textproduct: Burlington

WHAT HAS CHANGED

As of 315 AM EDT Tuesday...

A winter weather advisory has been issued for parts of northern NY and northwestern VT for up to a tenth of an inch of ice. See WSW for more details.

KEY MESSAGES

As of 315 AM EDT Tuesday...

1. River ice break up is expected to occur over the next few days. Ice jams and associated flooding are possible. Open water flooding is also possible, mainly later Wednesday through Thursday.

2. Unseasonable warmth will persist through Wednesday with near record daily high and low temperatures.

3. A strong low pressure system will create a temperature battleground over the region on Wednesday, resulting in large differences over short distances. Main precipitation hazard will be potential for freezing rain, with greatest likelihood of travel impacts over the northern St. Lawrence Valley Wednesday morning.

4. Much colder weather is expected on Thursday. Difficult travel could result from sharply falling temperatures that could freeze some standing water, along with gusty winds.

5. Unsettled weather expected late this week into this weekend.

DISCUSSION

As of 726 AM EDT Tuesday...

KEY MESSAGE 1: A Flood Watch remains in effect until 2 pm Thursday, for both potential ice jam flooding and open water flooding as well. Anyone who lives, drives, or works along area rivers and streams should remain alert for rapidly changing water levels through mid week.

With continued warm temperatures, some near record levels, additional snowmelt will continue pretty much unabated through the daytime on Thursday. The resultant river rises are pretty much certain to cause river ice to break up, especially since we already saw several ice jams on Sunday. While we can predict the conditions that cause ice jams fairly readily, when or where jams will specifically form and how significant any flooding will be are nearly impossible to pinpoint. That being said, those stretches that currently have ice jams in place, including along the Mad River, the Ausable River, and the Missisquoi River, will be particularly susceptible to additional flooding.

As we head into the middle of the week, these snowmelt-induced river rises will be exacerbated by widespread rain which is expected to occur later today into early Thursday. The rain will quickly turn over to snow from west to east on Thursday as a cold front crosses the region. Snowmelt will likewise end as temperatures drop back below freezing Thursday night. Total liquid precipitation amounts are expected to range from around 0.30 inch in the lower CT River Valley to around 1.6 inches in the St Lawrence valley in northern New York, though some of that may fall as frozen precipitation. Still, the rain combined with up to an additional 2-3 inches of snowmelt will likely be enough to flush out most of the ice from area rivers. However, there are indications that some rivers could rise above flood stage even once cleared of ice due to the combined runoff from rain and snowmelt. Otter Creek and the Ausable, Winooski, Lamoille, and Mad Rivers have the highest chances of exceeding flood stage, though really any river can't be ruled out at this point. Regardless, if open water flooding were to occur, the most likely crest time would be sometime Thursday. And remember, this is only applicable on rivers that completely flush out their ice.

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: Thus far temperatures have remained mild overnight, but as the north wind kicks in we are starting to see some temperatures begin to drop off more. Thawing continues areawide as temperatures remain above freezing until sometime Thursday night when cold air finally moves in and shuts down snowmelt processes. Maximum temperatures today will rise into the 50s and 60s, a 70 degree reading is not out of the question in southern Vermont. Coolest temperatures today will be in northern New York as a front drops into that area and northerly flow picks up. Some record temperatures are possible today, see climate section below.

KEY MESSAGE 3: Have continued to utilize some of the higher resolution model data to really hone in on the temperatures forecast as it will have a big impact on our potential for some freezing rain. Freezing rain accumulations are further complicated with antecedent warmth and daytime heating making it harder for ice to accumulate, particularly light precipitation and after sunrise. Therefore, the highest confidence in impactful freezing rain is in northernmost portions of New York where a winter weather advisory has now been issued for accumulations up to a tenth of an inch.

KEY MESSAGE 4: While there are typical timing differences for the passage of a strong cold front, there appears to be a consensus that temperatures will fall Thursday morning from west to east. Temperatures falling below freezing, especially in higher elevations, will lead to standing water to freeze. Given widespread rain Wednesday night and the potential for quickly falling temperatures, think that gusty westerly winds 30 to 40 MPH will not prevent potential travel concerns for black ice concurrent with the flood concerns discussed in Key Message 1. At this time precipitation, which would be in the form of snow, looks minimal with unblocked flow and a lot of dry air directly behind the front.

KEY MESSAGE 5: After a brief lull in precipitation Thursday night into Friday morning, a weakening clipper system is expected to track up the St. Lawrence Valley and across northern New York and northern Vermont. The best upper level support will remain north of the International Border but it appears a dusting to a few inches of snow will be possible across much of the region friday evening into Saturday morning. Another messy system looks poised to impact the North Country and northern New York late on Sunday. This time, the longwave pattern is expected to become more meridional in response to a strengthening trough over the central US. This should correspond to a messy p-type situation where surface temps could initially be below freezing with very warm air overrunning the stable cold dome at the surface. Both the GFS and ECMWF (deterministic and ensemble runs) show a freezing rain, to rain, to snow transition Sunday night into Monday morning. Timing is likely to change as this trough isn't expected to form until late this week but the clustering in the global guidance definitely gives some confidence in all precipitation types being on the table.

AVIATION /12Z TUESDAY THROUGH SATURDAY/

Through 12Z Wednesday...Fairly quiet TAF period is expected across the region with VFR conditions expected through 21Z before some MVFR to very localized IFR ceilings develop across the region. Some light rain is expected to start moving into northern New York between 00Z and 06Z with increasing chances for freezing rain after 06Z; mainly at KMSS. A noticeable wind shift will occur with a frontal passage this afternoon with winds shifting from the south to north but winds will remain below 10 knots.

Outlook...

Wednesday: Mainly MVFR, with local IFR possible. Definite RA, Definite FZRA. Wednesday Night: Mainly MVFR, with areas IFR possible. Definite RA, Likely SHRA, Slight chance TSRA. Thursday: Mainly VFR, with local MVFR possible. Chance SHRA, Slight chance SHSN. Thursday Night: VFR. NO SIG WX. Friday: VFR. Chance SHSN, Chance SHRA. Friday Night: Mainly MVFR, with areas VFR possible. Chance SHSN. Saturday: Mainly MVFR, with areas VFR possible. Slight chance SHSN.

CLIMATE

Many records are within reach this week. Read below for more details.

Record High Temperatures:

March 10: KBTV: 63/2002 KMPV: 60/2016 KMSS: 58/1992

March 11: KSLK: 60/1977

Record High Minimum Temperatures:

March 10: KBTV: 44/1992 KPBG: 39/1977

Record Precipitation:

March 11: KMSS: 1.69/1992 KSLK: 0.87/1955

EQUIPMENT

NOAA Weather Radio station WXM-44, transmitting from Mt. Ascutney, Vermont, on frequency 162.475 MHz is non-operational at this time. NWS technicians plan to restore its functionality tomorrow, March 10th. The following NOAA Weather Radio transmitters may be able to provide service during the 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...Flood Watch through Thursday afternoon for VTZ001>011-016>021. Winter Weather Advisory from 11 PM this evening to 2 PM EDT Wednesday for VTZ001. NY...Flood Watch through Thursday afternoon for NYZ026>031-034-035- 087. Winter Weather Advisory from 11 PM this evening to 2 PM EDT Wednesday for NYZ026>028-030-031-087.