textproduct: Burlington

WHAT HAS CHANGED

As of 315 AM EDT Friday... Added mention of small hail and gusty winds with thunderstorms this afternoon, mainly from 11 am to 5 pm.

KEY MESSAGES

As of 315 AM EDT Friday...

1. Widespread showers which moved through the region overnight are coming to an end. Additional showers with embedded thunderstorms are expected this afternoon, some may be strong.

2. Afternoon showers and thunderstorms will be possible both Saturday and Sunday, especially across the higher elevations.

3. A round of showers and thunderstorms may occur late Tuesday into Wednesday, followed by additional chances of thunderstorms later in the week.

4. Hot and humid conditions will likely build into the region, resulting in potential Heat Advisories in early July.

DISCUSSION

As of 315 AM EDT Friday...

KEY MESSAGE 1: A warm front is lifting north across our region and showers spread across the area associated with this feature. Had a pretty widespread wetting rain overnight. The widespread rain will be ending in the next few hours. Additional convective showers with embedded thunderstorms are expected this afternoon as a cold front pushes eastward across the forecast area. Models continue to indicate surface based CAPE around 500-1500 J/kg, and 0-6km bulk shear to around 35 kts. Noticing some clearing upstream on satellite, and this should move into our area this morning helping to develop the surface based instability for some thunderstorms to develop this afternoon. The Storm Prediction Center has Marginal Risk (level 1 of 5) for severe weather covering most of Vermont and a bit of northern New York in the Champlain valley. The main threats from these thunderstorms will be localized damaging winds and some isolated large hail, have added enhanced wording to the forecast. Pwats today 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. Rainfall totals will generally range from two tenths of an inch to an inch of rain. Locally higher amounts may be possible under any thunderstorms.

KEY MESSAGE 2: After soaking rain, some river valley fog is possible Friday night as dewpoints will remain elevated around 60 degrees. Into the weekend, broad upper level troughing will keep shower chances each afternoon. 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 wane 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: The weather details for the middle of next week are becoming a little clearer. The consensus idea is that a ridge roller dives southeastward from southern Canada into northern New York and western Vermont. This timing appears to be either late in the day Tuesday or Tuesday night. The air mass would be quite juiced with regards to heavy rain potential with PWAT surging well over 2 inches, and frequent lightning/loud thunder could occur with ample elevated instability.

The track of this relatively small system certainly could shift a bit west or east relative to the consensus, but overall at least a portion of the region will likely see this system come through. Note the upper level pattern looks fairly stagnant, in which we sit on the northeastern periphery of a heat dome. Potential for strong to severe thunderstorms with heavy rainfall rates will be something to watch through the rest of the week.

KEY MESSAGE 4: Overall, the potential for major heat risk is elevated for Wednesday and Thursday following a seasonably hot day on Tuesday when highs should range through the 80s. The risk is associated with expected greatly increased humidity (50-80% chance of dew points being in the 70s during the daytime hours) and hot temperatures (60- 80% chance in the Champlain and Upper Valley highs will exceed 90), leading to heat index values at least topping out in the mid and upper 90s in our valleys. Confidence in the heat being impactful is higher on Thursday than Wednesday, when the aforementioned ridge roller could temporarily cool/stabilize the air in at least portions of our region, such that temperatures struggle to recover and fail to reach the current forecast (mid 80s to low 90s).

AVIATION /12Z FRIDAY THROUGH TUESDAY/

Through 12Z Saturday...A mix of VFR and MVFR conditions continue amidst a broad area of clouds and pockets of showers. These showers with embedded thunderstorms are currently most widespread in a narrow corridor of northern New York just north of both SLK and PBG and south of MSS. Think that both these sites will see a combination of VCTS and TSRA this morning, but it was hard to feel confident enough to show a direct hit. Beyond the next four hours, the thunderstorm threat which could include gusty winds and small hail will shift more prominently into the Champlain Valley and then central Vermont.

Aside from brief intervals of LIFR early this morning and periods of heavier rain, conditions for much of the next 6 to 12 hours are expected to trend VFR as drier mid-level air moves into the airspace. Light winds will trend westerly this afternoon mainly under 10 knots aside from any thunderstorm wind gusts, then diminish towards 00Z.

Following the showers and thunderstorms, the light winds and clearing skies will support quick development of fog tonight. Have added mention of BR given strong support from model guidance and pattern recognition. Details on sites that are more likely to see FG in relation to footprints of rain this afternoon will need to be reassessed in future TAF packages.

Outlook...

Saturday: Mainly VFR, with local MVFR possible. NO SIG WX. Saturday Night: VFR. Patchy BR. Sunday: VFR. Slight chance SHRA. Sunday Night: VFR. NO SIG WX. Monday: VFR. NO SIG WX. Monday Night: VFR. Slight chance SHRA. Tuesday: VFR. Chance SHRA, Slight chance TSRA.

BTV WATCHES/WARNINGS/ADVISORIES

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