textproduct: Binghamton

WHAT HAS CHANGED

Winter storm warnings have been issued for central and southern regions of the Catskills, the rest of the area has been upgraded to Winter Weather advisories. Snow amounts have been increased slightly for CNY with a reduction of snow amounts in the western Southern Tier and western NEPA with increased confidence that some sleet will mix in.

KEY MESSAGES

1) Strong clipper system bringing widespread snow and some mixed precipitation to the region Friday mid day into Saturday morning.

2) Great Lakes low brings threat of some isolated pockets of freezing rain Sunday night prior to changing to rain Monday with gusty winds.

3) Cold weather returns late Monday through the rest of the week with persistent lake effect snow.

DISCUSSION

KEY MESSAGE 1...

A fairly potent clipper system moves through the northeast tomorrow into tomorrow night. Strong warm air advection will lead to good isentropic lift with a narrow corridor of heavier snow. There is still a good amount of uncertainty where this heavier band of snow will set up. This mornings model runs with the HRRR especially look to be way to bullish on snowfall across NEPA into the Southern Tier. Forecast soundings and vertical cross sections across the warm front show a 700 mb warm layer. The HRRR has a lack of vertical layers so likely the 700 mb warm layer is underdone while in the NAM, the warm nose is likely being overdone. The heavier precipitation in the FGEN band may be able to keep the layer below freezing on the northern fringe of the warm nose. Another issue with the models in regards to its snowfall amounts is how high the DGZ is. Cross sections show that the lift through the DGZ is maximized a little farther north than where the highest QPF is so would not be surprised if the snow band ends up being about 20 to 30 miles north of the northern extent of the sleet rather than just north of the mix line. Warning criteria snow will be possible under this band and with how narrow it is, guessing where it will be to issue warnings will be tough so warnings across CNY, and perhaps more of NEPA if the band ends up being well south, may be issued with short notice.

Snow for the Southern Tier and north was increased, with the coupled right entrance region and the lift exit region of two jet maxes with lift being fairly broad. For the Western Southern Tier and western NEPA, warm air looks to win out with sleet mixing in so the time of all snow may only be a few hours before changing over to sleet. Freezing rain threat continues to dwindle as the depth of cold air below the warm layer is deep and anything that melts will refreeze. How far north this mixed layer will get is critical for where the heaviest snow falls. Current snow map does not have as sharp of a gradient as there will likely be and as we get closer to the event, we will be able to refine where that mixing line may get to. Right now, highest confidence in where heaviest snow will be is in the Catskills where there is better moisture in place and with the help of terrain, snow amounts look to be near and above warning criteria.

KEY MESSAGE 2...

A strong low moves into the Great Lakes region Sunday night into Monday with warm air advection through NY and PA. 850 mb temperatures rise above freezing well prior to precipitation onset late Sunday into Sunday night. Given the timing, temperatures during the day Sunday should rise above freezing for most of the area but deeper, sheltered valleys in the Catskills up into the Tug Hill may hold on to below freezing temperatures. Pockets of freezing rain was kept in the grids for SE facing valleys in the Catskills as those valleys will be sheltered the best and maintain freezing temperatures longer with the SW flow aloft. By Monday morning, with 850 mb temps approaching 10C, it will be tough to maintain any below freezing surface temperatures so rain will be the dominant precip type. Winds will once again be gusty with the strong warm air advection but as typical this time of the year, a stable layer below the winds will prevent stronger winds from mixing down.

A strong cold front moves through Monday afternoon/night bringing a quick drop in temperature and a brief transition from rain to snow before colder, drier air brings an end of the precipitation outside of the lake effect areas. 850 mb winds on the back side of the low get up over 50 knots so there is a chance that wind advisories may be needed with steep low level lapse rates and efficient downward momentum transfer.

KEY MESSAGE 3...

Monday night into next week looks favorable for persistent lake effect snow. A stacked low forms south of the Hudson Bay which is climatology a favorable location for long lived lake effect events. 850 mb winds are mostly westerly and mean winds in ensembles hint at a multi-lake connection, while mean temperatures remain at or below -10C. It is too far out to really figure out band organization or orientation but something to watch over the next few days.

AVIATION /19Z THURSDAY THROUGH TUESDAY/

Lake related moisture and cold upslope northwest flow behind a front will continue to lead to MVFR ceilings for our NY terminals this afternoon. KAVP will see ceilings lower this afternoon but remain VFR behind front.

The low-level flow weakens this evening as MVFR ceilings in NY and VFR BKN clouds at KAVP will fade away to higher clouds and all terminals will be VFR into the overnight.

Cloud cover will thicken and lower as the next winter storm moves into the region. Ceilings and Visibilities will remain VFR except at KELM where light snow begins around 16z so have MVFR in light snow. Rest of terminals VFR to 18z. The snow and significant IFR restrictions don't arrive until Friday afternoon.

Winds will be 10 to 15 knots with gusts well into the 20s this afternoon from the northwest, then weaken this evening and shift to the southeast under 10 mph for Friday morning.

Outlook...

Friday afternoon into Saturday morning...Snow with associated restrictions. Sleet may mix in at times for KELM-KAVP Friday night-early Saturday.

Saturday afternoon through Sunday early morning...Mostly dry, but patchy flurries or even spotty freezing drizzle possible with lingering ceiling restrictions.

Sunday midday through Sunday night...Rain and restrictions likely.

Monday through Tuesday...Cold frontal passage and gusty winds as rain showers change back to lake effect snow showers, especially NY terminals as lake effect becomes dominant. Restrictions possible especially in NY terminals.

BGM WATCHES/WARNINGS/ADVISORIES

PA...Winter Weather Advisory from 1 PM Friday to 10 AM EST Saturday for PAZ039. Winter Weather Advisory from 1 PM Friday to 7 AM EST Saturday for PAZ038-043-044-047. Winter Storm Warning from 1 PM Friday to noon EST Saturday for PAZ040-048-072. NY...Winter Weather Advisory from 1 PM Friday to 10 AM EST Saturday for NYZ009-015>018-023-025-036-037-044>046-055-056. Winter Weather Advisory from 1 PM Friday to 7 AM EST Saturday for NYZ022-024. Winter Storm Warning from 1 PM Friday to noon EST Saturday for NYZ057-062.