textproduct: Burlington

WHAT HAS CHANGED

As of 223 AM EST Friday...

Chances for higher terrain light snow over the weekend has increased slightly.

KEY MESSAGES

As of 223 AM EST Friday...

1. Periods of showers will continue through early next week, becoming most widespread later Saturday through Sunday morning. There is an increasing chance of light snow accumulations at higher elevations early Sunday and again Monday as colder air moves into the region.

2. Unsettled weather will persist through much of next week, with a general trend toward cooler weather.

DISCUSSION

As of 223 AM EST Friday...

KEY MESSAGE 1: An active weather pattern will be present through the next several days as shortwave troughs move through our region. The first of these is a slow mover; an upper level low will cross New York and Vermont from Saturday afternoon through Sunday morning, when highest chances of rain generally are on the table.

To start with for today, we are within a dry slot ahead of the first upper level low and a plume of deeper moisture along a developing coastal front. It appears on the northwestern fringe of this plume showers tracking over southeastern New York will likely slide through southern and eastern Vermont, with a batch of showers arriving by noon and exiting soon after. As a wave of low pressure develops over southern New England, somewhat heavier showers will develop; there remains quite a bit of spread with how far west the rain will get. As such, have maintained roughly 40-60% PoPs over eastern Vermont with a more uncertain 0.1 - 0.3" of rain than typical in this time range.

Meanwhile, shower chances will increase Friday afternoon over western portions of northern New York as strong upper level divergence and some near surface convergent flow develops ahead of the aforementioned upper level low. Showers in this area will be light but persistent for much of the weekend, especially towards southern St. Lawrence, Franklin, and Essex counties, and will gradually expand eastward into the south central Vermont. As the upper level low crosses to our south Saturday night, sufficient cooling for a changeover to snow in higher elevations is becoming a bit more likely. Probabilities of at least some snow mixing in with rain, even down to elevations as low as 1000 to 1500 feet if precipitation is heavy enough, are above 20%, especially over northeastern portions of Vermont and the northwestern Adirondacks. In a reasonable high end scenario given a timeframe falling during the nighttime hours, up to a couple inches of wet snow could accumulate in some towns above 1500 feet.

The northward extent of rain showers, and potential for steadier rain particularly in the Saturday afternoon through Sunday morning timeframe, remains uncertain. The latest guidance has trended wetter in northern areas including north central and northwestern Vermont. The potential for a good soaking rain, with rainfall amounts in the range of 0.5"-1", would be tied to a more rapidly deepening surface low pressure area in the Gulf of Maine and an associated deformation zone across western Vermont/northeastern New York that is favored due to terrain enhanced convergence. Precipitation chances generally look at their minimum for the weekend later Sunday as brief ridging builds in before another shortwave trough quickly approaches for Sunday night.

On Monday, the most noteworthy part of the forecast may be related to seasonably gusty northwest winds as another trough swings through with typical cold season advection. Given the recent warm weather, this air mass will be notably chilly with apparent temperatures most likely in the 30s for most of the day in many locations. Unlike over the weekend, guidance is in good agreement on 850 millibar/mountain temperatures falling below freezing (estimated snow levels around 2500-3000 feet), so if there is sufficient moisture for showers, there should be some light snow/flurries, as well.

KEY MESSAGE 2: A broad upper trough will remain fairly entrenched across eastern Canada for mid to late week. As a result, shortwaves will periodically pinwheel around the trough and move across our region, bringing rounds of showers. There's some model consensus that by late week, one of these will develop a closed low at mid/high levels while a surface low develops off the East Coast. This would point toward cooler temperatures (the GFS has highs in the 30s and 40s by Thu/Fri), but there's still plenty of uncertainty given we're a week out. Have stayed with the WPC/NBM forecast for now, which while a bit on the warm side, does still indicate chances for nighttime snow showers over higher elevations, while precipitation should fall as rain during the daylight hours with highs mainly in the 40s.

AVIATION /12Z FRIDAY THROUGH TUESDAY/

Through 12Z Saturday...Other than localized and brief IFR/MVFR in patchy fog this morning, VFR will prevail at all terminals through much of the TAF period. Mid clouds will dominate through the day, gradually lowering this evening and overnight as low pressure approaches from the west. Anticipate widespread MVFR ceilings after 06z or so, but note guidance is indicating IFR conditions are likely late in the period. Have only included at KMSS/KSLK at this time as confidence was highest at those locations. Showers are possible at KMSS after 20z, but have kept mention at PROB30 for now. Light and variable winds generally trend N/NE through the day, except more easterly at KRUT.

Outlook...

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

BTV WATCHES/WARNINGS/ADVISORIES

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