447 FXUS61 KBTV 201757 AFDBTV AREA FORECAST DISCUSSION National Weather Service Burlington VT 1257 PM EST Sun Jan 20 2019 .SYNOPSIS... Winter storm conditions will continue across the North Country today with periods of heavy snow and blowing snow, especially this morning where 1 to 2 inch per hour snowfall rates are likely, making for hazardous travel. As low pressure departs to our east tonight, frigid temperatures and very low wind chills are expected to develop and continue through Monday night. Temperatures will moderate back into the teens on Tuesday, and into the low to mid 30s Wednesday when another storm system will bring another round of snow showers with some rain possible in the deeper valleys. && .NEAR TERM /THROUGH MONDAY/... As of 856 AM EST Sunday...Impressive UVV and snowfall rates next 2-4 hrs, as combination of synoptic lift, strong 850mb frontogenesis and strong moisture advection produce widespread 1.5-2"/hr snowfall rates. Seeing an increase in 35-40 dBZ echoes in the Champlain Valley since 13Z (amazing with -1F to -2F at the surface), and vsby is only 1/8SM at BTV. Temperatures remain below zero, so conditions are dangerous (wind chills 10 to 20 below) and travel is generally not advised thru early afternoon when snowfall rates start to taper off. Have increased snowfall amounts 1-2" most sections with this update, with widespread 10-18" storm totals expected, and generally 8-12" in the St. Lawrence Valley. SLRs remain near 10:1. The mix with sleet is also on track for Rutland/Windsor counties, and should mainly occur between now and 18Z. Please see our Local Storm Reports and Public Information Statements for observed snow totals across the region as we receive them. Previous Discussion...Winter storm warnings continue across the North Country today as surface low pressure over the central Appalachians this morning tracks to the tip of Cape Cod by later this afternoon and then off into the Gulf of St. Lawrence tonight. Little overall change was made to the forecast this morning but there are a few challenging parts to talk about. First and foremost is snow ratios and temps. Models continue to struggle mightily with low level cold air advection persisting down the Champlain and St. Lawrence Valleys where temperatures as of 4AM are still in the single digit below zero. Elsewhere across the central Adirondacks and central/southern Vermont where the 925mb flow has shifted southeasterly, temps have risen into the single digits and teens above zero. A handful of reports upstream indicate where southeasterly flow is more prevalent, snow ratios have been ranged from 10-20:1, while here at BTV where temps are much colder we've seen mostly needles falling with very low ratios in the 8-12:1 range. Ratios have increased recently across the Champlain Valley as a mesoscale band associated with an enhanced ribbon of 700mb fgen is lifting through, but expect after it passes we'll be back into lower ratios again until later this morning when better 850mb fgen will pivot through the area. All told, I've lowered our snow totals a couple inches from the previous forecast based on the lower snow ratios, but we're still highlighting a general 10-15" from the Adirondacks westward through Vermont, with lower totals of 7-9" across the St. Lawrence Valley through this afternoon. Snow tapers off later this afternoon and for this evening through Monday the focus shifts towards rapidly falling temperatures and areas of blowing snow as low pressure exits eastward and arctic high pressure begins to build in from the west. Strong pressure gradient between these features will support winds gusting 25-35 mph and when combined with temperatures falling well below zero, dangerously cold wind chills of -25F to -40F are likely. We've hoisting a wind chill warning for tonight through Monday mid-day, with some additional snowfall likely across northern areas as the parent upper level low shifts over the region and some enhanced 700mb moisture rotates in from the north. Could see an additional 2-4", and perhaps 6" at the higher elevations late tonight through Monday. && .SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/... As of 307 AM EST Sunday...Dangerously cold wind chill continue Monday night with values between -20 to -40 below, with coldest values across the northern Dacks into the central and northern Greens. Deep