299 FXUS61 KBGM 261958 AFDBGM AREA FORECAST DISCUSSION National Weather Service Binghamton NY 258 PM EST Sat Jan 26 2019 .SYNOPSIS... After a seasonably cold night tonight, a cold front and associated snow showers and flurries will sweep through the area Sunday. This cold front will usher in colder air for Monday. Another storm system will affect the region for Monday Night through Tuesday night with the potential for more snow. A bitter cold air mass is looming for the end of next week behind this next system. && .NEAR TERM /THROUGH SUNDAY/... Water vapor channels on the GOES-16 show one short wave moving off to the northeast of NY/PA and a much more significant upper level wave dropping southeast from the northern Plains. The left exit region of the upper level jet from this approaching wave will support the formation of a surface wave over the upper Ohio Valley and lower Lakes by Sunday morning. The low-level winds turn southwesterly and increase into NY and PA starting later this afternoon and continue into tonight. This will lead to increasing warm advection and moisture advection across central NY and northeast PA tonight. Given the very dry low-levels it will take a while to saturate the lower levels enough for snow showers to develop. So we have POPS increasing late tonight into Sunday morning. We expect just light snow showers and flurries Sunday morning most of central NY and northeast PA. The only exception is northern Oneida County where upsloping on southwest flow will increase lifting and lead to a little heavier snow. As this upper level wave and associated surface low moves northeast Sunday afternoon, a cold front will sweep across central NY/northeast PA from late morning in the Finger Lakes of NY to mid/late afternoon in our eastern zones from the Upper Mohawk Valley to Catskills/Poconos. High resolution CAMs are indicating a snow squall will form in advance of this cold front. Model soundings show around 50 J/Kg of CAPE well up into the maximum ice crystal growth regime in advance of the surface front. Cold air advection was slightly outpacing the front up through 850 mb which is typical in these patterns where there are very steep low-level lapse rates. There was also a rise-fall surface pressure couplet with the front and the isallabaric wind is nearly perpendicular to said rise/fall couplet. This is all suggestive of a decent snow squall. Surface temperatures will climb to the upper 20s to mid 30s by afternoon. Timing of the squall is a little early to pin down exactly but early thoughts are Finger Lakes region late morning, I-81 corridor around noon or early afternoon, and upper Mohawk valley to Catskills by early or mid afternoon. Timing could vary a couple hours this far out. The other question mark is how much moisture will this front have to work with. The Great Lakes as an aggregate will add moisture to this front and the Hi res CAM models suggest enough moisture for the squall in NY state. But as the front gets farther from the Lakes the snow squall breaks up. So places farther south like northeast PA will have less chance for a linear squall and instead will see more scattered snow showers/flurries. So have Likely POPs in NY zones for this snow squall and chance in northeast PA. Total snow accumulations for tonight and Sunday will likely range up to 1 inch in most areas with locally 2 inches in the hills of central NY. Northern Oneida County will see around 3 inches of snow. Will mention snow squall potential in HWO and provide a one- slide briefing graphic to partners. && .SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/... High pressure passing by to our north will provide a brief break in the pattern Monday before a fairly stout clipper system approaches our area from the southwest Monday night. This clipper system is expected to pass to our northwest but bring a warm frontal boundary through the region. Some moisture will advect into the region with ample forcing that is expected to result in a period of light snow Monday night into Tuesday. Highs should get into the 20's to around 30's Monday after a cold start in the single digits. Temperatures should only fall slightly Monday night due to the warm frontal passage. This clipper also looks somewhat slower with timing compared to the past few model cycles likely resulting in more sunshine on Monday and slightly warmer high temperatures than previously forecasted. QPF and snowfall look rather light with an inch or less of snow by Tuesday morning. The one exception is in Oneida county, where some model signaling is present for the snow to be a bit more persistent allowing for slightly higher totals. && .LONG TERM /TUESDAY THROUGH SATURDAY/... Tuesday through