687
FXUS61 KBUF 051740
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
140 PM EDT Wed Jun 5 2024

.SYNOPSIS...
A slow moving cold front will press through the region later tonight
and Thursday...and while this will lead to increasingly widespread
showers and possibly some drenching thunderstorms...it will also
bring an end to our stretch of summery weather. In fact...
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 THURSDAY NIGHT/...
It will be warm and humid across the region this afternoon...as a
deepening southerly flow ahead of an approaching cold front will
allow a sub tropical airmass to move in from the Ohio valley. Td`s
will climb to the mid and even upper 60s for much of the forecast
area...and this will set the stage for some potentially drenching
thunderstorms.

As of midday...an area of nuisance showers was in the process of
moving across the far western counties. This activity is in the
vcnty of an elevated warm front. During the course of the
afternoon...the showers will continue to move northeast while
spreading over much of the rest of the western counties. The
environment is already unstable to the tune of 1500-2000 j/kg of
SBCAPE...so its only a matter of having any weak boundaries from the
aforementioned area of showers being able to initiate the
convection. If this were to occur...it would be over the Genesee
valley and Finger Lakes after 2 PM. DCAPE values in the vcnty of
1000 j/kg would then promote the risk for gusty storms for those
areas. Otherwise...locally heavy rain would be the only real
concern.

Meanwhile...areas east of Lake Ontario will continue to enjoy sun
filled skies with only some cirrus to contend with. This area will
be the warmest with highs in the upper 80s to near 90...which would
once again be record territory for Watertown (87 in 1973).

The deep plume of sub tropical moisture will be situated over our
region tonight...while a cold front will SLOWLY move through. Given
the moisture rich airmass that will be in place...the forcing from
the front will generate numerous showers and thunderstorms...some of
which will include pockets of heavy rain. The activity will be
scattered in nature through much of the evening...then it will
become more focused along and just ahead of a cold front over the
western counties after midnight. This timing is a little slower than
previous forecasts. Along with the `heavy rainers`...there will
still be the risk for localized gusty winds with some of the storms.

As we move through the wee hours of the morning towards daybreak...
the most concentrated areas of showers and possible thunderstorms
will make their way to the Eastern Lake Ontario region. The risk for
gusty winds with the convection should drop off by this point.
Otherwise...tonight will be a warm and muggy night with mins in
the more populated regions not falling below 65.

Thursday...the slow moving cold front will make its way across the
Eastern Lake Ontario during the morning hours. This will continue to
support cat pops for that area along with the potential for locally
heavy rain. The scenario will be far more convoluted over the
western counties.

While a negatively tilted mid level trough will continue to dig
over the Lower Great Lakes on Thursday...weak sfc based ridging will
develop over the western counties. This combination will work
against organized shower activity...except within a pronounced area
of low level convergence that will become established from KIAG past
KROC...basically just north of the NYS Thruway. Showers will be
likely in this particular corridor. For the immediate BUF area to
near KGVQ...a lake shadow is expected with gusts to near 30 mph.

The real airmass change though will take place Thursday night in the
wake of a secondary cold frontal passage. This will bring a
temporary end to the scattered shower activity...as Tds will drop
into the 50s. Towards daybreak though...deeper moisture on the
backside of a deep mid level low in the vcnty of the SOO will start
to circulate across the Lower Great Lakes. Lift underneath the front
left exit region of an 80-90kt H25 jet should be enough to restart
at least scattered shower activity over the far western counties...
and particularly across Chautauqua county and srn Erie co.

&&

.SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...
A closed low will become centered over central Ontario and central
Quebec Friday. A stretch of cooler weather (compared to earlier
this week) will begin Friday with 850mb temperatures falling to
+4C by Friday afternoon. A sharpening shortwave trough will
move across the region during peak heating hours Friday. Showers
will blossom with a slight chance of thunderstorms Friday
afternoon. In fact, based off the lake temperature at Buffalo
(63F/17C,) lake enhancement is possible, however the open water
on Lake Erie and Lake Ontario is much cooler. A moist, cyclonic
flow will continue across the region Friday night and with some
lake enhancement, rain showers will continue overnight.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
A large closed low pressure system aloft will wobble about the
eastern Great Lakes through at least the weekend before slowly
transitioning to New England early next week. This will maintain the
cool, unsettled pattern across the region with chances for showers
and thunderstorms. There are differences in shortwave troughs and
timing of showers even though the overall synoptic pattern is in
agreement.

Coverage and intensity will mainly follow the diurnal insulation
trend each day, generally being greatest in the afternoon hours and
away from any stabilizing influence from the lakes. There is
considerable disagreement with timing of waves of shortwave energy
around the low aloft. PWATs don`t look to become anomalously
elevated at any point which should preclude the develop of more
widespread impactful storm complexes. The one possible exception to
this may come as the system`s main trough axis and cold front drop
southward and generate some heavy rain across the region sometime in
the second half of the weekend, but at this juncture uncertainty is
high in this occurring.

As alluded to previously, temperatures will run below normal this
period. Highs Saturday and Sunday will only manage to top out in the
60s for most, though warm a few degrees for Monday and Tuesday with
low 70s becoming more common. Lows each night will mainly be in the
low/mid 50s, with upper 40s possible further inland away from the
influence of the lakes.

&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
Some showers will be found over the western counties during the
remainder of the afternoon...along with a few heavy rain producing
thunderstorms. While VFR conditions will persist...MVFR cigs will be
possible in the vcnty of the convection. Meanwhile...fair VFR
weather will be found east of Lake Ontario.

As a cold front approaches and moves through tonight...more
widespread showers can be expected...along with some gusty
thunderstorms. The onset of the more widespread pcpn will include a
change to MVFR Cigs. IFR conditions will set up across the Srn Tier.

MVFR to IFR cigs Thursday morning will then gradually give way to
VFR weather. The most widespread showers and possible thunderstorms
will be east of Lake Ontario through 15z.

Outlook...

Thursday night...Mainly VFR weather.
Friday through Monday...VFR/MVFR with mainly daytime showers likely
with possible thunderstorms.

&&

.MARINE...
A southerly flow will strengthen today into tonight ahead of a slow
moving cold front approaching from the west. With the flow being
mainly offshore, the main impact will just be a bit of an uptick in
light chop toward the open waters.

The cold front will cross the lower Great Lakes late tonight and
Thursday morning, however expect a threat for thunderstorms this
afternoon through Thursday. SW to WSW winds will freshen on both
Lakes Thursday and 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 Thursday and
Friday afternoon, especially across eastern Lake Erie.

&&

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

&&

$$

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