231 
FXUS61 KBUF 090838
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
338 AM EST Sat Feb 9 2019

.SYNOPSIS...
Cold westerly flow across the lakes will continue to generate 
localized lake effect snow across the western Southern Tier and 
southeast of Lake Ontario this morning before ending by afternoon. 
Lake effect snow will re-develop southeast of Lake Ontario tonight 
with additional local accumulations. Outside of lake effect areas it 
will be mainly dry and cold through tonight. A weak front will bring 
some widespread light snow late Sunday and Sunday night with minor 
accumulations.

&&

.NEAR TERM /THROUGH TONIGHT/...
Lake effect snow will continue to be the main concern through the 
near term period. Lake induced equilibrium levels are still running 
at 8-9K feet early this morning, but will drop to around 6K feet 
from late morning through tonight as the cold airmass becomes more 
shallow. Despite the low inversion height, conditions beneath the 
inversion will still be favorable for a lake response with a fairly 
deep layer of dendritic crystal growth through the cloud bearing 
layer.

Off Lake Erie...

Multiple bands of relatively weak lake effect snow showers will 
continue into early this morning. The wind yesterday presumably 
opened up some of the ice on the lake, allowing for a better lake 
response. Furthermore, there is still sensible heat flux even 
through thin ice cover, just not latent heat flux. A surface ridge 
will build northward across the lake this morning, with associated 
increased shear, dry air, and lowering inversion heights bringing an 
end to the lake effect. Until then, expect additional accumulations 
of around an inch in the persistent bands through early to mid 
morning, along with blowing and drifting snow.

Off Lake Ontario...

The cellular structure of snow showers at the southeast end of the 
lake is indicative of shear at the moment. The disorganized nature 
of the band of snow is limiting accumulations right now. IR 
satellite imagery showing a convergence band from Lakes Superior and 
Huron sitting just north of Lake Ontario at 07Z. This feature is 
forecast to move southward through early morning as boundary layer 
flow veers, and will merge with the Lake Ontario band. The added 
convergence from this upstream connection should allow the band to 
intensify again for a few hours across central and southern Oswego 
County for one last gasp of higher snowfall rates. The veering 
boundary layer flow will then carry the band farther south and west 
across Northern Cayuga and eastern Wayne counties through mid 
morning before weakening by midday. The snow may end altogether for 
a few hours this afternoon as dry air and subsidence take hold 
across Lake Ontario following the trough passage.

Farther west, the western end of the Lake Ontario band with upstream 
help from Lake Huron will continue to produce light snow across 
Niagara, Orleans, and northwest Monroe counties through early 
morning. A band of snow may drift south across the rest of the 
Rochester area for a few hours mid morning as boundary layer flow 
becomes more northwest. 

As far as additional accumulations go, after 4AM expect another 3-5 
inches across southern Oswego, Northern Cayuga, and northeast Wayne 
counties with the greatest amounts in southern Oswego. An inch or so 
will fall from western Wayne County westward across Rochester to 
Orleans and Niagara counties. Blowing and drifting will continue 
through the morning hours.

Latest mesoscale model guidance continues to suggest the Lake 
Ontario band will make a comeback this evening. Strong surface high 
pressure will pass by just south of the lake tonight from PA to the 
Mid Atlantic states. Anticyclonic westerly flow on the northern edge 
of the high will interact cooperatively with a developing land 
breeze along the south shore of the lake, allowing a single band to 
re-develop by early to mid evening over the lake. Latest high-res 
guidance suggests the eastern end of this band will come onshore 
across Oswego and Northern Cayuga counties, producing local 
accumulating snow. These types of bands often drop their heaviest 
snow right near the shoreline given the strong land breeze forcing, 
and can have notoriously high snow-water ratios. That said, in the 
weak flow environment there is always a good deal of uncertainty as 
to whether the heavy snow will fall over the lake or just onshore. 

Given this uncertainty, have not raised any additional headlines 
yet, but did increase POPS and snow amounts to 3-6 inches in a small 
area from Fair Haven to Oswego for tonight. If the heavier portion 
of the band stays offshore, amounts will be lower. On the flip side, 
if the heaviest portion of the band extends to the shoreline for an 
extended period of time, warning criteria amounts are within the 
realm of possibility. 

Outside of lake effect areas, expect a mix of clouds and sun today 
and partly cloudy skies tonight. Temperatures have returned to below 
normal for now. Highs today will be in the low to mid 20s at lower 
elevations and teens across higher terrain. Lows tonight will be in 
the low to mid teens on the lake plains, with some single digits 
across the interior Southern Tier and east of Lake Ontario.

&&

.SHORT TERM /SUNDAY THROUGH TUESDAY NIGHT/...
Sunday, high pressure will begin over our region and gradually fade 
to the southeast. While this feature will bring a quiet day for most 
there will be lingering lake effect snow to the southeast of Lake 
Ontario. Lake Induced Equilibrium levels will remain around 4K feet 
through the day and a shallow band of snow will start over Oswego 
county, and lift northward before fading across Jefferson County. A 
weak synoptic boundary layer wind will create minimal convergence in 
the lower levels, with greatest lift right near the shoreline of the 
warmer and open water of Lake Ontario. An additional inch or two of 
fluffy snow is possible close to the shoreline Sunday morning. 

The next synoptic snows will arrive late Sunday and through the 
night as a fast moving upper level shortwave passes and a weak 
surface trough dips across the region in response to the fleeting 
surface high. The quick moving and sheared out shortwave will yield 
minor snow accumulations of a coating to an inch for most, and 
perhaps a inch or two closer to the state line. 

