textproduct: Burlington

WHAT HAS CHANGED

As of 242 PM EDT Thursday...

Rainfall amounts for Saturday have been adjusted upwards with the potential for strong to severe thunderstorms also increasing for Saturday.

KEY MESSAGES

As of 242 PM EDT Thursday...

1. Cooler, drier, and less smokey conditions expected tonight through Saturday morning.

2. Heavy rain and thunderstorms expected Saturday afternoon through Sunday morning.

3. Quiet to start the week, then showers and thunderstorms expected late Tuesday into Wednesday.

DISCUSSION

As of 242 PM EDT Thursday...

KEY MESSAGE 1: A frontal boundary is pushing through Vermont this afternoon bringing a burst of strong winds followed by much cooler air. There was a point where the frontal boundary was producing severe wind gusts but it appears the gust front has pushed ahead of the convective line and is beginning to weaken. Much cooler air in the upper 60s is following the passage of the front with a wind shift to the north. The good news is that the combination of the front and precipitation is scouring out the smoke which is quickly making the air quality across the region much better. The high-res smoke models keep the smoke out of the North Country for the remainder of the week with seasonal temperatures and dry weather expected for Friday. It'll be a nice end of the week before the upcoming rainfall on Saturday.

KEY MESSAGE 2: Moisture will stream northward Friday night into Saturday morning and push our dewpoints back into the mid 60s by Saturday afternoon. Model consensus shows PWAT values surging from 1.2 inches up to 1.8 inches (some individual models up to 2") during this timeframe showing the advection of deep layer moisture into the region. A strong cold front highlighted by good convergence should lead to widespread thunderstorms capable of producing heavy rain. As it stands now, rainfall totals between 1 to 1.5" will be fairly widespread with some localized areas potentially seeing in excess of 2". In addition, some strong to severe thunderstorms will be possible Saturday afternoon and evening but will largely be conditional given moist adiabatic profiles. Wet-microburst type damaging wind gusts will be the main player with high freezing levels keeping the hail threat rather limited. There will be the potential for some isolated flooding but widespread flooding is not anticipated given the 35 knot low level jet. Rainfall is expected to exit the region around sunrise on Sunday morning with drier conditions expected for the second half of the weekend.

KEY MESSAGE 3: High pressure expected to bring pleasant mid-summer conditions to the North Country on Sun/Mon with low humidity levels (dewpoints in the 50s). Return flow develops on Tuesday with valley temperatures climbing back into the mid 80s. Potential next frontal system approaches from the west on Tuesday night/Wednesday, with increasing chances for showers and thunderstorms during the mid-week period.

One concern: given potential strength of mid-atlantic 700-500mb ridge northward to east of Newfoundland...and PW values approaching 2 inches over the Northeast US, will need to monitor the Tuesday/Wednesday system for heavy rainfall potential as it approaches from the Great Lakes region. This will be especially true if the approaching trough from the Great Lakes and associated surface cold front are forced to decelerate while moving across the North Country due to the aforementioned downstream ridging. The 12Z GFS indicates positive 500mb height anomalies of around +2SD over the Canadian maritime processes to south of Greenland, suggesting a blocking pattern becoming established. We will continue to monitor.

AVIATION /18Z THURSDAY THROUGH TUESDAY/

Through 18Z Friday...Primary aviation weather concern is the gusty line of showers and embedded thunderstorms traveling southward along a cold front this afternoon. Surface wind gusts to 46kts were observed at PBG and 41kts at BTV just after 17Z. Anticipate additional gusts near 40kt possible at KSLK/KMPV and KRUT through 19Z before the line of showers and thunderstorms pushes south of our region. Brief MVFR conditions possible, but main hazard will be the thunderstorm wind gusts. Post-frontal winds will remain N-NW at moderate speeds, but skies should trend FEW-SCT050-100 with VFR conditions expected thru the balance of the TAF period once the storms pass. Skies become clear late tonight thru Friday.

Outlook...

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

BTV WATCHES/WARNINGS/ADVISORIES

VT...Air Quality Alert until 11 PM EDT this evening for VTZ005- 007>011-017>021. NY...Air Quality Alert until midnight EDT tonight for NYZ026>031- 034-035-087.