textproduct: Burlington

WHAT HAS CHANGED

As of 149 AM EST Sunday...

Unseasonably cold temperatures are expected today through Monday. Widespread snow looking less likely for late Tuesday into Tuesday night due to track of system shifting southward.

KEY MESSAGES

As of 149 AM EST Sunday...

1. Cold start to March with well below normal temperatures today and Monday. Light snow with minimal impacts through this morning.

2. Light rain/snow expected late Tuesday and Tuesday night, especially across southern sections of the forecast area.

3. Active weather with up to three rounds of precipitation Wednesday night through the weekend. Precipitation type will likely be mainly rain with some potential for freezing rain.

DISCUSSION

As of 149 AM EST Sunday...

KEY MESSAGE 1: Although the cold front has pushed well to our south early this morning, temperatures have been slow to fall. However, expect northern areas will be in the lower/mid teens by daybreak, with southern sections in the upper teens to around 20. Cold air advection will persist through the day as winds stay out of the north ahead of advancing high pressure. Light snow is already starting to spread over northern NY in response to the upper trough axis swinging overhead. This precipitation will shift southeastward through the morning hours, focusing mostly from the Adirondacks down into south central VT. Given the very dry airmass and lack of substantial forcing, this morning's snow will remain very light, with most areas seeing little more than flurries or perhaps a dusting of snow. Skies will begin to clear this afternoon into the evening as the high builds into our region. With the aforementioned cold air advection, anticipate daytime highs will be in the teens and 20s, even with afternoon sunshine. Actual 24-hr highs will likely have already occurred just after midnight this morning.

The building high and clearing skies point toward optimal radiational cooling conditions overnight tonight. Expect lows will be below zero just about everywhere, with the Adirondacks and Northeast Kingdom likely dropping into the negative teens. Though winds will be relatively light, wind chills by Monday morning will be in the -10F to -20F range areawide. Monday will likewise be cold, though with plentiful sunshine. Highs will range from the mid teens to the mid 20s. If you plan to be outdoors, please make sure to bundle up and wear appropriate clothing, especially Monday morning.

KEY MESSAGE 2: Latest model suite has trended quite a ways south with our next system. A nearly stationary frontal boundary will set up to our south, with a wave of low pressure to ride along it, moving across PA on Tuesday and then eventually somewhere along or just south of LI and the southern New England coast. This will place Vermont and northern NY on the northern periphery of the precipitation. In particular, the NAM and CMC models show a very sharp gradient, with the northern 2/3 of our region seeing little to no precipitation. The GFS is a little more broadbrushed and further north. Either way, precipitation would move in late Tuesday afternoon and continue through Tuesday evening, then come to a quick end by Wednesday morning as the low rapidly moves off the coast. There will be warmer air attempting to spread northward ahead of the low, but consensus at this time is that this will stay just to our south, with precipitation type to be determined by surface temperature as most of the column will be below freezing. With this in mind, expect we'd see higher elevation snow with a rain/snow mix in the wider valleys at the onset Tuesday afternoon given temperatures in the low to mid 30s. This would turn to all snow Tuesday night. With a fast forward progression and marginal temperatures, overall QPF and snow amounts look fairly minimal at this point. Central/southern VT and into the southern Adirondacks could see a general 1 to 3 inches of snow, perhaps a bit more across the highest summits. Further north, and in the wider valleys, mainly anticipate 2 inches or less, with perhaps just a dusting along the international border (or even nothing if the NAM/CMC hold true).

All that being said, there could be drastic changes if models change course with the storm's track. Confidence in the scenario stated above is somewhat lower than normal until a few more model runs are able to establish this more southward trend.

KEY MESSAGE 3: Late in the week it looks like temperatures aloft will be consistently milder such that snow is rather unlikely regardless of elevation with any precipitation. That being said, we'll need to watch for a cold air damming scenario on Friday as a strong polar high pressure area slides into northern Maine/New Brunswick. While we often stay away from mention of freezing rain this many days out, think the signals are good enough to at least have some indication in the forecast. At this point, the areas that would be most likely to be sub-freezing at the surface in this pattern, such as across the northern St. Lawrence Valley and pockets of eastern Vermont, are given this rain and freezing rain weather type. Depending on the low pressure track, a round of rain forced by a warm front also has some potential to be in the form of freezing rain at the onset, which could impact travel for the Thursday morning commute. Timing of this precipitation is rather uncertain at this time, with large differences among model clusters in the onset of precipitation ranging from Wednesday night to Thursday afternoon.

The signals for a large thaw are fairly weak at this time despite the warmth currently forecast for next weekend (high temperatures in the 50s each day with lows in the 30s). There is a lot of uncertainty in the longevity and magnitude of warm and humid air. Model clusters are split pretty evenly, although the GEPS seems to have a dominant warmer signal that taints the ensemble blend. If the amplitude of the ridging was to trend more definitively larger as shown in the Canadian model and its ensembles, the thawing degree hours that are indicated by the latest temperature forecast (between 300 and 500 from Saturday morning through Sunday evening) would be problematic for breakup ice jams. Given the potential impacts, it's something to keep an eye on, but at this time the risk is relatively low. Related to the uncertainty in the temperatures, the storm track and timing/amounts of rain over the weekend are also rather unclear relative to the Thursday-Friday timeframe.

AVIATION /12Z SUNDAY THROUGH THURSDAY/

Through 12Z Monday...Currently seeing variable flight conditions as an area of light, low density snow shifts to the east/southeast fairly quickly this morning. As snow comes to an end, ceilings and visibilities should quickly come up with VFR conditions largely expected by 16Z at all sites.

Winds have been gustier than expected, particularly at terminals in the Champlain Valley and central Vermont. Based on the continued cooling/cold air advection this morning, expect gusts to persist in the 20 to 25 knot range through at least the next several hours, with gradual diminishing of these northwest winds towards 00Z. Winds will eventually become calm overnight.

Outlook...

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

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...None.