Area Forecast Discussion
Issued by NWS Buffalo, NY

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000
FXUS61 KBUF 161741
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
141 PM EDT Wed Oct 16 2019

.SYNOPSIS...
A strong cold front will move east across the region this afternoon
before stalling east of Lake Ontario this evening. Widespread,
soaking rain will continue through Thursday morning east of Lake
Ontario. Meanwhile farther west, the steady rain today will give way
to lake enhanced showers tonight and Thursday. It will turn blustery
and chilly tonight and Thursday. Dry weather will return Friday and
Saturday as high pressure builds back into the region, with
temperatures warming steadily through the weekend.

&&

.NEAR TERM /THROUGH THURSDAY/...
Early afternoon radar imagery showing the leading edge of the rain
moving towards Central NY, with widespread rainfall across all of
Western NY and the Genesee Valley. The widespread rain will slowly
overspread the eastern Lake Ontario region through the rest of the
afternoon, while the steadier rain begins to taper off late today
across the western end of the state. Gusty south to southeast winds
will continue across the North Country until the rain arrives later
today. Gusts may exceed 40 mph at times, especially across the
northern lee slopes of the Tug Hill Plateau.

A strong mid level closed low and nearly vertically stacked surface
low will continue to move east across Lake Huron through this
evening, with an associated cold front moving slowly east across our
region. Strong DPVA, height falls, and diffluence aloft will combine
with strong moisture transport and convergence supported by a 50+
knot low level jet. The quality moisture and dynamics will continue
to produce widespread rainfall along the advancing cold front
through this evening, with the steady rain tapering off from west to
east from the Finger Lakes westward during the late afternoon and
evening as the cold front moves into Central NY.

Tonight the initial low over Lake Huron will give way to robust
secondary cyclogenesis off the Delmarva as additional strong
shortwave energy rotates through the trough and reaches the coast.
The ensuing coastal low will likely undergo bombogenesis (24mb or
greater pressure fall in 24 hours) as it moves northward to New
Hampshire by Thursday morning. The cold front which has been
advancing east across our area will stall this evening east of Lake
Ontario, and then evolve into a sharp inverted trough to the north
and west of the rapidly deepening coastal low. The low level focus
of the inverted trough will combine with strong ageostrophic flow
adjustments from the rapidly deepening coastal low and strong mid
level closed low to produce deep layer ascent across the eastern
Lake Ontario region tonight through Thursday morning. This will
support widespread, soaking rainfall east of Lake Ontario.

Meanwhile from the western Finger Lakes westward across Western NY,
the steady, soaking rain from the cold front will have tapered off
by early this evening. Wrap around moisture and a spoke of vorticity
orbiting the strong closed low will produce additional showers
across Western NY tonight. Lake effect rain showers will also
develop later this afternoon and continue tonight as cold air
deepens over Lake Erie. Southwesterly boundary layer flow in the
wake of the cold front will initially direct the lake effect rain
showers into the Buffalo area during the late afternoon and early
evening. Boundary layer flow will then quickly veer to the northwest
later this evening, carrying the bulk of the lake effect rain into
the western Southern Tier with a focus on the Chautauqua Ridge
overnight.

A dry slot will move into the Genesee Valley and western Finger
Lakes this evening and remain in place much of tonight. This will
keep a relative lull in rainfall for these areas much of tonight,
sandwiched between the soaking rain east of Lake Ontario and wrap
around/lake effect rain across much of Western NY.

On Thursday the strong coastal low will briefly stall near the
Connecticut River Valley in New England as the strong mid level
closed low moves east and becomes vertically stacked atop the
surface low. The well defined inverted trough over the eastern Lake
Ontario region will break down and swing south and west as the
surface low stalls, allowing the steady soaking rain to end across
the eastern Lake Ontario region. Deep wrap around moisture and low
level convergence will wrap back across the entire region Thursday
morning. The synoptic forcing will combine with moist northwest
upslope flow and moderately strong lake instability to produce
widespread showers across much of the region, peaking in coverage
during the late morning and early afternoon. The widespread showers
will begin to diminish in coverage and intensity later in the
afternoon as the vertically stacked coastal low begins to drift east
to the Maine coast, and deeper moisture and forcing start to move
away from the region.

Rainfall totals from today through Thursday will reach 0.75" to
1.25" for the bulk of the area. Lake enhanced upslope across the
Chautauqua Ridge will produce higher totals of 1.25"-1.75". Much
higher rain totals will be found east of Lake Ontario with a longer
duration of soaking rain. Rain totals will reach 2-3" east of
Interstate 81. This rain will fall over an 18+ hour period. It will
result in significant within-bank rises on area creeks and rivers
along with some poor drainage ponding, but significant flooding is
not anticipated.

Cold advection behind the cold front will bring temperatures into
the 40s areawide tonight. Widespread thick clouds and showers
Thursday will not allow for much recovery. Highs may briefly reach
near 50 at lower elevations and mid 40s across higher terrain. It
will turn quite windy Thursday as the pressure gradient tightens to
the west of the strong coastal low. Northwest winds will gust in the
30-40 mph range across much of the area. The strongest winds will be
found along the south shore of Lake Ontario, where gusts may reach
or possibly exceed 45 mph at times. These values are close to wind
advisory criteria, but only marginally so. If later model runs grow
confidence in an extended period of gusts in excess of 45 mph, a
Wind Advisory may be needed along the south shore of Lake Ontario.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/...
A mature Nor`easter will be over Northern New England Thursday night
with continued low level cold air advection over WNY and CNY under a
NW flow aloft.  An upstream ridge (currently over the Western U.S.)
will be approaching by this time, so expect ongoing lake effect and
upslope rain to be slowly tapering off overnight, first SE of Lake
Erie during the evening, and SE of Lake Ontario overnight.  A few
cooler spots/higher terrain could even end with a little non-
accumulating snow flakes toward Friday morning.

