textproduct: Burlington

WHAT HAS CHANGED

As of 242 AM EDT Sunday...

The Frost Advisory for this morning was canceled due to more extensive cloud cover than expected.

KEY MESSAGES

As of 310 AM EDT Sunday...

1. A substantial warming trend and breezy periods will occur through Tuesday.

2. Showers, with thunderstorms also possible Tuesday afternoon or evening, will be widespread midweek along a slow moving cold front.

3. No major impacts or significant weather expected late week into next weekend, as pattern supports unsettled conditions with below normal temperatures.

DISCUSSION

As of 310 AM EDT Sunday...

KEY MESSAGE 1: After a cloudy start to the day, skies will trend sunny as a shortwave trough pushes to our east. Behind this feature on satellite imagery early this morning is a large area of clear skies, giving confidence in this idea. Associated with the sunshine will be seasonably deep mixing, at least above 750 millibars during the afternoon, to support widespread breezy northwest winds in the 25 to 30 MPH range for gusts in central and eastern Vermont, with perhaps slightly lower values in northern New York and western Vermont where winds at the top of the mixed layer will tend to be a little lighter.

The first in a series of warm fronts will approach the region tonight. There will be a potent low level, west-southwest jet tied to some warm air advection, leading to breezy mountain and lake conditions overnight. These winds combined with the associated cloud cover suggest frost/freeze is unlikely. However, the timing and coverage of rain showers is still somewhat questionable leading to PoPs around 30-50% at this time. Some of the uncertainty is related to the amplitude of another shortwave progged to move eastward through this period. Some guidance dampens its motion such that it passes well to our north and we don't see extra large scale lift to promote more widespread rain. Think at least some light rainfall on the order of 0.01" to 0.1" will occur where the strongest frontogenesis slides through, which is favored as one goes farther north and west. Behind this warm front, deep layer ridging should lead to return of sunshine and again breezy daytime conditions. Winds aloft will diminish during the day to reduce risk of stronger winds mixing to the surface, with perhaps highest gusts above 30 MPH but under 40 MPH, particularly in the northern Adirondacks. High temperatures look remarkably normal for this time of year, ranging from the upper 50s to the mid 60s.

Finally, as we move into Tuesday, we remain on track to see a seasonably warm air mass become established over the northeastern US with southwest flow aloft. This pattern should result in breezy southerly flow, with again nothing particularly strong expected. Given the green up and/or recent wet conditions, fire weather concerns are minimal at this time as only wind gusts look to be at critical levels (relative humidity is unlikely to fall below 30%). Some of the warmest guidance shows a few spots approaching 80 degrees with 925 millibar temperatures well above the 90th climatological percentile; if these temperatures reach 17 Celsius during the afternoon, highs in the mid to upper 70s will be achieved in valley locations. However, precipitation chances will increase during the day; more on this is covered in Key Message 2.

KEY MESSAGE 2: A relatively long period of beneficial rain is increasingly likely from late Tuesday through Wednesday. Some of this rain could be heavy, although there are no signals for excessive rainfall with only modest heat and humidity on the warm side of the thermal boundary. That being said, the latest NBM is consistent with machine learning hazard guidance showing at least modest (chance) of thunderstorm activity in the warm sector of the system in most of Vermont and Adirondack region in New York. Some guidance shows too little instability to result in convection; surface based moisture does look modest and will be a limiting factor. Otherwise, decent ingredients for strong thunderstorms could line up, including good deep layer shear and increasing instability during the mid to late afternoon hours. If CAPE increases into the higher end of the progged 500 to 1000 J/kg range, isolated thunderstorms could be capable of localized wind damage.

Besides this potential hazard, the rain with this front should largely be beneficial. Much of the rainfall is still on track to occur on the cool side of the surface front as it slides through the region Tuesday night through Wednesday. Blended guidance currently shows 0.5" to 1" rainfall, and given the relatively slow movement of the front and the large feed of deep moisture from both the southeastern Pacific and the western Gulf, would expect these totals could trend upward closer to some of the operational deterministic models such as the GFS and ECMWF, which show more of a 0.75" to 1.5" event total for most locations. Again, a limiting factor for a more impactful event looks like limited warmth/low level humidity on the warm side of the boundary to support heavier rainfall rates.

KEY MESSAGE 3: The long wave pattern for late week into next weekend supports mid/upper lvl ridge acrs the western CONUS, while trough prevails over the Great Lakes into the ne CONUS. Still watching multiple embedded s/w's and amount of potential northern and southern stream phasing for eventual track of coastal system Thurs into Friday. Latest 00z trends have been for less phasing and more progressive mid/upper lvl flow, which supports a track of the SNE coast and less potential precip acrs our cwa. However, given mid/upper lvl trof passage with embedded s/w energy and developing northwest flow aloft, wl keep us unsettled and cool for Thurs into the upcoming weekend. Coolest day based on thickness values and 925mb to 850mb thermal profiles looks to be Friday, where temps struggle to reach the mid/upper 30s summits to upper 40s to mid 50s warmest valleys. WPC conts with likely pops in the mtns, which looks reasonable given the upslope flow, caa, and available moisture. General troughiness prevails next weekend with a slow rebound in temps anticipated. However, with cool pocket aloft with mid/upper lvl trof and weak embedded s/w's producing enough lift/instability, feel additional isolated/scattered showers are likely. Temps mostly in the 50s for highs and upper 30s to upper 40s for lows. Given the lack of strong high pres directly overhead and the potential for clouds, the probability of widespread frost in areas where the growing season has started is low attm.

AVIATION /12Z SUNDAY THROUGH THURSDAY/

Through 12Z Monday...Based on web cam at Rutland have placed VCFG for a few hours this morning, with low probability of IFR or lower conditions impacting the airport. Also, some lingering MVFR clouds may impact MPV/EFK this morning at times. Otherwise, expecting VFR clouds with multiple layers of mid/upper level clouds. Winds will increase 5 to 10 knots with localized gusts 15 to 20 knots possible. These winds shift to the south/southwest tonight as a warm front lifts across our taf sites. This boundary will produce a lowering cloud deck toward MVFR by 06z across our northern NY taf sites, along with some areas of light rain. Localized wind share is possible due changing of wind direction and speed with height overnight.

Outlook...

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

BTV WATCHES/WARNINGS/ADVISORIES

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