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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KBUF 111115
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
715 AM EDT Thu Apr 11 2024

.SYNOPSIS...
A warm front will finish moving north across the area this morning
with steadier rain tapering off to scattered showers by this
afternoon, however it will become quite windy for the second half of
today. Periods of rain will and gusty winds then continue tonight
through Friday night. The rain may end as some wet snow Friday night
through early Saturday, especially across higher terrain.

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
A strong southern stream trough moving through the lower Mississippi
Valley will phase with another strong northern stream trough digging
through the Upper Midwest today. This will support further
strengthening of an area of low pressure as it moves NNE through the
Ohio Valley through this afternoon, before reaching western Lake
Erie by early this evening. Deep low/mid level southerly flow ahead
of the trough will transport abundant moisture northward into the
region today.

Steady rain across western NY as we near dawn this morning ahead of
a warm front moving north through southern NY. By later this
morning/midday, the warm front will continue north across Lake
Ontario and into Canada with steady rain tapering off from south to
north. In fact, the back edge of the steady rain shield is now
moving north through far northern PA. Our region will then break out
into the warm sector of the deepening system this afternoon. Ongoing
warm advection and moisture transport along with periodic fast
moving mid level vorticity maxima will continue to cross the region,
producing a few rounds of showers. Mid level drying and SSE
downslope flow will also support some dry periods as well between
areas of showers. Temperatures will likely rise into the lower 70s
on the lake plains in the afternoon with the boost of SSE downslope
flow as long as there are long enough breaks in the rain.

A windy second half of the day on tap as the strong low level jet
and tightening pressure gradient will allow winds to increase in the
afternoon. Expect gusts of 30-40 mph areawide. Gusts will likely be
higher along the Lake Erie shore in the downslope flow regime,
possibly up to 45 mph at times this afternoon. Despite the strong
LLJ off the deck, warm temperatures and lack of a low level
inversion may inhibit the typical downslope process to some extent
due to the lack of static stability near the ridgetops for areas
along the Lake Erie Shore northwest of the Chautauqua Ridge and the
areas north of the higher terrain of the Finger Lakes.

Tonight, low pressure continues to deepen as it moves north just to
our west. As the low slides north toward Georgian Bay it will send
it`s attendant cold front into western NY tonight. Strong convection
is forecast to develop across eastern Ohio later today and push into
far western PA early this evening ahead of the cold front. These
storms will try to push into southwestern NY this evening, however
with the loss of daytime heating expect convection to weaken
rapidly, although if it can hold together long enough would not rule
out a few storms having the potential to produce some gusty winds.
-- End Changed Discussion --

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
-- Changed Discussion --
Wet and windy conditions will persist to close out the week and
usher in the weekend. This will come as an 980mb low pressure system
in the vicinity of Georgian Bay Friday morning lifts northeast, then
partially fills in and weakens to near 984mb over Quebec through the
first half of the weekend.

As we open the period Friday, the system`s wavy cold front will lie
just west of the Genesee Valley with the strong southerly 850H jet
well to our east over New England. The front will march east through
the forecast area through the morning hours, reaching and then
quickly exiting the North Country by early to mid afternoon.
Steadier rains with a few embedded rumbles of thunder along or just
out ahead of the front will move east in tandem, while wrap-around
moisture will cause showers to slowly fill back in across WNY from
the southwest through the course of the day. Areas across the Finger
Lakes and along the southern shore of Lake Ontario may see a more
substantial break in the precip.

As the system becomes increasingly sheared Friday night, its mid-
level trough axis will swing through the eastern Great Lakes. This
will promote another round of widespread showers crossing the area
from west to east overnight. 850H temps bottoming out around -4
to -5C could support a few wet flakes mixing in across the
hilltops of the Southern Tier late. Not out of the question that
some spots wake up to some minor accumulations here by daybreak
Saturday. As for rainfall amounts, between Friday and Friday
night rainfall amounts will vary widely by location, though be
greatest (close to 1") where orographic lifting will come into
play east of the lakes, with generally 0.25-0.5" elsewhere. This
may lead to minor rises on the Buffalo area creeks and rivers
as well as the Black River east of Lake Ontario, though MMEFS
guidance continues to show very low flooding potential
otherwise.

In regards to wind potential this period...Deepening boundary layer
mixing within the CAA regime behind the front on Friday will lead to
a fresh southwest breeze across WNY. Wind gusts of 30-40mph should
become common across areas along and west of the Genesee Valley
during the day, with gusts of 25-35mph where the steadier rains
persist to the east. The strongest winds Friday are expected
northeast of Lake Erie, where winds funneling down the long axis of
the lake could bring localized gusts to 45mph from Buffalo to
Niagara Falls. A weakening LLJ on the western periphery of the low
Friday night will cause gusty WNW winds to spread westward
overnight. Here the strongest gusts (40-45mph) are expected to be
east of Lake Erie, while gusts of 30-40mph will likely be found
elsewhere.

