Marine Weather and Tide Forecast for Shelburne, VT

NEAR TERM /THROUGH THURSDAY/
As of 347 AM EDT Wednesday...Pleasant weather is on tap today and tonight as high pressure drifts across the region. We're expecting ample sunshine today, with just some lingering clouds over portions of northeastern VT. Northwest winds will be a little on the breezy side, but not as strong as we saw yesterday. Highs will generally be in the mid 50s to mid 60s, with perhaps some lower 50s in the Northeast Kingdom if clouds hang around longer than anticipated.
Clouds will start to increase late tonight ahead of our next system, but most areas will likely remain mostly clear through daybreak Thursday. Lows will be in the 30s areawide.

Our dry weather comes to an end on Thursday as a weak shortwave will slide through zonal flow aloft. The associated weak surface low will likewise move eastward from the Great Lakes and directly over our forecast area during the day. Consensus of the latest CAM runs show an area of showers moving into our region with the preceding warm front Thursday morning. Given the amount of dry air in place, feel this is a bit overdone with the main impacts to be just increasing cloud cover during the morning hours. Better chances for showers arrive later in the day as the surface low moves through, somewhere in the northern/central portions of our forecast area, dragging a cold front along behind it. How much rain we get in the morning hours will impact thunderstorm potential with the afternoon showers.
While there will likely be at least some elevated instability in the afternoon, enough for a few rumbles of thunder, there are some indications that there could be 400+ J/kg of SB CAPE if any morning rain showers and cloud cover are minimal and/or move through fairly quickly, allowing the atmosphere to recover by the second round in the afternoon. There are still minor differences between model solutions with these factors, so we'll need to continue to monitor trends going forward. For now, have gone with a blend of a few different model solutions, which keeps precipitation chances fairly low in the morning, and keeps afternoon thunder chances limited to slight, mainly in the Adirondacks and south-central Vermont. These parameters will also play into highs for Thursday; note that there's a pretty big range in MOS guidance (the MET has 57 for BTV, while the MAV has 67). With more clouds expected in the north, have stayed with highs in the upper 50s to low 60s along the international border, with central/southern areas getting into the mid 60s to low 70s.

SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY/
As of 347 AM EDT Wednesday...A shortwave will continue to track across Quebec with some slight shower chances across northern Vermont. Any showers that develop, especially in southern Vermont, could have a few rumbles of thunder. QPF values remain on the lower side with this shortwave with only a few hundreths of an inch expected. Showers will quickly taper off late Thursday night with lows falling into the 40s. Friday looks to start off dry with brief ridging and widespread cloud cover throughout the day ahead of the next system tracking out of the Great Lakes. Ensemble guidance has trended the center of the system further north, which would lead to more southerly flow and increased waa. Deterministic guidance still indicates a low track over the region keeping temperature guidance on the low side. Temperatures thus could trend towards the warmer side of guidance Friday afternoon into the mid to upper 60s as winds shift from the south. A warm front associated with the low will slide into the area late Friday afternoon with increasing precipitation chances into the evening. A few rumbles of thunder are possible in portions of the Adirondacks and southern Vermont where surface CAPE and isentropic lift are most conducive for any instability to form. CAPE values remain low, however, in the 100-200 J/kg range.

LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/
As of 347 AM EDT Wednesday...A wet start to the weekend is in store, with dry and warming temperatures following to start next week. A low will track out of the Great Lakes Friday evening and track northeast across the St. Lawrence valley and into Canada. Ensemble tracks have trended this system further north which would draw in warmer air allowing for potentially more instability to form Friday night. While deterministic guidance shows low CAPE, ensembles show a slight upward trend, albeit still only in the 50-150 J/kg range.
Furthermore, any more northward trends would keep surface temperatures on the warm side with additional mixing of the column which could keep any instability in place longer through Friday night. Any thunderstorm chances look best across northern New York, and portions of the Champlain Valley. QPF from this system is also challenging given the northward uncertainty. If the system were to follow a more southerly path directly over the North Country, overrunning, and stratiform rain would lead to more uniform precipitation accumulations around a quarter to half an inch.
However, under the northward path across Quebec, more convective elements from an associated cold front are possible with less overall widespread precipitation. This is exemplified in the NBM 24- hour precipitation probabilities which show a 40-60% chance of 0.5 inches or greater, indicating for most that this will be a wetting rain, with an upward trend in greater than 0.75 inches to near 40% across portions of central Vermont, noting heavier precipitation from possible convective elements. Rivers and area waterways could see some rises, however, flooding risks remain low. Temperatures will be in the upper 40s to near 50 Friday night given the precipitation.

As the system exits Saturday, lingering precipitation chances remain uncertain. The ECMWF ensembles indicate the low will deepen over the area keeping precipitation chances through Saturday, however the GEFS shows the low deepening over portions of Maine, leading to a drier Saturday. The overall trough amplification will need to be monitored for trends for low track clarity. Regardless, Saturday night temperatures will fall into the 30s with slight rebounding temperatures Sunday in the 50s and 60s. Northerly flow Sunday could lead to breezy conditions across the Champlain Valley with top of the boundary layer gusts near 30 knots. Much drier air and warming temperatures are expected for the start of next week as a broad area of high pressure builds overhead.

AVIATION /08Z WEDNESDAY THROUGH SUNDAY/
Through 06Z Thursday...Outside of some possible MVFR ceilings at EFK, VFR conditions will prevail through the TAF period. Bank of low clouds over Northeast Kingdom of VT will continue to slowly erode from the west through 14z Wed, and ceilings may lower to below 3000 ft for a time through the early morning. Otherwise, FEW-SCT skies will prevail with any clouds generally 4000-5000 ft. W/NW winds around 5 kt through 14z Wed will become gusty to 15-20 kt through the daylight hours, then subsiding to light after 02z Thu.

Outlook...

Thursday: VFR. Chance SHRA.
Thursday Night: Mainly VFR, with areas MVFR possible. Slight chance SHRA.
Friday: VFR. Chance SHRA.
Friday Night: Mainly VFR, with areas MVFR possible. Definite SHRA.
Saturday: Mainly MVFR, with local IFR possible. Chance SHRA.
Saturday Night: Mainly MVFR, with local VFR possible. Slight chance SHRA.
Sunday: VFR. NO SIG WX.

BTV WATCHES/WARNINGS/ADVISORIES
VT...None.
NY...None.