697
FXUS61 KBUF 272336
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
736 PM EDT Thu Jun 27 2024

.SYNOPSIS...
High pressure will drift from the western Great Lakes to the New
England coastline tonight and Friday providing us with dry and
comfortable weather. Low pressure tracking from the upper Great
Lakes to Quebec will bring a return to much more unsettled
weather Friday night and especially Saturday with periods of
showers and thunderstorms. High pressure and drier weather
return later Sunday and early next week.

&&

.NEAR TERM /THROUGH FRIDAY/...
A compact shortwave dropping southeast out of southeast Ontario
has brought a few convective showers, that are flattening as
they exit Lewis County this early evening.

Surface high pressure centered over the Central Great Lakes this
evening will build into the region tonight, before drifting
east into New England on Friday. This will provide the region
fair dry weather through Friday.

Mainly clear skies and light winds will allow for ideal conditions
for radiational cooling tonight with overnight low temperatures
dropping into the mid to upper 40s across the interior Southern
Tier/North Country to the lower 50s elsewhere. Some patchy fog
is possible within the Southern Tier Valleys overnight.

On Friday, a developing southeasterly flow on the backside of
the departing high will help send temperatures into the mid 70s
across the North Country and the upper 70s to near 80 elsewhere.
Humidity levels will remain comfortable with surface dewpoints
in the mid 40s to lower 50s.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
An active period is expected this timeframe as a mid level shortwave
trough crosses the Great Lakes region. This shortwave trough will
carry a surface low from the western Great Lakes Friday night to
near the SOO Saturday morning and then deepen the surface low some
as it crosses southern Quebec through Saturday night. A warm front
ahead of this surface low will bring initial prospects for rain
showers, with the cold front arriving Sunday morning sweeping the
high humidity and precipitation chances eastward.

Friday evening will start dry, and still on the comfortable side
with dewpoints in the low to mid 50s. A deep southerly flow ahead of
this shortwave trough will begin to increase moisture, and
subsequently increase surface dewpoints and humidity through the
night. Moist isentropic lift Friday night as a warm front extends
eastward towards our region, coupled with convergence along the nose
of a 30 to 35 knot LLJ will bring scattered showers and even a few
late thunderstorms to our region as MUCAPE values rise to 500 to
1000 J/KG generally along and west of the Genesee Valley.

Scattered showers and a few rumbles of thunder Saturday morning will
only increase in coverage area as moisture deepens, and a mid level
convective shortwave trough passes across our region.

The early evening timing of the pre-frontal trough, cloud cover
holding elevated instability back to around 1000 J/KG or less and
poor mid level lapse rates under 6 C/KM are not favorable for strong
to severe storms. However, 0-6 km bulk wind shear values 35 to 45
kts could aid in strength and structure to better organized storms
such that stronger wind gusts within such storms remains possible.
SPC has our region within a marginal risk for severe storms for
Saturday. Hail should be little to none. Wetbulb zero heights are
just too high, around 15K and a very moist airmass encouraging
melting on the way down will make for smaller hail stones if they do
develop. It will be humid Saturday with dewpoints in the low to mid
70s.

Perhaps the bigger threat will be heavy rainfall Saturday afternoon
and evening. Pwats on the 12Z GFS/NAM/ICON/GEFS are forecasted to
near or even exceed 2.00 inches. A measured PWAT of 2.00 inches is
uncommon for late June on radiosondes launched at the Buffalo
Airport. Only 7 instances (12Z or 00Z) of a PWAT of 2.00 inches or
more have been recorded since 1948. The time period for heavy rain
will be roughly noontime through 10 pm when peak heating of the day
can increase instability, and 0-6 km bulk shear increases to 50
knots allowing for better storm structure. Clusters of showers and
thunderstorms collecting ahead of a convective shortwave will be
moving owing to the wind fields aloft, but any thunderstorm can
quickly deposit an inch or more of rainfall in a short period of
time, and any training to cells will aggravate the potential for
poor drainage flooding.

A wind fields weaken aloft through the night and instability lowers,
as well as the eastward shift to the axis of deeper moisture,
thunderstorms, becoming scattered showers will diminish through the
night. It will remain muggy Saturday night, with patches of fog
forming as the cold front will remain off to our west.

Sunday the cold front will slice across our region. Temperatures
around 14 to 15C at 850 hPa Sunday morning will fall to the upper
single digits by late Sunday afternoon. We could still see a few
showers Sunday along the front, with chances higher to the east as
increasing instability will encourage showers growth. Dewpoints will
be falling through the day, with a much more comfortable afternoon
in store with temperatures in the low to mid 70s.

Cool Sunday night as a ridge of high pressure passes overhead. The
850 hPa temperatures around 7C over the warm lakes may encourage
some lake induced clouds within a northerly flow. Towards the west
fog will likely form within the river valleys. Lows will drop back
into the 50s, and in the colder locations of the inland Southern
Tier and Tug Hill may even reach the upper 40s.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
Surface high pressure will move across the eastern Great Lakes
region Monday through Monday night. This will bring a period of dry,
and seasonable weather for the region Monday through Tuesday. Then,
warmth and humidity will increase as the high shifts to the east
Tuesday through Thursday. Weak troughing will replace weak ridging
and a cold front is expected to move across the region Wednesday
through Thursday. This will increase the chance for showers and
thunderstorms during this time.

Temperatures will begin below normal Monday with highs in the low to
mid 70s. Day to day warming will occur Tuesday through Wednesday
with highs averaging the upper 70s to low 80s Tuesday to the mid to
upper 80s Wednesday. Temperatures Thursday will depend on the timing
of the cold front with high temperatures ranging from the low to
upper 80s. Humidity values will increase Wednesday.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
For the 00Z TAFS VFR flight conditions are found and these will
largely continue through the TAF cycle as high pressure over the
central Great Lakes builds eastward towards the eastern Great
Lakes. Northwest winds will become light and variable a few
hours after sunset. Within these light winds, valley fog is
expected to form, that may near KJHW after midnight.

High clouds will spread across the TAF region tomorrow, with
VFR flight conditions after any morning fog dissipates.

Outlook...

Friday night...Mainly VFR with a chance of showers.

Saturday...Localized restrictions likely in increasingly
widespread showers and scattered thunderstorms...some of which
may produce locally heavy rainfall.

Sunday...A chance of a leftover shower or two...otherwise
mainly VFR.

Monday and Tuesday...VFR.

&&

.MARINE...
Winds on the lower Great Lakes tonight will become light and
variable as high pressure from the western Great Lakes builds into
the region. Mainly easterly winds at 12 knots or less will
develop Friday as the high departs across New England, but some
local onshore breezes will likely develop during the afternoon.

Southeasterly winds early Friday night will veer to southerly as
a warm front lifts into the lower Great Lakes. These southerly
winds may increase to over 15 knots Saturday, but wave heights
in US waters likely remaining 3 feet or less.

A cold frontal passage will bring scattered thunderstorms Saturday
afternoon and Saturday evening with the potential for locally
gusty winds and higher waves. Behind the frontal passage,
westerly winds will strengthening to near 20 knots with a period
of advisory conditions possibly developing Sunday on both Lake
Erie and Lake Ontario.

&&

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

&&

$$

SYNOPSIS...JJR/TMA
NEAR TERM...Thomas/TMA
SHORT TERM...Thomas
LONG TERM...HSK
AVIATION...Thomas
MARINE...TMA