textproduct: Burlington

WHAT HAS CHANGED

As of 256 PM EDT Wednesday...

The axis of the highest rainfall amounts through Thursday early morning has slightly shifted south into Central Vermont. Though, there still are no hydrological concerns expected.

KEY MESSAGES

As of 256 PM EDT Wednesday...

1. Widespread rain is expected to continue through tonight with gusty winds from the south and southwest.

2. A drier, fall-like, period is anticipated to end the week as gusty winds persist Thursday, decreasing toward the weekend.

3. A pair of similar cold fronts will likely pass through the region Sunday night and Tuesday night. Breezy periods and some showers are expected with no significant hazards anticipated.

DISCUSSION

As of 256 PM EDT Wednesday...

KEY MESSAGE 1: Our weather system has arrived in portions of northern New York at the time of this discussion, with radar denoting areas of stratiform rain showers across the Adirondacks and St. Lawrence Valley. Isentropic lift along a warm front will continue to spread east this afternoon with light to moderate stratiform rain moving into central and northern Vermont. Stratiform rain will become more broken and scattery by this evening as a strong low level jet of 40- 50kts at 850mb builds in. While most of these stronger winds aloft will not be realized due to concurrent precipitation, gusts between 25-35 MPH will be possible, especially in the favored south-north channeled valleys. For mariners, a Lake Wind Advisory is in effect for Lake Champlain through at least tomorrow morning. The low-level jet will be associated with a small warm sector ahead of a clearing cold front which will help transition showers around sunset to more convective driven showers. Instability will be elevated and not surface based, and likely will be competing with the preceding stable air from todays stratiform rain. That said, a few isolated rumbles of thunder, primarily in the St. Lawrence Valley and Adirondacks will be possible with just under 500J/kg of elevated MLCAPE analyzed currently, and subsequent strong 40-50knots of shear. No severe or strong storms are expected, however.

While the system will be fairly progressive, Pwats in the latest CAMs denote elevated values to around 1.8-2.25 inches areawide with warm cloud depths to 12,000ft agl. As rain turns more showery towards later this afternoon and evening, heavy downpours will be possible. Rain should be beneficial with the recent dry stretch and antecedent dry conditions through this summer, thus no hydrological concerns are anticipated with this system. Precipitation amounts will be highest across the St. Lawrence Valley, higher terrain of the Adirondacks and spine of the Greens, and near the International Border. Recent CAMs have begun to trend some higher rainfall amounts a bit south into central Vermont. While these are likely contaminated with more robust convection that appears unlikely, this trend south has been reflected in the latest QPF forecast, where rainfall amounts along a line from Tupper Lake, NY to eastern Addison have been slightly increased. Some shadowing and less robust convection will help to reduce the magnitude models are suggesting. Blocked flow with low Froude numbers will also likely lead to some orographic enhancement of precipitation totals along the spine of the Greens. Around three-quarters of an inch to and inch of rain will be possible in the aforementioned locations, with a quarter to half an inch most other locations; lower amounts likely in southeastern Vermont, and in portions of the central Champlain Valley due to shadowing from the Adirondacks. Temperatures tonight will be mild in the mid 60s with precipitation and humid conditions ongoing. Rain showers will taper off towards sunrise Thursday morning, with slightly weakening winds.

KEY MESSAGE 2: Our dynamic weather system today will slide east Thursday morning with drier low level conditions mixing in from the north and west. Mid level moisture will linger into Thursday afternoon with some clearing conditions, mainly in the wider valley; the higher terrain will likely remain partly to mostly cloudy tomorrow. Temperatures will be warmer than today with mixing and highs in the mid to upper 70s. Winds will become gusty once again Thursday afternoon with good vertical mixing associated with a lagging low level jet, and drying low levels behind the Wednesday system. Winds will gust between 20-30 MPH, primarily in the channeled north to south valleys of the Vermont and New York. Winds will trend weaker by late Thursday with calmer northwest cold advection by Friday. Depending on how fast winds slacken Thursday evening, and how fast drier low levels will advect, some patchy fog, mainly in the Adirondacks, and perhaps the St. Lawrence Valley, will be possible, as skies will begin to clear overnight from west to east. Vermont will likely lag behind in the clearing department with clouds lingering towards sunrise Friday. Thursday night lows will dip into the 40s for most of the region, outside of areas near Lake Champlain. The Adirondacks have the best opportunity to radiate out with some pocket upper 30s in the typical coldest hollows.

