Area Forecast Discussion
Issued by NWS Buffalo, NY

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828
FXUS61 KBUF 241508
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
1008 AM EST Tue Jan 24 2017

.SYNOPSIS...
A strong low pressure system will move along the New England coast
today and exit into the Canadian maritimes by Wednesday. This will
bring some light accumulations of wet snow making for slick travel
from the Genesee Valley eastward. High pressure will then cross the
region tonight and Wednesday. A wave of low pressure will cross the
region Thursday ushering in a pattern change back to mid-winter
conditions. Heavy lake effect snows are possible east of lower Great
Lakes through the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
A coastal storm is centered just east of New Jersey late this
morning. This system continues to circulate Atlantic moisture
westward across New York state. Thermal profiles across the
majority of the forecast area are below freezing as of 10am with
radar showing a wide swath of light snow. There may still be some
lingering pockets of freezing rain across Jefferson and Lewis
counties but 12Z NAM indicated that warm layer aloft will cool
before noon with freezing rain changing over to wet snow.

Meso models have keyed in on a deformation band that is showing up
on radar from about Rochester south into the Genesee Valley and the
western Finger Lakes. Highest QPF runs along this deformation band
where SLRs of 8-10:1 will yield additional snowfall amounts in the 2
to 4 inches range in this deformation band. Otherwise one to two
inches elsewhere. Snow will taper off tonight as cold advection
increases on the back side of the exiting low pressure system.
Winter Weather Advisories linger for the Genesee Valley eastward.

Temperatures will rise very little today, maxing out in the low 30s.
Although still not a big diurnal change, the increasing cold
advection tonight will drop temperatures into the upper 20s.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
A weak ridge axis surface and aloft will move across the area
Wednesday morning and early afternoon, with mainly dry conditions
and increasing mid/high clouds as a weak warm front moves across the
area. Model guidance has trended a few hours slower with the next
system, so dry weather should last much of the day Wednesday with
just a chance of a few rain showers by mid to late afternoon across
the western Southern Tier. Temperatures will warm to above average
again for one more day as warm advection increases ahead of the next
system. Expect highs in the low 40s across Western NY, with mid to
upper 30s across the North Country.

Wednesday night and Thursday a potent mid level closed low will move
east through the Central Great Lakes and open up with time as it
phases with another trough moving through Quebec. At the surface,
low pressure will pass just north of Lake Erie and Lake Ontario late
Wednesday night and Thursday, with a trailing cold front moving
southeast across the area Thursday afternoon and evening.
Precipitation will come in several batches with this system. A weak
baroclinic wave will develop ahead of the trough Wednesday evening
and produce a brief period of rain showers crossing the area from
west to east, with the best coverage found across the Southern Tier,
Finger Lakes, and Central NY. Precip type will be all rain with this
as temperatures remain in the upper 30s to lower 40s through the
evening hours.

The mid level trough will cross the area on Thursday, with
associated DPVA and deeper moisture supporting increasing coverage
of precipitation. The highest precip amounts and best coverage will
be found across the higher terrain east of the lakes due to
frictional convergence and upslope flow, with the airmass not yet
cold enough to support a lake response. Additional forcing will
arrive in the afternoon and evening as the cold front crosses the
region from northwest to southeast.

Precip type will be elevation dependent from Thursday morning
through early to mid afternoon, with mainly rain at lower elevations
and a rain/snow mix changing to all snow across higher terrain.
During the late afternoon and early evening cold advection will
allow precip to change to all snow even at lower elevations. Expect
an inch or so of accumulation across higher terrain on Thursday with
little at lower elevations through late afternoon.

Thursday night synoptic scale snow showers associated with the cold
front and mid level trough will slowly diminish. Expect some minor
(less than an inch) accumulations at lower elevations during the
evening, with a few inches possible across higher terrain from
upslope flow. Steady cold advection will allow the airmass to grow
cold enough to support lake effect snow overnight east and southeast
of the lakes. This will be the start of a very long lake effect
event discussed in more detail below in the long term section.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
Typical mid winter weather will become established again through the
long term period after a several week hiatus. A fundamental pattern
change will take place across North America, with a ridge building
over the west and a longwave trough becoming established over the
eastern half of the continent late in the week through next weekend.

Our area will be in the active region near the base of the longwave
trough, with numerous weak shortwaves moving through the base of the
trough. Each of these shortwaves may produce a few light snow
showers across much of the region, and will also bring subtle
variations to the low level flow, moisture depth, and cold air
structure which will impact ongoing lake effect snow.

The pattern appears favorable for a very long period of significant
lake effect snow starting Thursday night and going right through the
entire weekend. Model guidance is in good agreement initially from
Thursday night through Friday night with mean low level flow from
the west to WNW. This would target the western Southern Tier off
Lake Erie and the Southern Tug Hill and Oswego County off Lake
Ontario. By Saturday and Sunday model guidance begins to show some
spread, with several shortwaves moving through the longwave trough
and possibly backing winds more WSW at times.

The airmass is not overly cold by late January standards, with 850mb
temps starting at around -8C Thursday night and dropping to around
-12C over the weekend. Temperatures are fairly cold at 700mb
however, and this combined with deep moisture will allow lake
induced equilibrium levels to rise to near 10K feet. The favorable
instability and longevity of the setup suggest significant
accumulations are possible east of the lakes. A comparison of the
surface and upper level patterns to our locally developed lake
effect analogs show a good match to significant events for the
Chautauqua Ridge and Tug Hill/Oswego County. CIPS analogs also
support the idea of a significant event. 3-4 day storm totals may
very well reach several feet east of both Lake Erie and Lake
Ontario from late week into the weekend.

&&

.AVIATION /15Z TUESDAY THROUGH SATURDAY/...
Widespread IFR conditions continue to prevail today as a coastal
storm system moves north off New England. Any lingering freezing
rain and sleet at KART will quickly change over to some wet snow
shortly after 15z. Otherwise all sites will see visibility and
ceiling restrictions in light snow today. Snow will taper off and
end from south to north this evening. Conditions will remain mostly
IFR tonight with low stratus, except for some improvement to MVFR at
KIAG/KROC and possibly KBUF as winds turn westerly overnight.

Outlook...

Wednesday and Thursday...VFR/MVFR with a chance of rain and snow.
Friday...VFR/MVFR with a chance of snow showers.
Saturday...VFR/MVFR with a chance of snow showers.

&&

.MARINE...
A coastal storm system will churn northward off New England today.
Northeasterly winds this morning will turn northerly then
northwesterly tonight as the low tracks to our east. Winds 15 to 25
knots over Lake Ontario today will subside by tonight, however will
maintain small craft conditions along the south shore of Lake
Ontario into this evening.

Ridging will build in briefly after this storm system, which will
provide light winds and wave action mid week. We will return to more
typical mid-winter conditions by this weekend with lake effect snows
and likely much choppier conditions on both lakes.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Winter Weather Advisory until 7 PM EST this evening for
     NYZ003>008-011>014-020-021.
MARINE...Small Craft Advisory until 7 PM EST this evening for LOZ043-
         044.
         Small Craft Advisory until 1 PM EST this afternoon for
         LOZ042.

&&

$$

SYNOPSIS...CHURCH/SMITH
NEAR TERM...CHURCH/SMITH
SHORT TERM...HITCHCOCK
LONG TERM...HITCHCOCK
AVIATION...CHURCH/SMITH
MARINE...CHURCH/SMITH



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