Area Forecast Discussion
Issued by NWS Buffalo, NY

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172
FXUS61 KBUF 221945
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
245 PM EST Sun Jan 22 2017

.SYNOPSIS...
Warm and moist conditions will last through tonight with above
normal temperatures and some light rain showers or drizzle. Then low
pressure developing across the Southeastern states will move to
the mid-Atlantic on Monday and then into Southern New England on
Tuesday. This will bring rain and wet snow into our region with
potentially significant snow accumulations in some areas.

&&

.NEAR TERM /THROUGH MONDAY/...
For the remainder of this afternoon, the region will remain
between high pressure to the north, and low pressure developing
across the Southeastern states. The high will help maintain a
northeasterly flow across the Niagara Frontier, which will
strengthen with time. This will maintain a cool and moist flow off
Lake Ontario with areas of fog and drizzle expected to last much
of the night. This is probably best captured by the HRRR which has
been handling this fog and stratus fairly well over the past
couple days.

Otherwise, an area of showers near Buffalo has not been well
captured by guidance. Following a weak 700 mb flow, expect these
showers to very slowly drift northeast this afternoon before
dissipating this evening.

Temperatures will vary late this afternoon, with much warmer
conditions across the Western Southern Tier where a few breaks of
sunshine have allowed readings to climb into the upper 50s.
Temperatures should top out in the mid to upper 40s south of Lake
Ontario where stratus and fog will remain in place. For tonight,
expect lows in the upper 30s to lower 40s.

Low pressure will creep closer to our region, with a chance of
showers across the Southern Tier late tonight. A consensus of 12Z
guidance is slower than previous runs, so timing has been delayed
to account for this.

There still remains high confidence in precipitation with synoptic
scale lift from a deep moist easterly mid-level flow and divergence
aloft. By late Monday afternoon even slower model guidance has
precipitation to the south shores of Lake Ontario, with steady
precipitation expected across the Southern Tier and Upper Genesee
Valley expected during this time.

Thermal profiles will start off too warm for snow, but will cool
with dynamic cooling as the system taps into slightly cooler air from
the ENE. Even though model guidance is in generally good agreement,
thermal profiles are so close that even a small error in forecast
soundings will be the difference between rain and snow. Based on
model consensus, preciopitaiton is expected to change over to snow
first across the upper Genesee basin and Finger Lakes region, with
modest accumulations of a 1 to 3 inches possible by sunset Monday.
Elsewhere, expect mainly wet rain, with perhaps some wet flakes
mixing in through late Monday afternoon.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/...
The main focus through the short term period remains on the strong
and complex storm system moving up the east coast in the Monday
night through Tuesday time frame. High pressure positioned off to
our north and approaching milder air ahead of the approaching
surface low from the DelMarVa will set up a complex thermal profile
across western and north central New York.

Precipiation associated with the approaching low will have already
reached at least southern portions of the area Monday evening, with
higher elevations already have transitioned over to all snow. This
transition over to snow should take place for all areas as heavier
precipitation makes it way into the region. Latest ensembles showing
a high likelihood of more than an inch of liquid equivalent over
much of western and north central New York Monday night into Tuesday.

Later Monday night and into Tuesday, NAM and GFS forecast soundings
showing a warm layer, mainly between 800mb and 700 mb arriving on a
strengthening easterly flow, as strong as 75 knots in some of the
guidance. This will result in a period of sleet mixing in at times.

Better confidence has been gained this cycle, not only with a period
of heavy precipitation, but with thermal profiles as well.
Therefore, will issue a winter storm watch for the Genesee Valley
eastward. The placement of the heaviest snow totals within the watch
area still remains quite uncertain, but current thinking is there
will be a swath of 5 to 10+ inches over the higher elevations from
Allegany/Wyoming counties through the Bristol Hills, then up through
the Tug Hill.

On Wednesday morning, a narrow ridge axis will extend up the Eastern
Seaboard while low pressure tracks across the Central Great Lakes
Region. A warm front associated with this low will likely bring some
precipitation which may start off as rain or wet snow but trend to
all rain as temperatures warm. This will be followed by an ill-
defined cold front and surface trough which will move across the
region Wednesday night and bring more rain, which will mix with wet
snow overnight as weak cold advection begins. Outside of the
showers, Wednesday should be a breezy day with highs in the
upper 30s to lower 40s

&&

.LONG TERM /THURSDAY THROUGH SATURDAY/...
In general, model consensus for the long term period is in good
agreement. Temperatures will start off above average, but will
gradually cool to a more seasonable mid-winter pattern with
increasing chances for lake effect snow.

