661 FXUS61 KBTV 260751 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 351 AM EDT Sun Apr 26 2020 .SYNOPSIS... A storm system will track from the Ohio Valley into southern New England on Sunday into Monday and produce a widespread precipitation event for the region. Initially temperatures will be warm enough for all rain, but as profiles cool especially in the mountains above 1000 feet rain will mix and change to snow on Sunday Night. Snow accumulations of 2 to 6 inches is possible in the mountains by Monday morning with minimal accumulations expected in the valleys. Temperatures will warm into the mid 40s to lower 50s on Sunday, with lows mainly in the 30s Sunday Night, before slowly climbing back into the 40s on Monday. Another storm system will impact the region late Wednesday into Thursday with more rain. && .NEAR TERM /THROUGH MONDAY/... As of 344 AM EDT Sunday...Winter Wx Advisory will take effect 22z Sunday to 15z Monday for 2 to 6 inches of snow above 1000 feet for the eastern Dacks and mountains of central/northern and eastern VT. Slick travel and a few isolated power outages are possible in the higher terrain Sunday night into Monday. Impressive upper low lifting out of the Tennessee River Valley is quite photogenic on satellite. The impressive outflow is indicative of the favorable environment for the maintenance of this upper low as it gradually lifts northeastward. Starting to see heights fall as upper ridge erodes over our area. Not far behind will be some energy lifting northward in advance of the upper low. This will be the first batch of precipitation we see Sunday morning, which is beginning to see radar echoes impinge on St. Lawrence County in New York. This first round should be fairly light, as antecedent dry air will require some saturation before precipitation can reach the ground. Then the warm front begins to tighten up. This will be supported by strengthening, cool easterly flow from the maritimes, a 1030mb high to the north, and positive thickness advection to our south. The combination of the wet-bulb and then the developing thermal gradient should cause highs to be achieved around noon, and then temperatures will begin to gradually fall. The strong warm front lifts into the North Country around 5 PM. A sharp area of FGEN collocated with a deformation axis, a narrow tongue of enhanced SEPV along the feature, and a coupled upper jet structure are all the ingredients one needs for mesobanding precipitation. As the previous forecaster noted, low-level dry air will remain stubbornly entrenched, thanks to northerly flow from the 1030mb high near James bay. However, that dry air will also make it more favorable for dynamical cooling along with wet-bulbing to cool most areas such that a period of wet snow will occur as this intense band lifts over the region on then pivots eastward around midnight. There continues to be signs of dry air entrainment in the DGZ in forecast soundings, which look a bit messier compared to last night. Still, at the time of most intense precipitation, the strongest omegas are within the crosshairs of the DGZ and when that band does lift into the region, most soundings indicate supersaturation with respect to ice. However, once the warm front lifts northward, dry mid-level air should begin to periodically entrain. As the better dynamics push east after midnight, anticipate some areas to flip back to rain at times, except perhaps over the higher terrain. As Sunday night progresses, temperatures will begin to cool aloft while wrap around moisture efficiently streams into our area of a 40- 50 kt low-level jet. This will keep things fairly soggy into Monday, and will allow for more terrain-dependent snow showers. Most favorable conditions will be along eastern slopes from orographic lift in the easterly flow. It appears that snow levels will generally fall to 1000 ft. elevation overnight before lifting back upwards as we warm during the day. Would also expect precipitation to become more scattered during the daytime hours due to the higher solar angle. It will still be a raw day with high temps forecast in the low to mid 40s and 10-15 mph winds out of the north to northeast. Overall, just tweaked QPF and snow downwards, given the somewhat drier forecasts this evening. The forecast still looks good for around 1.00" of precip for eastern slopes of the Adirondacks and southern Greens with generally 0.25"-0.75" across the remainder of the region. Snow amounts below 1000 ft elevation an inch or less, and snow amounts above 2000ft should see around 2"-6". The Peaks of Whiteface, Mt. Marcy, and Killington are all around 8"-12". && .SHORT TERM /MONDAY NIGHT/... As of 333 PM EDT Saturday...Winter wx advisory from 22z Sunday to 15z Monday for 2 to 6 inches of snow above 1000 feet for the eastern Dacks and mountains of central/northern and eastern VT. Slick travel and a few isolated power outages are possible in the higher terrain Sunday night into Monday. Another challenging system with complex thermal profiles is expected to impact our fa late Sunday into Monday. A wet accumulating snowfall is possible for central/eastern and northern VT mountains, as well as the northern Dacks above 1200 feet on Sunday Night with areas of slick travel and a few power outages possible. Elsewhere, a cold rain develops on Sunday aftn/evening with some wet snowflakes mixing in at times overnight. Water vapor shows a potent closed mid/upper lvl circulation over the central MS Valley with developing 1004mb low pres south of St Louis. This system is expected to phase with northern stream energy and become a deep full latitude mid/upper lvl trof on Sunday, while sfc low pres track from the Ohio Valley toward the southern New England Coast. As this occurs, many ingredients are coming together to produce a widespread precip event acrs our