755
FXUS61 KBUF 290618
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
218 AM EDT Sat Jun 29 2024

.SYNOPSIS...
It will be quite unsettled the first half of the weekend...as a passing
warm front this morning will be the first of several boundaries that
will generate widespread showers and possibly some gusty...drenching
thunderstorms into tonight. Our sub tropical airmass will then give way
to less humid conditions in the wake of a cold front on Sunday...
although some showers will still be possible...especially east of
Rochester. High pressure will then guarantee perfect weather for
outdoor activities Monday and Tuesday.

&&

.NEAR TERM /THROUGH TONIGHT/...
...Torrential Downpours and Possibly Severe Weather Later Today...

Unfortunately...today will not be the nicest day for outdoor
activities. A broad storm system over the Upper Great Lakes will push
several frontal boundaries through our region during the next 24 hours
or so...and this will result in fairly widespread showers and possibly
some thunderstorms. The latter could include torrential downpours and
even isolated strong wind gusts. While there will be several hours of
dry time today...it will be difficult to try to time those breaks. Its
worth noting that any breaks in the cloud cover today will lead to a
notably greater risk for strong to severe thunderstorm activity.

The first boundary is a warm front that will push northeast across the
region during the course of this morning. A 40 knot low level jet
riding up and across this feature has been generating fairly widespread
light rain across the region since late evening and will continue to do
so for the Eastern Lake Ontario region into the initial daylight hours.
Meanwhile...scattered showers will be found across the remainder of
western New York. Some of these may be briefly heavy across the western
Southern Tier.

In the wake of the warm front...sub tropical air will flood northwards
across our forecast area within the associated warm sector. Tds will
surge into the lower 70s with PWAT values swelling to over 2 inches.
The latter is more than 2 STD above normal for late June and represent
values that are outside of 30 year climatology return intervals. This
warm plume of deep moisture will include high freezing levels that will
result in warm cloud depths in excess of 13k ft...maximizing the
efficiency of rainfall rates within the expected showers and
thunderstorms. This will elevate the risk for torrential downpours...
and with short MBE vectors expected...these downpours could be slow
moving or even build back to the southwest during their progression.

The forcing for the increasingly widespread showers and possible
thunderstorms today will be a pre-frontal trough that will trudge
through the area several hours behind the aforementioned warm front.
All of this has led to a slight risk for excessive rainfall...
especially across the western Southern Tier and Eastern Lake Ontario
region where CAMs and high-res guidance is favoring the most widespread
convection. Its worth noting that flash flood guidance suggests that it
would take roughly 1.5 to 2 inches of rain in an hour to induce
localized flooding concerns. A Marginal Risk of excessive rainfall will
be found elsewhere.

In regards to the risk of severe weather today...it will largely come
down to how much diurnally induced instability we can achieve. While a
few hundred joules/kg will be in the environment already...any breaks
in the cloud cover will potentially allow as much as 1000 j/kg of
SBCAPE to build. A 40-45kt low level jet will offer PLENTY of shear for
any true convection to become better organized. 6km bulk shear values
of 40kts or better will include 0-1km SRH that will exceed 200 m/s...
favoring the development of supercells...both in advance of any line
segments or within the convective clusters themselves. Given poor lapse
rates though...this threat will heavily depend on added diurnal
instability. The greatest chance for this will be across the western
Southern Tier with the highest risk of severe weather coming in the
form of damaging straight line winds along with isolated tornadoes.
Large hail is NOT anticipated given the poor lapse rates and likely
lack of SIGNIFICANT instability.

The plume of moisture will move east of the region as a cold front
approaches Saturday night. Showers and thunderstorms will remain
possible, however the threat for severe storms and heavy rain will
slowly diminish from west to east with the departure of the deepest
moisture and loss of diurnal instability.

&&

.SHORT TERM /SUNDAY THROUGH TUESDAY NIGHT/...
A shortwave trough will round the base of the mid-level trough
causing the longwave troughing pattern to pull east out of the lower
Great Lakes by Monday. This pattern aloft will support a secondary
surface cold front to pass from west to east Sunday, bringing with
it continued chances for showers and thunderstorms.

Surface high pressure and associated dry air will begin to filter
east across the Great Lakes Sunday night. High pressure will then
slide east across the lower Great Lakes into New England Monday and
Tuesday. With the dry air filtering in across New York Sunday night,
showers and thunderstorms will scatter out from west to east. Then
dry and quiet weather will persist through Tuesday.

With regards for temperatures late this weekend and into the start
of the week, expect a cool Sunday with highs in the upper 60s and
low 70s across Western New York and the North Country, however low
to mid 70s will lie across the Genesee Valley and northern Finger
Lakes. Low to mid 70s will then linger Monday before a rebound in
temperatures on Tuesday with highs in the upper 70s to low 80s due
to exiting high pressure.

&&

.LONG TERM /WEDNESDAY THROUGH FRIDAY/...
A mid level shortwave trough passing across southern Canada will
push a cold front slowly across our region Wednesday night, with
this front lingering near the NYS/PA state line Thursday and Friday.
Shower and thunderstorms through this period, and muggy, with
dewpoints in the low to mid 60s.

Wednesday will be the hottest day, with 850 hPa temperatures in the
upper teens (potentially topping 20C per the 12Z ECMWF) supporting
mid 80s to lower 90s. Clouds and storms around Thursday and Friday,
along with slightly cooler air aloft behind the front, will keep
temperatures in the 80 degree range.

&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
VFR conditions at the start of this TAF period will deteriorate shortly
after daybreak...as cigs will plunge to MVFR levels from west to east
near and in the wake of an advancing warm front. The lowering cigs will
be accompanied by some showers...and as we work through the initial
hours of Saturday...and increasing chance for thunderstorms.

MVFR to IFR conditions can then be expected regionwide Saturday
afternoon. A pre frontal trough pushing across the state will prompt
widespread showers and possible strong thunderstorms within a very
soupy sub tropical airmass.

While the heavy showers and thunderstorms will taper off from west to
east late Saturday afternoon and night...MVFR to IFR cigs can be
expected.

Outlook...

Sunday...VFR/MVFR with scattered showers.
Monday and Tuesday...VFR.
Wednesday...Mainly VFR.

&&

.MARINE...
An area of high pressure will move off the east coast tonight... a warm
front will approach the region from the southwest. Winds will respond
by swinging around to the south and increasing overnight.

It will then become quite unsettled on Saturday. Widespread showers and
possible strong thunderstorms will develop in the wake of the
aforementioned warm front during the course of the day...while fresh
to strong southerlies will generate more pronounced wave action. The
offshore wind for most shorelines will keep the larger waves in
offshore waters, but it will be quite choppy nonetheless. Small
Craft Advisory conditions will develop over the northeast end of
Lake Ontario where the wind direction is at least shore parallel,
allowing for more fetch to build waves.

Fresh southwesterlies Saturday night will then increase further and
become westerly on Sunday when SCA`s will be more likely...
especially on Lake Ontario.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...Small Craft Advisory from 7 AM this morning to 2 AM EDT Sunday
         for LOZ045.

&&

$$

SYNOPSIS...RSH
NEAR TERM...RSH
SHORT TERM...EAJ
LONG TERM...Thomas
AVIATION...RSH
MARINE...Hitchcock/HSK/RSH