Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 151146 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 746 AM EDT Mon Oct 15 2018 .SYNOPSIS... This week will feature several swings in the weather as we see warm showers move in today followed by a sharp cold front overnight. This pattern will be repeated mid week with more rain and mountain snow showers. Temperatures on the warm days will be in the mid to upper 50s with cold days in the upper 40s to near 50. Lows will vary widely between the low 30s behind cold fronts to mid 40s on warm days. Some minor snow accumulation is possible this week in the higher terrain. && .NEAR TERM /THROUGH TUESDAY/... As of 732 AM EDT Monday...Latest radar imagery shows some light rain has just moved into southern NY so we`re still on track to see the warm advection rainfall push into the North Country by mid morning. The ENX VWP is starting to show 35kt winds at 3-4kft and so the low level jet is starting to push into the into the region so we`ll see how much rainfall occurs over the Champlain Valley. Previous discussion...Current obs paint quite a different picture today than last night as the clouds have for the most part cleared out over Vermont rather than New York and thus in the cloud free areas temps are in the low 30s. The upper level system that will bring rain later today is featuring quite the warm conveyor belt on the WV satellite and is rapidly pushing clouds into northern New York so temps are a fair bit warmer in the upper 30s to low 40s. We are still on track today to see a warm front associated with that upper level cyclone bringing some warm advection showers to the North Country. I backed off pretty strongly on the amount of rainfall in the valleys with this system. The dynamics are strong enough that as the initial surge of warm advection moves in most areas should see some rainfall but there`s quite a different signal in the high res vs low res guidance. I`m leaning towards the idea that we may see some light rain move into the North Country between 13-16z ahead of the low level jet but once the 40-50kt low level jet moves in the rainfall will become orographically forced as any lee side valleys will be shadowed pretty strongly. The NAM has 45kts of wind at 925mb in the 18z sounding at BTV and so if that happens we`ll be on the outside looking in for rainfall. Given that I trended back on precip, I trended up on max temps with the idea that we`ll be in the upper 50s with a chance at a few spot 60`s in the Champlain Valley. The best chance for rainfall looks to be just ahead of the front as surface convergence rapidly increases between 20-23z as the front sweeps through. I think that`s when we`ll pick most of our rainfall. Even with backing off the chances for rainfall and total precip I still feel we`re on track to see generally a tenth in the valleys with between 0.25-0.5" in the higher elevations. In addition to the the rainfall we`ll see moderate to strong boundary layer winds. That 850mb jet mentioned earlier will push winds in the higher elevations up towards 45-55mph and will end up being funneled through the Champlain Valley. I could easily see gusts in the afternoon pushing towards 20-30 mph out of the south especially on the more exposed eastern side. Overnight behind the front the air turns quickly back to cooler than normal. Anticipate another round of low level strato cu developing which should limit how cold we get so I`ve bumped up temps above MOS guidance. Clouds continue through the day tomorrow as the local BTV CU sky rule shows we may not break out of the cloud cover til mid to late afternoon. So the combination of cloud cover and cold air advection means that we`ll likely be in for a brisk day with westerly winds turning southwesterly by the nightfall. Expect max temps Tuesday to peak in the upper 40s to low 50s. && .SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/... As of 431 AM EDT Monday...Tuesday night an extremely cold upper level trof will approach the region from the Great Lakes with falling heights and backing low level flow. In fact, this trof and its NAEFS forecasted 700/500 mb heights and temperatures are colder than any in the 1979-2009 CFSR climo with 30+ year return periods and -3 to -3.5 standardized anomalies making this a truly unusually cold event for this time of year. This trof will pick up some moisture from the lakes with some lake enhanced precipitation to northern areas especially in NY before midnight spreading across northern VT afterward. Most areas will be rain showers though some of the highest elevations could be mixed with snow. Low temps won`t fall too much with readings in the 30s except lower 40s in the St Lawrence and Champlain Valleys. On Wednesday a cold front will move across the region with rain showers changing to snow showers with high temps again in the 40s. Behind the front another period of NW upslope flow is expected and with 1000-500mb thicknesses falling as low as 516dm in the NEK and 850 temps falling to -10 to -12C (-2.5 std anoms) by Wed night into Thursday morning. With these temps could see some decent dendritic snow growth for some light fluffy snow shower accumulations possibly reaching the lower elevations along the western slopes. Still thinking the potential exists for total snow accumulations by Thursday morning of 1-3" in the mountains from 1500 ft to the summits, a dusting to an inch from 500-1500` and perhaps a few flurries at the valley floor. Lows will be mainly in the 20s in the lower terrain to lower 30s in the valleys. In addition NW winds will be picking up with wind chills falling into the teens and we won`t even talk about how cold it will be on the summits. && .LONG TERM /THURSDAY THROUGH SUNDAY/... As of 431 AM EDT Monday...Models in very good agreement in the long term which features a period of much cooler than normal temps as the anomalously deep upper level trof progresses quickly through the northeast US through Thursday followed by a brief warming with rising heights by Friday. On Saturday, another very cold digging Canadian trof and cold front approaches with another shot of very cold air. The upper level trof moves off to the east on Thursday so any lingering flurries will come to an end but it will be quite blustery and cold with highs mainly in the 30s but it will feel colder. Maybe SLK doesn`t get above freezing. By Thursday night and Friday some moderation in temps is expected as the upper level trof moves out followed by some warm advection and perhaps some weak warm frontal precip in northern areas. Lows in the 20s and highs rebounding into the upper 40s to lower 50s. The next cold front and chance of precipitation comes on Saturday for another round of chilly temperatures. Rain showers will be changing to snow showers once again. A cold blustery NW flow follows for Sat night into Sunday with snow showers continuing and it looks like more light accumulations. Looking at lows dropping back in the 20s and lower 30s and highs in the 30s to lower 40s. && .AVIATION /12Z MONDAY THROUGH FRIDAY/... Through 12Z Tuesday...Expect VFR conditions through 13-14z this morning before a warm front brings lowered ceilings and visibilities. The LIFR fog at MPV should mix out by 13z as the winds start to pick up. The latest thinking is that we`ll be mainly VCSH in at PBG and BTV with -SHRA at RUT beginning shortly after 13-14z and lifting towards the northeast. Ceilings will generally become MVFR with brief periods of IFR possible in showers. Winds will pick up quickly out of the south to southwest and become fairly gusty by mid afternoon as a modest low level jet will bring the potential for some low level turbulence as mountain waves will be possible. Anticipate the gusts ahead of the front to be as high as 25-30kts especially at SLK/MSS/BTV. Behind the front westerly 10-20kt winds will push in through the overnight hours Tuesday morning. Outlook... Tuesday: VFR. NO SIG WX. Tuesday Night: VFR. Chance SHRA. Wednesday: Mainly VFR, with local MVFR possible. Chance SHRA, Chance SHSN. Wednesday Night: Mainly VFR, with local MVFR possible. Slight chance SHSN. Thursday: VFR. NO SIG WX. Thursday Night: VFR. NO SIG WX. Friday: Mainly VFR, with local MVFR possible. NO SIG WX. && .MARINE... As of 431 AM EDT Monday...A lake wind advisory is in effect today as strong southerly winds will pick up in the morning hours becoming 20-30kts as the pressure gradient ahead of an advancing cold front tightens. Expect choppy conditions today on the lake as there should be a decently long fetch. Waves on the northern side of Lake Champlain will be approaching 2-4 feet with locally higher waves possible. This will impact Cumberland Bay and most of the broad lake. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Deal NEAR TERM...Deal SHORT TERM...Sisson LONG TERM...Sisson AVIATION...Deal MARINE...

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