Friday, will be a transition day between the slowly departing
downstream Nor`easter and the upstream ridge.  Abundant low level
moisture in the continued NW flow will likely result in an extensive
stratocu deck that may last all day over much of WNY.  With this in
mind, will lower temperatures a few degrees, with most areas in the
45-50F range.

Friday night, expect some clearing as subsidence is maximized.  This
will result in two non-precip concerns: frost and/or fog.  Most of
WNY and CNY will flirt with lows in the mid 30s, with colder spots
in sheltered valleys of higher terrain.  Typical valley fog is also
expected.

Saturday and Saturday night however should be uneventful as the
upper level ridge and associated surface high pressure move
overhead and then slowly east of the region.

&&

.LONG TERM /SUNDAY THROUGH TUESDAY/...
With the exception of a fast moving shortwave trough tracking across
the Central Great Lakes Saturday night, mid to upper level ridging
will be in place overhead.

Warm air advection will move into the eastern Great Lakes on the
backside of a mid-level ridge Sunday and 850mb temperatures will
rise to around +8 C. Clouds will likely be around as moisture
extends south across the region from the passing shortwave trough to
the north. ECMWF remains stubbornly consistent that there will be
enough moisture for this system to bring some showers to especially
western NY in the morning. Though don`t like to bet against the
ECMWF, especially when it is consistent, other guidance is not near
as bullish on pops. So, our pops will stay at slight chance for now
and we`ll go with a mix of sun and clouds with temperatures reaching
the mid 60s. If more sunshine occurs, temperatures could hit 70F.

The ridge will amplify off the east coast Monday while a closed low
moves into the Mid-West and Upper Great Lakes. A surge of moisture
from the south will move into the region Monday and showers are
likely by Monday night. Temperatures at 850mb will also soar into
the +10-12 C range and highs will be near 70F. A cold front will
likely move through the region Tuesday and showers and gusty winds
are possible. An isolated thunderstorm may be possible along the
front as well. Overnight lows will be in the 40s and 50s on Monday
night while highs on Tuesday should be held in check by clouds and
showers with mainly low to mid 60s expected. Still, these readings
are slightly above normal for mid October.

&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
A cold front will continue to move slowly east across the area this
afternoon and evening, producing widespread light to moderate rain
with a few embedded pockets of heavy rain. VSBY will be mainly MVFR
in the steadier rain, with a few pockets of IFR in the heavier rain.
The steady rain will taper off from west to east for the bulk of the
area late this afternoon and evening. The one exception will be east
of Lake Ontario, where steady moderate to heavy rain will continue
tonight through Thursday morning as a strong coastal low moves north
to New England. This will produce widespread IFR VSBY and MVFR to
IFR CIGS east of Lake Ontario tonight through Thursday morning.

Meanwhile farther west, the steady rain today will be replaced by
lake effect and upslope showers driven by moderate to strong lake
instability and northwest upslope flow. The showers will initially
focus near and east of Lake Erie late this afternoon and evening.
Late tonight and Thursday the lake effect and upslope showers will
become widespread across the entire area, peaking during the late
morning and early afternoon. The heavier showers will produce areas
of MVFR to IFR VSBY. Widespread lower CIGS will develop later
tonight and Thursday, with lower end MVFR across lower elevations
and IFR higher terrain.

Gusty south winds will continue this afternoon across the North
Country near KART and KGTB before diminishing as the rain arrives.
Northwest winds will become quite gusty on Thursday, with gusts of
25 to 35 knots common across the region, and approaching 40 knots
along the south shore of Lake Ontario.

Outlook...
Friday...Areas of MVFR CIGS early, improving to VFR.
Saturday through Monday...VFR.

&&

.MARINE...
Low pressure will continue to move east across Lake Huron through
this evening, with an associated cold front moving east across the
eastern Great Lakes this afternoon and evening. Moderate to strong
south winds ahead of this will continue to produce Small Craft
Advisory conditions at the northeast end of Lake Ontario through
late afternoon.

Southwest winds will increase behind the cold front on Lake Erie
this afternoon, with moderate to strong winds continuing tonight
through Thursday. The stronger west winds will take longer to
develop on Lake Ontario, ramping up later tonight and becoming
northwest on Thursday. Winds on both Lake Erie and Lake Ontario will
approach gale force later tonight and Thursday. Sustained winds are
expected to peak at 30 knots, although there will certainly be gale
force gusts at times. The end result will be high end Small Craft
Advisory conditions on both lakes through Thursday.

The winds will begin to diminish some Thursday night, and moreso
Friday as the pressure gradient relaxes across the eastern Great
Lakes.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...Small Craft Advisory until 5 AM EDT Friday for LEZ040-041.
         Small Craft Advisory until 5 PM EDT this afternoon
         for LOZ043>045.
         Small Craft Advisory until 5 PM EDT this afternoon
         for SLZ022.

&&

$$

SYNOPSIS...Hitchcock
NEAR TERM...Hitchcock
SHORT TERM...Zaff
LONG TERM...HSK/JLA
AVIATION...Hitchcock
MARINE...Hitchcock


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