk that slow moving convection could produce torrential
downpours and very localized rain loaded downdrafts that could
support wind gusts over 40 mph. The latter is also supported by
DCAPE values in excess of 1000 j/kg.

As of 21z (5PM)...the area to watch will be the far western
counties...and particularly Chautauqua and Cattaraugus counties.
This is where outflow boundaries and general forcing from upstream
convection would have the greatest influence. This area will be under
the gun through about 00z.

Any evening convection will then diminish overnight with just a
chance for a stray shower or thunderstorm. 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/...
...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.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
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.

&&

.AVIATION /22Z TUESDAY THROUGH SUNDAY/...
Mainly VFR flight conditions for the 18Z TAF cycle. Scattered
thunderstorms will develop early this evening over the far western
counties, and these may 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 Lower 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/RSH
SHORT TERM...SW
LONG TERM...SW
AVIATION...Apffel/RSH
MARINE...Apffel/TMA
CLIMATE...Thomas/TMA