Monday morning colder air will drop southward across Lake Ontario 
and behind this shortwave. It will become just cool enough for some 
streamers of lake effect flurries and light snow to form...initially 
over the lake on a land breeze...and then pushed inland across the 
northern Niagara Frontier on a northeast flow. Otherwise Monday will 
be quiet with Canadian high pressure nosing southward across our 
region. This will spread sunshine across our northern zones, though 
clouds may linger near the state line, and begin to increase Monday 
night ahead of our next storm system. 

Our next storm system is currently seen on Water Vapor imagery over 
the Northwest Pacific shoreline. The closed upper level low will dip 
southward along the California shoreline this weekend, and then 
advance across the Rockies and Plains early next week. This 
negatively tilted upper level long wave trough will deepen a surface 
low that will again cut through the central Great Lakes. 

Tuesday will start on the cold side with advancing precipitation 
starting as all snow late Monday night and Tuesday morning. A 
primary low will pass through the Great Lakes Tuesday and Tuesday 
night, moderating temperatures to above freezing for most of the 
area. This will change the snow/possible wintry mix over to plain 
rain later Tuesday and Tuesday night for much of WNY. A secondary 
lee side low will form off the Delmarva Peninsula Tuesday night and 
as this low deepens, the primary surface low to the north of Lake 
Ontario will begin to weaken. This will limit the northward push of 
milder air such that precipitation across the North Country Tuesday 
and Tuesday night may remain as all snow. Here is where confidence 
is high enough that there will be potential for significant synoptic 
snows and will add this to the HWO.

Cold air will wrap back across our region later Tuesday night 
changing precipitation back to all snow for the entire region. 
However moisture will be limited and additional snowfall along the 
cold front will be minor.

&&

.LONG TERM /WEDNESDAY THROUGH FRIDAY/...
Zonal flow to start this period will become more amplified as another 
closed upper level low forms across the central Plains. 

Within moist cyclonic flow aloft there will likely be snow showers 
across the region Wednesday and Wednesday night, favored to the east 
of the Great Lakes where temperatures become cold enough to support 
lake effect snow in addition to orographic lift snow showers. 

Thursday high pressure will pass across the region, with fair 
weather and a mix of clouds and sunshine. A southerly wind Thursday 
night will likely bring warming temperatures through the night.  

A mild flow will be found on Friday across our region to the east of 
a digging upper level low. This low will spread rain/snow showers 
across our region Friday. It is within the realm of possibilities 
that we may even reach into the lower 50s Friday across the Lake 
Plain.

&&

.AVIATION /09Z SATURDAY THROUGH WEDNESDAY/...
Lake effect snow will continue east of the lakes through this 
morning. East of Lake Erie, multiple bands of lake effect snow will 
continue to produce areas of IFR VSBY and MVFR CIGS through 14Z 
today, including KJHW. This lake snow will then come to an end later 
this morning as high pressure begins to build over the lake. East of 
Lake Ontario, lake effect snow will continue mainly across Oswego 
County through early morning near KFZY, with additional bands of 
snow along the south shore of the lake all the way west to Niagara 
County producing areas of IFR VSBY and MVFR CIGS. Most of the 
steadier snow will stay just north of KROC through 12Z, although a 
few hours of IFR is possible mid morning as flow becomes more 
northwest. The northwest flow lake effect will weaken by midday 
today with most of the IFR coming to an end. Outside of lake effect 
areas VFR will prevail.

Tonight VFR will prevail in most areas. The Lake Ontario lake effect 
will make a comeback at the southeast corner of the lake with local 
IFR developing in Northern Cayuga and Oswego counties. 

Outlook... 

Sunday...VFR.
Sunday night...Areas of IFR in light snow. 
Monday...MVFR with a chance of light snow showers early, 
otherwise VFR.
Monday night...Deteriorating to IFR late with snow developing.
Tuesday...Areas of IFR with snow changing to rain.
Wednesday...Areas of IFR with snow likely.

&&

.MARINE...
A tight pressure gradient in the wake of strong low pressure moving 
off the Labrador coast will continue to produce gales on Lake 
Ontario into this morning. WNW winds will then steadily diminish 
this afternoon and tonight as high pressure builds from the Ohio 
Valley to the Mid Atlantic states. Small Craft advisory conditions 
will gradually end from west to east later today and tonight.

The nearby high pressure will then bring a period of light winds 
late tonight through Sunday. ENE winds will then increase ahead of 
low pressure moving into the western Great Lakes. This will bring a 
round of Small Craft Advisory conditions from later Monday through 
Tuesday and beyond.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Winter Storm Warning until 1 PM EST this afternoon for NYZ006.
     Winter Weather Advisory until 1 PM EST this afternoon for 
     NYZ004-005.
MARINE...Small Craft Advisory until 10 AM EST this morning for LEZ020-
         040-041.
         Small Craft Advisory until 10 AM EST this morning for 
         LOZ030.
         Gale Warning until 10 AM EST this morning for LOZ043-044-
         063-064.
         Gale Warning until 7 AM EST this morning for LOZ042-045-
         062-065.

&&

$$

SYNOPSIS...Hitchcock
NEAR TERM...Hitchcock
SHORT TERM...Thomas
LONG TERM...Thomas
AVIATION...Hitchcock
MARINE...Hitchcock