textproduct: Binghamton

WHAT HAS CHANGED

Adjusted snowfall totals across most of the region. Less snow expected in portions of the Wyoming Valley and Poconos due to mixing with sleet. Slightly more snowfall is expected near the NY/PA line eastward toward the Catskills due to banding.

KEY MESSAGES

1) High confidence in a significant snow storm Sunday into Monday.

2) Lingering lake effect snow showers Monday night, with weak clippers and additional chances for scattered lake effect snow showers through much of next week.Temperatures remain below average right into next weekend, with only a slight moderating trend.

DISCUSSION

KEY MESSAGE 1...

Low pressure will track into the Ohio Valley then reform off the east coast during the day Sunday. Moisture will overrun an inverted trough to develop widespread snow which moves in during the morning hours from south to north. Snow should be heaviest from mid afternoon into the early evening hours. Snow looks to exit slightly faster though with lingering snow showers late Sunday night through Monday. Some additional lake effect snowfall should then start up Monday night. Blowing snow will be possible Monday as winds increase in the afternoon. Temperatures will continue quite cold as well with temperatures in the single digits and teens.

The potential for banding has increased on the latest model guidance with the NAM 600-800 MB layer now showing the potential for snowfall rates of 2-4 inches per hour at the peak of the storm from the NY/PA line eastward toward the Catskills. The experimental RRFS is showing quite a bit of banding as well with hourly QPF amounts of around .15 too in the mid afternoon till early evening. With that said snowfall totals have been increased to around 18 inches, locally up to 2 feet. The highest chances for this are in Susquehanna, Broome, Delaware and Sullivan counties. This banding has a tendency to shift northward as a storm gets closer but tried to offset that by already placing the highest totals a bit further north than model consensus.

Snow ratios still look to be in the 15-20:1 range for CNY given the cold temperatures and a favorable snow growth zone with lift in the -10 to -20C layer. Ratios have trended lower across the Wyoming valley and portions of the Poconos where sleet is now expected to mix in. This may cap totals for snowfall closer to 10 inches but increase the weight of the snow cover given the added sleet. The warm nose continues to trend slightly north with each model run and have forecasted totals based on the more northern model guidance such as the NAM to account for typical trends.

KEY MESSAGE 2...

An upper level trough will remain over the area Monday night behind the departing large winter storm. Very cold air will remain in place, with 850mb temperatures around -20C overnight. Model guidance is showing a west-northwest flow in place through the first half of Monday night, backing more westerly toward daybreak Tuesday. Parameters are good for lake effect snow bands off of Lake Ontario through the overnight, starting across the upper Susquehanna region, Finger Lakes then shifting north overnight toward I-90. Lake Erie is much more ice covered now, around 80-90% plus. Lake Ontario is starting to see some ice, around 20-25% coverage especially along the north and northeast shores. Overall, expecting a few inches (1-3") of lake effect snow across Onondaga, Western Madison and North-central Oneida County Monday night as the band is rather transient.

A weak clipper low passed by to our north and west on Tuesday, bringing weak warm air advection and the chance for some scattered snow showers to Central NY. Minor, light accumulations of less than 1 inch will be possible in some areas that see more snow shower activity. Otherwise, it remains cold and partly to mostly cloudy. Lows Monday night will be around 0 or in the single digits, with highs Tuesday only in the upper single digits to mid-teens.

Cold west-northwest flow continues Tuesday night and Wednesday, with some minor shortwave disturbances moving through. High pressure will be to our south and west Tuesday night, and if some locations can clear out, temperatures may plummet below zero, as winds are fairly light as well. The next deeper 500mb trough drops into the region Wednesday night and Thursday, along with a potential clipper system. This will keep chances for snow showers in the forecast, especially across our CNY counties. Temperatures remain steady, with lows 5 below to 5 above zero, and highs in the upper single digits to teens through at least Friday. At this time, model guidance keeps a rather stagnant pattern over the area right into next weekend, with the broad 500mb trough in place across the Great Lakes and Northeast, occasional clipper lows and lake effect snow showers off of Lake Ontario. Even by next Saturday, temperatures remain several degrees below average for the end of January.

AVIATION /00Z SUNDAY THROUGH THURSDAY/

Broken high level clouds and VFR conditions will remain in place across the area into the overnight hours. Light MVFR snow develops from SW to NE starting by 9-11z at ELM and AVP; 10-12z at BGM and ITH, and by 13-15z at SYR and RME.

A large winter storm will impact the area Sunday, Sunday night and linger into Monday. Snow and associated IFR/LIFR restrictions will start at AVP/ELM around 11-12z and spread northeast. IFR/LIFR snow reaches BGM and ITH by 12-13z Sunday, and SYR/RME by 15-16z. Periods of heavy snow are then possible starting at AVP/ELM/ITH and BGM by 16-17z, spreading north to SYR/RME by about 17-18z Sunday afternoon. Periods of moderate to heavy snow, freezing fog and blowing snow then continue through the end of the taf period at all of our TAF sites. Confidence is high at this time. Some sleet may try to mix in at AVP toward Sunday evening, confidence is low on this at this time. Snowfall amounts will be 5 to 12 inches at all terminals by 00z Monday. Snowfall rates of 1-2, locally 3 inches per hour will be possible in the afternoon and early evening hours. Some low level wind shear is possible at AVP Sunday evening as a low approaches, increasing ESE winds at 40 kts will be present at around 2k ft agl.

Light and variable surface winds expected overnight into early Sunday morning, less than 5 kts. East-southeast winds increase through the day on Sunday, between 7-15 kts. With the very cold temperatures and dry, powdery nature of the snow, even 10-15 kts of wind can create some minor blowing and drifting of snow in open areas.

Outlook...

Sunday Night...Period of snow continue, heavy at times leading to IFR or worse restrictions. LIFR restrictions are still possible. Some sleet may mix in at AVP before about 06-09z early Monday morning.

Monday...Lingering snow showers and/or lake effect possible with associated restrictions. Blowing snow in the afternoon as NW winds gusts 25-35 mph at times.

Tuesday thru Thursday...Isolated snow showers with associated restrictions, otherwise mainly VFR.

BGM WATCHES/WARNINGS/ADVISORIES

PA...Winter Storm Warning from 1 AM Sunday to 7 PM EST Monday for PAZ038>040-043-044-047-048-072. NY...Winter Storm Warning from 1 AM Sunday to 7 PM EST Monday for NYZ009-015>018-022>025-036-037-044>046-055>057-062.