Area Forecast Discussion
Issued by NWS Binghamton, NY

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000 FXUS61 KBGM 121146 AFDBGM Area Forecast Discussion National Weather Service Binghamton NY 646 AM EST Tue Dec 12 2017 .SYNOPSIS... Light snow will occur early today, heavier north of the Twin Tiers to Catskills. The snow will diminish by late morning, mixing with rain at lower elevations. However, an Arctic front may include gusty snow squalls into this afternoon through early evening. Much colder air will produce lake effect snow showers tonight through at least Wednesday with localized white-outs in Central New York. && .NEAR TERM /THROUGH TONIGHT/... 430 AM update... Very complicated situation, to say the least, which will have a variety of impacts for our region. Main concerns are light accumulating snow from clipper this morning, especially north, then snow squalls this afternoon along strong Arctic front that may cause icing up of roads as temperatures plummet. All of this, followed by developing lake effect snow tonight. Front side of clipper system has caused a shield of snow to break out across roughly the northern half of our area during the past several hours. Snow is falling at a clip of about an inch an hour towards the New York Thruway. Meanwhile, snow has so far struggled to reach the ground from the Twin Tiers southward but will gradually do so. Ithaca and Binghamton airports are now just getting into 2 mile snow and are starting to accumulate. Surface low is now in western Pennsylvania and it will track directly over the Finger Lakes region to northern Catskills. North of that track, snow will be more persistent through the day, but to the south things are complicated. Ripples in the flow aloft are alternating on-and-off snow, and temperatures at lower elevations are also getting above freezing. Thus, the lighter accumulations of snow from the Twin Tiers southward will also be prone to a little bit of melting, and rain may actually mix in with the snow showers after the initial shield of light snow shifts east. Concern is growing that with temperatures getting up to around/slightly above freezing, roads will become wet in many spots prior to arrival of Arctic front. This is a problem because the front appears probable to be accompanied by some snow squalls due to very steep lapse rates/convective mixing through the dendritic growth layer. Squalls themselves usually only produce about an inch or even less of snow, but it comes down fast and heavy with near whiteout conditions; and in this case will be followed by a rapid plummet in temperatures well below freezing. Thus, any roadways that are wet or become initially wet from squalls, may quickly ice up and become hazardous directly behind the front. Arctic front will reach Finger Lakes by late morning, the I-81 corridor early afternoon, and then Catskills-Poconos mid-to-late afternoon. With exit of Arctic front this evening, winds will be come gusty out of the west or west-northwest. This will begin to send at least scattered lake effect snow showers and flurries across the area. The snow will be very dry and fluffy, prone to blowing and drifting. Lake effect multibands will become more numerous overnight, especially in Central New York, with low visibilities. Snow accumulations are tough to summarize, given all of the above considerations. Basically, from Twin Tiers southward only an inch or two of accumulation will have occurred through midday; more like 3 to 6 inches as you make your way up to eastern Finger Lakes-Syracuse-Utica, and 6 to 9 inches north of the NY Thruway. However, snow squalls will occur late morning through afternoon, then lake effect gets going into tonight. The lake effect by itself will produce another few to several inches of snow tonight, mainly in Central New York, with blowing and drifting. And all told, by late tonight temperatures will be in the teens areawide with wind chills approaching zero. && .SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/... 