textproduct: Binghamton

WHAT HAS CHANGED

Lake effect snow this afternoon and early evening is more organized than forecast. Greater confidence in widespread accumulations of snow Monday night into Tuesday morning.

KEY MESSAGES

1) Lake Effect Snow persisting through tonight, mainly north of the Thruway.

2) Clipper system passing through Monday night into Tuesday bringing snow and mixed precipitation to the region.

3) Additional clipper systems into the end of the week; a favorable pattern for potential overrunning precipitation events.

DISCUSSION

KEY MESSAGE 1...

A fairly robust lake effect snow plume has developed off of Lake Ontario this afternoon. The band has not really organized but despite it being mostly cellular, webcams are still showing heavy snow and quick accumulations, especially at Camden NYSM site. Forecast soundings show the mean boundary layer winds remain out of the west for a few more hours, then winds shift to out of the NW. This should cause the band to drop more into the NY Thruway later this evening and into tonight. Upper level ridging with cold air advection weakening overnight will also help keep the lake effect band more diffuse overnight as it drops south so accumulations remain lighter overnight. Chances of snow were also kept into the early morning as the 850 mb ridge does not build in until after 8 AM tomorrow with winds shifting back SW and the 850 mb temperatures getting back above -7C.

KEY MESSAGE 2...

A weak clipper system moving through the Northern Great Lakes Monday night into Tuesday along with a ridge building brings a warm front into NY and PA. Overrunning precipitation moves in Monday night and with plenty of antecedent cold air in place, precipitation types overnight are expected to be all snow. QPF amounts look to be around a quarter inch and snow ratios are expected to be around 10:1 as temperatures warm aloft and near the surface towards freezing Tuesday morning. Right now, widespread 2 to 3 inches of snow is expected, with lower amounts likely over NEPA into the western Southern Tier where the temperatures rise to near freezing so some mixing to rain is possible.

Looking at forecast soundings, there is a small chance of freezing rain late Monday night into early Tuesday just as the precipitation is winding down. Surface temperatures remain just below freezing in parts of the Southern Tier and eastern NEPA while temperatures aloft rise just above freezing. The melt layer is small so complete melting may not happen and precipitation ends up being more partially melted snow to a sleet mixture rather than freezing rain. Confidence in its location and if it would even happen or not was too high so freezing rain and sleet were removed from the grids for now.

KEY MESSAGE 3...

The upper level pattern in the Northern Hemisphere looks to be blocked with 3 large ridges in Western Alaska, The central US, and Northern Europe. This means that we will be stuck on the backside of a trough off of the eastern US and the central US ridge leading to plenty of chances of clippers to drive out of the NW into the Mid Atlantic. Given the amount of warm air in the central plains as well as access to cold air in eastern Canada, the set up is favorable for overrunning precipitation events through Christmas week and into next weekend. Right now, there is no freezing rain or sleet in the forecast for Wednesday onward, if there can be strong enough high pressure over Northern New England during a passage of a shortwave, there can be some low level cold air advecting in while warm air aloft melts the precipitation so that.

AVIATION /00Z MONDAY THROUGH FRIDAY/

- Lake effect snow to impact RME and SYR this evening

A heavy lake effect snow band across Northern Oneida County will drop south this evening and cause restrictions for a few hours at RME and eventually SYR. Conditions are expected to fluctuate between MVFR and LIFR at RME through about 00-03Z before shifting south. There is some uncertainty with how quickly the snow showers drift south into SYR this evening with the trend continuing to be slower, generally after 01Z now. There is the potential for more of a defined band to develop for a few hours this evening if we get a multi-lake connection to set up. As high pressure begins to build in overnight and the lake effect snow will eventually come to end, but confidence remains low on the timing and intensity.

ITH and BGM are both expected to see some MVFR ceilings develop later tonight as the lake effect snow showers shift south. Confidence was too low to bring restrictions from the snow showers at this time here, but MVFR have been added.

Outlook...

Monday night...Snow overspreads the area along with associated restrictions.

Tuesday into Tuesday night...Occasional restrictions possible in rain and snow.

Wednesday...Mainly VFR.

Thursday...A low chance of rain and snow showers and associated restrictions.

Friday...Rain and snow showers likely along with associated restrictions.

BGM WATCHES/WARNINGS/ADVISORIES

PA...None. NY...Winter Weather Advisory until midnight EST tonight for NYZ009.