textproduct: Burlington

WHAT HAS CHANGED

As of 215 PM EDT Saturday...

No significant changes to the forecast.

KEY MESSAGES

As of 215 PM EDT Saturday...

1. Strengthening gusty south winds today and some showers tonight.

2. Additional rounds of showers and some embedded thunderstorms Sunday and Sunday night.

3. After cool conditions with potential for frost in outlying areas Monday night, the progressive pattern will continue to support periods of rain through the end of the week.

DISCUSSION

As of 215 PM EDT Saturday...

KEY MESSAGE 1: After a beautiful first half of the weekend, tonight will mark the transition to a more unsettled weather pattern with strengthening gusty southerly winds and multiple rounds of showers and some embedded thunderstorms expected through Sunday night/Monday morning.

As surface high pressure shifts east of our area tonight, strengthening southerly return flow will transport the higher PW air mass (currently over the Mid-Atlantic states) northward into our forecast area. Precipitable water values will increase from around 0.6 inch today to 1.50-1.75 inches tonight. Gusty southerly winds will continue to increase through the day today, especially channeled up the Champlain Valley. With relatively warmer Lake Champlain temperatures, forecast soundings are indicating enough mixing is maintained below a low-level temperature inversion to support Lake Champlain winds of 25 to 30+ knots overnight tonight. A Lake Wind Advisory is in effect for Lake Champlain, with winds expected to increase this evening and peak overnight between midnight and sunrise. Outside of the Lake, expect gusty winds 15 to 25 mph over the Champlain Valley, and 10 to 20 mph elsewhere. Higher peaks will see gusts 45+ mph tonight.

A southern stream upper-level shortwave moving through overnight will prompt the development of some showers tonight, with an embedded thunderstorm or two possible due to some elevated instability. Up to 500 J/kg MUCAPE is progged overnight, highest over our western counties in northern NY where the better chances for a rumble of thunder exist. Outside of low thunderstorm potential over northern NY, best chances for showers tonight will be across southern Vermont, with lower probabilities further north towards the International Border.

KEY MESSAGE 2: During the day on Sunday, some rain showers will linger over eastern and southern Vermont during the morning hours as the system mentioned in Key Message 1 gradually exits to our east. Meanwhile, most areas will then see a break in precipitation during the day before the next system moves in from the west. This next system will be supported by strong dynamics as a potent shortwave and associated cold front move into the region.

At this time, it continues to appear that the ingredients will not line up ideally to support the development of widespread storms later Sunday, though changes in the timing of the system and degree of destabilization could increase the thunderstorm potential. Current forecast has the break in rain during the day Sunday that will allow between 500 and 1000 J/kg SBCAPE to develop during the afternoon. However, the better forcing and dynamics do not arrive until the early overnight hours, after the peak of diurnal instability. Therefore, the most likely scenario is some scattered showers with a few embedded thunderstorms during the afternoon, with higher confidence in a brief round of a wetting rain overnight for most areas as the stronger forcing moves in. Additional thunderstorms cannot be ruled out overnight, but instability will be limited and primarily elevated. This will limit the severe threat, though any thunderstorms that do develop Sunday or Sunday night could produce gusty winds and cloud-to-ground lightning, especially given the stronger background flow already in place. The Storm Prediction Center maintains a Marginal Risk of severe weather for much of our area on the latest Day 2 Convective Outlook.

Conditions will trend drier Monday as high pressure builds in.

KEY MESSAGE 3: High pressure crests Monday night with ideal raditional cooling likely. Temperatures in the Adirondacks and northeastern Vermont are favored to cool into the mid/upper 30s supporting frost potential. Otherwise, 500 mb flow in the mid-high latitudes are favored to be mainly zonal with Arctic air trapped well north of the region keeping conditions near seasonal levels. Fast-moving troughs will be moving through this flow with model trends maintaining a weaker wave passing Tuesday night into Wednesday. Latest trends continue to point to another wave Thursday into Friday with models more consolidated resulting in higher probability of measurable rainfall in this time period. Some model guidance keep the surface boundary in the vicinity of Vermont/northern New York into the weekend with WPC hanging onto 20-40% chances of showers before another wave likely moves through sometime over next weekend. The main take away here is that there periods of showers with temperatures near seasonal levels during the day and above average overnight due to pervasive cloud cover.

AVIATION /00Z SUNDAY THROUGH THURSDAY/

Through 00Z Monday...VFR conditions for the first 6-12 hours of the TAF period, but conditions lower to MVFR with local IFR as showers spread from west to east overnight. Best chances for IFR ceilings will be at SLK, and perhaps MPV and EFK as well. Visibility to remain 4-6SM in showers, which will come to an end 10z-15z. Ceilings will lift thereafter, with all terminals to return to VFR by 21z. South winds will remain breezy this evening and overnight, especially in the Champlain Valley where gusts to around 25 kt are expected. LLWS will develop outside the immediate Champlain Valley overnight with showers spreading after 06Z.

Outlook...

Sunday Night: VFR. Chance SHRA. Monday: VFR. NO SIG WX. Monday Night: VFR. NO SIG WX. Tuesday: VFR. NO SIG WX. Tuesday Night: VFR. Chance SHRA. Wednesday: Mainly VFR, with local MVFR possible. NO SIG WX. Wednesday Night: Mainly VFR, with local MVFR possible. Chance SHRA. Thursday: Mainly MVFR, with areas VFR possible. Chance SHRA.

MARINE

As of 215 PM EDT Saturday...

A Lake Wind Advisory remains in effect this evening overnight tonight for strengthening south winds. Winds gusting 15-20 knots this afternoon will increase to 20-30+ knots late this evening into tonight. Winds will peak during the overnight hours, then will diminish through the day on Sunday. Waves at 1 to 3 feet this afternoon will build to 2 to 5 feet overnight, then become 1 to 3 feet again through the day on Sunday.

BTV WATCHES/WARNINGS/ADVISORIES

VT...None. NY...None.