915 FXUS61 KBTV 120519 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 1219 AM EST Wed Feb 12 2020 .SYNOPSIS... Light snow showers can be expected tonight as an upper-level disturbance moves through, but impacts will be minimal. High pressure will build in Wednesday, leading to a brief window of dry weather. Snow returns Wednesday night through Thursday as a low pressure system tracks northeastward through the eastern US. A general 3-6 inches can be expected by late Thursday. Friday and Saturday will be drier but much colder as arctic high pressure builds in from the northwest. && .NEAR TERM /THROUGH THURSDAY/... As of 947 PM EST Tuesday...No significant changes were needed with this update. Snow associated with the upper shortwave is pushing into our New York zones this evening, and it will continue to spread eastward overnight, focusing on the higher terrain. An inch or two of accumulation is possible in the northern mountains, locally more, with little to no accumulation elsewhere. Temperatures have been slow to fall given the abundant cloud cover, but they should drop later tonight as cold air moves in behind the shortwave. The forecast has this all covered, so no changes were needed with this update. Previous discussion...Light snow showers will reblossom this evening into early overnight tonight as an upper-level wave moves through. The passage of the upper wave will be accompanied by cold-air advection in the mid- and upper-levels, which will steepen low- level lapse rates overnight. Moisture will be limited, with forecast soundings progging dry atmosphere from 700 mb upward. The limited moisture in the mid-levels will be enough, however, to squeeze out an inch or two of snow in higher elevations of the northern Greens/northern Adirondacks...and just a dusting elsewhere. Wednesday will be dry throughout the forecast area as Mid-Atlantic high pressure provides a brief respite from this week's persistent snow showers. Temperatures will top out in the mid 30s, and we should see some breaks in clouds in the afternoon with the sun making a brief appearance midday. As high pressure shifts eastward later in the day, return southerly flow will develop over the area, resulting in some breezy southerly winds developing by the late afternoon. High clouds will spread over the area from the southwest starting Wednesday afternoon, thickening and lowering through the evening. Attention then turns to our southwest, where a low pressure system moving northeastward through the Appalachian Region will send a warm front through the BTV forecast area. Isentropic ascent will increase over the area Wednesday night, in tandem with increasing moisture advection. This will allow snow to spread over the area from southwest to northeast through the night. General timing of the onset of snow looks to be between 11 PM Wednesday night and 3 AM Thursday morning. Should see a pretty good thump of snow on the front end of the system, especially over southern Vermont, with enhanced mid-level frontogenesis progged on the leading edge of the warm front within a fully saturated DGZ. && .SHORT TERM /THURSDAY NIGHT/... As of 310 PM EST Tuesday...We will continue to be impacted by a 1000mb low pressure system moving across Central New York Thursday. Light snow will continue in the region, impacting the morning commute. Towards Rutland and Windsor Counties, eyes are still on how far north a warm nose will make it into the region. Max temperatures aloft range from 0 to 3 C, and occur at varying heights. Think there could be areas of wet snow or a mix of sleet and freezing rain in this transition zone. At least based on a thickness values output by the latest 12Z GFS, the p-type transition zone looks to reach Rutland and Windsor and perhaps Addison and Orange. Towards noon, warm air advection should cease and any mix should quickly jump back to snow. As for how much snow is left to fall, there are a few mixed signals. There's a second band of 700mb FGEN that is weaker than the first, but should be sufficient to maintain an organized band of snow over the North Country. Additionally, we will positioned at the nose of a 40-50 kt 850 jet with q-vectors indicating good low-level convergence. The main problem will be dry air entraining in the DGZ along with pockets of subsidence. This will hamper SLR values, with the Cobb technique dipping below 10:1 at times. This will be especially true over south-central Vermont and parts of eastern Vermont. In this dry slot, precipitation should transition towards drizzle. Surface temperatures will play a big role in whether this will be freezing drizzle or not as temperatures in the area will be around 32-35 F. Between this and lingering snow showers mentioned below, additional 2"-4" should be added to the north and an 1" or less south. A few locally higher amounts will be possible over northwestern slopes of the Dacks and Greens. As cold air advection sets in, there is a lingering trough behind the main feature that could produce additional snow showers as flow turns northwesterly in blocked flow. These snow showers should not linger long due to strong surface high pressure moving into the area, and will taper towards the summits over the course of Thursday night. This surface high will usher in Arctic air with brisk winds, leading to wind chills potentially as low as -20 with most regions in the single digits above and below zero. && .LONG TERM /FRIDAY THROUGH TUESDAY/... As of 310 PM EST Tuesday...Drying conditions for Friday, but it will be a solid 20 degrees below normal for daytime highs. Aside from south-central Vermont, most places will just creep into the single digits. Conditions remain somewhat breezy up until mid-afternoon when surface high will set directly overhead. Bundle up! Temperatures are expected to fall to the double digits below zero for most areas. Winds will be light and variable at that stage though. If we are lucky, maybe we will get a good before and after photo from polar satellites on the change in ice coverage over Lake Champlain for the day. Temperatures rapidly moderate over the weekend as upper ridging crests overhead Saturday and flow becomes southwesterly. A clipper system looks poised to reach the area on Sunday and bring a reinforcing shot of colder air to start the work week. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... Through 06Z Thursday...Mix of VFR/MVFR through 12Z with trough passage and scattered snow showers in higher terrain. Winds WNW to WSW in the 240-290 range generally from 6 to 10 kts. Brief IFR possible in these showers at KSLK during this period. After 12Z trending VFR at all terminals as winds slowly back to south/southwesterly and remain in the 6 to 10 kt range. Outlook... Thursday: Mainly MVFR, with areas IFR possible. Definite SN, Slight chance FZRA. Thursday Night: Mainly VFR, with local MVFR possible. Chance SHSN. Friday: VFR. NO SIG WX. Friday Night: VFR. NO SIG WX. Saturday: VFR. NO SIG WX. Saturday Night: VFR. Slight chance SHSN. Sunday: Mainly MVFR, with areas VFR possible. Chance SHSN. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Duell NEAR TERM...Duell/Hastings SHORT TERM...Haynes LONG TERM...Haynes AVIATION...JMG