237
FXUS61 KBUF 142319
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
719 PM EDT Wed Aug 14 2024

.SYNOPSIS...
High pressure centered over the Lower Great Lakes through Thursday
will guarantee fair dry weather for much of western and north
central New York. The area of high pressure will exit to our east
Thursday night, opening the door for a large, slow moving storm
system to impact our region later Friday through the upcoming
weekend. The most unsettled conditions will be Saturday and Sunday
when we can expect frequent shower activity.

&&

.NEAR TERM /THROUGH THURSDAY NIGHT/...
We can anticipate another beautiful night across the region, as a
large area of surface high pressure remains positioned over the
Lower Great Lakes.

Thursday will feature sun filled skies under the nearly stationary
surface high, but it will be a little warmer with temperatures
climbing into the low to mid 80s.

The area of high pressure will drift away to our east during the
course of Thursday night, slowly losing its control over the weather
across the area in the process. While dry weather will remain in
place, expect an increase in high level clouds across far western
New York.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY/...
The longwave pattern across the CONUS will evolve to bring the
forecast area a much more unsettled stretch of weather moving
towards the end of the week. This will come in the form of a deep
longwave trough digging south from Canada to the Ohio Valley across
the Great Lakes, flanked by ridges of high pressure across the
Rockies/central Plains and across the Canadian Maritimes. A
cyclonically curved jet streak rounding the base of this trough will
allow for a steady transport of GOMEX based moisture into the
eastern Great Lakes region, causing PWATs to sharply increase from
west to east Friday and remaining elevated through Sunday,
generally hovering in the 1.5-1.9" range. As these features
slowly shift eastward through the weekend, the trough will
become nearly vertically stacked while partially closing off in
the 850-700mb layer, as TC Ernesto slowly climbs north across
the western Atlantic. This will serve to slow the progression of
the trough, with the mid-level axis likely remaining upstream
through the period.

In terms of sensible weather, our stretch of mostly dry weather will
come to an end Friday and Friday night as a warm front and deep
synoptic moisture lifts into the eastern Great Lakes. While the day
should start off dry with just increasing mid/high cloud cover,
shower and thunderstorm chances will ramp up from west to east by
the afternoon. Convection could be as far east as the Genesee Valley
by early Friday evening, with showers and a few thunderstorms
`likely` ongoing in the western Southern Tier. Mid-range guidance
only indicating about 400-600J/kg of CAPE and < 30kts of bulk shear
in this area during peak heating, so while severe risk looks
limited, there`s a small chance in a few isolated strong wind gusts
Friday afternoon especially if any deeper convection that forms
upstream in the Ohio Valley (where CAPE values will be much higher)
manages to move into our region.

A period of widespread rain with embedded thunderstorms, some of
which could be heavy given the high PWATs, is expected Friday night
west of the Genesee Valley. With a lack of daytime instability this
activity should diminish some in coverage and/or intensity as it
moves towards the Finger Lakes and eastern Lake Ontario region
overnight. While there will likely be a brief break in the precip
back across WNY late in the night as a small dry slot works into the
region, the next slug of deep moisture will arrive back across the
western zones by Saturday morning. Thereafter, with the trough and
associated surface low slowly moving into the eastern Great Lakes,
expect very unsettled weather with occasional showers and
thunderstorms punctuating nearly the entire period. Coverage is
expected to be fairly widespread during peak heating in the
afternoon hours both days, though with large scale support present
convection could persist well into (or even through) Saturday night.
WPC has maintained a Marginal Risk for excessive rainfall across the
entire forecast area for both Saturday and Sunday.

In regards to temperatures this period. Friday and Friday night will
be warm and humid, with highs in the upper 70s/mid 80s and mid
60s/low 70s respectively. Thereafter, a general day-to-day cooling
trend is expected through the weekend.

&&

.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
A stacked low pressure system will be directly over the eastern
Great Lakes moving into Sunday night. This will likely displace the
greater forcing for ascent just east of the region as diurnal
instability falls off by Sunday evening. While this should reduce
the overall coverage and intensity of convection overnight, given
the proximity of the low, scattered showers and thunderstorms will
continue to be possible.

The mid-level trough axis should then slowly cross the region Monday
quickly followed by a period of strong cold advection, with the
latest suite of guidance trending a bit faster with this pattern
overall. While a few showers or thunderstorms are not yet out of the
question through Tuesday, have trended PoPs downward this period as
the airmass with the front looks very dry. Should this trend
continue to hold, could see Monday and especially Monday night into
Tuesday being even drier than NBM/continuity. Surface high pressure
should then guarantee a period of areawide dry weather Tuesday
night, though with the cooler airmass advecting overhead, precip
chances increase some again for Wednesday.

Much cooler and less humid air will arrive with the front Monday and
last through Wednesday. High temperatures will range from the upper
60s across the hilltops to the mid 70s across the lower terrain,
while overnight lows will fall back in the 50s to near 60 each
night.

&&

.AVIATION /23Z WEDNESDAY THROUGH MONDAY/...
High pressure anchored over the Lower Great Lakes will continue to
supply the vast majority of the region with fair VFR weather tonight
through Thursday night. The exception to this will be patchy fog
late tonight that could reduce vsbys to 2-4SM at sites like KJHW and
KELZ.

Outlook...

Friday...VFR but with scattered afternoon showers and thunderstorms
over the western counties.
Saturday and Sunday...MVFR to IFR with occasional showers and
thunderstorms.
Monday...VFR to MVFR cigs with scattered showers and possible
thunderstorms.

&&

.MARINE...
High pressure across the eastern Great Lakes will maintain quiet
conditions on Lake Erie and Lake Ontario through Thursday. The light
flow will favor the development of afternoon lake breezes through
Thursday. A southeasterly flow will develop by Thursday night and
Friday as a warm front approaches the region, but speeds should
remain less than 15 knots. A general south-southwest flow develops
behind the warm frontal passage for the weekend period as low
pressure meanders north of the lower Great Lakes.

Speeds could exceed 15 knots both Saturday and Sunday afternoons,
so cannot completely rule out the potential for marine headlines
this weekend. The risk for thunderstorms increases on the lower
Great Lakes Friday through Sunday.

&&

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

&&

$$

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