177
FXUS61 KBUF 151320
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
920 AM EDT Mon Jul 15 2024

.SYNOPSIS...
An area of thunderstorms will move across the area this
afternoon and evening, bringing a risk of gusty winds and heavy
downpours. An unsettled pattern will continue through mid-week, bringing
periodic chances for showers and thunderstorms. A cold front
will sweep across the area midweek with high pressure building
in its wake bringing mainly dry weather along with cooler and
much less humid conditions for the second half of the work week.

&&

.NEAR TERM /THROUGH TONIGHT/...
...RISK FOR SEVERE THUNDERSTORMS WITH DAMAGING WINDS AND HEAVY
DOWNPOURS THIS AFTERNOON AND EVENING...

IR satellite imagery shows an MCV across eastern Michigan this
morning, with this expected to track across Lake Ontario this
afternoon and evening. MCVs are commonly linked to severe
weather in our area since they increase wind shear to the south
of its track. In this case, timing is diurnally favorable.
Most mesoscale guidance and in particular the HRRR show a
potent area of convection moving from west to east across the
area this afternoon and evening. Feel the HRRR may be a bit slow
compared to current radar trends but it shows a realistic
depiction of what is likely to happen. The timing for the
greatest risk for severe weather in the Niagara Frontier
(Buffalo area) 2 - 5 p.m., Genesee Valley (Rochester area ) 3 -
7 p.m., and Eastern Lake Ontario (Watertown area) 4 - 8 p.m.

There is not as much wind shear as last week (July 10th) when
there were multiple tornados in the forecast area, but there is
ample shear to support damaging winds in-line winds. However,
this should not be downplayed, since damaging winds typically
impact a larger area and can still cause significant damage. The
risk for tornados is non-zero, but for most areas in-line wind
gusts will be the main concern. SPC is on board as well with
much of western and northcentral NY in Slight Risk.

With PWATs up around 1.75 inches, any storms could produce
torrential downpours, although the localized flash flooding risk
is a lesser risk as this activity will be moving fairly
quickly.

Otherwise, the very warm and humid conditions will continue
today with highs mainly in the mid to upper 80s and dew points
in the upper 60s to lower 70s. With the growing confidence for
convection today, believe apparent temperatures will remain
below Heat Advisory criteria across the Genesee Valley and
northern Finger Lakes with the system impacting the area during
the afternoon hours.

Convective wave moves east of the area tonight. Can`t rule out a few
scattered showers or an isolated storm overnight, however expect
bulk of the area to remain dry. The next convective wave progged to
bring the next round of showers and storms on Tuesday will approach
western NY as it moves east over western Lake Erie/northern OH late
tonight. It will be another warm and very stick night with lows in
the upper 60s to low 70s.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
Tuesday, a longwave trough will remain well upstream of the area
over northwest Ontario. A weak low level trough axis will remain
from the Ohio Valley to New England, with its position modulated by
numerous rounds of convection and associated composite outflow.
Another convectively generated vorticity maxima is forecast to move
east along this boundary Tuesday, supporting another round of
showers and thunderstorms crossing the area from west to east.

Latest model guidance suggests a relatively early arrival of this
feature, moving into Western NY in the morning, then Central NY and
the eastern Lake Ontario region by early afternoon. The arrival of
forcing, clouds, and showers early in the diurnal cycle will likely
limit potential instability and brings a great deal of uncertainty
to the severe weather potential. Deep layer shear is not
particularly strong, up to 30 knots, but the MCV will likely bring a
mesoscale region of enhanced low/mid level shear, convergence, and
ascent as it crosses the region. If stronger storms develop in the
presence of this more favorable MCV environment, localized strong
winds would be the primary hazard.

In the wake of the MCV, a few more showers and thunderstorms may
develop along lake breeze driven convergence zones in the afternoon
and evening, mainly from the Southern Tier through the Finger Lakes
and Central NY. Increasing southwest flow off Lake Erie will likely
produce a stable lake shadow northeast of the lake with mainly dry
weather following the morning/midday convection.

It will be very warm and humid again Tuesday, with highs in the low
80s for Western NY and mid to upper 80s from the Genesee Valley into
Central NY. There may be a brief window of mid 90s heat index from
the Genesee Valley into Central NY, but clouds and convection may
keep temperatures a few degrees lower and prevent Heat Advisory
criteria from being reached.

Tuesday night through Wednesday night the longwave trough will
gradually dig through the Great Lakes, ending up in Quebec by
Thursday morning. One or more convectively augmented shortwaves may
cross NY/PA Tuesday night through Wednesday, supporting ongoing
chances of a few showers and thunderstorms at times. The cold front
will cross the region later Wednesday afternoon, with the chance of
showers and thunderstorms then ending from northwest to southeast
late Wednesday through Wednesday night. Drier and less humid air
will arrive later Wednesday night in the wake of the cold front.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
A period of much drier, less humid, and somewhat cooler weather will
arrive Thursday and likely last through next weekend. A strong ridge
will remain centered over the 4-corners and Great Basin late week
through next weekend, with a downstream trough over eastern
Canada, the Great Lakes and New England. The persistent trough will
keep true heat and humidity at bay.

Thursday will be relatively cool by mid summer standards as a pool
of cool air aloft crosses the region, supporting highs in the mid to
upper 70s for lower elevations and lower 70s for higher terrain.
The airmass will quickly modify, with highs around 80 Friday and
then into the low to mid 80s over the weekend for lower elevations.
Humidity will remain tolerable however, with dewpoints in the 50s to
low 60s.

Surface high pressure will remain over the Great Lakes, Ohio Valley,
and New England much of the time Thursday through Sunday with dry
weather prevailing. A weak cold front will move south towards the
area Sunday, but more favorable large scale forcing and moisture
remain north and east of the area.

&&

.AVIATION /13Z MONDAY THROUGH FRIDAY/...
Area of mainly MVFR/IFR CIGS will continue through mid to late
morning across the far western NY terminals (KBUF/KIAG/KJHW) as
enhanced low level moisture moves in across these areas in advance
of approaching wave. These CIGS may last for several hours before
mixing out late this morning.

Otherwise, a convectively augmented shortwave will push across the
region this afternoon and evening with growing confidence for
showers and thunderstorms. Expect brief periods of MVFR/IFR in
heavier showers and storms, with mainly marginal MVFR to low VFR
CIGS otherwise.

Aforementioned wave will move east of the area late in the day/early
evening with a return to predominantly VFR conditions tonight.

Outlook...

Tuesday and Tuesday night...VFR/MVFR with scattered to numerous
showers and thunderstorms.
Wednesday...VFR/MVFR with a chance of showers and thunderstorms.
Thursday and Friday...VFR.

&&

.MARINE...
Southwest winds will increase in response to the passage of an
MCV, resulting in a brief period of small craft conditions on
Lake Erie this afternoon and evening. Southwest flow will
increase again late tonight through Tuesday, producing more
notable chop on both lakes, with possibly a brief period of
Small Craft Advisory conditions on Lake Erie Tuesday.

There will be periodic chances for thunderstorms across eastern Lake
Erie and Lake Ontario through Wednesday, with the potential for
locally higher winds and waves in and near any storms.

&&

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

&&

$$

SYNOPSIS...JM
NEAR TERM...Apffel/JM
SHORT TERM...Hitchcock
LONG TERM...Hitchcock
AVIATION...JM
MARINE...JM/Apffel