textproduct: Burlington

WHAT HAS CHANGED

As of 823 AM EDT Tuesday...

The Frost Advisory and Freeze Warning have ended as temperatures have risen above Frost/Freeze thresholds.

KEY MESSAGES

As of 232 AM EDT Tuesday...

1. Cool and frosty this morning with low relative humidity in the afternoons through midday Wednesday.

2. Widespread, beneficial rainfall expected by midday Wednesday and remaining active through the late week.

3. Seasonably warm temperatures are expected for the weekend into early next week, with a few chances for showers possible.

DISCUSSION

As of 232 AM EDT Tuesday...

KEY MESSAGE 1: Temperatures this morning are widely variable. A subtle upper trough has managed to produce a few sprinkles and clouds, especially along the international border. So temperatures range from the upper 20s to mid 40s. We'll trend towards fair weather cumulus during the day with very dry air in place. Northwest flow will keep conditions cool across the region, but abundant sunshine should push temperatures into the 50s to near 60 at least. 850mb dewpoints will be around -5 to -7 C, and should mix to the surface by afternoon. Surface dewpoints will likely be close to yesterday's observed values down to the low to mid 20s. This will result in minimum relative humidity values around 25 to 35 percent this afternoon. Fortunately, winds will be relatively relaxed today, with 5 to 10 mph northwesterly winds and a few gusts around 15 mph.

Overnight, the next approaching system will start to spread some clouds eastwards. So northern New York will observe greater cloud cover for tonight than Vermont. Most of the frost potential will reside in the Northeast Kingdom, which has yet to enter their thermally defined growing season. Still it'll be plenty cool with near freezing temperatures to around 40 F.

KEY MESSAGE 2: An upper trough will close off into an upper low and slowly amble southeastwards. There are some timing differences with the arrival of precipitation. Some have precipitation arriving fairly early in the day Wednesday, while some wait until afternoon. The NBM forecast follows a fairly typical middle road given it is a blend. It may be entirely based on saturation, as the initial wave of precipitation may fall as virga for a time given the dry air mass being replaced. Nevertheless, by late morning and early afternoon, a solid shield of precipitation will translate northeastwards. By evening, our forecast area will be in the warm sector as the stacked system matures. Some instability on the order of 150-350 J/kg will develop over northern New York, and this could produce a narrow strip of convection with a rumble or two of thunder not out of the question, mainly towards St. Lawrence and Franklin Counties of New York.

By nightfall on Wednesday, the surface low loses steam and the loss of daytime heating results in a collapse of the frontal boundary. However, the upper low will continue to intensify. A secondary low will attempt developing near Long Island, but another low will also track near or just east of the 40 N, 70 W benchmark, and the coastal low will probably absorb the secondary low. Upper level southeasterly flow will develop as the upper low intensifies and shifts to our southwest over western New York. So moisture will get advected back over our region, in particular across Vermont during the day Thursday. The coastal low will amble towards the Gulf of Maine as the upper low passes south, and moisture wrapped up in the upper level feature will likely keep precipitation going into Friday. However, another system will approach from the west and act as an escort for this slow moving upper low. Rainfall amounts between Wednesday and Thursday will generally be a needed 0.50- 1.25", locally up to 1.50" possible.

KEY MESSAGE 3: Heading into the weekend, low pressure looks to shift out of the region towards the Canadian Maritimes, with high pressure trying to nose into the region. Some drier weather is expected in comparison to the mid-week system, although some showers will be possible as a shortwave disturbance looks to move through the region. As of now, it looks like precipitation this weekend into early next week will be more showery, with no day looking like a complete washout, but trends will need to be monitored as we get closer as there is still plenty of uncertainty. Temperatures look to be near or above seasonal normals for this time of year, with daytime highs in the 70s and overnight lows in the 40s to mid 50s as we head into next week, with some locations in southern Vermont possibly nearing 80 depending on precipitation and how much warming is able to take place.

AVIATION /12Z TUESDAY THROUGH SATURDAY/

Through 12Z Wednesday...Currently VFR conditions at all terminals, which is expected to persist through the forecast period. West to northwest winds increase during the day and trend light overnight. Dry weather is expected with high clouds expanding east. Rain will arrive from the west towards 12z Wednesday and winds will become southeasterly.

Outlook...

Wednesday: Mainly MVFR, with areas VFR possible. Likely SHRA. Wednesday Night: Mainly MVFR, with local IFR possible. Definite SHRA. Thursday: Mainly MVFR, with local IFR possible. Definite SHRA. Thursday Night: Mainly MVFR, with local IFR possible. Likely SHRA. Friday: MVFR/IFR conditions possible. Chance SHRA. Friday Night: Mainly VFR, with local IFR possible. NO SIG WX. Saturday: Mainly VFR, with areas MVFR possible. Slight chance SHRA.

BTV WATCHES/WARNINGS/ADVISORIES

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