closed mid/upper level circulation and associated sfc low pres will be lifting across eastern Canada while 1039mb high pres builds into our cwa. This continues to support brisk northwest winds thru 06z at 10 to 15 knots with localized gusts. However, expect winds to slowly weaken toward sunrise, as high pres builds into the cwa, especially over northern NY and temps will fall quickly btwn 09z- 12z. Expecting lows btwn -5f and -25f with coldest values over the northern dacks/parts of the SLV. Any lingering snow shower activity will quickly end over the northern Greens by 03z, soundings show limited moisture. By Tuesday, low level waa develops as winds shift to the southwest and sfc high pres moves into eastern New England. Tues will be dry with temps warming back into the teens. The warming trend continues overnight Tuesday Night with strong low level waa on breezy 850mb winds of 30 to 40 knots. Progged 925mb temps warm btwn -4c and -10c by 12z Weds with increasing clouds and snow showers developing by sunrise. NEK will see temps fall quickly in the evening, before all areas warm into the mid teens to mid 20s with likely pops entering the slv by 12z Weds. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... As of 307 AM EST Sunday...The combination of waa lift/moisture will produce a period of mainly snow showers on Weds morning. Initially thermal profiles support all snow with 925mb to 850mb temps <0c thru 18z, before 925mb temps warm above 0c across the slv/western dacks. Thinking as temps warm enough to support a mix, best lift/moisture will be exiting our cwa, with just some lingering light rain/snow showers possible. In addition, gusty 850mb southwest winds of 40 to 50 knots will create some shadowing across the cpv on Weds, which will limit qpf/snowfall. A general 1 to 3 inches likely with localized 4 inch amounts for high peaks and northern Greens. Temps warming mainly 20s east of the greens to mid 30s. Uncertainty develops associated with potential wave along the boundary on Weds Night into Thurs. In addition, plenty of uncertainty with regards to low level thermal profiles and associated ptype. Have kept things simple for now with high chc/low likely pops and rain or snow showers. System sweeps off the east coast overnight Thursday with much cooler air arriving for Friday into the weekend. Some lingering mountain snow showers are possible with temps falling back to below normal values. && .AVIATION /18Z SUNDAY THROUGH FRIDAY/... Through 18Z Monday...IFR/LIFR conditions will continue through much of the period as a winter storm affects the area with widespread moderate to locally heavy snow. The heaviest snow with visibility 1/2sm or less will affect the terminals through about 20z this afternoon, but overall anticipate snow to wane in intensity through the evening hours as the storm pulls away. However, winds have intensified in most spots and gusts to 22kt will be possible the remainder of the period. These winds will keep visibility in the IFR category due to BLSN at most terminals. Ceilings AOB 1500 ft will continue through the period, though KRUT may pop up to 2500 ft after 02z tonight. The heaviest snow with vsby 1/2SM or less will affect terminals in the through about 16Z with some sleet possibly mixing in at KRUT. Snow lightens in intensity beyond 16-18Z as storm starts to pull away but northerly winds gusting >20kts will keep vsby IFR or below at many sites in BLSN through the remainder of the period. Exception on winds will be KRUT where east-southeasterlies will continue. Outlook... Monday Night: VFR. NO SIG WX. Tuesday: VFR. NO SIG WX. Tuesday Night: VFR. Chance SHSN. Wednesday: Mainly VFR, with areas MVFR and IFR possible. Definite SHSN, Likely SHRA. Wednesday Night: MVFR/IFR conditions possible. Likely SHSN, Likely SHRA. Thursday: Chance SHSN, Likely SHRA. Thursday Night: Chance SHSN. Friday: Chance SHSN. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...Winter Storm Warning until 4 PM EST this afternoon for VTZ001>012-016>019. Wind Chill Warning from 6 PM this evening to 1 PM EST Monday for VTZ001>012-016>019. NY...Winter Storm Warning until 4 PM EST this afternoon for NYZ026>031-034-035-087. Wind Chill Warning from 6 PM this evening to 1 PM EST Monday for NYZ026>031-034-035-087. && $$ SYNOPSIS...Lahiff NEAR TERM...Banacos/Lahiff SHORT TERM...Taber LONG TERM...Taber AVIATION...Hastings