Marine Weather and Tide Forecast for Geneva, NY

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 /18Z SATURDAY THROUGH THURSDAY/
Finger Lake effect driven MVFR continues at ITH this afternoon.
Guidance is not handling the restrictions well so used mostly satellite patterns and surface obs for the forecast. MVFR ceilings should stick around into the late afternoon. A wind shift after 22z should end the restrictions here with VFR through the overnight.

A large winter storm will impact the area starting Sunday morning. Snow and associated IFR/LIFR restrictions will start at AVP around 11-12z and spread north. Dry air near the surface should suppress initial snowfall and restrictions to a short period of MVFR visby before IFR fills in shortly afterward.
AVP/ELM/BGM/ITH will be IFR and lower by mid morning with SYR/RME by noon.

Outlook...

Sunday afternoon into Sunday Night...Snow overspreads the area, heavy at times leading to IFR or worse restrictions. LIFR restrictions expected during the afternoon hours at all terminals.

Monday...Lingering snow showers and/or lake effect possible with associated restrictions.

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.