textproduct: Burlington

WHAT HAS CHANGED

As of 1028 AM EDT Monday...

No significant changes have been made to the forecast at this time.

KEY MESSAGES

As of 222 AM EDT Monday...

1. Mostly dry today and Tuesday with additional frost and fire weather concerns.

2. Widespread rainfall expected Wednesday with unsettled weather continuing into Thursday.

3. Cool, showery conditions to persist into the weekend before warming up.

DISCUSSION

As of 222 AM EDT Monday...

KEY MESSAGE 1: A weak upper level trough will push across the International border this afternoon and may spark a few light rain showers. Antecedent dry conditions will limit rainfall totals to less than 0.05" and will also limit far south these showers will be able to spread. Afternoon dewpoints and RH values are expected to dry significantly as we are able to mix into a very dry layer extending up to 800 mb. This will likely result in RH values in the Champlain and Connecticut River Valleys to drop between 20% and 30% with slightly higher values expected outside of the wider valleys. These low dewpoints will recover slightly overnight tonight but will leave a lot of room for temperatures to drop rapidly. Widespread lows in the mid 20s to mid 30s are expected under clear skies and light winds which will likely support widespread frost across the North Country and northern New York. Additional frost headlines will likely be needed but will be issued with the afternoon issuance of the forecast package. Tuesday will be similarly dry with afternoon RH values in the 25% to 40% range but there will be no chances for any showers as high pressure will become entrenched across the region. Additional frost will be possible again Tuesday night but will likely be tied to eastern Vermont as cloud cover moves in from the west ahead of the next storm system.

KEY MESSAGE 2: A developing upper level trough will begin to displace the synoptic scale ridging Tuesday night which will begin to usher in an unsettled period of weather for the second half of the week. Rainfall is expected to spread from west to east early Wednesday morning with good upper level diffluence helping to maximize precipitation rates with seasonal precipitable water values. Rainfall totals, at this time, are forecast to be highest across southern Vermont and the Adirondacks of New York with a quarter to half of an inch possible with around a tenth of an inch near the International Border. A strengthening low level jet is expected to create some cross-barrier flow which could eat up a significant portion of the rainfall due to downsloping. We will want to keep an eye on this as some guidance does show the potential for 30-45 mph wind gusts on the western slopes of the Greens with southeasterly downslope winds but the exact track of several smaller features will dictate how the winds interact with the Green Mountains. Unsettled conditions will continue through the day on Thursday as the upper level low will be directly overhead. Steep mid-level lapse rates and broad cyclonic flow will be favorable for widespread shower activity with a slight uptick in intensity during the daylight hours.

KEY MESSAGE 3: Model scenarios continue to trend in the direction of an upper trough consolidating into an upper low while a weak surface reflection develops off the coast Thursday night into Friday. Moisture will pinwheel as these become vertically stacked. Dry air will begin to impinge on the western hemisphere of the cyclone. So rain chances will be higher across Vermont. The upper low will delay the onset of warmer temperatures for just a little longer. NBM guidance has slowly shifted towards below normal for the remainder of the week.

However, by late Saturday into Sunday, a fast moving northern stream system will act to displace the upper low. There could be some precipitation moving quickly eastward associated with the zipping vort max, but ensembles remain widely varied on its placement. Nevertheless, an upper ridge will likely settle overhead Sunday night into Monday. Temperatures will nudge upwards well into the 70s by Monday. The NBM indicates roughly a 75% chance of occurrence.

AVIATION /12Z MONDAY THROUGH FRIDAY/

Through 12Z Tuesday...Mainly VFR conditions are expected. West to west-northwest winds will increase 16z-22z to 7 to 11 knots sustained with gusts 16-20 knots possible. A few isolated showers will be possible, mainly over KSLK and KMSS about 17z-22z with PROB30s noted at both. Cloud bases this afternoon will mostly range between 5000-8000 ft agl, and then trending clear overnight. KSLK has some potential for fog, but there is uncertainty with dry air. However, if KSLK does receive some precipitation, then conditions appear relatively favorable. For now, noted 3SM from about 08z-11z.

Outlook...

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

BTV WATCHES/WARNINGS/ADVISORIES

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