textproduct: Binghamton

WHAT HAS CHANGED

Increasing confidence for a light to moderate snowfall, with some light mixed precipitation tonight through Tuesday. Winter Weather Advisories have been issued for much of the forecast area for this potential. Model guidance is trending much colder Friday into Friday night and further south with the low pressure track. A lot of uncertainty remains with this winter weather system as model guidance and ensemble suites try to hone in on the thermal profiles, precipitation amounts and ultimate low track. With that said, probabilities for another accumulating snow or wintry mix event are increasing over our Central NY and NE PA in this timeframe.

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 light wintry mix or drizzle on Tuesday afternoon and evening. Winter Weather Advisories have been issued for most of the forecast area.

2) Quiet and seasonable weather expected Christmas Eve and Christmas Day across the area.

3) Additional weather system could bring a period of snow and/or a wintry mix to the area Friday into Friday night; the pattern is trending more favorable mixed precipitation events, or all snow if enough cold air is in place.

DISCUSSION

KEY MESSAGE 1...

A weather 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. Snow will continue across the area Tuesday morning, starting to mix by late morning over the central southern tier zone.

By Tuesday afternoon forecast soundings show a warm nose moving in, which would likely change the steady snow to a light wintry mix of of snow, sleet, and freezing drizzle, and eventually all rain or drizzle in the valleys by the mid to late afternoon hours.

The timing of this transition is trending later, but still results in a tricky snow accumulation forecast. The best chance for seeing accumulating snow will of course be tonight and Tuesday morning with snow being the predominate ptype for most of the area. Snow amounts tonight through midday Tuesday will likely be 2 to 5 inches for most of the area with locally higher amounts in the highest elevations Central NY & Catskills. 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. Lower amounts of 1 to 2 inches are expected for the lower elevations of the Lake Ontario plain (Syracuse), western Finger Lakes and Mohawk Valley, where rain could mix slightly earlier on Tuesday and overall QPF amounts are lower.

Once precipitation changes to a light wintry mix Tuesday afternoon, while there could be some minor ice accumulations over the higher elevations, overall impacts are expected to be limited since this light accumulation would be on top of fresh snow. Eventually, temperatures warm enough by late 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. The winter weather advisory will run until 4 PM Tuesday afternoon for all of NE PA and most of Central NY.

A limited lake enhanced response develops Tuesday night as 850 mb temperatures fall to -10C, with more snow showers and light additional accumulations expected over the northern portion of the area (S. Cayuga, Onondaga, Madison and Oneida counties); the Winter Weather Advisory will be in effect until 7 AM Wednesday for these areas. Some light lake effect snow or flurries could linger into Wednesday morning before completely ending.

KEY MESSAGE 2...

High pressure builds over the area on Wednesday with gradually decreasing cloud cover through the day. After a cool start in the upper 20s to low 30s, temperatures only recover a few degrees warmer in the afternoon. Northwest winds will be breezy in the morning to early afternoon with gusts 20 to 30 mph expected; this could allow for localized blowing/drifting freshly fallen snow in the rural, open exposed areas.

Seasonably cold Wednesday night into Christmas morning with high pressure centered over the Mid-Atlantic to our south. There is a very low chance for a stray snow shower/flurry or even patchy freezing drizzle; but more than likely it remains dry. It warms up to above average levels in the afternoon into the mid-30s to lower 40s.

KEY MESSAGE 3...

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 states. 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 snow or mixed precipitation events through the end of the week and into next weekend.

Of particular note is the colder trend in the model guidance for Friday and Friday night with the surface low track trending further to the south and a high to the north supplying colder air to the region. Considering this trend is now continuing, temperatures on Friday are expected be much colder than previously forecast, with upper 20s to mid 30s for highs. In fact, the 13z NBM continues to show this drastic forecast change. This would also mean snowier scenario for Friday, rather than a wintry mix to rain scenario.The probability for 3 inches or more of snow is increasing across the area in this time period, with the 13z NBM now showing 40-50% chance along and east of I-81, with 15-35% west. This will continue to be closely monitored with our upcoming forecast packages.

AVIATION /00Z TUESDAY THROUGH SATURDAY/

***IFR or worse conditions likely Tuesday morning through Tuesday evening with widespread snow*** Tonight, VFR conditions are expected through much of the night, but restrictions will quickly move in early Tuesday morning. Conditions will begin to deteriorate after 06Z for most sites as a system approaches from the west. Snow overspreads the region early Tuesday morning, with ceilings lowering to MVFR and periods of fuel alt between 06Z and 10Z. Snow will pick up in intensity Tuesday morning around or just after sunrise and IFR or worse conditions are then expected through the morning in snow. Snow will lighten up early Tuesday afternoon and there is potential for a changeover to freezing rain or drizzle during the afternoon across NE PA and into the Southern Tier. SYR will see warmer air push in from the west by early afternoon with a changeover to rain. As warmer air pushes in tomorrow afternoon and evening, all sites will see at least IFR ceilings and visibility. RME should hang onto the snow the longest tomorrow afternoon and with a changeover to rain or fzra or drizzle late in afternoon or evening. However, due to uncertainty with the timing for a changeover, decided to just leave the weather type as snow for now.

Outlook...

Tuesday night...Restrictions will likely linger with fog and drizzle into the overnight hours

Wednesday...Mainly VFR with some lake effect snow showers or clouds in the morning before high pressure pushes in.

Thursday...A low chance of rain and snow showers and associated restrictions.

Friday into Saturday...Wintry precipitation is likely along with associated restrictions at some point this period, but timing is uncertain at this time.

BGM WATCHES/WARNINGS/ADVISORIES

PA...Winter Weather Advisory from 1 AM to 4 PM EST Tuesday for PAZ038>040-043-044-047-048-072. NY...Winter Weather Advisory from 1 AM Tuesday to 7 AM EST Wednesday for NYZ009-017-018-036-037. Winter Weather Advisory from 1 AM to 4 PM EST Tuesday for NYZ023>025-044>046-055>057-062.