Showers will taper off from west to east through the day Saturday as
a flattening ridge moves into the region. While wet weather will
likely persist across the North Country for a sizable portion of
the day, partial clearing should return to the western zones by the
afternoon. Mainly dry weather for the entire area then expected
through Saturday night.

For temperatures...A fairly large spread is expected Friday owed to
the initial frontal passage timing. Temperatures will likely top out
in the upper 40s across the hilltops of the western Southern Tier,
while highs in the mid 60s occur across the lower terrain of the
North Country earlier in the day. It will be on the chilly side
Friday night with lows in the 30s, while temps Saturday should
average near or just below climatological norms in the 40s to low
50s for most. Lows Saturday night will then range from the mid 30s
across the hilltops to the low 40s across the Lake Plains.
-- End Changed Discussion --

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
As we move into the latter half of the weekend...weak/transient
surface-based ridging will quickly slide off to our east
Sunday...allowing a weak surface low and its attendant warm front to
quickly approach our region. Increasing isentropic lift and
deepening moisture associated with these features will bring
increasing cloud cover and shower chances back into our region for
Sunday and Sunday night...with enough weak instability even present
to support the potential for a few isolated to widely scattered
thunderstorms south of Lake Ontario.

Following the passage of this weak system...another round of weak
surface-based ridging will slide across our area Monday and Monday
night and bring another brief interlude of mainly dry weather.
Another (and notably stronger) cutter-type low will then track from
the central Plains States to western Ontario Province Tuesday and
Wednesday while ushering in our next general chance of showers.

With respect to temperatures...these should average out a solid 5 to
10 degrees above normal for the first half of this period...before
trending even more strongly above normal for Tuesday and Wednesday
as the aforementioned cutter low spreads even warmer air across our
region.

&&

.AVIATION /11Z THURSDAY THROUGH MONDAY/...
-- Changed Discussion --
Widespread MVFR/IFR conditions across the terminals south of Lake
Ontario this morning as a batch of steady rain moves north through
the area. Still VFR east of Lake Ontario as the rain shield has yet
to reach that far north, but it will soon flight conditions
deteriorating there over the next couple of hours. Otherwise, as the
warm front moves north of the area by midday, steadier rain will
taper off from south to north through the mid to late morning hours
south of Lake Ontario and by around midday east of Lake Ontario.
Flight conditions will likely improve as well to at least low VFR
across most lower elevation sites during the afternoon with our area
now solidly in the warm sector, while MVFR hangs tough across the
higher terrain. It will also become quite windy by this afternoon
with southeasterly wind gusts generally in the 25-35 knot range.

The next batch of rain with scattered thunderstorms will approach
the area from the south and southwest late today into this evening
as a cold front moves into western NY. Downsloping southeasterly
flow may allow VFR conditions to continue through the evening hours
across the Niagara Frontier and northwest of the Tug Hill. MVFR/IFR
will redevelop elsewhere. Expect a return to MVFR/IFR conditions
across much of the area for the second half of tonight with
scattered showers and storms across the area.

Outlook...

Friday...MVFR/IFR with occasional showers and possibly a
thunderstorm.
Friday night...MVFR/IFR with rain, mixing with wet snow
overnight.
Saturday...MVFR/IFR early with rain/snow showers, gradually
improving to VFR.
Sunday...VFR/MVFR with a chance of showers and possibly a
thunderstorm.
Monday...Mainly VFR.
-- End Changed Discussion --

&&

.MARINE...
A strong low pressure system will move from the Ohio Valley this
morning to western Lake Erie by this evening, then continue north
across Lake Huron tonight before reaching western Quebec Friday.
This will produce a period of moderate east to southeast winds today
through tonight for which Small Craft Advisories have been issued
across portions of Lake Ontario. There may be a few gusty
thunderstorms this evening as well, mainly on Lake Erie.

A cold front will cross the region Friday, with moderate to strong
southwest winds behind the front Friday becoming west Friday night
through Saturday, with an extended period of high end Small Craft
Advisory conditions.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Wind Advisory from 6 PM this evening to 5 AM EDT Friday for
     NYZ007-008.
MARINE...Small Craft Advisory from 2 AM Friday to 11 PM EDT Saturday
         for LEZ040-041.
         Small Craft Advisory from 11 AM this morning to 8 PM
         EDT this evening for LOZ042.
         Small Craft Advisory from 8 PM this evening to 6 AM EDT
         Friday for LOZ044.
         Small Craft Advisory from 5 PM this afternoon to 8 AM EDT
         Sunday for LOZ045.

&&

$$

SYNOPSIS...Hitchcock/JM
NEAR TERM...Hitchcock/JM
SHORT TERM...PP
LONG TERM...JJR/PP
AVIATION...JM
MARINE...Hitchcock/JM