Area Forecast Discussion
Issued by NWS Burlington, VT
Issued by NWS Burlington, VT
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946 FXUS61 KBTV 270752 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 352 AM EDT Thu Jun 27 2024 .SYNOPSIS... A cold front will continue to produce scattered showers this morning across the region, before drier weather with increasing amounts of sunshine returns by this afternoon. Temperatures will only warm into the mid 60s to lower 70s with northwest winds 5 to 15 mph. A cool and clear night with some patchy valley fog is anticipated tonight, before a beautiful Friday is expected with plenty of sunshine and comfortable temperatures. Unsettled weather returns on Saturday afternoon into Sunday, along with breezy south winds. && .NEAR TERM /THROUGH FRIDAY/... As of 320 AM EDT Thursday...Surface analysis places cold frnt along the International Border this morning with scattered showers along this boundary. As this front drops south this morning, expect areas of scattered showers to prevail from northern NY into central/northern VT, with greatest concentration and highest qpf acrs the dacks into the northern VT mtns. A relatively strong area of high pres for late June wl continue to build southeast this aftn into Friday with much cooler and drier air developing on brisk north/northwest winds this aftn. As mixing develops this wl cause sfc dwpts to drop back into the 40s with increasing amounts of sunshine this aftn. As 1028mb high pres settles directly overhead by 12z Friday, expect mostly clear skies tonight with light north winds under 5 knots. Given these conditions and recent rainfall, anticipate some localized patchy fog, especially where cross over values are reaches, such as the northern Dack valleys and parts of the CT River Valley. Some uncertainty in fog/br coverage over central/northern VT, due to gradient. Also, a cool night is anticipated with lows mid 30s SLK to upper 40s/lower 50s CPV. Would not be surprised to see some patchy frost near SLK. Friday wl feature plenty of sunshine with just some fair wx cumulus acrs the trrn with temps warming into the upper 60s to mid 70s with very low humidity values. && .SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/... As of 352 AM EDT Thursday...Changeable weather will continue. The dry air mass will allow temperatures to cool quickly after sunset Friday but lows will end up much milder than the previous night as temperatures steady overnight. The air will be modulated by warm air advection as high pressure moves to our east. An unseasonably strong pressure gradient will develop as said high pressure sits to our east and low pressure moves northeastward near the central Great Lakes. This pattern will promote increasingly strong southerly winds, especially in the northern Champlain Valley due to channeling. Expect rough conditions on Lake Champlain due to good mixing as air temperatures aloft will be cooler than the lake water; several hours of sustained 30 knot winds are likely on the broad lake. Mean hourly wind gusts will tend to increase during the day and peak in the late afternoon hours, with maximum values most likely in the 40 to 45 MPH range in the northern slopes of the Adirondacks, much of the Champlain Valley, and favored. There is some uncertainty in the strength of the 850 millibar southwesterly flow, however. The latest model blend shows 50 to 55 knots looks reasonable, higher than what global ensemble data suggested. But there is also some more alarmingly strong winds shown in the 00Z NAM12, which increases the jet to 65 knots and shows the inversion height just above. At the very least, if you are on the higher mountain summits, strong winds near 60 MPH will be possible Saturday evening. The extent of gusty winds will be dependent on how quickly rain showers overspread the area. Generally chances of rain will be focused earlier in the day in western areas, gradually expanding eastward across Vermont by the evening hours, which will reduce the chances of mixing down the stronger winds aloft. The focus Saturday evening into the overnight will then turn to heavy rainfall potential. At this time, excessive rainfall looks unlikely but there are some things going for it such that a marginal risk is reasonable. While lapse rates will tend to be moist adiabatic such that thunderstorms are unlikely, the atmosphere looks supportive of efficient, heavy rain processes. Most parameters, save wind shear, are favorable for torrential rain in any convection. However, elevated instability looks limited such that thunderstorms are very unlikely through this period. Any heavier elements also are unlikely to be training over a single location as bulk shear vectors look west- southwesterly, not parallel to the pre-frontal trough that will be the focus for these showers. This trough will gradually slide eastward, followed by another area of showers approaching ahead of perhaps another pre-frontal trough. Given the messy pattern and continued forcing for precipitation, have maintained chances of showers areawide through the period. Under the continuous southerly low level flow, temperatures will be steady and mild Saturday night in the 60s. Rainfall amounts look to average 0.5" to 0.75", although that will need to be refined moving forward. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... As of 352 AM EDT Thursday...A moderately strong cold front will pass through the region Sunday from the west. A blend of model guidance suggests CAPE of 500 J/kg could develop ahead of this boundary if it passes through late enough in the day; a morning passage would put a damper on the instability. At this time, have maintained a slight chance of thunder for all of northern New York and Vermont for the afternoon. Following this system, another period of refreshing air will arrive. Save an isolated shower Monday morning associated with an upper trough swinging through, the first half of next week looks stellar for outdoor activities as anticyclonic flow dominates our weather. Wednesday we will see more seasonable humidity return as southerly flow develops, but chances for showers are low, especially east of the Adirondacks. && .AVIATION /08Z THURSDAY THROUGH MONDAY/... Through 06z Friday...Crntly VFR conditions at all sites except MVFR cigs at SLK with periods of light rain showers. These showers will slowly exit our terminal sites by 12z Thursday, but as winds shift to the northwest expect some lowering cigs toward MVFR at many sites. A period of blocked flow near sunrise could produce localized IFR conditions at BTV for an hour or two, but probability and confidence is too low attm to mention in TAF at BTV. Otherwise, higher confidence of IFR CIGS associated with upslope flow is expected at SLK, so have utilized tempo`s to indicate this potential. Otherwise, CIGS become VFR with clearing skies by 16z today with northwest winds 5 to 15 knots. Tonight winds become light north/northwest under 5 knots with some patchy fog possible toward 06z at SLK. Outlook... Friday: VFR. NO SIG WX. Friday Night: VFR. NO SIG WX. Saturday: Mainly VFR, with local MVFR possible. Likely SHRA, Slight chance TSRA. Saturday Night: Mainly MVFR, with local IFR possible. Definite SHRA, Slight chance TSRA. Sunday: MVFR/IFR conditions possible. Chance SHRA, Chance TSRA. Sunday Night: VFR/MVFR conditions possible. Slight chance SHRA, Slight chance TSRA. Monday: VFR. Slight chance SHRA. && .MARINE... Unseasonably strong winds are expected on Saturday when a Lake Wind Advisory will be needed for Lake Champlain. South winds may exceed 25 knots by daybreak and will likely be above 30 knots on the broad lake at times during the day. Rough waves will develop quickly. Wave heights on the broad lake and inland sea may build into the 3 to 5 feet range Saturday morning. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Taber NEAR TERM...Taber SHORT TERM...Kutikoff LONG TERM...Kutikoff AVIATION...Taber MARINE...Kutikoff