textproduct: Burlington

WHAT HAS CHANGED

As of 229 PM EDT Wednesday...

Forecast rainfall amounts continue to increase, mainly across the eastern slopes of mountains and the spine of the Greens through Thursday night. Totals from early this morning through Thursday night range around 0.50-1.50 inches, with some localized around 2.00 inches. This will still be largely beneficial for the region.

KEY MESSAGES

As of 229 PM EDT Wednesday...

1. Wet weather continues for the second half of the week with beneficial rains expected across the region.

2. Weather will be drying out into the weekend, allowing temperatures to warm above seasonal normals.

3. Notable warm up for the beginning of next week.

DISCUSSION

As of 229 PM EDT Wednesday...

KEY MESSAGE 1: Vertically stacked closed low pressure continues to track across Lake Huron this afternoon. An associated warm frontal boundary approaches northern New York and Vermont from the southwest as well, producing a wave of rainfall that has spread across northern New York and northern Vermont. Some drying within the warm sector will take place this afternoon and evening, resulting in non- zero instability values ahead of another boundary/trough axis bringing more organized convective showers this evening and tonight. High resolution models are projecting Surface CAPE values up to 300- 500 J/kg this afternoon in portions of northern New York, mainly west of the Adirondacks, so a rumble of thunder is not out of the question. The line of showers will move relatively slowly from west to east across the forecast area tonight as winds decrease but remain southerly, keeping temperatures above seasonal normals overnight in the 40s and lower 50s. Additional rainfall amounts tonight will be up to 0.45", highest amounts in the northern Adirondacks. Where rain has fallen across northern New York, patchy fog may develop as winds become lighter tonight.

Upper low pressure will track through New York and the mid-Atlantic states on Thursday as its associated surface low pressure weakens. It should eventually get absorbed into a strengthening surface low pressure moving northeasterly out in the Atlantic Ocean late Thursday. This will result in another round of rain with focus of precipitation in the Adirondacks and eastward while the St. Lawrence Valley misses out on much of the steadier rain (prob of precip 20- 60% in this area). Adirondacks and eastward, rain could be heavy at times Thursday afternoon. A rumble of thunder is also not out of the question in the afternoon, but overall instability looks minimal. We're expecting rain amounts of up to 0.75" over the course of the day, highest amounts in the southern and central Greens, locally one inch possible. Winds on Thursday should remain relatively light out of the north for northern New York and the Champlain Valley, and out of the east for the Greens and east of the Greens. Because of the increased rain and clouds, high temps will remain below seasonal normals in the mid 50s to lower 60s.

Thursday night, mid/upper low is expected to track into the Atlantic Ocean east of New Jersey as the deep surface low in the ocean speeds out to the Canadian maritimes. This will send more moisture through the forecast area as well as light northerly to northeasterly surface flow. Probability of precipitation is around 60-100%, highest on eastern slopes of the mountains with easterly flow aloft. Total rainfall amounts from early this morning through Thursday night are expected to come to around 0.50-1.50 inches, with some localized around 2.00 inches on the favored eastern slopes of mountains as well as the spine of the Greens. With the more northerly surface flow on Thursday night, we'll see temperatures near seasonal averages overnight with lows in the 40s. Where winds are on the lighter side in the valleys of the Adirondacks and eastern Vermont, we could see some patchy fog or mist develop as well.

KEY MESSAGE 2: Friday will be a day of gradual drying as the upper low finally shifts eastward, though showers may linger throughout the day, mainly in higher terrain. The general drying trend will allow temperatures to reach into the 60s for most areas, approaching normal for this time of year. By Friday night, multi-layer ridging will make for a drier night with lows again seasonable in the 40s. Southwesterly flow will begin to increase late Friday night and early Saturday morning, allowing temperatures to climb into the 70s Saturday afternoon. Another trough and weak frontal boundary will approach the region Saturday evening. There remains some uncertainty on the timing and whether precipitation can develop, especially with little in the way of forcing or instability beneath this ridge axis, but a low end chance for some rain is possible in the late afternoon and evening, mainly in the St. Lawrence Valley, Adirondacks, and northern Vermont, up to 35% chance of measurable precip. After a warm day, Saturday night should also be mild with lows in the upper 40s to mid 50s.

KEY MESSAGE 3: Ridging builds into the region from the southwest for the beginning of next week, and surface high pressure becomes centered near Bermuda. This will easily cause the warmest temperatures of the year so far. By Tuesday, temperatures should be in the 80s for most places, with a run at 90 possible for the valleys. NBM probabilities range between 50-75 percent for the lower Connecticut River Valley and between 25-50 percent for the Champlain Valley away from the lake. Surface low pressure is expected to track well to the northwest, so any wobbles in storm track should still keep the region in the warm sector, though the exact extent of the heat remains uncertain. A strong cold front will come through mid- week with potential showers and thunderstorms.

AVIATION /00Z THURSDAY THROUGH MONDAY/

Through 00Z Friday...Showers and thunderstorms are edging into St Lawrence County as of 23Z; it's likely that -TSRA will impact MSS 00-02Z with storms dissipating into showers afterwards while they track eastward. The strongest convection is winding down with loss of diurnal heating, so elevated instability will be the only thing to sustain convection going forward. It seems that a gap is forming in radar coverage and may largely miss SLK through 06Z. Still rain chances will be increasing so light rain/mist is possible through the nocturnal hours at all terminals. Upper low is progged to stall over the region after 12Z with moisture conveyance off the Atlantic. Warm rain processes will take over and allow CIGs to sag 06-12Z for most terminals with IFR becoming increasingly likely. IFR could become more intermittent 12-18Z, but continued rain and upsloping is favored to win out with more widespread IFR probable after 18Z. LLWS will be possible through 12Z mainly from the Champlain Valley eastward as lljet tracks eastward.

Outlook...

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

BTV WATCHES/WARNINGS/ADVISORIES

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