A picture perfect weekend looks to be in store, beginning Friday through Saturday. Temperatures will trend slightly below seasonable levels Friday as northwest flow advects cooler air from Canada. Highs will be in the mid 60s to near 70 with clear skies. A few light breezes near the International Border, and Champlain Valley, to 10-15 MPH could bring a slight bite to the air Friday afternoon. Clear skies will persist Friday night with areawide strong radiational cooling. Temperatures will cool into the low to mid 40s for most locations, and near 50s for areas around Lake Champlain. Raw guidance is hinting at potentially low to mid 30s for areas in the heart of the Adirondacks and within the climatologically favored sheltered valleys of the NEK and Adirondacks. Friday night, as opposed to Thursday night, looks like the better night for patchy valley fog in the favored river valleys of Vermont and northern New York. Saturday looks to be a repeat of Friday with slightly warmer highs into the mid to upper 40s with mostly clear skies. Some breezy channeled winds in the Champlain Valley will be possible Saturday afternoon with winds turning more southerly, hence our warmer temperature advection. Other than some breezy conditions, Saturday looks to be another gorgeous day.

KEY MESSAGE 3: An active pattern from Sunday through Tuesday will be present across the US with a storm track persistently well to our northwest, as low pressure systems move from near Lake Superior into the vicinity of Hudson Bay. Fast moving, mainly westerly mid and upper level flow will help push frontal boundaries through with modest pooling of moisture as strong low level advection and convergence occurs. So rounds of scattered to numerous showers both on Sunday and Tuesday, especially in the afternoon to evening hours, are expected.

For Sunday, it appears a shortwave passing to our south may bring some light rain to our southern areas earlier in the day ahead of the primary event; PoPs have increased as high as 20-29% in southern portions of Vermont by daybreak. Otherwise, no real changes are noted in the rainfall forecast with most of the moderate rainfall chances closer to the International Border. The Tuesday system looks more dynamic with stronger wind fields, including high probabilities of 40 MPH gusts in the vicinity of Lake Champlain out ahead of its cold front. Heavier rainfall potential likewise is elevated for this event, with 1" in 24 hours ending daybreak Wednesday in the 10-20% range fro much of northern New York and much of northern Vermont.

AVIATION /06Z THURSDAY THROUGH MONDAY/

Through 06Z Friday...Current radar is showing rain showers exiting the Champlain Valley and should be thru MPV and EFK in the next 1 to 2 hours. Currently a mix of MVFR/VFR, which should trend toward VFR by 12z this morning as much drier air aloft builds across our taf sites. Winds continue from the south/southwest 5 to 10 knots with localized gusts 10 to 20 knots this morning, but shift to the northwest at similar speeds by noon-time today. Another weak system will produce more clouds and maybe a few showers this evening, with some MVFR cigs possible at EFK and SLK toward sunset.

Outlook...

Friday: VFR. NO SIG WX. Friday Night: VFR. Patchy BR. Saturday: VFR. NO SIG WX. Saturday Night: VFR. Chance SHRA. Sunday: Mainly MVFR, with areas VFR possible. Chance SHRA, Slight chance TSRA. Sunday Night: Mainly VFR, with local IFR possible. Slight chance SHRA. Monday: VFR. NO SIG WX.

MARINE

Southerly wind gusts 15 to 30 knots are expected on Lake Champlain through this evening, weakening back to 10 to 20 knots after midnight tonight. Waves will be around 1 to 3 feet on the southern and northern waters, and 2 to 4 feet on the broad waters through midnight. Wave heights will lower to 1 to 3 feet for the entire Lake after midnight tonight. Winds will become weaker tomorrow morning to 10 to 15 knots, increasing to 15 to 20 knots by tomorrow afternoon.

BTV WATCHES/WARNINGS/ADVISORIES

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