textproduct: Burlington

WHAT HAS CHANGED

As of 242 AM EDT Sunday...

No significant changes have been made.

KEY MESSAGES

As of 242 AM EDT Sunday...

1. Pleasant weather conditions will continue through Monday with comfortable humidity, light winds, and seasonable warmth. A transition towards hot and humid weather will occur on Tuesday, with potentially dangerous heat and/or thunderstorms following on Wednesday.

2. Hot and humid weather expected for late week, with multiple rounds of showers/thunderstorms possible right through the holiday weekend.

DISCUSSION

As of 242 AM EDT Sunday...

KEY MESSAGE 1: Today looks pretty similar to yesterday across our region. Looking at the upper air analysis over the past 24 hours, the air mass aloft has become a touch more moist while near surface conditions have trended a touch warmer and drier. So while high temperatures will almost certainly be a few degrees higher than recent days, dew points will slip a little bit. Have noted greater CAPE in excess of 500 J/kg will be in southern Quebec and our northernmost areas, where slightly more moisture and steeper mid- level lapse rates will be present. A few thunderstorms will likely push southward late in the day, so can't rule out an evening shower or thunderstorm in northern portions of Vermont. Following this activity, high pressure will be in charge through Monday with the next chance of rain beginning Tuesday, when the forecast details become quite challenging.

On Tuesday, a warm front will lift northeastward towards New England associated with a pronounced thermal ridge, which will have built northward early this week over the Midwest and then amble towards the east. The air mass under the ridge is quite humid with dew points in the 70s already as far north as central Ohio as of this hour. There will be a sharp instability and humidity gradient near the warm front, with thunderstorms more likely across western portions of New York Tuesday morning and relatively low chances of showers as one heads eastward during the day. As such, Tuesday may be mainly dry and we have continued to back off PoPs from the six hour Precipitation Potential Index.

Increasingly humid air will advect in from the west such that uncomfortable heat and humidity is possible as early as Tuesday afternoon, especially in northern New York. However, the greater potential for significant heat and humidity appears to start on Wednesday for our region when current maximum heat index values are forecast to top out in the mid 90s or higher nearly areawide below 2000 feet elevation. Note these values are unusually uncertain, as they will be sensitive to the footprint of a possible mesoscale convective system that will arrive from the northwest.

Overlap of very high instability (CAPE values in the 2000-3000 J/kg range) and at least moderate deep layer shear (30 knots) will be possible during the day Wednesday, which would fuel thunderstorms capable of damaging winds and hail. A volatile situation could unfold, but this is dependent on the position of the upper level ridge on Wednesday. The latest guidance remains somewhat split, with one camp of models farther south and west than the consensus idea such that we stay out of both the extreme heat and instability. Please keep abreast of the forecast for midweek, as impactful thunderstorms and/or heat is likely.

KEY MESSAGE 2: Summery conditions expected late this week onward into the holiday weekend as high pressure builds eastward from the Ohio River Valley. The overall trend will be toward hot and humid weather as this high moves in; however, we also look to be active as models indicate the potential for ridge roller-type systems to ride up over the top of the ridge and across our region. Daytime temperatures will rise well into the mid 80s to mid 90s on Thursday, with a few locations in the wider valleys perhaps warming into the upper 90s. Dewpoints will be in the 60s and 70s, so quite uncomfortable, and serving to keep nighttime conditions mild and muggy. As mentioned above, periods of showers/thunderstorms are expected, especially in the afternoons as the heat and humidity will provide ample CAPE for storm development. Any precipitation could keep daytime highs a cooler than currently indicated, but it's hard to pinpoint timing of these systems with any skill this far out. Regardless, it will be dangerously hot and humid, especially Thursday and perhaps Friday, when heat index values could approach 100F. We see a bit of a reprieve heading into the weekend, but still expect daytime temperatures in the 80s to around 90F and muggy overnights. Anyone with outdoor plans next week should stay aware of future forecasts and include both hot weather and thunderstorm safety steps in your plans.

AVIATION /18Z SUNDAY THROUGH FRIDAY/

Through 18Z Monday...High pressure continues to build across our taf sites this afternoon with VFR conditions and light terrain driven winds under 6 knots. Given surface dewpoints are already 4 to 8 degrees lower this afternoon and another day removed from precipitation, the probability of fog at MPV/SLK and EFK is < 20% at this time. Maybe a brief window of 20 to 40 minutes near sunrise of IFR cigs/vis, but otherwise VFR conditions prevail thru 18z Monday. Winds eventually turn to the south by Monday at 4 to 8 knots.

Outlook...

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

CLIMATE

Extreme heat and humidity is possible later this week, especially on Wednesday and Thursday, 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:

June 30: KBTV: 93/2018

July 1: KBTV: 96/2018 KMPV: 92/2018 KPBG: 94/1968 KMSS: 94/2018

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

July 3: KMPV: 91/2002

Record High Minimum Temperatures:

July 1: KBTV: 76/2018 KPBG: 73/1971 KSLK: 69/2018

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...None. NY...None.