000 FXUS61 KBGM 041738 AFDBGM AREA FORECAST DISCUSSION National Weather Service Binghamton NY 1238 PM EST Mon Mar 4 2019 .SYNOPSIS... Cold air behind a departing storm will generate lake effect snow showers today and tonight. Arctic air will move into NY and PA on Tuesday and potentially cause snow squalls to form across the region. && .NEAR TERM /THROUGH TUESDAY/... 1055 AM UPDATE...Westerly flow developing which will end the Finger Lake enhanced lake effect over central NY into the northern tier of PA. Have updated the grids to reflect the trend and adjust the temps. No major changes at this update. 620 AM update... Scattered snow showers will continue this morning in cold northwest flow behind a departing Atlantic cyclone. As snow showers taper off across much of the region by late morning, lake effect snow showers will form downwind of Lake Ontario today and tonight. Light snow accumulations are forecast. Temperatures will reach the 20s today and fall into the single digits tonight. An Arctic front will blast through the region on Tuesday. Model soundings depict a high degree of instability in place across NY and portions of PA. Squalls are likely to form along the front on Tuesday with brief, heavy snow, low visibilities, and gusty winds. Stay up to date with our latest forecasts on this potential snow squall event by visiting our website at: weather.gov/bgm && .SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/... 345 AM Update... The midweek period will feature very cold Arctic air, and fluctuating lake effect snow for counties along the New York Thruway, with at least scattered snow showers and flurries generally within the Twin Tiers and especially northward. 850mb temperatures dive to about minus-20 Celsius for Tuesday night through Wednesday evening, before starting to moderate slightly into Thursday. Thus the dendritic growth layer will reside in the lowest 5 kft agl, with just about any cloud cover producing airy dry snowflakes. Also, in addition to the instability already offered by the very cold air mass aloft with 1000-500mb thicknesses falling to about only 500 decameters, the ever-increasing sun angle of March will also produce diurnal instability Wednesday and Thursday afternoons, to eke out additional snow showers and flurries. The airmass will indeed be very dry, limiting coverage and accumulations of snow in a general sense. However, the primary lake feed off of Lake Ontario will be capable of yielding several inches of snow across portions of Onondaga-Madison-Oneida counties. One trend in the models, though, is that there will be several embedded shortwaves within the main upper trough that pivots through and then gradually lifts out during the period. So while confidence in lake effect-supporting environment remains high, the positioning of the lake band or bands will fluctuate considerably. Confidence getting greater than 7 inches in any 12 hour period is not high enough for any of our counties yet for a Watch or a Warning, but that cannot be ruled out. As it stands now, Winter Weather Advisories easily appear likely be needed for at least Onondaga-Madison counties, if not some of Oneida as well at some point. In particular, late Tuesday night to midday Wednesday may include a Huron-to-Ontario connection which would produce higher snowfall rates. Unsure at this time how far south this banding gets; some portions of Seneca-Cayuga could get involved at times as well. Look for these details to be better ascertained over the course of the next day or so. When adding up all of Tuesday night through Thursday, 5 to 10 inches total will probably be realized in some of the above-mentioned counties, and if the primary Lake Ontario band manages to persist over a localized area, there could be more. Lows Tuesday night and Wednesday night will be mainly single digits above zero, yet with wind chills often below zero. Highs Wednesday will be roughly 20 degrees below climatology by only reaching mid teens to near 20. Temperatures Thursday will bump just slightly higher by about 4-6 degrees. && .LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/... 345 AM update... Small adjustments made based on model trends. The Canadian GEM model has joined the ECMWF at keeping Friday dry under high pressure, whereas the GFS still skims the area with the north side of a low pressure system. At this point we are maintaining only slight to low chances of light snow, with the somewhat higher chances mainly to the south. Confidence has increased that late Friday night through Saturday evening will be dry, with temperatures starting to moderate as discussed below. Previous discussion... Lake-effect snow showers linger Thursday night, then weak ridging may help to bring a brief dry period to most of the area into Friday morning. There continues to be quite a bit of uncertainty the rest of Friday due to model differences. The GFS continues to drag a surface low through the Ohio River Valley and towards the Mid Atlantic Friday afternoon, while the ECMWF, keeps high pressure in control the rest of Friday. Given the uncertainty, slight chances for snow showers will continue through the area the rest of the day Friday. Another low pressure system starts to move towards the Lower Great Lakes into Sunday morning, which will bring in better chances for snow from SW to NE across our area. This changes over to a rain/snow mix across most of our western zones into the afternoon hours. As for temperatures, expect a warming trend Friday into the weekend. Friday morning starts off in the teens and single digits, then we'll see highs in the 20s and low 30s. Temperatures Saturday and Sunday should fall into the teens and 20s, but should peak generally in the 30s and even near 40F Sunday. && .AVIATION /18Z MONDAY THROUGH SATURDAY/... Developing westerly flow is lifting the lake effect snow showers north into SYR and eventually to RME. This will bring some MVFR restrictions to those sites, while VFR returns to ITH and BGM. Lake effect will then lift further north bringing all stations to VFR overnight and continuing through the end of the TAF period. Outlook... Wednesday and Thursday...Occasional restrictions possible for primarily the NY terminals from lake effect snow. Mostly VFR at AVP. Friday and Saturday...VFR. && .BGM WATCHES/WARNINGS/ADVISORIES... PA...None. NY...None. && $$ SYNOPSIS...DGM/DJP NEAR TERM...DGM/DJP SHORT TERM...MDP LONG TERM...HLC/MDP AVIATION...DGM