Marine Weather and Tide Forecast for South Burlington, VT

KEY MESSAGES
As of 259 PM EDT Friday...

1. Scattered showers are possible over northern New York on Saturday afternoon, which spread eastward into Vermont by evening with warmer temperatures expected this weekend.

2. Warmer temperatures midweek with showers and some thunderstorms.

DISCUSSION
As of 259 PM EDT Friday...

KEY MESSAGE 1: Upper air analysis shows a complex pattern acrs the Great Lakes into the NE CONUS with deep closed cyclonic circulation near the 40/70 benchmark, while weak ridge is located over the central Great Lakes. This ridging is associated with weak axis of mid lvl moisture and deeper waa with developing westerly flow aloft.
Initially band of moisture dissipates and passes to our north tonight, but additional s/w energy and moisture over the northern Plains wl race eastward and impact northern NY by Sat aftn. For tonight have continued with previous forecaster thinking with some patchy fog over the central/eastern VT valleys. The bl winds acrs northern NY are in the 3 to 7 knot range, but are slightly less over VT. Also, still some uncertainty on how quickly clouds dissipate tonight with sounding data showing some moisture btwn 850-700mb layer. Vis satl imagery shows only a narrow axis of clearing slowly approaching the SLV with some breaks developing over CPV and southern VT this aftn. Lows generally in the 40s to near 50F tonight.

Timing and areal coverage of precip has increased slightly from previous 12 to 24 hours on Sat aftn/evening, as the GFS/HRRR is most aggressive with precip progs, while NAM is less. We are still not anticipating a washout and any precip wl be <0.10" with greatest probability of measurable precip over northern NY, especially the higher trrn. Have bumped pops into the low likely range btwn 21-01z acrs northern NY and kept pops in the chc range for VT. Developing southwest 925mb to 850mb jet of 35 to 45 knots should limit threat of rain showers in the CPV on Sat evening with some downslope shadowing likely. Did increase winds acrs the SLV and northern slopes of the dacks on Sat aftn, where localized gusts 25 to 35 mph are possible. An additional progged 850mb jet of 45 to 60 knots develops behind the weak sfc boundary late Sat night into Sunday, but mixing profiles are limited. Strongest winds wl be on summit lvl on Sat night into Sunday, but localized gusts 25 to 35 mph will be possible acrs central/southern VT. Progged 925mb temps are 14C to 16C on Saturday supporting highs well into the 70s. Sunday behind the boundary progged 925mb temps drop btwn 9-13C, supporting highs mid 60s to mid 70s, except near 80F lower CT River Valley near VSF.

A warm front wl lift acrs our region on Monday with a ribbon of mid lvl moisture and weak embedded s/w energy, which could produce a few very light rain showers. Instability develops behind the warm frontal boundary, so any convective threat would be elevated. Highs mid 70s NEK to mid 80s southern SLV with developing south to southwest winds.

KEY MESSAGE 2: Tuesday will be a very warm day - the warmest of the year for most of our area. The peak of the warm air advection will occur leading into Tuesday afternoon, with 925 mb temperatures maxing out 20-25 deg C. This suggests some of our valley locations could reach into the upper 80s, though just how warm we get will depend on cloud cover and coverage/timing of showers. Our forecast has highs in the upper 80s Tuesday for much of the Champlain Valley and the Connecticut River Valley, and highs in the low to mid 80s elsewhere. Dewpoints will also be ticking upwards going into Tuesday, resulting in an increasingly muggy feel to the air. Gulf moisture wrapping up and around the Bermuda high will bring dewpoints to around 60 degrees by Tuesday. All in all, expecting Tuesday to feel like full-swing summer after a seasonably cool start to the month.

The heat and humidity will also result in increasing instability, which will support the development of some showers with the potential for some embedded thunderstorms. These could throw a bit of a wrench in the temperature forecast; earlier showers/thunderstorms may mean we underperform on high temperatures.
Will have to watch how it all works together with regards to timing, as there isn't a well defined front to track but rather disorganized vort maxima rippling through the flow.

Showers and thunderstorms will become more widespread on Wednesday as a front sinks southward through our area. Temperatures south of the front will still be quite warm (low to mid 80s in southern/eastern VT), while seasonably cooler conditions are expected further north near the International Border.

The end of the work week will trend drier and cooler with high pressure settling overhead.

AVIATION /18Z FRIDAY THROUGH WEDNESDAY/
Through 18Z Saturday...We started off the morning with highly variable ceilings across the forecast area. These ceilings have lifted to VFR levels at all TAF sites except KMSS and KRUT as of 18Z. Still observing some scattered clouds around the 1500-3000 ft level, so have included some tempo groups for the first few hours of the TAF for brief periods of MVFR ceilings. However, expect improving trend to continue, with all TAF sites forecast to lift to and remain VFR from 21Z onward.

The fog forecast tonight is a little tricky with mixed signals... increased moisture from recent rainfall but still some winds just off the surface that will keep most areas somewhat mixed. Thinking the 5-15 knot flow just off the surface will limit fog development to just the sheltered valleys of eastern Vermont. Have kept mention of fog out of all the TAFs at this moment, but there remains a small chance of some fog overnight tonight at KMPV, most likely between 09Z and 11Z.

Outlook...

Saturday Night: VFR. Slight chance SHRA.
Sunday: VFR. NO SIG WX.
Sunday Night: VFR. NO SIG WX.
Monday: VFR. NO SIG WX.
Monday Night: VFR. Chance SHRA.
Tuesday: VFR. Chance SHRA, Slight chance TSRA.
Tuesday Night: Mainly VFR, with local MVFR possible. Chance SHRA, Slight chance TSRA.
Wednesday: Mainly VFR, with areas MVFR possible. Likely SHRA, Slight chance TSRA.

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