textproduct: Burlington

WHAT HAS CHANGED

As of 237 AM EDT Thursday...

No significant changes were made to the previous forecast.

KEY MESSAGES

As of 237 AM EDT Thursday...

1. A significant heat wave will continue across much of the Northeast with unusually hot and humid conditions causing a sharp increase in the risk for heat related illnesses.

2. The chances for thunderstorms and showers will continue into this weekend with potential for a few strong to severe storms.

3. Warm weather will linger into next week, along with daily chances of showers and thunderstorms.

DISCUSSION

As of 237 AM EDT Thursday...

KEY MESSAGE 1: The oppressive dome of heat and high pressure will continue to be the primary influence on our weather into this weekend. 925mb in the mid/upper 20s (C) will continue to point to widespread high temperatures in the 90s while dew points remain in the upper 60s and low/mid 70s. This will push heat indices into the upper 90s to around 106. The combination of heat and humidity remains dangerous for most of the population, but especially for those without adequate cooling or to those working outdoors. Nocturnal temperatures will not provide much relief through Friday as we swelter under the northern periphery of large high pressure centered over the Mid Atlantic states and portions of the Ohio River Valley. Temperatures begin to trend cooler Friday, but heat is cumulative and impacts may linger despite relatively cooler conditions as heat index values generally range in the 90s. The first true break in heat will be on Independence Day as drier air begins to move into the region begin a front sweeping out of Canada. Widespread dew points in the 50s with temperatures in the upper 70s to mid 80s Sunday will feel quite pleasant after this bout of excessive heat.

KEY MESSAGE 2: Thunderstorm and shower chances will continue through Saturday. With the region on the northern periphery of the ridge, we've been susceptible to troughs roller along this northern extension. Heat and humidity have been fueling bouts of stronger thunderstorms. After some morning showers and isolated thunderstorms, a subtle shift in the ridge axis may shunt these waves slightly farther north. the result will be for southern Vermont/Adirondacks to be potentially clearer of convection today. Still, isolated showers/thunderstorms cannot be completely ruled out of these locations, but focus for scattered convection will shift northward towards the Canadian border this afternoon and evening. A caveat would be if outflow/cold-pool interactions develop into a line, then some more organized elements could occur just about anywhere. While some supporting dynamics will be less than the last couple of days (EML layer departing/modifying) we remain under a marginal risk for severe thunderstorms. This is mostly rooted in our unusually high CAPE environment coupled with the conditional threat of areas of forcing moving through the region. Model placement of the CAPE gradient that would impact our area remains west of the St Lawrence Valley and will be the likely source for convective initiation again this afternoon.

For Friday, the axis of highest instability is favored to shift southward but remain in the vicinity of the St Lawrence Valley to far southern Vermont; SPC continues a marginal risk for severe storms along and south of this line with more general convection northward. This tracks well given the expected decreasing temperatures/dewpoints. By Saturday, a drier variety front is expected to drop south out of Canada and through the region. Forcing increases, but PWATs drop sharply. Still, some isolated to scattered storms will be possible given lower level forcing. The area of storm chances may shift south quickly by the early afternoon. Some CAMs are pointing to lower chances of showers Saturday while global and blended guidance leans to keeping chances into the afternoon.

KEY MESSAGE 3: Heading into next week, warm weather looks to linger, although temperatures and heat indices will not be as warm as the week above. Deterministic model guidance diverges sharply for next week, increasing uncertainty for the long range forecast. At this time, high temperatures are most likely to range in the 80s and lower 90s with chances for showers and thunderstorms each afternoon through midweek. Overnight lows look to remain on the warmer side, generally in the 60s, which may lead to accumulating heat impacts. Although it looks like it won't be quite as hot as earlier in the week, it is important to remember to drink water and take frequent breaks if working outside, especially with such an extended period of warmer weather.

AVIATION /12Z THURSDAY THROUGH MONDAY/

Through 12Z Friday...VFR conditions VFR conditions are expected to prevail throughout most of the forecast period. Additional chances for showers and thunderstorms will be possible throughout the forecast period, with little confidence in areal coverage and intensity. Winds will become more south to southwesterly throughout the day, trending light and variable overnight. Towards the very end of the forecast period some guidance suggests the potential for fog development, but given the low confidence, future forecasts will have to take a closer look.

Outlook...

Friday: VFR. Isolated SHRA, Isolated TSRA. Friday Night: VFR. Isolated SHRA. Independence Day: VFR. Scattered SHRA, Scattered TSRA. Saturday Night: VFR. NO SIG WX. Sunday: VFR. Slight chance SHRA. Sunday Night: VFR. Chance SHRA. Monday: VFR. Chance SHRA, Slight chance TSRA.

CLIMATE

Extreme heat and humidity will affect the region for the latter half of the week, which could lead to some daily records. Below are the current daily high and low temperature records in jeopardy at our area climate sites.

Record High Temperatures:

July 2: KBTV: 97/2018 KMPV: 90/2018 KMSS: 94/2018

July 3: KMPV: 91/2002

Record High Minimum Temperatures:

July 2: KPBG: 77/2002 KSLK: 68/2002

July 3: KBTV: 76/1911 KPBG: 73/2002

July 4: KPBG: 71/1973 KSLK: 67/1952

BTV WATCHES/WARNINGS/ADVISORIES

VT...Heat Advisory until 7 PM EDT Friday for VTZ003-004-006>008-010- 016>020. Extreme Heat Warning until 7 PM EDT Friday for VTZ001-002-005- 009-011-021. NY...Heat Advisory until 7 PM EDT Friday for NYZ026-027-029>031-034- 087. Extreme Heat Warning until 7 PM EDT Friday for NYZ028-035.