502 FXUS61 KBTV 302336 AFDBTV AREA FORECAST DISCUSSION National Weather Service Burlington VT 736 PM EDT Sat Mar 30 2019 .SYNOPSIS... Scattered light showers will trend more numerous overnight into Sunday morning as a cold front crosses the area. Behind this front cooler and drier air is expected by Sunday night into Monday with perhaps a light coating of snow across higher northern terrain as high pressure builds eastward. Temperatures moderate considerably from Tuesday onward into late week as mainly dry weather continues. && .NEAR TERM /THROUGH SUNDAY NIGHT/... As of 625 PM EDT Saturday...Made some modest adjustment to PoPs in the 6-10 pm hour this evening to account for band of showers and/or light rainfall pushing across northern NY and Adirondacks toward VT. This activity appears to be forced by increasing mid level flow out ahead of the frontal wave currently progressing through the SLV. Models aren't picking up on this to well, especically in regard to it's more southerly position. Increased PoPs for a few hours across the Dacks and VT to account for this accordingly. Rest of forecast remains in good shape. Prior discussion... Typical early spring frontal system bringing a wide range of temperatures and weather conditions across the North Country over the next 12-24 hrs. As of 18Z, quasi- stationary front extends from low pressure near Toronto, Ont. newd across the St. Lawrence Valley of NY into far srn Quebec. North of the front, temperatures remain in the mid-30s with nely low-level flow around KMSS and surrounding portions of far nern NY. Meanwhile, the remainder of the North Country has emerged into the warm sector with moderately strong southerly low-level flow. Some downslope flow (up to 29kts at KRUT) is resulting in localized clearing in the Champlain Valley, and the partial sunshine/insolational heating is allowing temperatures to climb rapidly into the 50s across wrn VT. It's possible a few sites will reach 60F across s-central VT later this afternoon. The quasi-stationary frontal system is anafrontal in character with the vast majority of precipitation confined to the frontogenetic region north and west of the surface bndry per mosaic composite reflectivity imagery. This anafrontal character should be maintained through tonight into Sunday. Thus, looking at breezy and mild conditions overnight from the Champlain Valley ewd with just a few sprinkles possible in broad southerly flow regime (and limited convergence). Lows at BTV should hover near 50F tonight with good low-level mixing as low- level jet strengthens to near 70kts at 4kft during the pre-dawn hours Sunday. Fog is possible over snowpack in very sheltered locations, but ample low-level turbulent mixing should preclude any more widespread fog. Eventually, mid-level shortwave trough approaching from the Ohio Valley helps to "kick" the frontal zone ewd, with the front and frontal zone precipitation finally reaching the Champlain Valley by 12-18Z Sunday. Will see a period of steady rainfall with the front, with 0.20-0.30" rainfall across VT during the morning hours. In the meantime, most of the rainfall will be confined to St. Lawrence/Franklin NY counties, where 0.3-0.5" is expected this afternoon thru tonight. May see some gusts to 30-35 mph in advance of the front during the pre-dawn hours, especially in the Champlain Valley with sly valley-channeled low-level flow fields. On Sunday, winds eventually shift W-WNW with precipitation ending as a brief period of wet snow with intense temp gradient and strong low-level CAA. Little or no snow accumulation expected in valley locations, but continued orographic snow showers later Sunday through Sunday night will yield 1-2" snow accumulation above 1000', with up to 3" possible for the higher summits of Vermont and northern New York. Temperatures early Sunday will be in the 50s across VT, but only upr 30s to lower 40s across the northern Adirondacks and St. Lawrence Valley based on expected progression of the cold front. Temperatures fall areawide Sunday afternoon and evening. Overnight lows Sunday night are expected in the low-mid 20s, except teens possible in the northern Adirondacks. && .SHORT TERM /MONDAY THROUGH MONDAY NIGHT/... As of 300 PM EDT Saturday...Upslope snow showers in the Adirondacks and Northeast Kingdom quickly draws to a close on Monday as upper trough shifts east. Temperatures will be below average as modestly cold air mass advects across the North Country. We should see highs reach the 30s across much of the area. Steep lapse rates during the day will allow us to efficiently mix during the day, with breezy northwest winds and gusts of 25 mph to isolated 30 mph during the afternoon and quickly subsiding overnight. Mixing will also lead to low dewpoints into the single digits. Overnight low temperatures will remain just below average as light, southerly winds persist, preventing us from achieving maximum radiational cooling. Expect 20s in the valleys