Gale Warning 10, NWS Buffalo, NY

Area Forecast Discussion
National Weather Service Buffalo NY
1009 AM EDT Tue Apr 2 2024

.SYNOPSIS...
A large, complex storm system will stall over the Midwest and bring
periods of rain to the forecast area through Wednesday. The rain
may become heavy enough by Wednesday to result in some minor
flooding across Western NY. Colder air will flow across the region
Wednesday night through Friday as the system re-develops off the
East Coast. This will result in accumulating snows especially across
the higher terrain areas east of Lake Ontario.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
A west to east oriented boundary across PA will be the focus for a
series of disturbances today...as an initial weakening sfc low and
shortwave trough will track across PA. This will increase rain
coverage through the morning and into the afternoon as these
features track east. Enough instability is expected for some rumbles
of thunder, mainly across the Southern Tier. Out ahead of a large
mid-Mississippi sfc low, an influx of GOMEX moisture will push
northeast into the Great Lakes and Northeast through the day today.
This will provide the chance for some steadier and possibly moderate
rain as the moisture moves into the region and the sfc low and
trough track through. The best chance for some of the more moderate
rainfall is expected for the Southern Tier due to proximity of the
sfc low and trough track. Behind the passing sfc low and trough,
late this afternoon and into the early evening there should be a
break in the steadier rain, with showers lingering. Rainfall today
will range from under a quarter inch over the North Country, to
around an inch toward the NY/PA line.

Tonight, showers early on in the evening should start to increase in
coverage and density as a cold/occluded front slowly approaches from
the southwest and a as a shortwave trough crosses the area. The
front will extend from the large sfc low over the mid-Mississippi
Valley that will continue to strengthen today as a powerful trough
drops south out of Canada. A 650mb PV intrusion within the trough
will help strengthen sfc low down to around 980 mb by this evening.
As the sfc low strengthens, the entire system will become vertically
stacked and occlude as the low centers over southern Lake Michigan.
Again for tonight as coverage increases, rainfall may be moderate at
times as Pwats increase this evening to over an inch within the warm
sector of the large system. Rainfall amounts tonight of around a
quarter to two thirds of an inch will be possible.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
...LATE SEASON ACCUMULATING SNOW WEDNESDAY NIGHT THROUGH FRIDAY...

Northern and southern stream phasing will be complete by Wednesday
morning, with the result a deep mid level closed low centered near
southern Lake Michigan. A surface low will wrap up and become
occluded beneath the mid level closed low Wednesday before weakening
and giving way to secondary triple point cyclogenesis over the Mid
Atlantic by Wednesday evening. This secondary low will move slowly
NNE along the east coast, reaching the Maine coast by Friday.
Meanwhile, the mid level closed low will gradually move east across
the Ohio Valley Wednesday night and Thursday before taking up
residence over the New England coast Friday and Saturday.

Wednesday, a plume of deep moisture and strong forcing on the
eastern flank of the mid level closed low will bring periods of rain
to the region, some of which may be heavy at times. Precipitation
type will stay all rain in most areas through Wednesday evening,
with the possible exception of the highest terrain east of Lake
Ontario where some wet snow may mix in by late in the day.

Wednesday night, temperatures through the column and at the surface
will gradually cool as the closed low and associated cold pool aloft
move towards the area. At the surface, colder air over Quebec will
also feed into the area on low level northeast winds, aiding in
cooling the boundary layer. This will allow the rain to change to
wet snow overnight. The change to snow will occur first across the
higher terrain east of Lake Ontario, then progress to the lower
elevations east of Lake Ontario as the column cools. The change to
snow will then spread westward overnight, with a change to snow in
Western NY first across the higher elevations and then last along
the lakeshores.

Thursday through Friday, widespread precipitation will continue
across the region with deep moisture in the cyclonic wrap around
regime on the western side of the system. Precipitation intensity
will wax and wane many times through the several day period, with
numerous mid level vorticity maxima and low level trough features
orbiting the strong closed low and providing periodic enhanced
ascent. Precipitation type will be wet snow much of the time
Thursday through Friday, although the lower elevations may mix with
rain at times, especially during the higher sun angle times of day.

Snowfall accumulations will be highly dependent on elevation and
time of day, with better accumulations favored across higher terrain
where temperatures will be slightly cooler, and at night when the
influence of the high early April sun angle is not a factor. The
greatest accumulations from Wednesday night through Friday will
likely be found across the Tug Hill Plateau and western foothills of
the Adirondacks, with lower accumulations across the surrounding
lower elevations. Across Western NY, expect minor slushy
accumulations for areas inland from the immediate lakeshores, and
somewhat higher accumulations for the higher terrain of the western
Southern Tier and western Finger Lakes.

