textproduct: Burlington

WHAT HAS CHANGED

As of 444 AM EDT Thursday...

Total rainfall amounts for today have increased slightly, around 0.50-1.50" expected. The Wind Advisory remains in effect today 8 AM through 8 PM for all areas except Orange and eastern Windsor counties with no significant changes. Tree limbs could be blown down with isolated to scattered power outages possible.

KEY MESSAGES

As of 444 AM EDT Thursday...

1. Strong gusty southerly wind gusts of 40-55 mph are expected areawide today, and gusts up to 55-65 mph are possible at higher elevations. Due to the unseasonable strength of this storm and the fact that trees have fully developed leaves at this point in the year, tree damage and power outage likelihood is increased.

2. Widespread rain and thunderstorms are anticipated today. Some storms may become strong to severe with embedded damaging winds and moderate to heavy rain.

3. Unsettled and cool weather expected for Monday and Tuesday, followed by brief drying for midweek.

DISCUSSION

As of 444 AM EDT Thursday...

KEY MESSAGE 1: Strong low pressure over the Great Lakes early this morning is expected to track eastward throughout the day today, crossing from Ontario to Quebec sometime this afternoon, then stalling near the mouth of the St. Lawrence River tonight. A west- southwesterly upper level jet streak with winds 100-125 knots will stretch across northern New York and Vermont with correlated 850mb level south-southwesterly winds up to 55-60 knots. Model soundings continue to indicate efficient mixing of wind gusts to the surface of 40-55 mph, as high as 55-65 mph possible at higher elevations. Therefore, a Wind Advisory remains in effect for all four of our New York counties as well as all of our Vermont zones except for Orange and eastern Windsor counties where peak gusts range 40-45 mph for most of the area. There are portions of northern Orange County that could see higher gusts, but areal coverage of this was not enough to add it to the Advisory. Highest winds are anticipated along the northern and northwestern slopes of the Adirondacks and Route 11 corridor this morning (8 AM to 12 PM) in downsloping southerly winds. Winds will also be particularly strong in the northern Champlain Valley later this morning and in the early afternoon (9 AM to 1 PM) due to southerly channeled flow. It will not be a pleasant day to be on Lake Champlain. There may be another round of strong winds, more southwesterly, around 3 PM to 8 PM in northern New York, particularly in the St. Lawrence Valley, along Route 11, and at higher elevations. Impacts from strong winds throughout the day today will be downed tree limbs, isolated to scattered power outages, unsecured objects blowing around, and difficult driving, particularly for high profile vehicles. Seasonally speaking, this type of windstorm is more common in colder months while tree limbs are bare and wind can more easily pass through gaps between branches. However, since this event is occurring in June, trees have developed full leaves, which will result in more tree damage and therefore power outages than with similar wind speeds during the colder months of the year. Main question with the forecast is when precipitation saturates the atmospheric profile, this may inhibit the full potential of wind gust mixing. Wind gusts are forecast to weaken tonight but remain breezy at 25 to 35 mph from the west- southwest, higher on Lake Champlain. Cyclonic flow will keep conditions unsettled through Saturday with widespread northwesterly wind gusts in excess of 20 mph and waves 1 to 3 feet on Lake Champlain.

KEY MESSAGE 2: Strong low pressure over the Great Lakes early this morning is expected to track eastward throughout the day today, crossing from Ontario to Quebec sometime this afternoon, then stalling near the mouth of the St. Lawrence River tonight. This low will drag a warm front through northern New York and Vermont this morning, which has already started kicking off rain across much of the area. The low level jet at 850mb south-southwesterly winds 55-60 knots plus initial southeasterly surface flow will likely contribute to rain shadowing in the Champlain Valley and northern/western slopes of the mountains. The forecast area should see a brief afternoon window of a warm sector between the departure of the warm front and the arrival of a cold front, which would be a key period to build instability. However, the rainy start to the day and warm layer aloft should help keep instability on the lower side overall. One issue that may arise is that shear is just too strong for the minimal CAPE anticipated and storms can't develop enough to become severe. The tricky thing is that we have such strong winds just aloft today (see key message one for winds today) that any thunderstorm that reaches up to 2500 feet could help mix those high winds down to the surface. Strong to severe storms are most likely in southern areas of the forecast area where ideal heating is more likely to be achieved. Highs today should largely be in the upper 60s and 70s, which is seasonable for this time of year. The most likely severe impact from any stronger thunderstorms this afternoon will be damaging wind gusts. There is, however, also a low, conditional potential of a weak tornado in the Connecticut River Valley with modeled effective shear values coming in around 50-55 knots. Heavy rain is also always a potential when we have thunderstorms in the forecast, and projected precipitable water values are as high as 1.50-1.75 inches by the afternoon. Considering the synoptic high winds, we expect any storms to move relatively quickly through the region, limiting flood risk. Also, rainfall rates today should generally remain below an inch per hour. Total precipitation today will be 0.50-1.40 inches, highest in the Greens and eastern Vermont as well as the St. Lawrence Valley in New York. Chances of thunderstorms drop dramatically this evening with perhaps a shower or two lingering into tonight as temperatures stay relatively mild in the upper 40s to lower 60s. Cyclonic flow will keep conditions unsettled through Sunday with terrain focused upslope showers along the Adirondacks and Greens. Temperatures will be near or below average into the weekend with highs in the mid 60s and 70s and lows in the mid 40s and 50s.