On Wednesday morning, a narrow ridge axis will extend up the Eastern
Seaboard while low pressure tracks across the Central Great Lakes
Region. A warm front associated with this low will likely bring some
showers which will start off as rain or wet snow but trend to all
rain as temperatures warm. This will be followed by an ill-defined
cold front and surface trough which will move across the region
Wednesday night and bring more showers, which will mix with wet snow
overnight as weak cold advection begins. Outside of the showers,
Wednesday should be a warm and breezy day with highs in the 40s.

A gradual cooling trend will begin after this, with thermal profiles
marginally cold enough to support a mix of wet snow and rain on
Thursday. Cold air advection will continue with any precipitation
likely to be all snow by Thursday night through the weekend.
Precipitation will mainly be from upsloping and residual moisture on
Thursday with 850 mb temps running -4 to -6C there will not be any
lake induced instability.

The pattern becomes more favorable for lake effect snow late in the
week and going into the weekend. The mean flow will be westerly,
however winds will meander some during this time with the passage of
any shortwaves. The most significant one is likely to come Friday
night or Saturday, though model consensus differs slightly on the
timing. By this time, there should be some lake induced instability
but more importantly the moderately strong flow should will likely
run down the length of the lakes which will provide favorable
conditions for snow bands to develop. Uncertainty in wind direction
makes it difficult to pin down exact locations, but in general the
typical snow belts east of the lakes would be the most likely areas
to see the most snow.

&&

.AVIATION /20Z SUNDAY THROUGH FRIDAY/...
At 18Z, there was VFR conditions in place across most of Western
New York with the exception of areas south of Lake Ontario which
includes the BUF/IAG/ROC terminals. This is because the northeast
flow is pushing cool and moist air off the lake into an area of
higher dew points which is helping maintain LIFR cigs and areas of
fog. Some showers may help improve conditions briefly this
afternoon at these sites, but an increasing northeasterly flow
should push fog back into these terminals early this evening.
Expect IFR or lower conditions to continue at these terminals
most of the night with areas of drizzle and fog. There continues
to be a potential for dense fog, though it is lower tonight
because of the stronger flow which will provide better boundary
layer mixing.

Otherwise, expect mainly VFR conditions to continue until this
evening when low moisture spreads into the Southern Tier and
lowers conditions at JHW. In terms of guidance, TAFS are fairly
close to a blend of HRRR and NAM BUFKIT guidance.

On Monday, rain will gradually spread from south to north during
the day as low pressure tracks into the mid Atlantic.
Precipitation will start as rain, but may mix with wet snow in
spots toward sunset Monday evening. Expect mainly IFR/MVFR
conditions as this precipitation moves in.

Outlook...

Monday night...Areas of MVFR/IFR with rain changing to wet snow.
Tuesday...Areas of MVFR/IFR with wet snow mixed with rain.
Wednesday and Thursday...VFR/MVFR with a chance of rain and snow.
Friday...VFR/MVFR with a chance of snow showers.

&&

.MARINE...
Easterly winds will increase across Lake Ontario and Erie through
tonight as we get caught between high pressure over Quebec and a
deepening low pressure system moving into the Mid Atlantic. Small
craft advisories have been issued for the western half of Lake
Ontario as the east- northeasterly winds strengthen to 20 to 25
knots. Winds and waves will remain elevated until the low pressure
system passes on Tuesday. Lake Erie remains less of a concern as
wave action will directed away from the eastern end of the lake.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Winter Storm Watch from Monday evening through Tuesday
     afternoon for NYZ003>008.
     Winter Storm Watch from Monday afternoon through Tuesday
     afternoon for NYZ012>014-021.
MARINE...Small Craft Advisory from 7 PM this evening to 1 PM EST
         Tuesday for LOZ042-043.

&&

$$

SYNOPSIS...APFFEL
NEAR TERM...APFFEL
SHORT TERM...TMA
LONG TERM...APFFEL/HITCHCOCK
AVIATION...APFFEL
MARINE...APFFEL



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