textproduct: Burlington

WHAT HAS CHANGED

As of 340 AM EDT Wednesday...

Have lowered ice amounts for advisory area as temperatures have been slow to fall overnight.

KEY MESSAGES

As of 340 AM EDT Wednesday...

1. The threat for ice jam flooding continues through tonight as mild temperatures keep snowmelt runoff flowing into rivers. Open water flooding will also be possible later today through tomorrow.

2. Cold air will sink southward into our area tonight along the international border in New York, and some freezing rain is possible in that area. We also expect rain with possible thunder today as a dynamic front crosses the area, followed by strong winds on Thursday morning.

3. Seasonable temperatures return by the end of the work week with a chance for accumulating snow Friday into Saturday.

4. An active end to the weekend will set up a more quiet start to next week.

DISCUSSION

As of 340 AM EDT Wednesday...

KEY MESSAGE 1: No significant changes in thinking for the overall flood threat for the next 24-36 hours. Temperatures will fall to near or below freezing early this morning in the northern Champlain and St Lawrence Valleys and northern Adirondacks, which will help slow melt by this morning.

While the bulk of the area will then warm back up into the 50s and 60s this afternoon, the St Lawrence Valley and eastern VT will likely remain in the 30s due to east/northeast winds keeping the cold air wedged in. This too will limit snowmelt during the day. So flows on northern and eastern rivers may recede somewhat, while central/southern waterways will continue to have snowmelt across their basins. In addition, showers will become fairly widespread today into tonight, and this too will add to the runoff. So further rises and ice movement/jams are possible. In fact, wouldn't be surprised to see ice flush out completely of some rivers and smaller streams. For some of those waterways, such as Otter Creek, open water flooding will still be possible even once the ice is gone. Should this occur, peak flows should occur sometime Thursday, depending on the waterway.

Whether it's ice jam flooding or open water flooding, we strongly urge everyone to remain cautious along area waterways. River ice can break up very suddenly, and water can rise rapidly if jams do occur. River ice is very unstable and it is absolutely not safe to approach ice jams or walk on the ice. And even if rivers and streams remain within their banks, the water will be running high and fast and it will be very cold, so please stay well away from river banks.

KEY MESSAGE 2: Things are pretty much on track with the dynamic system bringing a variety of weather to our area today. Some precipitation is currently lifting across our area, and more will follow as low pressure crosses our region this afternoon. Some shallow cold air advection will allow some colder air to seep down from Canada, and there continues to be a threat for some freezing rain with ice accumulation especially in the northern St Lawrence valley. Most areas should be plain rain by about early afternoon, and will also have a chance for some thunder as cold front approaches then crosses our area. Rainfall totals will range from around a quarter of an inch in the Connecticut river valley up to around an inch in the St Lawrence valley. As the cold front pushes through the area tonight into Thursday precipitation will change to snow before ending. Snowfall accumulations will be light, an inch or less. Winds will also pick up with the front as an 850 jet around 75 kts passes overhead. A little uncertain how much wind will mix down if there's ongoing precipitation, but something to keep in mind.

KEY MESSAGE 3: Behind a strong cold front on Thursday, temperatures will return to more seasonable levels for mid March. Highs on Friday will be in the mid to upper 30s, with perhaps near 40 in southern Vermont, as northwest flow will keep things relatively cool throughout the day. Temperatures will not be able to warm up much Friday as clouds will increase into the evening as a clipper system moves across the Great Lakes into our region Friday night. The center of the low is progged to pass directly over the area, which does not bode confidence in a lot of snow. However, a quick few inches will be possible, mainly across the Adirondacks and Greens Friday night into Saturday morning. NBM Probabilities of > 2" of snow are greater than 90% across the Adirondacks, with a 50-60% chances for the rest of northern New York, 30-50% east of the Greens in Vermont, and a 20-30% chance in the northern Champlain Valley. The track of this system is likely to lead to some shadowing effects in the Champlain Valley from the Adirondacks, where little to no snow in the Champlain Valley could be possible. Another wrinkle will be that temperatures will only be marginal for snow, with temperatures during precipitation in the at or just above freezing. Some wet-bulbing may lead to mainly snow, but a mix with rain cannot be ruled out, particularly in the Champlain Valley and southern Vermont. Temperatures remain seasonable into Saturday with highs just above and below the freezing mark, with the northern New York progged to be cooler than locations in Vermont.

KEY MESSAGE 4: A lee trough is expected to develop east of the Rockies this weekend and track east across the Midwest. While the exact track remains uncertain, ensembles depict the system to lift into the region Sunday Night. The question will be how close does the center of the low get to our region which will impact the precipitation type and duration, as well as temperatures. The GEFS depicts a solution closer to the St. Lawrence Valley with a more robust mid latitude cyclone with chances for more precipitation in the overrunning portion of the system, as well as potentially increased winds. This solution would favor cooler temperatures with even the potential for some frozen precipitation. The Euro depicts a more north center over northeastern Ontario, which would lead to less overall precipitation, and favor more of a frontal passage precipitation chance and warmer temperatures. Both solutions, however, depict a strong thermal boundary associated with the system which could lead to the potential for enhanced shower activity and strong winds. NBM probabilities for wind gusts exceeding 30 MPH are in the 50 to 75% range over the Champlain Valley and Adirondacks early Monday morning.

AVIATION /06Z WEDNESDAY THROUGH SUNDAY/

Through 06Z Thursday...As a strong cold front pushes closer to the region, aviation impacts from lowering ceilings and strong LLWS will be the main concerns. Ceilings will lower to areawide MVFR 2000-3000ft agl, with further lowering towards 1000-2000ft agl MVFR by 18Z. MSS may see IFR cigs given the closer proximity to the center of the low and northeast drainage flow. As strong low level jet will move into the area after 10Z today and will strengthen throughout the day. Upper air winds will sharply rise to 55-65kts at 2000ft AGL. Showers associated with the approaching front will be possible through much of the morning with a slight chance for -FZRA close to sunrise at MSS, but for the most part, any shower activity across the region will remain rain. Heavy more steady rain will arrive beyond 18Z. Winds will trend towards the south for most of the day, outside of the St. Lawrence Valley where northeast drainage flow should dominate the morning before also transitioning to the south by this afternoon. Winds could gust up to 25kts at times for most sites this afternoon outside of MSS.

Outlook...

Thursday: Mainly VFR, with local MVFR possible. Windy with gusts to 30 kt. Chance RA, Slight chance SHSN. Thursday Night: VFR. NO SIG WX. Friday: VFR. Chance SN. Friday Night: Mainly VFR, with local MVFR and IFR possible. Likely SN, Definite RA. Saturday: Mainly VFR, with areas MVFR possible. Slight chance SN. Saturday Night: Mainly VFR, with areas MVFR possible. Slight chance SN. Sunday: VFR. Likely RA, Chance SN.

CLIMATE

As of 340 AM EDT Wednesday...

More records will be threatened today.

Record High Temperatures:

March 11: KSLK: 60/1977

Record Precipitation:

March 11: KPBG: 0.50/1964

EQUIPMENT

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...Flood Watch through Thursday afternoon for VTZ001>011-016>021. Winter Weather Advisory until 2 PM EDT this afternoon for VTZ001. NY...Flood Watch through Thursday afternoon for NYZ026>031-034-035- 087. Winter Weather Advisory until 2 PM EDT this afternoon for NYZ026>028-030-031-087.