textproduct: Binghamton

WHAT HAS CHANGED

Cold front has slowed slightly Friday morning with frontal passage not expected until after 7 AM for much of the region. Lake effect snow accumulation behind the front was increased slightly along and north of I-90 Friday afternoon into Saturday morning.

KEY MESSAGES

- 1) Strong frontal passage Friday morning with high winds and potential QLCS, lake effect snow Friday afternoon into Saturday morning.

- 2) Rising rivers with moving ice likely through Sunday. Ice jam risk increasing, but not definite.

- 3) Zonal flow with clipper systems bringing light precipitation Christmas Week.

DISCUSSION

KEY MESSAGE 1... Strong frontal passage Friday morning with high winds and potential QLCS, lake effect snow Friday afternoon into Saturday morning.

KEY MESSAGE 1 DESCRIPTION... A negatively tilted trough passing through along with a strong low pressure system passing through the Great Lakes region tonight into tomorrow brings widespread rain and strong winds. Forecast soundings show wind speeds at 850 mb approaching 70 mph tonight into tomorrow out of the SW ahead of the front. Right now, there is an inversion below the strong winds so that will reduce how much winds mix down but gusts to 50 mph are likely at higher elevations across NY and PA. Valleys may be a bit more sheltered overnight so winds look to be more in the 30 to 40 mph range.

The cold front moves through between 7am and 10am for NY and PA. Looking at current conditions along the front in Illinois into Wisconsin, there is a well developed QLCS with damaging wind gusts and this QLCS has potential to hold together overnight as it approaches our area. Given the lack of surface instability ahead of the line with the early morning passage and low level inversion in place, spin ups are not anticipated but just behind the line, the strong winds aloft will have a brief window to mix down to the surface with isolated 55+ mph gusts.

Once the front is through, temperatures are expected to fall all day with Fridays high temperature likely occurring early in the morning. Temperatures will be back below freezing by the afternoon with a brief change over from rain to snow right before the precipitation ends but little to no snow accumulation is expected.

Lake effect snow develops several hours after the front moves through once 850 mb fall below -10C in the mod afternoon. Winds aloft will be more westerly to slightly WSW keeping the main band of snow north of Northern Oneida county Friday afternoon. Overnight Friday with the low progressing east, winds shift more northwesterly dropping the band into Oneida county. High pressure is already starting to build in with a subsidence inversion lowering through Friday night so the snow band should weaken as it moves into Oneida with sub advisory snow accumulations. Trends in todays runs have been to a slower decent of the subsidence inversion

KEY MESSAGE 2... Rising rivers will increase the possibility for ice jams and localized flooding through Sunday.

KEY MESSAGE 2 DESCRIPTION... Unseasonably mild temperatures and strong winds will deplete several inches of snow cover, releasing its associated water equivalent today and tonight. This coupled with rainfall between 1-2 inches falling tonight and Friday will produce enough runoff within area streams and rivers to cause a significant increase in flows. Several foot rises in stage will likely be enough force to break up and dislodge river ice that has formed over the past few weeks of cold weather. Ice jam potential at the commonly known areas near river bends and structural impediments, such as bridges, will increase as a result of the ice breaking free. It is impossible to determine exactly where or if an ice jam will form, however, these key factors are coming together to highlight the potential for jams and the associated flood risk. A limiting factor to the overall risk of natural flooding outside of an ice jam is that the river levels are currently running much below normal and soil moisture around the region is on the dry side which will help to limit the effects of significant runoff. Emergency managers and first responders should prepare to monitor river ice activity at historically sensitive areas in their districts tonight through at least Saturday.

KEY MESSAGE 3... Zonal flow with clipper systems bringing several chances of light precipitation Christmas Week.

KEY MESSAGE 3 DESCRIPTION... 250 mb flow becomes mostly zonal through next week with several quick moving shortwaves. With mostly off shore flow in the SE US, there is not much moisture return into the Northeast so any shortwave moving through are not expected to produce much QPF. They will likely just help enhance lake effect snow with their passage with any accumulating snow limited to the eastern Finger Lakes into CNY.

AVIATION /00Z FRIDAY THROUGH TUESDAY/

Ceilings lower to MVFR overnight. Low level wind shear of 40-50 knots is expected to develop and persist through much of the TAF period till around 12-15Z ahead of a frontal passage. Slightly stronger LLWS can not be ruled out. A round of showers may lead to brief IFR restrictions in that same time period as well. Winds with strong 20-30 knots will shift from Southerly to westerly around the same time. Colder air could end things as a few VFR snow showers late Friday.

Outlook...

Friday night... Windy, a few snow showers near KSYR and KRME.

Saturday...Mainly VFR.

Saturday night through Sunday night...Scattered snow showers across Central NY with occasional restrictions possible.

Monday...Mainly VFR.

Tuesday...Low pressure system moves through the area with restrictions possible.

BGM WATCHES/WARNINGS/ADVISORIES

PA...Wind Advisory until 1 AM EST Saturday for PAZ038>040-043-044- 047-048-072. NY...Wind Advisory until 1 AM EST Saturday for NYZ009-015>018- 022>025-036-037-044>046-055>057-062.