textproduct: Burlington

WHAT HAS CHANGED

As of 237 AM EDT Sunday...

Beneficial rainfall remains on track for tonight. Slightly greater potential for a thunderstorm Monday afternoon/evening.

KEY MESSAGES

As of 237 AM EDT Sunday...

1. Pleasant conditions through the daylight hours today. Widespread showers with beneficial rainfall tonight will be followed by scattered showers and localized thunderstorms Monday.

2. A narrow ridge of high pressure and seasonable warmth for Tuesday will give way to another weak frontal system that brings shower and thunderstorm chances Wednesday.

3. Climatological conditions persist through the second half of the week.

DISCUSSION

As of 237 AM EDT Sunday...

KEY MESSAGE 1: A mid-level trough and the associated warm air advection ahead of this feature should produce enough ascent for widespread showers this evening, generally starting in New York and spreading north and east with time. A band of heavier rainfall rates still appears possible overnight, and model guidance that shows this feature continues to favor northern and northeastern Vermont primarily with greater likelihood of rainfall amounts of around 0.5" to 1" and locally greater than 1". Meanwhile a quarter inch or less, with many areas seeing only 0.1" or so, is expected for most areas through the nighttime hours. While we continue to expect a surge of PWAT and warm cloud depth values that typically are associated with our heavy rainfall events, instability looks scant (Most Unstable CAPE < 300 J/kg) and rain showers fast moving such that downpours will be very brief in nature. The upper level pattern doesn't appear conducive to a heavy rain event, as there will be a split in the flow with two competing areas of forcing; one passing to our north, which will primarily affect our region, and another wave well to our south, where the primary deep moisture and convective threat will lie.

Perhaps more interesting will be the showers that develop during the day tomorrow, which may be capable of producing lightning as the environment becomes marginally conducive for thunderstorms. Overall the threat for any strong thunderstorms is very low and severe weather is not expected. The greatest risk area seems to be from eastern Essex County, New York and into the southern Champlain Valley, although broadly a 20-25% chance of thunder during the afternoon exists for the Adirondacks and much Vermont. Dew points increasing into the mid and upper 60s and limited sunshine will aid in some modest surface-based instability with showers developing with relatively shallow cloud bases. PWAT remains elevated (roughly 1.4 to 1.6 inches) with ensemble mean surface based instability climbing into the 750-1250 J/kg range during peak heating in northeastern New York, where a subtle convergence line should set up to help showers blossom and organize. Effective shear looks relatively low (25 or so knots), limiting the potential for any stronger storms, although terrain driven convergence in the western Champlain Valley could help strengthen cells that move through. The showers will gradually move south and eastward, as the boundary/trough exits Vermont sometime in the evening. Rainfall will be highly variable, with some localized areas likely seeing around an inch of new rainfall but most areas seeing only an additional few hundreths to a quarter inch.

KEY MESSAGE 2: The next noteworthy period of weather will be on Wednesday when there is broad consensus that a fairly weak cold front will pass through the Northeast. Timing of the front is generally appears to be during the day with primarily chances for showers and thunderstorms during the afternoon and evening hours. The details and potential for multiple boundaries to move through the region will need to be hashed out in the coming days. That being said, some deterministic model guidance suggests the pre-frontal environment will be devoid of instability and moisture such that little in the way of thunderstorm, let alone shower, activity will occur. Per ensemble guidance, the risk of thunderstorms, along with rain chances, is perhaps a bit higher in the St. Lawrence Valley than areas to the east, but we'll watch trends in the coming days.

KEY MESSAGE 3: Lingering showers will move out through the day Thursday, as broad cyclonic flow slowly migrates eastward. After the system moves off, a period of drier weather looks to return for the latter half of the week. Daytime temperatures will fluctuate near climatological normals in the mid 70s, with overnight lows falling into the low 60s. There is potential for another system to sweep through next weekend bringing some sustained showers. We'll continue to monitor as the models lock in.

AVIATION /06Z SUNDAY THROUGH THURSDAY/

Through 06Z Monday...Fog formation will be slightly less widespread than last night, but we continue to anticipate development in the favored areas. Dew point depression has reached zero at SLK, with MPV and EFK not far behind. The fog will burn off in the morning, leaving us with VFR conditions throughout the day tomorrow before rain falls tomorrow night.

Outlook...

Monday: MVFR/IFR conditions possible. Slight chance SHRA. Monday Night: Mainly VFR, with areas MVFR possible. Chance SHRA. Tuesday: Mainly VFR, with local MVFR possible. NO SIG WX. Tuesday Night: VFR. NO SIG WX. Wednesday: VFR. Chance SHRA, Slight chance TSRA. Wednesday Night: VFR. Chance SHRA. Thursday: VFR. Slight chance SHRA.

BTV WATCHES/WARNINGS/ADVISORIES

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