cwa. This includes a very strong 850 to 700mb fgen forcing couplet, with pivot anticipated over central/northern VT, given track of closed 850/700mb circulation. In addition, a favorable 250mb jet structure will promote deep synoptic scale lift, while 925mb to 850mb easterly llvl jet of 45 to 55 knots will help enhance moisture advection and associated forcing. The dynamics are very strong with this system, however pws are in the 0.50 to 0.75 range, so thinking storm total qpf will range in the 0.50 to 1.25 with isolated amounts 1.50 to 1.75 within the mesoscale band. Thermal profiles are complex with guidance having significant differences on handling the evaporational cooling process. NAM is 2 to 4C cooler than the GFS, especially sfc to 925mb, with both showing a deep isothermal layer near 0C from 2000 to 8000 feet or so. Initially on Sunday 2m temps warm well into the upper 40s to l/m 50s areawide, however 2m dew point temps will hold in the -2c to -6c range. As precip arrives temps will fall 10 to 15 degrees within a few hours and hover in the mid/upper 30s to near 40f, except near freezing within the heaviest precip rates associated with mesoscale banding. Sounding data shows elevated DGZ near 15kft, but does indicate favorable intersection with moisture and omega couplet, helping to produce enhanced snowfall rates within the band above 1500 feet on Sunday Night. Thinking as the better dynamics arrive the column cools just enough to support a 2 to 4 hour window of intense snowfall rates acrs the eastern dacks of northern NY, as well as the mountains of central/northern and eastern VT, mainly above 1000 feet. Accumulations of 2 to 6 inches looks possible with snowfall rates of 1 to 2 inches per hour on Sunday Night. Areas of slick travel and a few isolated power outages are possible. Snowfall accumulations will be highly elevational depend with minimal accumulations expected in the valleys and up to 10 inches above 4000 feet. Have issued winter wx advisory to highlight potential for 2 to 6 inches above 1000 feet from 22z Sunday to 15z Monday. Monday...looks like a cold and damp day with areal coverage of precip becoming trrn focused with mid/upper lvl trof directly overhead. Expect snow levels to quickly increase during the morning hours with any accumulations near summit level by midday. Temps will be 10 to 15 degrees below normal for late April with highs only in the upper 30s to mid/upper 40s. Monday night will feature partly cloudy skies with cool temps again, ranging from the upper 20s to mid 30s areawide. && .LONG TERM /TUESDAY THROUGH SATURDAY/... As of 333 PM EDT Saturday...No significant changes made from previous forecast...Lingering upper level trough remains overhead Tuesday morning coupled with an inverted surface trough. This will continue to keep clouds and scattered showers around throughout much of the day Tuesday. Despite shortwave ridge building in Tuesday afternoon, below normal temperatures are expected in the low to mid 40s as low level moisture is tough to scour out. This period of drying will be relatively short-lived as another full latitude, negatively-tilted trough approaches the North Country late Wednesday into Thursday. General consensus among global models is fairly good as far as develop and location of this feature, however there are some small timing differences on arrival of precipitation. This system will once again bring widespread precipitation to the North Country, however as surface low tracks more west of the area precipitation type will be mainly rain. Additionally, gusty southeast downslope winds will exist along the western slopes of the Green and Adirondack Mountains Thursday as 40 kt 925mb jet moves overhead. As always, questions on low level stability will factor in to the ability for these gusts to mix down. We'll refine these details at we get closer. Once again, the cut off upper level low will slowly dumbbell overhead through Saturday with continued chances for cloudiness and precipitation. Generally, below normal temperatures are expected through the extended period. && .AVIATION /08Z SUNDAY THROUGH THURSDAY/... Through 06Z Monday...Expect VFR conditions through about 15z as mid and high level clouds move up into the region. Conditions will then change as precipitation gradually increases in areal coverage, especially after 18z. Expect ceilings and visibilities to lower into the MVFR and IFR categories during this time period. Winds light and variable, though with an easterly preference through 12Z, then becoming northeasterly to northerly with time at speeds in the 8 to 15 knot range with. Expect a snow and rain mix across MPV around 22Z Sunday and at SLK around 02Z Monday. Visibilities improve after 02Z, but ceilings likely remain MVFR to IFR as precipitation becomes more intermittent. Will have to reassess if there increasing gusts after 02Z when precipitation becomes more intermittent. This will be relevant for potential low-level wind shear across RUT and MPV at 45 kt easterly jet sets up around 2000ft agl starting around 22Z-02Z. Outlook... Monday: Mainly MVFR, with areas VFR possible. Likely RA, Likely SHRA. Monday Night: Mainly VFR, with areas MVFR possible. Likely SHRA, Chance SHSN. Tuesday: Mainly VFR, with local MVFR possible. Slight chance SHRA. Tuesday Night: VFR. NO SIG WX. Wednesday: VFR. Slight chance SHRA. Wednesday Night: Mainly VFR, with local MVFR possible. Chance SHRA. Thursday: Mainly MVFR, with areas VFR possible. Likely SHRA. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...Winter Weather Advisory from 6 PM this evening to 11 AM EDT Monday for VTZ003-004-006>008-010-012-018-019. NY...Winter Weather Advisory from 6 PM this evening to 11 AM EDT Monday for NYZ031-034. && $$ SYNOPSIS...Haynes NEAR TERM...Haynes SHORT TERM...Taber LONG TERM...LaRocca AVIATION...Evenson/Haynes