339
FXUS61 KBUF 210555
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
155 AM EDT Sun Jul 21 2024

.SYNOPSIS...
A weak, limited moisture cold front will drop southward across our
region today, with a few isolated showers upon it. Humidity begins
to build Monday, and along with this increasing chances for showers
and thunderstorms, especially during the afternoon and early evening
hours. Temperatures through the first half of the week will be near
to just above normal.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Tonight through Sunday, a mid level trough will dig southeast across
Quebec, forcing an associated weak backdoor cold front south across
NY and New England. DPVA ahead of the trough and low level
convergence along the frontal zone, along with a narrow axis of
moisture will support scattered showers tonight across the Saint
Lawrence Valley, although the best chance of rain will stay mainly
north of Jefferson and Lewis counties most of the night. The best
chance of rain for our portion of the North Country will be late
tonight through Sunday morning. Otherwise the rest of the area will
stay dry tonight. Expect some patchy valley fog across the western
Southern Tier.

The weak backdoor cold front will continue to drift south Sunday,
crossing the remainder of the area before stalling and washing out
across northern PA Sunday night. The majority of the large scale
forcing for ascent will move east across northern New England later
Sunday, leaving the weak low level front orphaned from synoptic scale
forcing. The weak zone of low level convergence will support a band
of cloud cover and perhaps in isolated shower. The best chance of a
few showers will likely be found along a line from near or just
northeast of Buffalo down through the western Finger Lakes where the
advancing weak cold front will interact with the Lake Erie lake
breeze, resulting in a WNW to ESE oriented zone of low level
convergence.

Any showers that do materialize will taper off and end Sunday
evening, leaving mainly dry weather to prevail Sunday night. Clouds
may linger for a portion of the night across Western NY as the
frontal zone stalls just south of the region, and a weak mid level
shortwave begins to move northeast out of the Ohio Valley. Expect
patchy valley fog once again across the western Southern Tier.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY NIGHT/...
The persistent surface ridge which has kept our weather dry will
gradually break down early next week. The weakening ridge will keep
most area rain-free Monday, but a weak mid-level shortwave will
approach the region bringing small chances for showers and
thunderstorms inland of northeasterly lake breezes. This includes
the Western Southern Tier, western Finger Lakes, and the upper
Genesee Valley. Showers and a few thunderstorms may linger into
Monday night at these locations.

12Z model consensus is a bit faster with this shortwave, with some
models having the shortwave exit into New England by Tuesday
afternoon. As a result, will scale back PoPs some on Tuesday,
although a broad cyclonic flow and diurnal instability have the
potential to generate some showers and thunderstorms. Weak flow
aloft will lead to slow moving storms, but PWAT values will be
modest at around 1.4 inches so the flood potential will be limited
by non-zero. WPC has southern portions of the forecast area in a
marginal risk for excessive rainfall.

Temperatures will be slightly above normal with daytime highs in the
upper 70s to mid 80s. With dew points in the lower to mid 60s it
will not feel as muggy as it could be in July.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
An upper level trough will dig across the Great Lakes region
Wednesday and Thursday before sliding east across New England on
Friday. This will tap into some GOMEX moisture, with dew points
increasing into the upper 60s and PWAT values increasing to about
1.7 inches. The approaching trough will result in persistent chances
of showers and thunderstorms Wednesday and Thursday, especially
during the afternoon and evening hours when diurnal instability will
peak. A few strong thunderstorms can`t be ruled out, but forecast
wind profiles show modest winds aloft which suggest locally heavy
rain is the greater risk. Typical long range model discrepancies on
how the trough will evolve limits certainty in timing, placement,
and amounts.

There will be some lingering cloud cover and possibly a few showers
Friday as the trough exits into New England. Then fair weather
returns just in time for the weekend, with high pressure building
across the region Saturday.

Temperatures will depend on convection and cloud cover, but in
general will average near to slightly above normal during the period.

&&

.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
For the 06Z a cold front dropping southward across across the Saint
Lawrence Valley will continue to push southward through the TAF
cycle. Moisture is limited upon this front, and though VFR clouds
will thicken upon the front, shower chances will remain low.

Ahead of the front this morning, clear skies across the Southern
Tier will allow for fog formation. As in past nights, this fog bank
is struggling to reach KJHW, and will just place VCFG in the TAF.

By evening clouds will begin to diminish as well as chances for any
isolated showers. Clearing in the Southern Tier will again allow for
some fog formation in the valleys of the Southern Tier.

Outlook...

Monday...Mainly VFR. A chance of showers and thunderstorms in the
afternoon, mainly across the Southern Tier and Finger Lakes.

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

Thursday...Areas of MVFR with showers and thunderstorms likely.

&&

.MARINE...
A weak backdoor cold front will drift south across Lake Ontario
overnight through early Sunday with little fanfare other than
forcing winds to veer from the west-southwest this afternoon to the
north overnight, and then northeast on Sunday. Winds will generally
remain 10 knots or less with little wave action through the rest of
the weekend.

Monday, east to northeast winds will increase into the 10-15 knot
range on Lake Ontario and Lake Erie, producing some chop on both
lakes.

&&

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

&&

$$

SYNOPSIS...Thomas
NEAR TERM...Hitchcock
SHORT TERM...Apffel
LONG TERM...Apffel
AVIATION...Thomas
MARINE...Hitchcock