textproduct: Burlington

WHAT HAS CHANGED

As of 334 PM EDT Monday...

A Flood Watch was issued for all of northern New York and northern/central Vermont through Thursday afternoon. The Wind Advisory that was in effect in the St. Lawrence Valley has been canceled.

KEY MESSAGES

As of 334 PM EDT Monday...

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 tomorrow 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 differences. 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. Seasonable temperatures are expected for the later half of this week into the weekend, with an active weather pattern continuing to bring several chances of precipitation to the region.

DISCUSSION

As of 254 PM EDT Monday...

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

We've seen a bit of a lull in river conditions so far today as runoff slowed due to colder temperatures and less snowmelt overnight. However, with temperatures well into the 50s and even close to 60F this afternoon, this downward trend will soon reverse, with river levels starting to rise again by this evening. We'll remain mild overnight and will warm back into the 50s and 60s on Tuesday, so snowmelt will continue pretty much unabated over the next 24-36 hours. 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 Wednesday into 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. Total liquid precipitation amounts are expected to range from around 0.50 inch in the lower CT River Valley to around 1.25 inches across much of northern New York, though some of that may well 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: It has been a warm and breezy day as expected with temperatures in the upper 50s to mid 60s this afternoon. However, persistent, thicker high clouds in northern New York and northern portions of Vermont have limited insolation/sunshine. The reduced solar radiation may have contributed to slightly less steep surface lapse rates and potential for higher magnitude gusts, and the Wind Advisory that had been in effect was canceled. The gusty south/southwest winds have still helped lower humidity to the point that if we had dry fuels, fire weather would be a concern as relative humidities are 20 to 30% this afternoon in much of the region.

Given how dry the air is, where winds die off temperatures tonight will fall quite a bit, with sub-freezing values possible in sheltered portions of the Adirondacks and eastern Vermont. Otherwise, continued thawing will persist and with clear skies, temperatures will quickly rise tomorrow back into the 50s and 60s by afternoon. Still expecting winds to shift fairly abruptly to northerly as a cold front slips southward during the day; north of the front we'll see temperature stabilize or even fall during the afternoon. There is some uncertainty on the timing/location of this wind shift such that high temperatures are a bit tricky. Think southern portions of Vermont will easily be about as warm as today, while most other areas could be up to several degrees cooler. That being said, record high temperatures for the day at long term observing sites are several degrees lower than they were today, so record highs will be possible (see Climate section for details).

KEY MESSAGE 3: Of primary concern for winter weather on Wednesday will be strong cold air drainage from southern Canada, with a very cold, shallow air mass being drawn down our valleys tomorrow night. Think the ensemble guidance that goes into our default model blend is a little misleading at this time with regards to temperatures, so we have heavily used some of the more skillful, higher resolution/mesoscale data for the forecast at this time. This results in much lower temperatures in some areas, especially valleys in northern New York, the northern Champlain Valley, and east of the Green Mountains. Those eastern areas in particular are much colder during the day as it will be hard to dislodge the cold air with heavily inverted temperatures expected. Freezing rain accumulations are 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.

Among the 12Z GEFS, the storm track looks pretty well clustered near or just north of the International Border Wednesday night, which was a shift northward from the 00Z guidance. By comparison, the 12Z ENS members shifted less but trended deeper with low pressure. A track farther north/west will tend to limit potential for widespread heavy rain, and erode the shallow cold air a bit faster in northern New York, but a stronger system could help maintain the cold air damming/northeasterly flow.

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 tumble 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: Seasonable temperatures and an active weather pattern are expected across the region late this week into the weekend. After the warmth earlier in the week, high temperatures for Friday into the weekend will be in the upper 30s and low 40s, which is more typical for this time of year. A clipper system looks to bring widespread light snowfall late Friday into Saturday, especially across the Adirondacks, with overnight low temperatures dropping into the teens and 20s areawide. After the clipper system exits on Saturday, another system looks to impact the region on Sunday into the beginning of next week, with the associated warm front lifting across the reign on Sunday and then the trailing cold front pushing across late Sunday into Monday. At this time period, there is still plenty of uncertainty regarding this system, especially in regards to precipitation type, with more details expected as we get closer.

AVIATION /18Z MONDAY THROUGH SATURDAY/

Through 18Z Tuesday...VFR conditions are expected across all terminals over the next 24 hours, with winds being the primary concern for aviation. Some high clouds remain across portions of the region, with clear skies elsewhere. Breezy south to southwesterly winds will continue this afternoon into the evening hours, with sustained winds of 10 to 20 knots and gusts up to or even in excess of 30 knots, especially at KMSS. Gusts are expected to diminish this evening, between 22Z and 00Z for most terminals, with winds trending light and terrain driven overnight. LLWS will persist across most terminals for a period of time tonight, especially at KSLK and KRUT.

Outlook...

Tuesday Night: Mainly MVFR, with areas VFR possible. Chance RA, Likely FZRA. Wednesday: Mainly MVFR, with areas IFR possible. Definite RA, Definite FZRA. Wednesday Night: Mainly MVFR, with areas IFR possible. Definite RA. Thursday: Mainly VFR, with areas MVFR possible. Chance SN, Chance RA. Thursday Night: VFR. Slight chance SN. Friday: Mainly VFR, with local MVFR possible. Chance SN. Friday Night: Mainly VFR, with areas MVFR and IFR possible. Likely SN, Likely RA. Saturday: Mainly MVFR, with areas VFR possible. Slight chance SN.

CLIMATE

Record High Maximum temperatures are possible Tuesday. As of now, this is favored at Montpelier (MPV) where the current forecast matches the daily record:

MPV: 60/2016

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. NY...Flood Watch through Thursday afternoon for NYZ026>031-034-035- 087.