Areal Flood Warning 4, NWS Buffalo, NY

Area Forecast Discussion
National Weather Service Buffalo NY
1111 AM EDT Fri Apr 12 2024

.SYNOPSIS...
Deep low pressure will cross the central Great Lakes today before
reaching Quebec late tonight and Saturday. This system will continue
to produce periods of soaking rainfall and a few scattered
thunderstorms through the daytime hours. The rain will mix with or
change to wet snow later tonight and early Saturday before ending
from west to east later Saturday. Some slushy accumulations are
possible across the high terrain tonight and Saturday morning. It
will also be quite windy much of the time through Saturday.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
A very large and dynamic low pressure system over the eastern Great
Lakes late this morning will gradually broaden into deep longwave
trough over the eastern CONUS into the weekend. As it does so, its
987mb surface low centered just west of the forecast area early this
morning will slide northeast and deepen to 982mb across Quebec by
this evening. Its associated cold frontal boundary will drag through
our area from west to east this morning, with latest sfc obs and
analysis suggesting this boundary is already moving through WNY.
This trough will then translate east of the region tonight, with a
cooler airmass accompanying a secondary cold front supporting a
changeover to snow across the higher terrain areas late.

Precipitation...

Deep moisture transport and multiple spokes of vorticity ejecting
northward out ahead of this front will support additional periods of
soaking rain this morning, with enough instability present to
support a slight chance for thunderstorms and locally heavy
downpours as well. The steadiest rain will shift east through the
morning hours as the cold front marches through, with the main swath
of precip expected to exit the North Country by around noon. In all
this is expected to produce another 0.25-0.75" of new rain across
the region before a lull in the precip works in behind the front.
Thereafter, the system's mid-level trough axis will swing in from the
west and cause additional rains to fill back in, first across the
western Southern Tier this afternoon before spreading eastward this
evening and overnight. Heaviest QPF with this second round of precip
will be where orographic lifting will become a factor across the
hilltops of the Southern Tier.

A solid 1-1.5" with localized amounts of 2" of new rain overnight
has caused minor rises across the Buffalo and Southern Tier area
creeks and rivers, as well as some localized flooding in poor
drainage areas, though wider flooding concerns remain low at this
time. Minor rises below action stage are expected on the Black River
as the front marches towards the region. Rises to action stage and
eventually minor flood stage are expected on portions of the
Allegheny River near the end of the period as the secondary round of
precip moves through the region.

Winds...

Southwest winds will ramp up quickly within the CAA regime behind
the front this morning. Gusts of 40-45mph are expected today across
the Niagara Frontier as strong winds funnel down the long axis of
Lake Erie, with gusts of 30-40mph in other areas from the Genesee
Valley westward.

As previously mentioned, once the secondary cold front moves through
this evening, winds will shift westerly and increase, then spread
eastward overnight. Gusts of 40-45mph will be likely east of Lake
Erie, especially along the shoreline and across the ridges and
hilltops of the higher terrain areas of the Southern Tier and Finger
Lakes.

A Wind Advisory is in effect through 2 PM Saturday for the areas
directly downwind of Lake Erie (Chautauqua, Erie, Niagara, Orleans,
and Wayne counties).

Snowfall...

850H temps within the wake of the secondary cold front are expected
to bottom out around -4 to -5C tonight which will support a
changeover to snow across the higher terrain areas east of the
lakes. Moist westerly upslope flow will result in some wet snow
accumulations in these areas. As of this update, several inches of
snow is expected across the hilltops of Cattaraugus, Wyoming, and NW
Allegany counties, as well as up on the Tug Hill. This may warrant
an advisory down the road but confidence is low. Multiple
deterministic models show significantly higher totals across the
Southern Tier, though am highly skeptical of any of these being
realized as ground conditions will be a major limiting factor here,
with the surface likely wet and above freezing for a good deal of
the night. This being said, if snowfall rates are high enough
overnight it could overcome this obstacle.

Temperatures...

Finally, expect a wide range of highs today as the primary cold
front marches through the region. Far western NY has likely already
hit their highs for the day and will continue to slowly tumble
through the 40s. The eastern Lake Ontario region should remain in
the 60s until later this morning before the front moves through and
quickly drops temps back into the 50s.

Low temperatures tonight will average in the 30s across the region,
coldest across the interior Southern Tier and east of Lake Ontario.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/...
Rain and higher elevation wet snow will taper off from west to east
Saturday as main upper level trough axis and pesky surface low
pressure finally move northeast of the area. Additional snowfall
amounts will be an inch or less Saturday morning. High pressure will
start to nose northeast into western NY Saturday morning with mainly
dry weather west of the Genesee Valley by midday, then continued
slow drying from the Finger Lakes east through the afternoon.
Otherwise, it will be a windy day with westerly gusts of 30 to 40
mph areawide, with some 45 mph gusts possible as a tight pressure
gradient remains in place and a strong LLJ off the deck is at least
partially mixed with modest LL lapse rates in place. It will a much
cooler day with mainly 40s for highs and some higher terrain areas
potentially not getting out of the upper 30s. Transient ridging
slides across the area Saturday night bringing a short break in the
precipitation with winds dropping off overnight as well. Mainly 30s
for lows.

