textproduct: Burlington

WHAT HAS CHANGED

As of 207 AM EST Monday...

Confidence in widespread and mixed precipitation types in the Thursday night-Friday timeframe has increased.

KEY MESSAGES

As of 207 AM EST Monday...

1. Very cold temperatures this morning, especially high elevations and much of the Adirondack region where wind chills are below -20 F, which elevates the risk of hypothermia. Slightly less cold later today through Tuesday morning.

2. A minor snowfall for Tuesday evening remains likely for southern portions of the region. Greatest travel impacts will tend to be higher elevation passes.

3. Confidence in widespread precipitation for the end of the week continues to increase, along with the potential for a wintry mix sometime in the Thursday/Friday timeframe.

DISCUSSION

As of 207 AM EST Monday...

KEY MESSAGE 1: So far the forecast for very cold conditions, especially for early March (normal lows are in the teens), is playing out well with ideal radiational cooling conditions and frigid air mass in place. Mesoanalysis shows the center of high pressure actually still to our west over southern Ontario/Eastern Great Lakes region, which has helped maintain some west winds at higher elevations and some more exposed mid-slope locations, which is supporting wind chills more easily reaching Cold Weather Advisory levels. Winds at 925 millibars between about 5 and 10 knots and at 850 millibar level 15 and 20 knots will persist through the morning such that light winds will likely continue, although sunny skies and a shift to light southwest winds will help ease the cold, with even mountain summits possibly getting wind chills back above -20 this afternoon.

High temperatures today will recover from the single digits and teens below zero into the upper teens to mid 20s, and then drop back off towards sunset. Near calm winds should help temperatures fall quickly this evening, but then tonight enough southwesterly flow should develop to somewhat reduce potential for frigid temperatures, especially in the wider valleys. Cloud cover also could disrupt temperatures as upstream in the west- northwest flow some moisture will stream across our region, although coverage of clouds looks fairly sparse and mainly thin. At 6 AM, at the time of the "Blood Moon", sky cover is most likely mainly clear, with greatest chances for some partial cloud cover (unlikely to be opaque) at this time over northeastern Vermont, northern Champlain and northern St. Lawrence Valley.

KEY MESSAGE 2: A remnant frontal boundary over the Ohio Valley will lift northward with a weak wave of low pressure, intensifying as it passes to our south and east Tuesday night. The track and timing of precipitation remains fairly consistent amongst guidance, but with thermal profiles only marginally cold, there is relatively low confidence on precipitation type being mainly snow, particularly in Rutland County where westerly low level flow will produce potentially large variations in snowfall given terrain influences of both the Taconics and Greens. Will note that the latest FV3, which brings in warmer air across northern New York and Vermont with a changeover to rain as precipitation winds down, is more consistent with some other ensemble data in the NBM. Have stayed with mainly snow at this time, but probabilistic data is a little more mixed, especially in southern areas.

Precipitation amounts look modest in the 0.2" - 0.33" with locally higher amounts, and with wet snow character snow to liquid ratios near or a bit below 10:1 will limit snowfall amounts. Although snowfall has trended upward a bit, given short duration and relatively limited frontogenesis and surface convergence, potential for more significant precipitation is low. Also think that with the March sun angle and onset timing of precipitation after temperatures rise above freezing, any snow that begins during the evening commute will have trouble accumulating on primary roads. Related to the expected upslope with west-southwesterly flow and slightly colder temperatures, there is strong consensus on the Green Mountain National Forest seeing the most snowfall from this event, with a swath of 3 to 5 inches favored in this relatively localized area.

KEY MESSAGE 3: Overall, there have been no significant changes in the forecast for the latter half of the week, though confidence that we'll see at least a couple rounds of precipitation has increased somewhat. There's some model consensus that after a mainly dry Wednesday, our next round of precipitation arrives late Thursday and continues into Friday as a wave of low pressure rides along a frontal boundary positioned somewhere across central/southern New England. The concern continues to be precipitation type. Light east flow ahead of this system would keep cold air locked in place east of the Greens and into the northwestern Champlain Valley and northern St Lawrence Valleys. Meanwhile, 850mb southwest flow would spread warm air over the colder air at the surface, resulting in a period of wintry mix, potentially freezing rain in the aforementioned areas. Longer range and coarser resolution models/blends tend to over estimate how quickly warming is able to take place in the sheltered regions, but some of the deterministic guidance is indicating the potential for cold air damming well into Friday, particularly east of the Greens. Indeed, some areas may actually be cold enough to see mostly snow rather than sleet/freezing rain. Have stayed close to the NBM for now and tried to keep precipitation type somewhat simple, but small changes in the low's track and/or amount of warming aloft and at the surface will have significant impacts to precipitation type. Please make sure to follow future forecast updates, especially if you'll be traveling later Thursday through Friday.

Regardless of the above uncertainty, it does still look like we should see much warmer temperatures for the weekend. Another round of precipitation is possible sometime through the weekend as well, though this should be mostly rain. Temperatures are currently expected to reach into the 40s and even 50s during the day, with lows remaining above freezing. Total rainfall doesn't look overly concerning at this point, though that with snowmelt will result in runoff into area rivers. An initial perusal of potential thawing degree hours for Friday through Sunday shows a range of 400 to 800 hours, which could be enough to cause some river ice movement. While widespread river ice breakup isn't expected, we'll continue to monitor trends moving forward.

AVIATION /06Z MONDAY THROUGH FRIDAY/

Through 06Z Tuesday...VFR conditions will prevail through the entire TAF period under high pressure and clear to mostly clear skies. Winds light and variable through the period, as well, generally 3-7 kt or less.

Outlook...

Tuesday: Mainly VFR, with local MVFR possible. Chance SN. Tuesday Night: Mainly MVFR, with local VFR possible. Chance SN. Wednesday: Mainly VFR, with local MVFR possible. NO SIG WX. Wednesday Night: Mainly VFR, with local IFR possible. Slight chance RA, Slight chance FZRA. Thursday: Mainly MVFR, with local IFR possible. Chance RA. Thursday Night: Mainly IFR, with areas MVFR possible. Likely RA, Likely 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 until 8 AM EST this morning for NYZ029>031.