A Winter Storm Watch remains in effect east of Lake Ontario. The
best chance of seeing low end Watch/Warning criteria snow is likely
limited to the higher terrain of the Tug Hill Plateau and western
Adirondacks, but even here its questionable if accumulations will
reach 7+" in a reasonable amount of time. The one caveat to the
above, high snowfall rates can overcome the limitations of marginal
temperatures, if a band of heavier snow develops amounts may be
higher than currently forecast.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
Friday night through Saturday the large and lumbering closed low
will still influence our weather as it spins over the Gulf of Maine.
Cold air aloft and moist cyclonic flow will maintain occasional wet
snow showers across the region, with some rain possibly mixing in at
times on the lake plains. There will be some minor additional
accumulations especially across higher terrain, but impact will be
minor by this point.

The mid level low will finally weaken and move farther out to sea
Saturday night and Sunday, allowing precipitation to end across the
eastern Great Lakes and gradual clearing to arrive.

Deterministic and ensemble model guidance are in good agreement on
the longwave pattern early next week, with the sensible weather
across our area being dry and on the warmer side, featuring high
temperatures mainly in the 50s and possibly near 60 in the typical
warmer locations. At this range however, uncertainty is very high in
the amount of total cloud cover and how it will be structured,
especially across Western NY. Long-range guidance suggests increasing
mid and/or high clouds increasing from west to east through the day.

&&

.AVIATION /14Z TUESDAY THROUGH SATURDAY/...
Cigs will lower across the region today as the boundary layer will
become increasingly saturated. CIGS will drop to IFR levels for much
of the area by the afternoon south of Lake Ontario. For KART, mainly
VFR CIGS will lower to MVFR for late in the afternoon. Showers this
morning will become a steady rain for areas south of Lake Ontario
through the day. Models are starting to come into better agreement
in a break in the steadier rain during the late afternoon as a weak
sfc low and trough move away from the area.

Tonight, MVFR to IFR CIGS expected to remain in place as another
batch of rain moves into the area with steady light to moderate rain
expected for most of the TAF sites. Reductions to VSBY down to MVFR
and brief IFR possible with the increased moisture tonight.

Outlook...

Wednesday...MVFR/IFR with periods of rain.
Wednesday night and Thursday...MVFR/IFR with snow, mixed with rain
at times at lower elevations.
Friday...VFR/MVFR. Rain or snow showers likely.
Saturday...Mainly VFR. A chance of rain or snow showers.

&&

.MARINE...
A large storm system deepening over the Mississippi valley today
will track northeast and stall over Lake Michigan tonight. This will
generate fresh to strong easterlies across the bulk of the Lower
Great Lakes through tonight...with the winds gradually veering to
the southeast on Lake Erie. The exception will be on the western
third of Lake Ontario...where frequent gale force gusts for areas
well offshore will support a gale warning from this evening through
tonight.

The impactful storm system will slowly cross Lower Michigan on
Wednesday before significantly weakening Wednesday night and
Thursday...as a secondary storm will blossom off in the vicinity of
Long Island. This scenario will support high end small craft
advisories for fresh to strong easterlies on Lake Ontario...while
winds and waves will diminish on Lake Erie.

&&

.HYDROLOGY...
Storm total rainfall amounts are expected to average 1.5 to 2.25
inches through Wednesday night. Forecast rainfall amounts have
increased since yesterday, and there is a chance of a period of
moderate to heavy rain Wednesday. This will increase the flood
potential, especially across Western NY.

The latest MMEFS river ensemble forecasts have shown a notable
increase in flood potential on rivers across Western NY with the
increase in expected QPF. The flood potential would come with
the final batch of rain Wednesday and Wednesday night after the
initial rain today through tonight works on saturating the soil.

A Flood Watch will likely be necessary for much of Western NY.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Winter Storm Watch from Wednesday afternoon through Thursday
     evening for NYZ006>008.
MARINE...Small Craft Advisory until 10 PM EDT this evening for LEZ040.
         Small Craft Advisory until 2 AM EDT Wednesday for
         LOZ030.
         Small Craft Advisory until 2 AM EDT Friday for LOZ042.
         Small Craft Advisory until 8 AM EDT Friday for LOZ043.
         Gale Warning from 6 PM this evening to 5 AM EDT Wednesday
         for LOZ062.

&&

SYNOPSIS...PP
NEAR TERM...SW
SHORT TERM...Hitchcock
LONG TERM...Hitchcock/PP
AVIATION...RSH/SW
MARINE...RSH
HYDROLOGY...Hitchcock/RSH

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