-- Discussion containing changed information from previous version are highlighted. --
394
FXUS61 KBUF 061301
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
901 AM EDT Thu Jun 6 2024

.SYNOPSIS...
A slow moving cold front will press through the region with
showers likely today, and thunderstorms possible this
afternoon. Today will be the final day of this stretch of
summery-like weather as temperatures are slated to average below
normal from Friday through Monday of next week. The cooler
weather will be accompanied by fairly frequent shower activity.

&&

.NEAR TERM /THROUGH TONIGHT/...
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...Strong Thunderstorms Likely East of Rochester Today...

The first of two cold fronts is in the process of slowly pressing
across the far western counties. An area of moderately heavy showers
associated with this front will move to the northeast...but
additional showers and likely strong thunderstorms will then develop
over parts of the Finger Lakes and Eastern Lake Ontario region ahead
of the first cold front.

The airmass in the area of concern east of Rochester and Dansville
is certainly sub tropical in nature with PWAT values arnd 1.7" and
Td`s in the upper 60s...so there is no doubt that convection will
generate some heavy rain. There will also be the risk for strong to
severe weather. Breaks in the cloud cover should allow current
MLCAPE values of 500 j/kg to transition to SBCAPE values of 1000-
1500 j/kg by early afternoon. The final ingredient is enough shear
to be of concern...and current forecasts for bulk shear during peak
instability suggest values of 25-30kts. CAMs are forecasting linear
convection ahead of the front...with the highest risk for strong to
severe storms coming between 11 AM and 1 PM over the Finger Lakes
region...and between 1 and 4 PM across the Eastern lake Ontario
region.

Otherwise...partial clearing will take place in the wake of the
first front over the far western counties...although an area of sfc
convergence will stretch from IAG to ROC with some towering Cu
expected in that area for a few hours in the afternoon.

The second cold front will push through the area tonight. THIS...
front will lead the charge of a cooler and less humid airmass. While
the vast majority of the region will experience fair dry weather
tonight...deeper moisture circulating around a deep longwave trough
over eastern Canada will nose across the far western counties after
midnight. This will support the chance for some nuisance showers
over the far western areas...and with H85 temps forecast to drop to
arnd 6c...there could actually be some lake enhancement east of both
lakes. Otherwise...it will be a night to open those windows to allow
the fresh new airmass indoors. Mins will range from the mid and
upper 50s across the lake plains to the lower 50s across the bulk of
the Srn Tier and across the Tug Hill.
-- End Changed Discussion --

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY/...
A very unsettled pattern will continue Friday through the weekend as
a mid level closed low moves very slowly from near Georgian Bay
Friday morning eastward across southern Quebec over the weekend. A
multitude of shortwaves will round the base of the closed low and
bring periods of enhanced ascent and deeper moisture to our region,
producing frequent rain chances. These smaller scale shortwaves
become more difficult to place in time and space beyond a few days,
with the finer details of the forecast becoming more uncertain
beyond Saturday.

Friday, the base of the mid level low will move across the eastern
Great Lakes, bringing with it a period of deep moisture and ascent.
Cool temperatures aloft will support steepening lapse rates with
modest diurnal heating. The coverage of showers should still be
rather sparse early in the morning, but expect a quick expansion of
shower coverage and intensity by late morning into the afternoon as
the deeper moisture and forcing arrive and interact with steepening
lapse rates. Instability will be weak, but still may support some
isolated thunder in the afternoon and evening. Stable lake shadows
will keep shower coverage lower east and northeast of Lake Erie and
Lake Ontario, but the synoptic forcing may be strong enough to
overcome the lake shadows to some extent.

Friday night, showers will continue as the trough moves slowly east.
Temperatures aloft become cool enough to support lake enhanced
showers east of the lakes, especially east of Lake Ontario overnight
as 850MB temps fall to around +5C or so. This is a rarity in June,
but the cool temperatures aloft combined with well above normal lake
temperatures will bring our first lake effect rain showers of the
2024-2025 season.

Saturday through Sunday, the closed low and trough axis will
continue to move slowly east. Cyclonic westerly flow will continue
across the Great Lakes, along with a series of difficult to time mid
level shortwaves. The 00Z model guidance suggests the most notable
of these waves will move across the eastern Great Lakes Saturday
night, bringing a greater chance of more organized rainfall.
Otherwise, weak diurnal instability, lake breeze boundaries, and
general weak large scale forcing will continue to support scattered
to numerous showers and possibly a few isolated thunderstorms
Saturday through Sunday.

Temperatures will run below average through the period with the
persistent trough and cool air aloft in place. Highs Friday through
Sunday will generally be in the 60s.

&&

.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
The same general longwave pattern will remain in place across North
America through early next week, with an expansive ridge in the west
and a trough in the east. The trough and associated forcing, deeper
moisture, and cool air aloft will continue to support showers and
cool temperatures through at least Monday. By Tuesday, forecast
model guidance continues to show the trough axis making some
eastward progress to along or just off the east coast. There may
still be a few spotty showers, especially in the afternoon across
higher terrain inland from the lakes, but the coverage of showers
should be much lower than previous days.

Tuesday night and Wednesday height rises will spread across the Ohio
Valley and eastern Great Lakes ahead of another trough digging into
the upper Great Lakes. This will bring a brief interlude of dry
weather, but shower chances may start to increase again as early as
Wednesday afternoon with the approach of the upstream trough.
Temperatures will warm through midweek as the pool of cool air aloft
exits.

&&

.AVIATION /13Z THURSDAY THROUGH MONDAY/...
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While VFR conditions will dominate the region today...IFR to MVFR
cigs will be found in areas experiencing the showers and
thunderstorms. The storms could become strong to severe for sites
east of Rochester after 15z.

Mainly VFR weather will be in place for tonight...despite the
passage of a second front.

Outlook...

Friday through Monday...VFR/MVFR with mainly daytime showers likely
with possible thunderstorms.
-- End Changed Discussion --

&&

.MARINE...
A cold front will cross the Lower Great Lakes this morning. Showers
will continue with the threat for thunderstorms increasing across
the eastern half of Lake Ontario this afternoon. SW to WSW winds
will freshen on both Lakes today through Friday in the wake of the
cold frontal passage with choppy waters developing. Conditions may
possibly near Small Craft Advisory criteria for a couple of brief
periods, especially across eastern Lake Erie.

&&

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

&&

$$

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