textproduct: Burlington

WHAT HAS CHANGED

As of 259 AM EDT Sunday...

A High Wind Warning for portions of northern NY and a Wind Advisory for St. Lawrence County and the northern Champlain Valley has been issued from 11 PM Sunday until 8 PM Monday.

KEY MESSAGES

As of 259 AM EDT Sunday...

1. A wide spectrum of weather hazards are expected through Tuesday.

2. High Wind Warning and Wind Advisories for portions of northern New York and the northern Champlain Valley. Strong south winds could produce isolated to scattered power outages.

3. Brief abnormal cold behind the early week front will be followed by seasonable weather conditions with a few chances for showers.

DISCUSSION

As of 259 AM EDT Sunday...

KEY MESSAGE 1: A strong 1034mb surface high will shift eastwards over the course of the day. The relatively clear and calm conditions even managed to produce a little freezing fog near Massena. Increasing cloud cover is expected today, as a warm front will nose northwards once high pressure moves offshore. This will bring a period of light snow, mainly over northern New York this afternoon before quickly skirting north. The combination of dry air and weak forcing will result in minimal accumulations. Behind the warm front, winds will begin to accelerate. Winds are expected to be the most significant hazard for this event, but will give the winds their own segment. These south wind gusts will presage a strong cold front. Ahead of that front, a moisture plume off the Atlantic will lift north pre-dawn Monday into the early afternoon. Most of the moisture is confined to the lower levels. The focus will mainly be along the Vermont-New Hampshire border before pivoting back to the east. Temperatures in cold hollows of eastern Vermont will still likely be about 30 degrees, and so localized patchy freezing rain or drizzle is possible. Aloft, the strong inversion overhead will result in some elevated instability. Some high res guidance is evening suggesting some thunder is possible in the St. Lawrence Valley early Monday morning if some convection can fire. The period of freezing rain/drizzle will be short-lived, as the strong southerly flow will push temperatures above freezing around sunrise. Given the localized, conditional nature of the freezing drizzle, no Winter Weather Advisories have been posted for this.

South flow will warm temperatures well into the mid 50s to mid 60s across the region. The combination of increasing temperatures, winds, and dewpoints will start to eat away snow. However, most of the forecast area below 1500 foot elevation has lost its snowpack, and any snow from yesterday doesn't have too much liquid in it. Additionally, the frontal boundary to arrive on Monday evening will be fast moving with cold air quickly filling in to the east. Unlike before, this stint of warm weather isn't going to be prolonged. Liquid amounts for Monday and Monday night are about 0.40-1.00", and some of this will be in the form of snow on the backside of the front. We'll likely see river rises, but it doesn't appear likely that hydro will be a significant concern.

The dynamics of a strong upper jet streak and vort max behind the front, along with the strength of cold air advecting immediately after the cold front, will change precipitation over to snow. This will be most pronounced over northern New York, where 1-5" will be possible. Sections of western Vermont may approach 1", and then better dynamics lift north before snow gets into eastern Vermont. Temperatures may cool 20-30 degrees in 3-4 hours, but if temperatures are in the mid 50s-mid 60s, this means we may not quite get below freezing to meet flash freeze criteria. Winds may also help dry surfaces before black ice can form. Still, we'll monitor this potential as well with precipitation tapering off Tuesday morning.

KEY MESSAGE 2: Upgraded the High Wind Watch to a High Wind Warning, and expanded Wind Advisories along the periphery into St. Lawrence County and the northern Champlain Valleys. Strong pressure gradients will develop as 1030-1033mb surface high pressure remains in the Canadian Maritimes while a 985-988mb surface low moves up the Great Lakes. The strongest winds gusts up to 60 mph will be along the Route 11 corridor across northern slopes of the Adirondacks between 2AM and Noon Monday.

The incoming low-level jet will lift northwards behind today's warm front. Initially, stable conditions may limit the ability for winds to move downslope. However, once the warm front properly clears the region later tonight and surface temperatures begin increasing, we will see winds quickly ramp up. The intensity of the low-level jet seems to be settling towards 65-75 kts, with embedded areas around 80 knots. Although the inversion layer is fairly low to the ground, winds just under 1000 feet will be about 60 knots already. So it will not take much mixing to filter strong winds to the surface. The period of gusts will be somewhat prolonged, with a nearly 6-10 hour span of 50-60 mph gusts along Route 11 in New York. So power outages and down trees could occur.

Over the St. Lawrence Valley and the Champlain Valley, the strength of gusts will likely range more in the 40-50 mph range, perhaps locally to 55 on northwest slopes of the northern Greens. Stronger stability could limit how far downslope winds get down the valley. In spite of this, it appears winds around 1000 ft aloft are still about 55-60 knots out of the south to southeast. The southeasterly direction is more favorable for downslope gusts, and a little less favorable for channeled flow in the northern Champlain Valley. Winds will shift out of the south at some point, and the strong warming should allow mixing to reach the surface later in the day.