KEY MESSAGE 3: Mid/upper lvl trof prevails acrs the Great Lakes into the northeast CONUS for days 4 thru 7 with no significant or hazardous weather expected. Northern and southern stream s/w energy moving thru the mean trof wl remain unphased until reaching eastern Canada on Monday into Tuesday. This should suppress coastal low pres to our south as fast/progressive mid/upper lvl flow prevails. However, with northern stream energy and some lingering mid lvl moisture persisting, showers with a few embedded rumbles of thunder are possible on Monday and Tuesday. A 1024mb high pres system builds into our region by Weds into Thursday with brief drying before our next system arrives. Given the mean trof axis position, the deepest moisture and best instability wl be south of our region for most of next week. Also, the cool temps aloft and northern trajectories, pw values wl remain below 1.0" for most of the week, before climbing higher toward next Friday associated with another full latitude trof. Temps wl remain below normal for most of the upcoming week with highs in the upper 60s to mid 70s and lows mid 40s to mid 50s, except slightly warmer in the Champlain Valley.

AVIATION /12Z THURSDAY THROUGH MONDAY/

Through 12Z Friday...Surface low pressure is approaching the Ottawa Valley, while a warm front is producing a widespread light to moderate rain across our taf sites. This rainfall is causing areas of MVFR cigs/vis with brief periods of IFR conditions. This precip should lift north of our taf sites by 15z, with another round of gusty showers and embedded thunderstorms moving across our taf sites between 15-19z today. This line of storms could produce localized gusts up to 45 knots, along with mvfr conditions and brief ifr possible in the heavier elements. Line quickly shifts eastward by 19z with developing vfr conditions and gusty south to southwest winds at 15 to 35 knots. Areas of low level wind shear and turbulence is likely, especially near terrain and non-aligned runways with the wind direction. Winds slowly decrease this evening with a mix of mvfr/vfr cigs returns.

Outlook...

Friday: Mainly VFR, with local MVFR possible. Chance SHRA, Chance TSRA. Friday Night: Mainly VFR, with areas MVFR possible. Likely SHRA. Saturday: Mainly MVFR, with local IFR possible. Definite SHRA, Chance TSRA. Saturday Night: Mainly VFR, with areas MVFR possible. Chance SHRA. Sunday: Mainly VFR, with areas MVFR possible. Chance SHRA, Chance TSRA. Sunday Night: Mainly VFR, with local MVFR possible. Slight chance SHRA. Monday: VFR. Chance SHRA, Slight chance TSRA.

MARINE

A Lake Wind Advisory is in effect today into tonight. Strong gusty southerly winds of 15-30 knots are expected on Lake Champlain today, and gusts up to 40-50 knots are possible. Thunderstorms may produce additional gusty winds this afternoon, and waves will build to 3-5 feet. Winds remain elevated tonight with west-southwesterly 15-20 knots sustained and gusts 30-40 knots, resulting in waves 1-3 feet. Winds should finally fall below 25 knots early Friday morning, though additional showers and thunderstorms are possible Friday afternoon.

BTV WATCHES/WARNINGS/ADVISORIES

VT...Wind Advisory until 8 PM EDT this evening for VTZ001>009-011- 016>020. NY...Wind Advisory until 8 PM EDT this evening for NYZ026>031-034- 035-087.