textproduct: Burlington

WHAT HAS CHANGED

As of 245 AM EDT Friday...

No significant changes have been made at this time. Well above normal temperatures are expected today with a few strong to severe thunderstorms possible this afternoon and evening.

KEY MESSAGES

As of 245 AM EDT Friday...

1. Heat Advisory in effect today with above normal temperatures expected to continue through the weekend. Noticeable cool-down to start next week.

2. Strong to Severe thunderstorms possible this afternoon and evening and again on Sunday.

3. More seasonable temperatures return next week with continued chances for showers and a few thunderstorms.

DISCUSSION

As of 245 AM EDT Friday...

KEY MESSAGE 1: Today will be the hottest day associated with the ongoing period of well above normal temperatures. We will see temperatures climb into the 90s in most, if not all locations. We will include a climate section late in the AFD to highlight the potential record highs today at all of out climate sites. In addition to these warmer temperatures, dewpoints will remain between 68-72 degrees leading to heat indices in the 92-100 degree range. The Heat Advisory remains in effect from noon to 8 PM for the Champlain Valley in Vermont and New York as well as the lower Connecticut River Valley where the highest heat indices are expected. The good new is that "slightly" cooler air will filter in behind a cold front for this weekend. High temperatures on Saturday and Sunday will only be in the 80s with dewpoints down in the 50s instead of the 60s. Another cold front will move through on Sunday which will bring much more seasonal air to the region to start the week with high temperatures in the upper 60s to mid 70s on Monday.

KEY MESSAGE 2: There are two rounds of thunderstorms that we are currently watching with the first event expected to unfold this afternoon. With temperatures in the 90s and dewpoints in the 60s to low 70s, we will have ample instability this afternoon and evening. However, the one thing we are really lacking today is shear. The latest CAMs show between 1500 and 2500 J/kg of CAPE developing this afternoon but deep layer shear will likely be limited to 20-25 knots. The shear should be sufficient help thunderstorms become organized but the fear as that near vertical updrafts could become contaminated by the downdraft as rain falls through the storm. We could see a few supercells develop given the environmental parameters but may not be long-lived unless we see an uptick in deep layer shear. In addition, the forcing will come through very piecemeal with the actual cold front, wind shift, and dewpoint boundary being between 2-4 hours offset. This will likely limit convergence along the leading edge of the cold front and thus limit the potential for widespread strong to severe storms. A few strong to severe storms will still be possible this afternoon and evening, nevertheless, given the copious amount of instability present.

On Sunday, a much stronger cold front is slated to move through during the afternoon hours and bring an abrupt pattern change to more seasonal temperatures. The strong thermal gradient associated with the cold front will yield strong frontogenesis/convergence along the frontal boundary and help interact with a sufficiently unstable air mass with more deep layer shear than is present today. The AI models and machine learning algorithms are actually flagging Sunday to be the more active severe weather day which actually fits the conceptual model of a strong change in air mass equating to stronger thunderstorms. The Storm Prediction Center has a slight risk for day 4 just to our south and it seems reasonable that we will see a northward extension in the coming days if model trends continue to look as favorable as they do today.

KEY MESSAGE 3: Mean longwave troughing is favored to settle over the Great Lakes region with cyclonic flow aloft across the Northeast. The beginning of the week will likely feature transient low level ridging with temperatures in the 70s. Behind the ridge, southwest flow through mid week should allow for some warming with some locations reaching the low 80s. This and subtle embedded trough coupled with cyclonic flow aloft could promote some daily shower chances Tuesday through Thursday. Model consensus points to a more consolidated front potentially moving through late week that could increase shower/thunderstorm chances. Overall, a fairly pleasant week is expected with increasing shower/thunderstorm chances possible for late in the week.

AVIATION /12Z FRIDAY THROUGH TUESDAY/

Through 12Z Saturday...Fog is lifting and scattering the initial hour with MPV keeping an IFR CIG through 13Z. VFR returns for all terminals by 13Z with heat building. A trough will pass through 18- 02Z promoting shower and thunderstorm chances. Some gusts could be strong should a thunderstorm move into the vicinity of a terminal. Showers could also produce IFR or lower VIS with localized heavy showers possible. MVFR CIGs will be possible 00-06Z and some fog possible if skies can clear enough 06-12Z.

Outlook...

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

CLIMATE

Record High Temperatures:

June 12: KBTV: 94/2017 KMPV: 88/2017 KPBG: 94/2017 KMSS: 89/2005 KSLK: 90/1933

Record High Minimum Temperatures:

June 12: KBTV: 71/2017 KPBG: 67/2017 KSLK: 62/1996

BTV WATCHES/WARNINGS/ADVISORIES

VT...Heat Advisory from noon today to 8 PM EDT this evening for VTZ001-002-005-009-011-021. NY...Heat Advisory from noon today to 8 PM EDT this evening for NYZ028-035.