textproduct: Binghamton

WHAT HAS CHANGED

Winter storm warning issued. Snowfall ratios lowered slightly in NEPA Sunday afternoon into the evening. Other smaller changes with the storm such as QPF, onset timing and snowfall amounts. Confidence for a high impact snow storm continues to increase on Sunday into Monday.

KEY MESSAGES

1) Lake effect snow showers through Saturday morning and much colder heading into the weekend. Expect dangerously low wind chills Friday night into Saturday morning.

2) Confidence continues to grow for a high impact snow storm Sunday into Monday.

3) Lake effect snow and another shot of bitter cold follows.

DISCUSSION

KEY MESSAGE 1...

Cold air continues to filter into the region with westerly flow in place. This has allowed lake effect snow showers to trail into central NY this afternoon off of Lake Erie. As the afternoon progresses westerly flow is expected to shift northwest. This will allow a more pronounced lake effect band from Lake Ontario to down into north central NY. With very cold air in place model soundings continue to show ice crystal formation with temperatures ranging -25C to -30C. This is not supportive efficient accumulations. Snowfall totals are ranging around 2 to 3 inches with local amounts up to 4 inches possible. This is just below advisory criteria for Onondaga County, but it could be close. Decided to hold off and not issue at this time. If a lake effect band is looking really well organized later this evening, we can always issue a short fused advisory. Temperatures fall this evening and especially overnight with wind chills down to -10F to -30F. An Extreme Cold Warning is in effect over northern Oneida county and Cold Weather Advisories are in effect for the rest of the area. Little relief from the cold is expected Saturday as temperatures will mainly be in the single digits through the day and wind chills will stay below zero for most of the region.

KEY MESSAGE 2...

Not much change synoptic wise with the setup. Low pressure has tracked into the Rockies today with broad strong high pressure to the north of it. The low pressure system is still expected to track up the Apalachin mountains then reform near Delmarva. This is a classic track for a high impact winter storm to impact the region. Plenty of gulf moisture looks to be lifted along an inverted trough Sunday developing widespread snow to our south which moves through Sunday into early Monday. Snow showers then will linger through Monday. Arctic air should hold firm keeping temperatures in the single digits and teens.

In terms of snowfall rates we look to start off light with virga initially occurring early Sunday morning. However, the heaviest of snow looks to be Sunday afternoon and night. Modeled FGEN between 800-600 MB is indicative of snowfall rates of around 1-2 inches per hour. Also seeing some signs for localized banding of even higher totals across portions of the Western Catskills southward into the Poconos as well for a few hours late Sunday afternoon. Snowfall rates should then decrease during the evening and diminish to snow showers as the low exits off of the east coast.

With regards to any mixing the 12Z Hires model guidance has trended slightly colder overall. This currently looks to keep any mixing with sleet south of the region at this time. Will continue to monitor the trend of any mid-level warm noses as that would imply more sleet and less snow in NEPA. Also, if we get a dry slot late Sunday night into Monday some freezing drizzle would be possible though regionwide.

Moving onto snow ratios. This is perhaps the most challenging part of the forecast. Right now a range of 10-17:1 throughout the event appears to be a good fit. Mid-level warmth aloft across NEPA perhaps into portions of CNY looks to be a potential counter to the typically fluffy snow with such cold temperatures. However, a look at the GFS soundings show a very favorable environment for snow growth in the -10 to -20C layer which would imply ratios closer to 20:1.

This gets us to a general 12-18 inch snowfall across the region by Monday afternoon. NEPA faces the highest amount of uncertainity with both localized banding potentially leading to 18+ and lower ratio potential. The western Catskills have the best chance for totals of 18+ due to any localized banding.

KEY MESSAGE 3...

Winds look to be westerly to west northwesterly for most of next week keeping the chance for some lake effect snow in the forecast at times. Another bitter shot of cold air is expected to Monday night into Tuesday. Combined with winds, wind chill values may reach -15F again in spots. NBM guidance is likely a little low on the wind in this timeframe as well. Highs are only forecasted to reach the 10's and 20's most of next week with single digit lows. If we get clearing any particular night, lows would likely fall well below zero given snow cover.

AVIATION /06Z SATURDAY THROUGH WEDNESDAY/

Some lingering lake effect snow is making its way south through CNY with potential near MFVR vis and cigs at ITH, SYR and BGM. Trends have been towards lighter snow so IFR restrictions were taken out but some Lake Cayuga snow flurries may result in brief IFR at ITH but confidence in the band forming is low.

Later this morning, the snow band will dissipate with VFR conditions expected after 12Z at all sites. Some lower cigs begin to move in from the south around 6Z but AVP should remain VFR.

Outlook...

Saturday Night...Mainly VFR until snow moves into AVP-ELM-BGM late at night or early Sunday morning (after 09z).

Sunday into Sunday Night...Snow overspreads the area, heavy at times leading to IFR-LIFR or worse restrictions.

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

Tuesday and Wednesday...Isolated snow showers around, 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. Cold Weather Advisory until 10 AM EST this morning for PAZ038>040-043-044-047-048-072. NY...Extreme Cold Warning until 10 AM EST this morning for NYZ009. 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. Cold Weather Advisory until 10 AM EST this morning for NYZ015>018-022>025-036-037-044>046-055>057-062.