305
FXUS61 KBUF 222025
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
425 PM EDT Mon Jul 22 2024

.SYNOPSIS...
A more humid air mass combined with a series of weak systems will
bring periodic chances of showers and thunderstorms through
Thursday, along with some rain free time. A cold front will then
cross the area late Thursday, followed by high pressure bringing a
return to dry weather Friday through next weekend.

&&

.NEAR TERM /THROUGH TUESDAY/...
A west to east frontal boundary is across our region early this
evening. This boundary will lift northward and a more moist and
unstable air mass will move into the region tonight. Diurnal
instability and a shortwave trough will result in showers and
thunderstorms developing this evening, with the frontal
boundary providing a focus for this convection. The main concern
is that storms will train or stall along the boundary,
resulting in locally heavy rainfall. Precipitable water values
are 1.5 inches which is moderate for this time of year, but
definitely ample to cause flash flooding if storms are slow
moving. Convection will be slow to develop, but should expand in
coverage when a weak shortwave moves through this evening (4 to
10 p.m.). The most widespread showers and thunderstorms will be
just south of the boundary, including the Western Southern
Tier, Upper Genesee Valley, and Western Finger Lakes. This is in
line with most mesoscale guidance and the latest WPC outlook
which has a marginal to slight risk for excessive rain in these
areas.

Otherwise, temperatures will rise into the 80s this afternoon and
with dewpoints rising into the mid to upper 60s it will be more
humid and less comfortable than the past several days.

The showers and thunderstorms will gradually taper off from west to
east later tonight, although rain chances will not end entirely with
moisture and weak forcing still lingering. Lows will average in the
lower to mid 60s.

On Tuesday there will be a broad trough across the Great Lakes
region, but model guidance doesn`t really show any disturbances
moving across the region. Diurnal instability will support generally
scattered showers and thunderstorms during the afternoon hours, and
mainly located along and inland of lake breeze boundaries. Slow
moving storms could produce locally heavy rainfall, but expect
coverage to be more sparse than today.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
A longwave trough will slowly dig across the Great Lakes through
midweek as it translates eastward to New England by Thursday. A
strengthening southwesterly 250mb jet streak between this trough and
the Bermuda High over the Atlantic will allow for a plume of GOMEX
based moisture to advect into the Northeast and especially the Mid
Atlantic region. This will be reflected in surface dewpoints across
the forecast area climbing into the upper 60s to low 70s Wednesday
as PWATs peak around 1.75" Wednesday night. With the encroaching
trough and moist airmass in place, expect an unsettled stretch of
weather with on and off chances for showers and thunderstorms, some
of which could produce locally heavy rainfall.

Looking a bit closer at the details...While scattered convection
leftover from Tuesday should diminish in coverage Tuesday night into
Wednesday morning, enough elevated instability will be in place to
allow for low-end chances for an overnight shower or thunderstorm
across the interior. Moving into Wednesday, there could be some
upper level support from the aforementioned strengthening jet
streak, and this will be reflected at the surface by a broad area of
weak low pressure across the eastern Great Lakes and southern
Ontario. Though, greater synoptic forcing will otherwise be absent
with weak to modest flow through the mid-levels and a lack of height
falls aloft. Thus, given the setup would expect convection Wednesday
to be driven primarily by diurnal instability, with coverage of
afternoon showers and storms maximized inland from the lakes. While
the possibility of better organized convection looks marginal at
best Wednesday with 0-6km bulk shear around 25kts, short to modest
MBE vectors and PWATs in the 90th percentile compared to climatology
will allow for slow moving storms with elevated rainfall rates,
highlighting localized excessive rainfall as the primary concern
at this range.

Later Wednesday evening and into Thursday morning, the longwave
trough`s primary axis will begin to more quickly pivot through the
Great Lakes region. This will push a cold front through the region
from the northwest, preceded by a weak prefrontal trough. More
pronounced height falls will maintain chances for showers and
thunderstorms through the pre-dawn hours Wednesday night, with
chances being greatest across the North Country and Finger Lakes
region late Wednesday night into Thursday morning. Given the poor
diurnal timing would again expect organized convective potential to
remain limited, though locally heavy rainfall will remain a
possibility. Model guidance has been trending a bit faster with this
system overall, and thus a faster FROPA Thursday morning. With very
limited moisture in the wake of the front, if current trends hold
much of western NY could be completely dry by late morning, with the
interior locations dry by mid afternoon. Outside of a few lingering
showers up across the North Country Thursday night, mainly dry
weather will prevail areawide thereafter.

Temperatures Wednesday will top out in the low to mid 80s with
increased humidity in most spots, upper 70s being more common across
the hilltops. With the frontal passage occuring earlier in the day
Thursday, expect a more pleasant day temperature and humidity wise
with a range of 70s for highs. For overnight lows, expect warm and
somewhat muggy conditions Tuesday and Wednesday nights, turning much
cooler in the post-frontal airmass Thursday night.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
A trough axis will lie across the Northeast Friday morning.
Meanwhile as the trough axis exits the Atlantic coastline, a broad
ridge across the upper Great Lakes will also advance east towards
the lower Great Lakes. This ridge will then sit across the Northeast
for the weekend into the start of the new work week. Translating
this pattern aloft down to the surface, high pressure overhead of
northern Ontario and the Great Lakes, will continue to nudge east
across the area Friday. This surface high will then slide southeast
across the Northeast into the Atlantic this weekend into the start
of the work week.

This all being said, showers across the eastern Lake Ontario region
early Friday morning will be ushered east out of the area as the
surface high pressure enters the region. Then dry weather will
persist through the weekend and into the start of the new work week
with the surface high overhead.

Surface temperatures will gradually increase each day. Highs Friday
will range in the mid to upper 70s and topple out this weekend and
Monday in the mid to upper 80s.

&&

.AVIATION /20Z MONDAY THROUGH SATURDAY/...
Mainly VFR flight conditions this evening. Diurnal instability,
a shortwave, and a stalled frontal boundary will result in
showers and thunderstorms developing this evening. Most of this
activity will be south and east of our TAF sits, but it may
clip them at times resulting in temporary MVFR or lower flight
conditions. Showers and storms will exit to the east late
tonight, leaving mostly rain free weather through Tuesday
morning. Low stratus may re-develop across the Southern Tier
tonight with a risk of MVFR or even IFR flight conditions at
KJHW late tonight and into Tuesday morning.

Scattered showers and storms develop Tuesday afternoon, possibly
temporarily impacting TAF sites even if the vast majority of the
time will be VFR.

Outlook...

Tuesday night through Thursday...VFR/MVFR with showers and
thunderstorms likely at times, especially inland from the lakes.

Thursday night through Saturday...VFR.

&&

.MARINE...
Winds are expected to remain relatively light through much of the
week. There is a chance of a few thunderstorms at times from this
afternoon through Thursday, although the better chances will be
inland from the Lake Erie and Lake Ontario.

&&

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

&&

$$

SYNOPSIS...Apffel
NEAR TERM...Apffel/HSK
SHORT TERM...PP
LONG TERM...EAJ
AVIATION...Apffel/HSK
MARINE...Apffel