textproduct: Binghamton

WHAT HAS CHANGED

10 PM Update: Dense Fog Advisory has been issued for all of Central NY and NE PA until 8am Wednesday. Visibilities may drop to one quarter to one half mile at times in dense fog.

Slightly increased expected snowfall amounts late Wednesday and Wed night in the southern Tug Hill Plateau. Issued a Winter Weather Advisory for snow and freezing rain for portions of central NY.

KEY MESSAGES

1) A wintry mix will impact portions of central NY Wednesday and Wednesday night.

2) Another wintry mix will spread across the region Friday into Saturday.

3) We are closely watching the potential for accumulating snow from a coastal low Sunday into Monday.

4) The threat of ice jams increases later this week and into the weekend.

DISCUSSION

KEY MESSAGE 1...

A favorable setup will develop Wednesday morning as a broad warm front extending from an area of low pressure in the western Great Lakes to the interior Northeast US lifts a considerably warmer airmass northward over northeast PA and central NY. Upper level forcing supported by a low-amplitude 500mb trough and much of the area within the left exit region of a 150 kt jet streak in the Ohio Valley will provide the necessary large scale lift for a broad area of precipitation. A decent layer of isentropic lift within the warm/moist sector will also combine with weak low-level fgen to support an enhanced axis of heavier qpf.

The precip will move in from the west and start around 8-10 AM west and sw of the Finger Lakes. The warm air aloft and surface temperatures above freezing in this area should keep precip in the form of rain along and west of I-81 and over most of ne PA. The challenging part of the forecast occurs when this precipitation runs into the cold air that is pushed up against the Catskills and southern Adirondacks and southern Tug Hill.

The warm front will stall its northward movement just after noon as high pressure to the north helps pull down colder air from Canada and reinforces the cold air near the surface while undercutting the warm air aloft. There is increasing confidence among the model guidance that a 6-12 hour window will occur where snow will accumulate (north of this warm nose over northern Oneida County) and freezing rain will occur along and south if the NY Thruway to roughly the I-88 corridor. Areas farther to the south should stay warm enough to keep all precip in the form of rain.

A Winter Weather Advisory has been issued for parts of central NY. Portions of northern Oneida County could see 2 to 5 inches of snow Wed afternoon through Wed night...and areas to the south of there will likely see a wintry mix with the threat of snow and ice.

KEY MESSAGE 2...

The next wintry system will move in from the southwest Friday morning and interact with a sub-freezing surface air mass east of I-81 (in NY and ne PA) to produce a mix of snow, sleet and freezing rain. This system will be somewhat similar to the Wednesday system but the warm nose looks to be able to reach a bit farther north given that the system is a bit more amplified than Wed.

Strong forcing from the upper low and strong dynamics aloft will trigger a broad area of precipitation within the area of warm air advection. Cold air east of I-81 will remain in place over the warm air aloft to produce the wintry mix. At this time, the precipitation amounts look to be slightly less than Wed given the fast movement of the system through the area and the decreased amount of deep moisture.

Another round of Winter headlines is possible once we get closer to this event.

KEY MESSAGE 3...

An embedded upper level short will round the bottom of the larger long wave trough over the eastern CONUS Saturday night. This s/w will trigger surface cyclogenesis off the East Coast Sunday which will impact a section of the Northeast US later Sun and Sunday night. The uncertainty at this time revolves around the track of the coastal low and how far offshore it develops. The airmass on the backside of the low will be cold enough for all snow over the interior Northeast, but if the low is far enough offshore, the snow will be mostly confined to locations of the I-95 corridor.

Taking a quick look at the ensembles and a cluster analysis of the 500mb height field, it appears that there is not a strong consensus of the members with respect to the location and intensity of the coastal low. As we get closer to the event hopefully we can get a better handle on the potential for accumulating snow in the Northeast.

KEY MESSAGE 4...

We continue to monitor the threat for river ice jams through the rest of this week. With the potential for liquid precipitation, combined with warmer temperatures which will melt the snowpack into the basins, there is an increasing threat for river ice to break up and move down stream. Two to 5 foot rises on area rivers and streams could dislodge and break up the river ice. If the ice moving downstream were to get caught in certain confluences of the river or near bridges this could cause ice jams that may lead to localized flooding.

AVIATION /03Z WEDNESDAY THROUGH SUNDAY/

Mostly widespread IFR and MVFR conditions expected this evening with the exception of several hours of VFR at AVP and ELM due to a narrow corridor of clearing that developed earlier. This clearing is expected to fill in over the next few hours allowing ceilings and visibilities to drop rather quickly. Another round of low clouds and fog overspreads the region tonight with MVFR and IFR cigs and fog redeveloping before the onset of precipitation occurs between 12-15Z in the form of rain or a rain/snow mix initially Wed morning. With perception continuing through most of tomorrow, conditions are not expected to improve for most sites during this period.

Outlook...

Wednesday...IFR and MVFR restrictions likely for most of the forecast terminals as the precipitation moves through Wed afternoon and Wed night. Confidence moderate to high.

Thursday...Potential restrictions Thu morning due to low clouds and fog, otherwise mainly VFR, with just a slight chance for a few rain showers in the afternoon. Confidence low to moderate.

Friday...Rain likely with associated restrictions. Could mix with snow north, near RME. Confidence low to moderate.

Saturday...Lingering snow to the north and rain south with associated restrictions. Confidence remains low on restrictions given the uncertainty with precipitation type and intensity.

Sunday...Potential coastal low could impact central NY and ne PA Sunday with restrictions from snow showers. Confidence is low.

BGM WATCHES/WARNINGS/ADVISORIES

PA...Dense Fog Advisory until 8 AM EST Wednesday for PAZ038>040-043- 044-047-048-072. NY...Dense Fog Advisory until 8 AM EST Wednesday for NYZ009-015>018- 022>025-036-037-044>046-055>057-062. Winter Weather Advisory from noon Wednesday to 4 AM EST Thursday for NYZ009-018-036-037-044>046-057.