and teens in the Northeast Kingdom and Adirondack Mountains. && .LONG TERM /TUESDAY THROUGH SATURDAY/... As of 300 PM EDT Saturday...Generally quiet conditions are expected for much of the extended. Temperatures will be much warmer on Tuesday as high pressure shifts off the US East Coast with good southwesterly return flow. Temperatures will warm into the 50s across much of the valleys. The steep lapse rates will make for quite the temperature contrast at the higher peaks which will remain in the 30s for the most part. Lows will be in the upper 20s to mid 30s. Conditions on Wednesday will be mostly dry. A trough and associated cold front is forecast to graze the International Borde, and a coastal low will develop remaining outside the benchmark. As a result, better dynamics are forecast to remain outside our region, lending to generally spotty shower chances. Temperatures will warm into the 50s across most of the North Country. Thursday will be mostly dry as well. It will be slightly cooler behind the passing cold front. Late Thursday, a warm front will begin to lift northward ahead of a developing area of low pressure. With it, precipitation chances will gradually increase into the weekend, while temperatures remain near to above average. && .AVIATION /00Z SUNDAY THROUGH THURSDAY/... Through 00Z Monday...Mainly VFR through the late night hours as quasi-stationary frontal system remains parked across the St. Lawrence Valley. Only exception will be at KMSS where occnl MVFR cigs and periods of -ra expected in closer proximity to the boundary. Otherwise any -shra activity further east should be scattered and very light at best. Winds overnight mainly south to southeasterly 8-15 kts and occnly gusty to ~20 kts at selected terminals where developing south/southwesterly LLWS into the 35-45 kt range expected in the 06-12Z time frame. Again, exception will occur at KMSS where flow will be more westerly in proximity to the front. After 09Z front begins steady progress east with a steadier period of light rain occurring at other terminals through the 13-18Z time frame along with MVFR cigs. Behind the frontal passage winds shift west/northwesterly 6-10 kts and cigs gradually improve. Outlook... Sunday Night: Mainly VFR, with areas MVFR possible. Chance SHSN. Monday: VFR. NO SIG WX. Monday Night: VFR. NO SIG WX. Tuesday: VFR. NO SIG WX. Tuesday Night: VFR. Slight chance SHRA. Wednesday: VFR. Slight chance SHRA. Wednesday Night: VFR. NO SIG WX. Thursday: VFR. Slight chance SHRA, Slight chance SHSN. && .HYDROLOGY... Isolated/minor flooding is possible Sunday through Sunday Night, but most rivers are expected to hold at or below bankfull. A slow-moving frontal system will bring periods of rain to the St. Lawrence Valley this afternoon and evening, with rain developing eastward across the northern Adirondacks overnight, and eventually across the Champlain Valley and central/eastern Vermont during Sunday morning. Precipitation will likely end as a period of wet snow across the higher elevations during Sunday, with snow showers possible Sunday night, mainly across the northern Adirondacks and central to northern Green Mountains. East of the frontal zone - mainly from the northern Adirondacks eastward across western Vermont, temperatures are climbing into the 50s this afternoon. South winds will hold temperatures in the 40s to low 50s overnight, resulting in continued snow melt. Rainfall amounts will be highest across St. Lawrence County NY, locally up to 1", as the frontal zone remains quasi-stationary into this evening. The boundary will be accelerating eastward as a cold front later tonight into Sunday morning, when most of the precipitation will occur across the Champlain Valley, and central/ern VT. Given the limited time window for rainfall in the frontal zone, rainfall amounts are only expected between 0.25 to 0.50" from Franklin County NY eastward across the Champlain Valley and central/ern VT. The combination of some rainfall and some snowmelt will result in rising river levels areawide as we head through late tonight into Sunday. At this time, the duration of warmth and expected rainfall amounts are not expected to be sufficient for widespread flooding issues. That said, a few rivers will reach bank full or experience minor flooding during Sunday/Sunday night/early Monday, when river crests are ultimately expected to occur. There is still an ice jam threat across the far northern river basins including the Ausable, Passumpsic, Missisquoi, and Great Chazy in NY. Ice jams may also lead to an isolated flood threat through Sunday night, and we will continue to monitor for potential ice jams as rivers rise and remaining river ice breaks up. The latest river forecasts can be found on our AHPS page here: water.weather.gov/ahps2/index.php?wfo=btv && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...JMG NEAR TERM...JMG/Banacos SHORT TERM...Haynes LONG TERM...Haynes AVIATION...JMG HYDROLOGY...TEAM BTV