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WHAT HAS CHANGED

As of 132 PM EST Sunday...

A Cold Weather Advisory has been issued for the northern Adirondacks tonight from 1 AM to 8 AM Monday. Much of the area will be below zero tonight. The southward trends in precipitation have stabilized, and there's been little change to snowfall amounts in southern Vermont.

KEY MESSAGES

As of 132 PM EST Sunday...

1. Very cold temperatures expected tonight, with cool drainage basins of the Adirondacks likely to approach -20 F, which elevates the risk of hypothermia. A Cold Weather Advisory is in effect for the northern Adirondacks from 1 AM to 8 AM Monday.

2. Light snow of 1 to 3 inches likely across the southern half of Vermont for Tuesday evening into early Wednesday morning.

3. An active weather pattern is expected to continue, with several chances for precipitation and warmer temperatures.

DISCUSSION

As of 132 PM EST Sunday...

KEY MESSAGE 1: Right now, it's a brilliantly sunny afternoon. Northerly flow is pushing cool, dry air into the region. A tiny strip of reflectivity suggests some shallow moisture may still allow some light snow showers near Jay Peak through evening, but everyone else will be dry. Surface dewpoints are in the single digits and falling below zero. So once a strong 1038mb high shifts overhead later tonight, the light coating of snow this morning will likely help produce very efficient radiational cooling. MOS based products take sheltered hollows of the northern Adirondacks well into the teens below zero, and recent HRRR highlights microclimates sinking below - 20 F. HREF and REFS indicate about a 50-70% chance of -20 F, whether by wind chill or air temperature overnight. It's right at the cusp, but given the recent warmth and since this likely will be the final real dip of the season, a Cold Weather Advisory has been published for the northern Adirondacks. Even outside the Adirondacks, almost the entire region is likely to experience below zero readings today. The extended forecast guidance looks warm. So this is probably the final below zero readings for the season. Bundle up to avoid hypothermia for Monday morning.

KEY MESSAGE 2: A subtle shortwave and very weak surface low will track along a thermal gradient. How much moisture can lift north of the boundary against a 1028-1030mb surface high around James Bay remains in question. The southern range of model scenarios for Tuesday evening still suggest the potential the international border receives little to no snow, while northern range tracks at least push snow all the way to the international border for a couple hours. Up north, the initially dry, clear conditions will promote warming into the upper 30s. Precipitation at the onset may contain some mix of rain in the warmer valleys. Farther south, a warm nose will possibly infiltrate, with forecast soundings at KRUT indicating a shallow 1-1.5 C warm nose moving in after sunset Tuesday, which might suggest some sleet or freezing rain could mix in. At this stage, did add some sleet wording, since the majority of guidance envelope is south, and that everyone else should remain snowy. That said, the combination of weak forcing and fast forward motion means about 1-3" across southern Vermont and less than 1" in northern New York and northern Vermont. Flow will remain zonal and become more southwesterly underneath clearing skies. So any snow around is likely to quickly melt on Wednesday beneath the incoming 40s.

KEY MESSAGE 3: An active weather pattern is expected to continue for the later half of the week into the weekend, although at this time range there continues to be a lot of uncertainty regarding precipitation type and timing, with global deterministic guidance showing a wide range of solutions. The predominant precipitation type during this time period will be rain across the entire forecast area, however some freezing rain will be possible. The most likely period of any freezing rain and mixed precipitation will be on Friday for locations east of the Green Mountains where cold air at the surface is more likely to remain.

In addition to the chances of precipitation chances, temperatures look to trend warmer throughout the week, with high temperatures well above normal by Friday. Current temperature forecast shows high temperatures climbing well into the 40s on Friday, with many locations hitting the 50s on Saturday, much warmer than the climatological high temperatures of low to upper 30s. With these warmer temperatures and some possible rainfall, the potential for any breakup ice jams exists, especially with the extensive ice coverage this winter, so trends will need to be monitored as we get closer.

AVIATION /18Z SUNDAY THROUGH FRIDAY/

Through 18Z Monday...VFR conditions currently prevail across all terminals, and are expected to continue throughout the forecast period. Skies remain mostly clear across the region, with just a few scattered clouds generally above 3500 ft AGL, with these sky conditions expected over the next 24 hours. Northerly winds will generally continue to be a bit breezy over the next few hours, with gusts of 15 to 25 knots possible. Gusts should taper off towards 00Z, with winds trending calm overnight.

Outlook...

Monday Night: VFR. NO SIG WX. Tuesday: VFR. Chance RA, Chance SN. Tuesday Night: Mainly MVFR, with local IFR possible. Chance SN. Wednesday: Mainly VFR, with areas MVFR possible. NO SIG WX. Wednesday Night: Mainly VFR, with local IFR possible. Slight chance RA, Slight chance FZRA. Thursday: Mainly MVFR, with areas IFR possible. Chance RA. Thursday Night: Mainly IFR, with areas MVFR possible. Chance RA, Chance FZRA. Friday: Mainly MVFR, with local IFR possible. Chance RA, Chance FZRA.

EQUIPMENT

The KBTV ASOS has suffered a communications failure. The issue has been diagnosed, but there is currently no estimated time of return to service. The affected communications line is not serviced by the NWS. Terminal Aerodrome Forecasts will continue, but regular observations may not be available.

NOAA Weather Radio station WXM-44, transmitting from Mt. Ascutney, Vermont, on frequency 162.475 MHz is non- operational at this time. NWS technicians have diagnosed the problem, but repairs will likely not be able to occur for quite some time due to circumstances beyond our control. Therefore, the time of return to service is currently unknown. The following NOAA Weather Radio transmitters may be able to provide service during this outage: WWG 50 from Burke Mtn, VT at 162.425 MHz and WNG 546 from Hanover, NH at 162.525 MHz.

The Colchester Reef meteorological station is out of service. This site is not serviced by the NWS and there isn't an estimated return to service at present. Please contact us if you observe winds significantly deviating from the recreational forecast.

BTV WATCHES/WARNINGS/ADVISORIES

VT...None. NY...Cold Weather Advisory from 1 AM to 8 AM EST Monday for NYZ029>031.