A compact area of low pressure will then drop across western and
northcentral NY on Sunday. This will bring another shot of rain to
the region to finish out the weekend. Cant rule out few rumbles of
thunder as well. Basin average rainfall amounts will be around 0.25"-
0.50" overnight. It will become breezy, but nothing like we saw the
past couple of days. Highs rebound into the 50s and low 60s toward
the NY/PA line. Low pressure exits southeast Sunday night as high
pressure builds in from the west bringing a return to mainly dry
weather with lows ranging from the mid 30s to low 40s.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
Another round of weak surface-based ridging will slide across our
area Monday and Monday night and bring another period of mainly dry
weather. This ridge will then slide off to our east on Tuesday...
while giving way to a sprawling cutter-type low that will lumber its
way from the central Plains states to near James Bay through the
rest of the period. This next system will usher in warmer and more
unsettled weather that will feature frequent opportunities for
showers from Tuesday afternoon through Thursday...though there will
also likely be some drier periods interspersed. In addition...
diurnal instability may also support the potential for a few
thunderstorms across far southwestern New York Tuesday afternoon and
early evening...then again south of Lake Ontario both Wednesday and
Thursday afternoons/evenings.

With respect to temperatures...these should average out a solid 5 to
10 degrees above normal Monday and Monday night...before trending
even more strongly above normal for Tuesday through Thursday as the
aforementioned cutter low spreads even warmer air across our region.
During the latter three days of the period...it currently appears
that highs will range from the mid-upper 60s east of Lake Ontario to
the 70s across much of western New York.

&&

.AVIATION /15Z FRIDAY THROUGH TUESDAY/...
A deepening low pressure system sliding just northwest of the region
across the central Great Lakes will continue to send multiple rounds
of rain showers through the region, resulting in highly variable
flight conditions through the 12z TAF cycle.

Rain showers will continue to produce areas of MVFR and localized
IFR cigs/vsbys, mainly across western NY (KIAG/KBUF/KJHW) through
the morning hours. A cold front arriving closer to daybreak will
push the bulk of the precipitation through the region from west to
east, exiting the eastern Lake Ontario region around 18z. A return
to low VFR or MVFR cigs may occur within this lull in the precip.
Wrap-around moisture will then produce additional showers with IFR
conditions across western NY later this afternoon and evening.

The arrival of the cold front this morning will cause winds to shift
southwesterly and strengthen, especially northeast of Lake Erie.
Gusts to 40kts will be possible across KBUF/KIAG for a sizable
portion of the day.

A secondary cold front will move into the region this evening. This
will cause winds to shift westerly and increase over a larger
footprint of the region. Gusts of 30-35kts will become common with
gusts to 40kts possible east of Lake Erie. The colder airmass will
also bring a changeover to snow across the higher terrain of the
Southern Tier (possibly including KJHW) and east of Lake Ontario.

Outlook...

Saturday...MVFR/IFR early with rain and wet snow, gradually
improving to VFR from west to east in the afternoon. Windy.
Sunday...VFR/MVFR with a chance of showers and possibly a
thunderstorm.
Monday...Mainly VFR.
Tuesday...Mainly VFR with a chance of showers late.

&&

.MARINE...
A strengthening low pressure system cutting to our northwest will
send two cold fronts through the region. The first will move east of
the lakes by early this afternoon, causing southwest winds to
quickly ramp up on the lakes from west to east. The second cold
front will arrive later this evening and cause winds to shift to the
west.

These fronts are expected to cause gale force winds on both lakes,
first across Lake Erie into Saturday morning, then across Lake
Ontario tonight through Saturday night. Small Craft Advisories
precede the Gale Warnings across the western and eastern ends of
Lake Ontario.

A more substantiative calming of the winds and waves will arrive by
Sunday as surface high pressure crests over the region.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Wind Advisory until 11 PM EDT this evening for NYZ001-002-010-
     011-019-085.
MARINE...Small Craft Advisory until 2 AM EDT Sunday for LEZ020.
         Gale Warning until 11 AM EDT Saturday for LEZ040-041.
         Small Craft Advisory until 11 PM EDT this evening for
         LOZ042-045.
         Gale Warning from 11 PM this evening to 2 PM EDT Saturday
         for LOZ042-062.
         Gale Warning from 11 PM this evening to 11 PM EDT Saturday
         for LOZ043>045-063>065.

&&

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

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Special Weather Statement
National Weather Service Buffalo NY
702 AM EDT Fri Apr 12 2024

NYZ003>005-013-014-121315-
Monroe-Wayne-Northern Cayuga-Livingston-Ontario-
Including the cities of Rochester, Newark, Fair Haven, Geneseo,
and Canandaigua
702 AM EDT Fri Apr 12 2024

An area of moderate to heavy rain will move slowly north and
northeast through the area over the next two to three hours.
This will cause some ponding and low-lying poor drainage flooding
in areas. Motorists should also be aware of the ponding on area
roadways. Slowly down and allow for extra time to reach your
destination this morning.

AR