For south-central and eastern Vermont, there's somewhat greater uncertainty due to how long the plume of Atlantic moisture lingers before shifting east. The smaller window for drying and southeasterly winds producing even stronger stability will likely limit mixing until winds trend south-southwesterly just ahead of the front. So whether strong gusts in these areas are currently in the 30-40 mph range.

KEY MESSAGE 3: Strong caa will follow close behind the strong cold front early this week. Temperatures will struggle to warm during the day Tuesday with our high temperatures occurring early Tuesday as temperatures fall throughout the day. Temperatures will bottom out Tuesday night in the single digits east of the Greens, the low teens in the Champlain Valley, and low to mid single digits across northern New York. The colder hollows of the Adirondacks may even flirt with zero degrees. The strong caa will be aided by a lingering 850mb jet to 50kts, with a well mixed boundary layer. Surface gusts during the morning and afternoon on Tuesday could gust up to 30-40 MPH, with the strongest winds across the northern St. Lawrence Valley. Apparent temperatures subsequently on Tuesday will be in the single digits for most locations, with some below zero apparent temperatures Tuesday night across northern New York. Temperatures will slowly rebound Wednesday and into the latter half of next week with highs returning to seasonable levels in the upper 30s to low to mid 40s by the end of next week.

Precipitation chances will be hard to come by for most of next week, with the best chances immediately following the cold front earlier in the week. Behind the strong cold front Monday Night, southwest winds with lingering instability to 60-110 J/kg should be enough to sustain some light lake effect snow during the day Tuesday across southern St. Lawrence County and the western Adirondacks in New York. The temperature difference across the lake and air will not be large enough for significant snow amounts, with the forecast favoring only an inch or two in the aforementioned areas. Winds will shift more westerly by Tuesday evening shifting the band south of the region, but as it does so, a dusting downstream in the central Greens cannot be ruled out. High pressure will build in for mid week and give us a few generally dry couple of days, but shower chances increase as a couple shortwaves traverse the area under nearly zonal flow aloft. There's still some uncertainty with these as they do appear rather weak, but better chances appear more likely by the end of next week. Temperatures would support some mountain snow with any shower chances next week, with more rain/snow in the valley with boundary layer temperatures in the mid to upper 30s.

AVIATION /12Z SUNDAY THROUGH THURSDAY/

Through 12Z Monday...Most sites will remain VFR through the majority of this TAF period. Ceilings will remain above 5000ft agl today for all sites with winds areawide trending towards the south ahead of a warm front by 18Z. As the warm front pushes from south to north around 18Z, mainly only MSS should see any precipitation in the form of snow, with MSS seeing a chance at potentially some brief reductions in visibility to MVFR for a few hours. SLK/BTV/PBG could see a brief snow shower with the front, however confidence remains low for any terminal impacts as observing sites upstream in the warm front have yet to report snow, with the leading expectation that the snow will likely be virga when it arrives at the aforementioned sites. Have used a tempo at MSS for this package where confidence is higher for any realized terminal impacts, and PROB30s at BTV/PBG/SLK where lower confidence exists. Behind the warm front, winds will become southeasterly and rapidly increase with gusts by 00Z rising to 15- 20kts, and 30-40kts by 06Z. LLWS will be a concern after 00Z Monday with a LLJ of 65-75kts, leading to LLWS at 2000ft between 50-70kts, strongest at SLK/PBG/EFK, though all sites will see strong LLWS. Flights this evening into tonight should expected low to mid level turbulence. Beyond 06Z, another round of showers will trend ceilings at at most sites to MVFR by 12Z, with chances for rain and freezing rain at MPV between 06-12Z tomorrow early morning.

Outlook...

Monday: MVFR/IFR conditions possible. Strong winds with gusts to 40 kt. Chance RA, Chance SHRA. Monday Night: Mainly MVFR, with local IFR possible. Windy with gusts to 35 kt. Definite SHRA, Chance SHSN. Tuesday: VFR. Windy with gusts to 35 kt. Chance SHSN. Tuesday Night: VFR. NO SIG WX. Wednesday: VFR. NO SIG WX. Wednesday Night: VFR. Slight chance SN. Thursday: Mainly VFR, with local MVFR possible. Chance RA, Slight chance SN.

CLIMATE

A daily record high temperatures and calendar day precipitation total are possible at KMSS (Massena, NY) on March 16th. The present forecast of 66 would be the previous record of 65 set just last year. Consensus forecast for KMSS is about 0.50-0.75", which would beat 0.44" set in 1994.

EQUIPMENT

The Colchester Reef meteorological station is out of service. This site is not serviced by the NWS and there isn't an estimated return to service at present. Please contact us if you observe winds significantly deviating from the recreational forecast.

BTV WATCHES/WARNINGS/ADVISORIES

VT...Wind Advisory from 11 PM this evening to 8 PM EDT Monday for VTZ001-002-005-016>018. NY...Wind Advisory from 11 PM this evening to 8 PM EDT Monday for NYZ026-028-029-035-087. High Wind Warning from 11 PM this evening to 8 PM EDT Monday for NYZ027-030-031-034.