Area Forecast Discussion
Issued by NWS Buffalo, NY

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586
FXUS61 KBUF 182000
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
300 PM EST Wed Jan 18 2017

.SYNOPSIS...
Low level moisture lingering across the region will maintain
cloudiness tonight through much of Thursday. A few periods of
drizzle are possible this evening, possible lasting into Thursday
morning east of Lake Ontario. There will be some clearing across
the Southern Tier and portions of Western New York, but the cloud
cover will remain across Northern New York. After partial clearing
regionwide on Thursday night into Friday morning, there will be a
returning rain chance Friday night, then a cloudy but dry weekend
is expected.

&&

.NEAR TERM /THROUGH THURSDAY/...
Low level moisture beneath a mid level subsidence inversion will
maintain low clouds tonight and early Thursday. There will be a few
periods of drizzle across Western New York with some drizzle mixing
with some snow across the higher elevations east of Lake Ontario
this evening through much of early Thursday. Although the surface
winds will be mainly from the southwest and west, the upper level
flow will be northwesterly and will carry a few ripples of vorticity
to provide sufficient lift to invoke a few periods of the light
precipitation across the North Country through Thursday morning.

High pressure building across New York state on Thursday afternoon
will bring some clearing to the Southern Tier, but the shallow layer
of low level moisture will remain over the Lake Ontario basin to the
Saint Lawrence Valley the the North Country, as will the low cloud
cover.

Temperatures tonight will fall to the lower to middle 30s with the
colder readings across the Southern Tier and the Tug Hill regions.
High temperatures on Thursday will reach the middle to upper  30s
across the Eastern Lake Ontario region and Saint Lawrence Valley
with the continued clouds cover with upper 30s to low 40s across
Western New York and the Western Southern Tier where cloud cover
will be less during the afternoon..

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/...
Increasing amplitude within the southern stream upper height field
will yield a period of rather benign weather Thursday and Thursday
night. Increasing subsidence and dry air advection will allow for
some sunny breaks Thursday especially during the afternoon.
Otherwise, looking at a continuation of above normal warmth, as even
neutral or weak warm air temperature advection of the resident air
mass yields afternoon readings of upper 30s to lower 40s.

An upper level low lifting northward through the Central Plains on
Friday will bring a chance for rain to western New York as a upper
level wave and weak surface low lift northward through the Great
Lakes. Some uncertainty remains among latest model solutions
regarding rain probabilities. European favors a higher chance of
rain with a stronger wave and surface low lifting northward. GFS/CMC
favor lower chances with a weaker low. A developing southerly flow
over the eastern Great Lakes will bringing unseasonably mild
temperatures with highs in the 40s to near 50 both Friday and
Saturday.

&&

.LONG TERM /SUNDAY THROUGH TUESDAY/...
A progressive...yet highly amplified upper level pattern will be
found across the country during this period...with the Great Lakes
region being dominated by mild Pacific modified air. While this will
mean that temperatures will remain well above normal...the period
will be highlighted by what could be a soaking to problematic rain
on Monday into early Tuesday. More on this in a moment.

A ridge axis over eastern New York will support one more fairly nice
day across our forecast area on Sunday...although clouds will likely
prevail across the western counties. Temperatures will be some 15
deg F above normal values...with highs ranging from the upper 40s
across the far western counties to the lower 40s on the Tug Hill
plateau.

The fair weather will deteriorate Sunday night as a deep stacked low
over the Deep South will start to work its way up the western slopes
of the Appalachians. Ahead of this very dynamic system...a plume of
sub tropical moisture will stream northward from the Caribbean and
Gulf stream of the western Atlantic to Virginia and Pennsylvania. As
the leading edge of this moisture will make its way across our
western counties late Sunday night...it will be lifted by a strongly
divergent upper level flow. This will start the process whereby our
region could pick up a soaking rain.

On Monday...the vertically stacked storm system will slowly drift
north across the Upper Ohio Valley while the plume of sub tropical
moisture off the Atlantic will edge over our region. This will lead
to some widespread rain for our forecast area Monday and Monday
night. The highest risk for significant rains will be east of the
Finger Lakes.

Guidance continues to suggest that this storm system will also
support strong...potentially damaging...downslope winds between Lake
Erie and the Chautauqua Ridge. A southeast low level jet of 50-55
knots just above a staunch inversion is very similar to events that
local research has shown to be problematic. Stay tuned.

The slow moving storm system is forecast to cross Pennsylvania on
Tuesday while its plume of moisture will push across far eastern New
York into New England. Meanwhile..drier air in the mid levels will
advect across the western counties on Tuesday with dynamics
weakening considerably in the process. This will lead to a tapering
off of the rain from east to east.

&&

.AVIATION /20Z WEDNESDAY THROUGH MONDAY/...
Widespread IFR to LIFR conditions will prevail tonight as trapped
low level moisture will maintain a low stratus deck. Light rain
showers and drizzle will taper off this afternoon, with just low
stratus clouds remaining. Low ceilings will lift a bit to MVFR for
most locations on Thursday morning but moisture off Lake Ontario may
keep KROC at IFR ceilings through the day. Expect clearing from
south to north later in the day.

Outlook...

Thursday...MVFR and areas IFR early...then becoming VFR late.
Friday...Mainly VFR. Friday night and Saturday...MVFR to IFR with a
chance of rain.
Sunday...MVFR ceilings.
Monday...MVFR to IFR ceilings with scattered showers. Windy.

&&

.MARINE...
A tightening pressure gradient between departing low pressure and
approaching high pressure will increase the winds on the lakes,
requiring small craft advisories for the nearshore waters of Lake
Erie and the south shore nearshore waters of Lake Ontario into
tonight. Winds will lessen on Thursday as the center of the high
pressure moves across the lakes. Lighter winds are expected into the
weekend.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...Small Craft Advisory until midnight EST tonight for LEZ040-041.
         Small Craft Advisory until 7 AM EST Thursday for
         LOZ042>044.

&&

$$

SYNOPSIS...WCH
NEAR TERM...WCH
SHORT TERM...TMA
LONG TERM...RSH
AVIATION...WCH
MARINE...WCH



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