textproduct: Binghamton

WHAT HAS CHANGED

Increased PoPs, QPF and snow amounts down wind of the Finger Lakes into the Twin Tiers as multi-bands of lake effect snow have developed this evening. Snow amounts will still be light, but could see localized narrow bands of up to 1 or 1.5 inches by around midnight, and as it shifts north slowly overnight another dusting to 1 inch for portions of Central NY.

KEY MESSAGES

1) Light lake effect snow across the Finger Lakes expected this evening and tonight.

2) Cold clipper system with light accumulating snow moves through the Northeast late Tuesday night through the day Wednesday.

3) Another potential winter system is possible late Thursday into Friday, but may move by to the south.

4) Widely varying temperatures this weekend with warm conditions Saturday, followed by a cold blast Sunday.

DISCUSSION

KEY MESSAGE 1...

Cold Canadian air on the back side of the departing, deep coastal low will be drawn south and sewd across the eastern Great Lakes starting this evening and tonight. With 850mb temperatures around -15 to -16 deg C moving across unfrozen Great Lake waters around 0-4 deg C, a brief period lake effect snow showers will develop. The potential for significant snow accumulations will be very low given the relatively shallow depth of the boundary layer and the minimal amount of residence time of any band that does organize over a particular area. The flow pattern will be mostly northwesterly around 295-315 deg this evening, but then back to around 275-285 later tonight...pushing any LES bands to the north toward sunrise.

At this time we are looking at around 2 inches or less into the central and southern Finger Lakes where slight upslope enhancement may help with accumulation. Would not be surprised to see amounts near 3 inches in and around northern Tioga County, especially if there ends up being some Finger Lake enhancement.

There may also be a wind/blowing snow component with this event tonight, with wind gusts 20-25 mph causing some reduced visibilities and also helping to keep secondary roads snow- covered and potentially hazardous.

KEY MESSAGE 2...

The next system is expected to move through late Tuesday and through the day Wednesday in the form of a fast-moving clipper system across the Northeast US.

The challenge with this system will be related to the potential for a mix of rain with the snow during the day Wednesday. A notable push of slightly warmer air is expected to be seen ahead of the short wave, with 850mb temperatures around -7 deg C. These conditions will likely keep the precip all snow Tue night and Wed morning with surface temperatures in the mid to upper 20s. This period is when the majority of the accumulating snow is expected to fall. Ensemble guidance is indicating around a 50-60 pct chance of at least 2 inches of snow...and the higher probabilities really drop off above 4 inches.

The challenge arrives later in the day Wednesday when surface temperatures look to rise into the upper 30s and lower 40s on the back side of trough axis...at least for a brief period of time. These temperatures will cause the lingering light snow to mix with and change to rain...before tapering off Wed evening. There could be weak lake influence Wed night, but with limited snow accumulations at least at this time.

KEY MESSAGE 3...

We are also tracking another short wave rounding the bottom of the long wave trough late Thu into Fri. However, at this time it appears the short wave will dive far enough south to keep most of the significant precipitation (likely in the form of snow) just to our south. Current forecast produces an additional 1-2 inches of snow across our area, but this could very well be too high. Ensemble guidance is in fairly good agreement with the southern track of this wave, but we will continue to monitor the trends through the next 24 to 48 hours as any significant shift northward would be seen soon.

KEY MESSAGE 4...

Behind the departing long wave trough, heights are expected to rise aloft and bring with it a noticeably warmer air mass for a very brief period of time on Saturday. Ensemble guidance is indicating a 60-70% chance of temperatures above 45 deg F on Saturday afternoon. This would be in combination with a fair amount of sun to make it feel even warmer.

Do not get too used to this because on Sunday the cold air is expected to return as another clipper system moves eastward across the northern Great Lakes and into southern Quebec. This system should be mostly a glancing blow for precipitation, but it may open the door to a bout of cold air with high temperatures on Sunday only into the 20s and overnight lows Sun night down into the single digits and teens above zero. Additional rounds of lake effect snow are possible during this time and into early next week as well.

AVIATION /00Z TUESDAY THROUGH SATURDAY/

SYR and RME are currently VFR but will fall to MVFR later this evening as lake clouds move in from the west. Lake effect snow showers are also expected to impact SYR, bring MVFR vsbys by 03-05z this evening, and perhaps some tempo IFR vsbys from about 05-09z tonight/early Tuesday AM. The MVFR snow showers taper to flurries and end by mid to late morning, with MVFR CIGs scattering and lifting to VFR by late afternoon at both SYR and RME.

Lake effect snow bands off of Lake Ontario and the Finger Lakes will impact ITH and BGM this evening and into the overnight. The snow shower activity is forecast to continue into the early or mid morning hours Tuesday, with prevailing MVFR vsbys; and tempo IFR vsbys this evening (mainly 00-04z). The snow showers taper to flurries and end by 13-15z Tuesday morning. MVFR CIGs linger until 18-19z, then scatter out for VFR conditions into Tuesday afternoon and early evening. ELM will see snow showers for the next few hours, with mainly MVFR restrictions. The snow showers then move north and east, likely exiting this terminal by 02-03z this evening. MVFR CIGs persist here until around 17z Tuesday, with it then scattering out and becoming VFR.

AVP is VFR now, but is forecast to see MVFR CIGs settle over the terminal from around 02z this evening until midday Tuesday. The clouds then lift and scatter for VFR conditons Tuesday afternoon and evening here.

Expect northwest winds 8-15 kts with gusts 20-30 kts, gradually diminishing overnight. West northwest winds 10-20 kts continue Tuesday morning, before decreasing further in the late afternoon and evening back under 10 kts.

Outlook...

Tuesday night through Wednesday: Restrictions likely with a period of widepsread light to moderate snow overnight, becoming mixed snow and rain showers Wednesday. Confidence moderate to high.

Late Wednesday Night - Thursday morning...Mainly VFR. Confidence moderate

Thursday afternoon and night...Restrictions possible with another round of snow and/or rain-snow mix. Confidence low at this time.

Friday and Saturday...Mainly VFR. Confidence moderate to high.

BGM WATCHES/WARNINGS/ADVISORIES

PA...None. NY...None.