textproduct: Burlington

WHAT HAS CHANGED

As of 232 PM EDT Thursday...

The Marginal Risk for Severe Weather for tomorrow has been expanded northward to the International Border in Vermont. Otherwise, no significant changes were made to the forecast at this time.

KEY MESSAGES

As of 232 PM EDT Thursday...

1. Widespread showers will move through the region tonight with chances for thunderstorms by the early afternoon tomorrow. A strong thunderstorm or two may be possible.

2. Daily afternoon chances for showers and thunderstorms, mainly over the Adirondacks and spine of the Greens will be possible into the weekend. Temperatures will begin to steadily climb through the weekend.

3. Heat and humidity will gradually build early next week, however significant heat is not expected at this time. Isolated or scattered showers and thunderstorms will be possible.

DISCUSSION

As of 232 PM EDT Thursday...

KEY MESSAGE 1: A few pop up garden variety showers with an isolated rumble of thunder will continue this afternoon, before waining this evening. Showers may bubble over the Adirondacks and northern spine of the Greens. More widespread rain will overspread the region beyond midnight tonight as an upper low over southern Quebec and associated surface low over the Ohio Valley slide east. A warm front will lift north through the overnight period tonight with a swath of rain, focused over Vermont. The HREF model depicts pockets of heavier rain between 0.25-0.5 inch/hour rates embedded in this swath of rain. The warm front and associated precipitation should lift north of the area by sunrise with some lingering clouds and light showers trailing behind. As the more stratiform rain comes to an end, there should be a break in the precipitation for an hour or two before precipitation activity transitions to more convective. A cold front will begin to sweep into the area from the west with decent SBCAPE to 500-1500J/kg, and 0-6km bulk shear to around 35 kts. The question remains how much clearing there will be between the morning rain the approach of the cold front. As is usual in the North Country, expectations are that there will likely be some convective debris or lingering mid to upper level clouds trailing the morning rain which could limit more widespread clearing and larger instability parameters. However, under more clearing conditions, some shower activity may grow vertical enough to garner thunder activity. Should any storms become entrenched in the environment, conditions may be favorable for a stronger thunderstorm or two. The Storm Prediction Center has expanded the Marginal Risk (level 1 of 5) for severe weather north to the International Border in Vermont and the Champlain Valley for tomorrow. The main threats from these thunderstorms will be localized damaging winds and some isolated large hail. Confidence in damaging winds and large hail is relatively low at this time however. 12Z CAMs have been fairly stable developing thunderstorms between 12-2 PM tomorrow across the Champlain Valley with cells drifting eastward into the central and northern Greens by the mid afternoon. Limitations tomorrow will be 1) the question of clearing post the morning rain; 2) Meager mid level lapse rates aloft which may act as a capping mechanism to deeper convection, and 3) increasing dry air aloft which will may lead to dry air entrainment and less deep moist convection. Showers and any thunderstorm activity looks to move out the area by 7-8 PM tomorrow. Pwats tomorrow will be lower than recent events only to an inch or inch and a quarter which which will be unlikely to cause many flooding concerns. Current rainfall totals will be maximized over southern Vermont and the central Greens where up to an inch will be possible. Elsewhere a quarter to three quarters of an inch will be possible, with lesser amounts in the southern St. Lawrence Valley. Locally higher amounts may be possible under any thunderstorms. Most of the rain from this system will occur tonight into early tomorrow morning.

KEY MESSAGE 2: Behind our system tomorrow, some river valley fog may be possible Friday night as dewpoints will remain elevated around 60 degrees. Into the weekend, broad upper level troughing will keep shower chances present in the afternoons. Diurnally driven terrain showers and embedded isolated thunderstorms will be possible both Saturday and Sunday afternoons, mainly over the Adirondacks and spine of the Greens. Best chances will be on Saturday. These showers may drift briefly into the Champlain Valley or eastern Vermont by the mid to later afternoons, but will likely weaken as they become detached from better convergence and mesoscale forcing. Rainfall with these showers will be light to a few hundreths to a tenth under any more developed showers. Any afternoon shower activity will wain after sunset with the loss of diurnal heating. Temperatures will begin a steady warmup leading into next week. Highs this weekend will rise from the mid to upper 70s Saturday to the upper 70s to low 80s by Sunday. Humidity will also linger with dewpoints in the low 60s, keeping overnight lows relatively warm into the upper 50s to low 60s.

KEY MESSAGE 3: Summertime heat and humidity is expected to build for the beginning of next week, with high pressure centered over the Ohio Valley slowly nudging into the region. High temperatures for Monday look to be in the mid to upper 80s, with light light winds and mostly clear skies under the influence of surface ridging. Beyond Monday the forecast becomes a little more uncertain given the potential for cloud cover and thunderstorm chances, which will influence how warm afternoon high temperatures are able to climb. The current forecast shows a warming trend through the middle of the week, with temperatures warming into the upper 80s and possibly the lower 90s by Wednesday. Despite the uncertainty, the risk of significant heat remains low compared to our south and west with the upcoming weather pattern. Although significant heat is not expected, it is good to remember to stay hydrate and take frequent breaks if working outdoors during warm temperatures. Dewpoints look to increase towards the middle of the week, making it increasingly humid as the week progresses, which will aid in the possibility of thunderstorm development.

AVIATION /00Z FRIDAY THROUGH TUESDAY/

Through 00Z Saturday...Showers are spreading southwest to northeast as evident on radar and surface observations. However, dry surface air has been slow to modify keeping conditions VFR. Therefore, have kept VFR conditions longer with 30% chance of MVFR CIG/VIS 03-06Z for most terminals with more pervasive CIG degradation after 06Z. Some IFR possible for MPV/SLK/EFK, but will depend on how much saturation occurs over the next 3-6 hours. CIGs improve after 12-15Z with more isolated shower chances tomorrow. Best chances of showers/thunderstorms will be 16-21Z as a front sweeps west to east with surface winds turning westerly.

Outlook...

Friday Night: VFR. Slight chance SHRA, Patchy BR. Saturday: VFR. Slight chance SHRA, Slight chance TSRA. Saturday Night: VFR. NO SIG WX. Sunday: VFR. Slight chance SHRA, Slight chance TSRA. Sunday Night: VFR. NO SIG WX. Monday: VFR. NO SIG WX. Monday Night: VFR. NO SIG WX. Tuesday: VFR. Slight chance SHRA, Slight chance TSRA.

BTV WATCHES/WARNINGS/ADVISORIES

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