textproduct: Binghamton

WHAT HAS CHANGED

Lake effect snow along the NY Thruway corridor is dissipating and therefore the Winter Weather Advisory for Onondaga County has been cancelled.

There is also increasing confidence for a round of light to moderate snow tonight, changing to a wintry mix during the day on Tuesday. Winter Weather Advisories may need to be issued later today.

KEY MESSAGES

1) A clipper system will pass through the area tonight into Tuesday, which will bring light to moderate snow to the area tonight, changing to a wintry mix on Tuesday.

2) Additional clipper systems are possible through the end of the week; a favorable pattern for mixed precipitation events, or all snow if enough cold air is in place.

DISCUSSION

KEY MESSAGE 1...

A weak clipper system moving through the Northern Great Lakes tonight into Tuesday will bring a warm front into NY and PA. Overrunning precipitation moves in tonight and with plenty of antecedent cold air in place, precipitation type tonight is expected to be entirely snow. However, by daybreak on Tuesday, forecast soundings show a warm nose moving in, which would likely change the snow to a wintry mix of of snow, sleet, and freezing rain, and eventually all rain in the valleys.

The timing of this transition results in a tricky snow accumulation forecast. The best chance for seeing accumulating snow will of course be tonight with the form of precipitation likely remaining all snow. Snow amounts tonight will likely be 1-3 inches for most of the area with locally higher amounts in the upslope areas of Central NY. With there being decent omega through the DGZ and indications there could be a mid-level FGEN band bisecting Central NY, there is certainly a potential for some locations to see some snow amounts a bit higher than currently forecast.

Once precipitation changes to a wintry mix Tuesday morning, while there could be some minor ice accumulation, overall impacts are expected to be limited since this light accumulation would be on top of fresh snow. Eventually, temperatures warm enough by Tuesday afternoon (highs in the mid 30s to lower 40s) to have any lingering showers be mainly in the form of rain or a rain/snow mix.

After coordinating with our surrounding WFOs, it was decided to hold off on any Winter Weather Advisory decisions until the day shift due to the high degree of uncertainty regarding if criteria will even be reached and low confidence in the wintry mix impacts (or if the wintry mix will even occur long enough to cause problems).

KEY MESSAGE 2...

The upper level pattern in the Northern Hemisphere looks to be blocked with 3 large ridges in Western Alaska, the Central U.S., and Northern Europe. This means that we will be stuck on the backside of a trough off of the Eastern U.S. and the Central U.S. ridge leading to plenty of chances of clippers to drive out of the northwest 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 setup is favorable for overrunning mixed precipitation events through the end of the week and into next weekend. Right now, our official forecast keeps things simple with just rain/snow showers, but additional p-types could be introduced as the week progresses and if confidence increases.

Of particular note is the colder trend in the model guidance for Friday with the surface low track trending further to the south and a high to the north supplying colder air to the region. Should this trend continue, temperatures on Friday would be much colder than previously expected, with upper 20s to mid 30s for highs, rather than upper 30s to near 50 degrees for highs. In fact, the change from the 01Z NBM to the 07Z NBM shows this exact drastic difference. This would also mean snowier scenario for Friday, rather than a wintry mix to rain scenario. This will continue to be closely monitored with our upcoming forecast packages.

AVIATION /12Z MONDAY THROUGH FRIDAY/

Lake effect snow has hung on longer than expected, with IFR visby currently at SYR and looking to move into RME in the next hour or so. Conditions should become VFR at SYR by 13z and RME by 14z. MVFR ceilings should also hang around the rest of CNY until mid morning before VFR returns through the evening hours.

Another system will move in later this evening from the west, bringing snow showers across the area. The latest guidance has slowed the development of snow by a couple of hours, but with many models showing different placement and timing of where the snow will start, confidence is low as to the exact time of when IFR will move in. Current thinking is IFR should start between 7z and 10z for CNY terminals and around 12z at AVP. Hopefully we will have a better picture for the next TAF set.

Outlook...

Tuesday and Tuesday night...Snow and IFR and lower restrictions expected through the morning hours. Occasional IFR restrictions possible in rain and snow during the afternoon. Restrictions may linger into the overnight hours

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...None.