textproduct: Burlington

WHAT HAS CHANGED

As of 217 PM EDT Saturday...

The forecast wind gusts have increased for some areas, and Wind Advisories have been expanded to now include all of Essex County in NY as well as adding Lamoille and Orleans County in Vermont. Otherwise, the forecast remains on track.

KEY MESSAGES

As of 217 PM EDT Saturday...

1. An impactful system will move through tonight, bringing strong winds and widespread rainfall.

2. Showery weather is expected to start the week, with unseasonably cold temperatures expected for Tuesday and minor snow accumulations possible.

3. High pressure will build into the region and bring a stretch of dry weather for mid week. Precipitation chances will increase towards the weekend, with temperatures remaining seasonable for the latter half of the week.

DISCUSSION

As of 217 PM EDT Saturday...

KEY MESSAGE 1: A dynamic system will move through tonight and bring a period of strong winds and rain. The most impactful aspect of the system will be the strong winds, and Wind Advisories have been expanded across northern portions of the CWA to account for the winds. The core of a very strong jet (65-75 knots at the 850 to 900 mb layer) will move over our forecast area tonight. Just how strong winds will get at the surface is always tricky in these situations, due to the development of a strong inversion near and just below the core of the strongest winds aloft. In addition, spotty precipitation ahead of the main front also would locally stabilize the lowest levels, limiting mixing potential. All these factors taken into account, forecast soundings suggesting the strongest winds will be observed over the northern slopes of the Adirondacks, over the northern Champlain Valley, and over portions of the northern Green Mountains.

Looking closer at each of these areas, more specific details follow. For the northern slopes of the northern Adirondacks, the strongest winds of the event are expected in this area. Winds will peak along the NY-Route 11B corridor between 11 PM this evening and 3 AM Sunday morning with localized gusts 55+ MPH. Wouldn't be surprised if the Malone to Altona area sees some briefly higher gusts, though these would be localized. For the Champlain Valley, the slight southeasterly component of the winds will result in strongest gusts over the northwestern part of the valley, where portions of eastern Clinton County along with Grand Isle County will see gusts peak in the 50 to 55 mph range around 2 AM Sunday morning. A third area of peak winds will be focused over the western slopes of the northern Green Mountains, especially over eastern Franklin and eastern Chittenden Counties in Vermont. The overall southeasterly trajectory of the winds favors these areas for localized stronger winds due to downsloping off the spine of the Greens. Higher elevations in these areas (especially furthest north, near the International Border) can expect wind gusts peaking in the 50 to 55 mph range as well. Mountain summits both in the Adirondacks and the northern Greens will see gusts to 70 mph. Elsewhere in the advisory, including the Saint Lawrence Valley, the northern Adirondacks (outside of the northern slopes and highest peaks, where locally stronger winds are expected), the eastern Champlain Valley, and Orleans County VT, wind gusts will peak around 45 to 50 mph in the overnight hours.

We have continued mention of Slight Chance for thunderstorms in areas of northern NY this evening into early tonight based on marginal instability, but thunderstorm potential is limited to the early part of the event. Any thunderstorms that form would result in locally heavier rainfall rates, and the more convective aspect of the rain earlier in the event over the western portions of our northern NY zones translates to a slightly higher QPF forecast for those areas. No severe weather is expected.

While a slight chance of thunderstorms is possible in northern NY, higher elevations of eastern and southern Vermont will be looking at a brief window for the development of patchy freezing rain early tonight. However, this window is brief and temperatures will only lower to freezing in very localized areas. Temperatures will quickly warm back above freezing by 3 or 4 AM, so impacts will be minimal. Even in areas where air temperatures fall below zero, most surfaces won't be cold enough to accumulate any ice. There may be some patchy slick spots on elevated surfaces or bridges however, so use caution if travelling overnight in these areas.

The system's cold front will sweep through as a period of rain that will translate from west to east during the early to late morning hours Sunday. All said and done, storm total QPF amounts will range from 0.1 to 0.6 inches for most areas, which will result in a marginal rise in area rivers but no hydro concerns are expected.

Behind the system, some gusty west winds are expected Sunday, especially over northern NY, though these wont be near as strong as the overnight winds. Temperatures will lower to below normal to start the work week.

KEY MESSAGE 2: A stretch of more winter-like weather is expected to start the week, as much colder air works its way into the region. Upslope snow showers will be possible throughout the day Monday as northwesterly flow develops across the region, although any accumulations would be minor and limited to the higher terrain. Another shortwave looks to move through the region on Tuesday, bringing more widespread chances for snow showers and minor accumulations. Model soundings show steep low level lapse rates, plenty of cold air, and decent moisture in the snow growth zone which will help with any snowfall accumulations. The current forecast continues to show about an inch of accumulation throughout the Adirondacks and in portions of the Green Mountains. Temperatures on Tuesday will be unseasonably cold for early April, with high temperatures only climbing into the upper 20s and 30s for most locations, although some portions of southern Vermont may be able to warm into the 40s. Overnight lows will also be quite cold, dropping into the teens and 20s, nearly 10 degrees below normal.

KEY MESSAGE 3: After a cold and showery start to the week, high pressure looks to build into the region towards the middle of next week, bringing a stretch of drier weather. Temperatures on Wednesday will be more seasonable, with high temperatures warming into 40s to near 50 and overnight lows in the mid 20s and 30s. A gradual warming trend is expected through the end of the week, with temperatures on Thursday and Friday climbing into the 50s and 60s. Chances for precipitation look to increase late in the week towards the weekend as low pressure passes well to our north and a frontal boundary drags across the region. There's still a lot of uncertainty regarding the front and how much precipitation to expect across our region, with a wide range of solutions supported by ensemble and deterministic guidance, so trends will need to be monitored as we get closer.

AVIATION /18Z SATURDAY THROUGH THURSDAY/

Through 18Z Sunday...After the lingering cloud cover this morning, most terminals have improved to VFR conditions, which will continue for a few more hours this afternoon. Conditions are expected to lower to MVFR once again later this evening as showers move across the region. In general ceilings are expected to drop to 1500 to 2500 ft AGL, with some localized IFR ceilings possible, especially at KMPV. Some reductions in visibility will also be possible within any rain showers, generally between 4-6SM. The main threat to aviators during this time period will be gusty winds and widespread LLWS at all terminals. Winds this afternoon are generally northerly, but will become more variable as they become more south/southeasterly this evening. Wind gusts will increase to 25 to 35 knots towards 00Z or so, continuing through the overnight hours before gradually lessening towards the end of the forecast period. LLWS is expected at all terminals for a period overnight as the strong low level jets moves across the region.

Outlook...

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

EQUIPMENT

The Colchester Reef meteorological station is out of service. This site is not serviced by the NWS. An estimated return to service is May 1st. Please contact us if you observe winds significantly deviating from the recreational forecast.

BTV WATCHES/WARNINGS/ADVISORIES

VT...Wind Advisory from 8 PM this evening to 8 AM EDT Sunday for VTZ001>003-005-006-016-017. NY...Wind Advisory from 8 PM this evening to 8 AM EDT Sunday for NYZ026>031-034-035-087.