Wednesday: An arctic cold front associated with the clipper will then move through the region during the day Tuesday. In the warmer sector, we will likely see a break in the steadier precipitation allowing for temperatures rebounding into the 30's and staying a bit over blended and ensemble guidance values. However, modeling has trended a little less aggressive with the warm air advection with fewer GEFS members are keying in a change to rain during the afternoon. The arctic front is expected to move through the area Tuesday night with modeling and the vast majority of ensemble members keying in a wave of low pressure forming along the front with a period of light to moderate snow which will develop over the region and intensify as it moves east. The ECMWF suite continues to be most aggressive with QPF and our national center trended in this direction as well. However, given the vast majority of model guidance is still lower with QPF we kept the amount of precipitation a few tenths short of the ECMWF at this time. Also, this forecast lowered ratios from blended guidance as well given warmer surface temperatures Tuesday afternoon and into the evening. With all that being said, several inches of snow is definitely possible from this system with the highest amounts north and east of Binghamton where the low will be a bit stronger. Much colder arctic air whips in behind the front with temperatures Tuesday night and Wednesday falling into the single digits with high model agreement that this is the start of a very cold period. Winds look rather gusty as well for now edged them closer to what Bufkit soundings would indicate with some top westerly gusts around 20-25 mph and wind chills falling well below zero. Wednesday night through Saturday: An upper-level low drops through the region as the associated surface low tracks up the coast Wednesday evening, ushering in very cold arctic air with 850mb temperatures falling to as low as -20 to -30C by Thursday morning. Morning lows Thursday fall to around 0 to -10F and struggle to climb out of the single digits above zero Thursday afternoon. Otherwise, lingering snow showers continue Wednesday night and Thursday. This will be most likely across the lake effect areas. Another wave possibly swinging through Friday will allow snow showers, with some lake enhancement, to continue throughout the day. This could also help to bring in slightly warmer temperatures for Friday, so while Friday morning lows in the single digits above and below zero are expected, afternoon highs may reach into the teens. High pressure starts to build in by Saturday, and while a few lake-effect flurries/snow showers will not be completely ruled out, most of the area should turn dry with more sunshine especially across NE PA. Warmer air continues to move in Saturday, with morning lows in the single digits to just below zero and highs in the teens to mid 20s. && .AVIATION /20Z SATURDAY THROUGH THURSDAY/... VFR this afternoon and into the overnight with mainly mid to high level clouds. There was a diurnal cumulus/stratocumulus layer forming at KSYR and KAVP. This should mainly VFR but KSYR might have a small window of MVFR ceiling between 18z and 20z. Then after 10z, guidance suggests LLWS as a southerly low-level flow sets up with warm air advection and the associated inversion. Confidence in this extent and severity of the LLWS is low at this point except for KRME where southerly flow tends to back southeast with flow up the Mohawk Valley. Hence have LLWS in TAF for KRME 13z to 16z. This amount of LLWS in the other terminals may expand with the next TAF update. Some light snow showers and flurries will spread over all the NY terminals between 12z and 14z with mainly MVFR conditions. There also is the potential for a snow squall late in the TAF period which could lead to VLIFR conditions for a 15-30 minute period but this likely won't occur until 17z-18z and even well beyond. Confidence in timing is low and confidence in the extent and severity of this potential snow squall is also low so left out of this TAF forecast. NY terminals will have mainly MVFR in light snows for the end of the TAF period. KAVP will remain VFR for the whole TAF period. West/SW winds 5-10 kts for most of the afternoon will become light under 5 knots tonight and then SW 10-15 knots gusts to 20-25 knots later Sunday morning. Outlook... Sunday afternoon...chance for LIFR in a brief snow squall with mainly VFR or MVFR ceilings and lighter snow showers. Sunday night-Thursday...Chance of snow or snow showers and associated restrictions. && .BGM WATCHES/WARNINGS/ADVISORIES... PA...None. NY...None. && $$ SYNOPSIS...DJN NEAR TERM...DJN SHORT TERM...MWG LONG TERM...HLC/MWG AVIATION...DJN