3 AM Update... Just minor changes. Lake effect continues this period as the deep negatively tilted upper level trough over eastern NY moves east Wednesday. Deep NW flow of arctic air into the area. Lake effect will have a short fetch but other factors compensating for this. 850mb air is -15 to -20 providing moderate instability and lift to 10k ft to start. In addition a short wave moves east across central NY in the morning. Lake effect will extend across the Finger Lakes and Mohawk Valley into the southern tier and Catskills in the morning. Strong surface winds will cause drifting and blowing of the lake effect snow. Snow amounts for the day of 2 to 4 inches across the eastern Finger Lakes east through the northern Susquehanna Region and north to Syracuse/Rome/Utica for the day but isolated higher amounts. The flow shifts as the trough shifts east. Lake effect will move northeast to be across the far northeast counties late Wednesday into Wednesday night. Wednesday night moisture levels drop to 5k ft in the evening then lower overnight. Weak warm air advection. Lake effect will diminish slowly in place but continue into Thursday and beyond. Wednesday night snow amounts focused in Onondaga, Oneida, and Madison Counties. Winds also drop. Upper pops Wednesday night in NEPA as a surface low moves southeast from sw PA to Delaware. Will be on the edge of a large area of light snow. Snow Amounts less than an inch. Temperatures recover only slightly into the low and mid 20s but with strong winds, wind chills will be mostly in the single digits. Wednesday night temperatures fall to mostly 10 to 15 degrees. Wind chills remain about the same as wind speeds drop. Sustained winds during the day of 15 to 25 mph with higher gusts will blow around around any snow that has fallen or is falling. && .LONG TERM /THURSDAY THROUGH MONDAY/... 3 am update... Little change to the long term. Slow moderation as the deep upper level trough weakens. A stalled front across the Great Lakes will provide better chances of continued snow showers and flurries in central NY. A front will cross Sunday night with some snow but best precipitation will be south and east of the CWA. 400 PM Update...A cold, broad upper level trough will remain over the Northeast through much of the extended period. Lingering lake effect snow showers/bands will be around the area Wednesday night, especially across Onondaga/Madison/Oneida counties on a 290-300 flow. A weak low pressure system also likely passes to the south later Wednesday night and Thursday. This could scrape our NE PA zones with a period of light snow. Otherwise, scattered lake effect snow showers continue across north-central NY through the day on Thursday. High temperatures will only be in the lower to mid 20s. Another trough and low pressure system move toward the Northeast Friday into Saturday. Right now, the latest guidance splits the area with one low pressure system moving off the Atlantic coast and another, clipper like system moving into the Great Lakes. For now, went with chance PoPs for another period of light snow areawide. There will be a brief break on Saturday, but a cold west- northwest flow continues. This should lead to additional scattered lake effect snow showers...mainly in Central NY. Models are in good agreement that another trough/surface low will approach for Sunday into next Monday. The guidance differs on the exact track of this system. However, the latest guidance is trending colder with this system. Therefore, lowered temperatures a few degrees for Sunday, and brought a chance of snow or rain/snow to the deeper NE PA Valleys during this time. Daytime temperatures over the weekend look to be mainly in the lower to mid-30s..with overnight lows in the 20s. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/... Clipper system bringing restrictive snow to most terminals this morning, but duration and persistence will be longest for KSYR-KRME, whereas for KITH-KBGM and especially KELM-KAVP there will be breaks. Visibility will be below alternate minimums for KSYR-KRME at times for KBGM-KITH. Though there will be relative lull snow-wise mid morning up to early afternoon, unfortunately an Arctic front will sweep through this afternoon accompanied by snow squalls for most terminals. General east to southeast winds 10 knots or less early this morning, will veer south- southwest ahead of the front up to midday before an abrupt west- northwest shift with the frontal passage this afternoon-evening with gusts of 20-25 knots. Lake effect snow will keep restrictions going for at least KRME-KSYR this evening, and intermittent restrictions will eventually be possible across the remainder of the NY terminals as the night progresses. Outlook... Wednesday through Thursday...Gusty lake effect snow showers and associated restrictions, especially NY terminals. Blowing and drifting snow could be a significant problem Wednesday. Thursday through Saturday...Still a chance for snow showers and intermittent restrictions. && .BGM WATCHES/WARNINGS/ADVISORIES... PA...Winter Weather Advisory until 6 PM EST Wednesday for PAZ039- 040. NY...Winter Weather Advisory until 6 PM EST Wednesday for NYZ015- 022>025-046-055>057-062. Winter Storm Warning until 6 PM EST Wednesday for NYZ009- 016>018-036-037-044-045. && $$ SYNOPSIS...MDP NEAR TERM...MDP SHORT TERM...TAC LONG TERM...MJM/TAC AVIATION...MDP

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