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Area Forecast Discussion
Issued by NWS Burlington, VT
Issued by NWS Burlington, VT
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516 FXUS61 KBTV 131057 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 657 AM EDT Tue Aug 13 2024 .SYNOPSIS... After some morning fog burns off, mostly sunny skies develop today with temperatures warming into the mid 70s to lower 80s most locations. A cool and comfortable night is anticipated with lows in the upper 40s to upper 50s across our region. The chances for afternoon showers and thunderstorms increase again on Wednesday into Thursday with temperatures warming into the upper 70s to mid 80s. && .NEAR TERM /THROUGH WEDNESDAY NIGHT/... As of 647 AM EDT Tuesday...Areas of dense fog acrs the southern CPV near RUT and over the lower CT River Valley should burn off in the next 1 to 2 hours. Otherwise, expecting plenty of sunshine today with temps warming into the mid 70s to l/m 80s, which is all covered in crnt fcst. Previous discussion below: A beautiful day is on tap with developing sunshine, mild temps, and comfortable humidity values, resulting in a classic North Country Chamber of Commerce type day. Water vapor shows large scale subsidence directly overhead, which is confirmed by area soundings indicating a deep dry layer btwn 850-300mb. After some morning fog/clouds burn off plenty of sunshine is anticipated with just a few fair wx cumulus clouds over the trrn. Progged 925mb temps btwn 18-20C support highs mid 70s to l/m 80s acrs our region. Tonight mid/upper lvl trof prevails as sfc high pres remains anchored acrs the central Great Lakes. Some high level moisture may advect into our cwa from the north aft 06z, but given lighter wind fields and temps dropping to near cross over values anticipate some areas of fog, especially climo favored areas. Have continued with previous fcster thinking for fog with most likely areas valleys of the northern Dacks and mtn valleys of central/northern VT, including the NEK and CT River area. Lows range from the upper 40s to upper 50s with comfortable humidity. For Weds continued a 15 to 30% probability of showers/storms, with highest pops over the eastern Dacks and mtns of VT btwn 21-00z. Latest NAM solutions indicate sfc based CAPE values in the 1200-1800 J/kg, which maybe a bit overdone, especially if a dry pocket near 850mb mixes toward the sfc. Either way, a weak disturbance in the northerly flow aloft drops south acrs our cwa after 18z, which should provide enough lift for widely scattered showers/storms. Temps warm back into the upper 70s to mid 80s, a few degrees warmer than today. Deep layer shear is very weak and unidirectional on Weds, so not anticipating a severe threat, maybe a brief stronger storm is possible, but coverage wl be limited. && .SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/... As of 335 AM EDT Tuesday...Daytime showers may linger Wednesday night, with a diminished opportunity for lightning, as sufficiently steep lapse rates and cyclonic flow promote scattered shower activity. At the surface, weak high pressure will remain over the area. So aside from any precipitation, expect another round of patchy dense fog to develop. While not a washout, Thursday is likely to be showery. The latest model guidance continues to suggest we will se numerous showers with a chance of thunder to redevelop after a lull, peaking Thursday afternoon, before again winding down Thursday night. A very weak surface trough approaching from the west will aid in surface convergence with some southerly winds developing in Vermont and northern New York while the upper level low over Maine continues to spin and bring impulses pinwheeling on its western flank across our area. Six hour thunderstorm probabilities are fairly robust in the 32 to 41% range between 2 and 8 PM areawide, with slightly greater chances centered near Orange County and lowest in southernmost St. Lawrence County. Thunderstorms are unlikely to be severe, but stronger ones will be capable of small hail and gusty winds. Fairly low freezing levels, perhaps down to 8000 feet, suggest a taller storm could produce some brief small hail. While low level flow will be weak, moderate northerly winds aloft suggest in a stronger updraft, a taller thunderstorm would have sufficient deep layer shear for a cell to be balanced such that gusty winds could make it to the surface in a downdraft, aided by dry low level air and the associated steep lapse rates. High temperatures will probably end up very close to seasonal normals. However, compared to the previous forecast, these temperatures have trended a touch cooler, especially in many Vermont locations, probably due to greater likelihood of numerous showers. The cloud cover associated with these showers will limit solar radiation, although a partly cloudy sky generally is still indicated; periods of mostly sunny skies will be interspersed with cloudy ones. Precipitation chances will wind down Thursday night as mid-level ridging slides in from the west. Nighttime temperatures will be seasonable again, probably ranging from the low 50s to low 60s. && .LONG TERM /FRIDAY THROUGH MONDAY/... As of 335 AM EDT Tuesday...Friday will be the pick of the long term for outdoor activities, easily. High confidence of dry weather with a ridge of high pressure cresting overhead. Then Saturday, Sunday, and Monday look unsettled, to say the least. While none of these days currently is favored to see any significant event, the potential for heavy rainfall will need to be monitored. A potentially deep trough will only slowly move eastward through the weekend, as a Rex block in the western Atlantic develops due to the track of what is now Tropical Storm Ernesto. The longwave pattern will maintain the trough near or west of the region into Monday. Through the period, the 500 millibar heights continue to show some variability in global models. These differences don`t change the rainfall chances much, but they will have subtle effects on the amount of instability and shear available for thunderstorms each day. As an example, with the 00Z LREF, the combination of these parameters in each of the four ensemble clusters Saturday afternoon varies. The mean of only one of the four scenarios suggests a low end severe weather threat, and even that would be primarily in the southwestern portions of northern New York. That is consistent with the pattern of NBM probability of 24 hour rainfall exceeding 0.5" through Sunday morning. Rainfall totals through Monday currently have a 10 to 30% chance of exceeding 2" using the same model guidance. While not dramatically so, there generally is a consensus on deep moisture and forcing for precipitation peaking on Sunday across our area; That may be the day to focus on with regards to any potential impactful weather, so stay tuned. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/... Through 12Z Wednesday...VLIFR conditions associated with dense fog developed at RUT overnight, with intervals of fog/br at SLK, otherwise rest of our TAF sites stayed VFR. Expecting the fog to burn off at RUT by 1330Z based on cigs/vis trends in AvnFPS with < a 25% IFR persists until 14z. VFR conditions prevail from 14z thru 06z today, before additional fog and IFR or lower conditions develop at SLK/MPV and RUT toward 06z as shallow but sharp inversion develops. Winds are generally north/northwest at 5 to 10 knots and become light trrn driven after 00z this evening. Outlook... Wednesday: VFR. Slight chance SHRA, Slight chance TSRA. Wednesday Night: VFR. Slight chance SHRA. Thursday: VFR. Chance SHRA, Chance TSRA. Thursday Night: VFR. NO SIG WX. Friday: VFR. NO SIG WX. Friday Night: VFR. NO SIG WX. Saturday: Mainly MVFR, with areas VFR possible. Chance SHRA, Slight chance TSRA. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Taber NEAR TERM...Taber SHORT TERM...Kutikoff LONG TERM...Kutikoff AVIATION...Taber