textproduct: Burlington

WHAT HAS CHANGED

As of 322 PM EDT Tuesday...

Chances for scattered showers Thursday afternoon/evening have increased in much of northern New York and northern Vermont.

KEY MESSAGES

As of 322 PM EDT Tuesday...

1. Widespread beneficial rain, along with a chance of thunderstorms this evening, will taper off overnight. Modest rises on area rivers are expected with no significant impacts.

2. Periods of breezy winds are expected over the next couple of days, resulting in apparent temperatures as low as the mid 20s and 30s by late week.

3. A sharp cold front Friday night into Saturday with bring sharply cooler temperatures into the weekend with continued gusty winds and scattered terrain snow showers. Anyone with outdoor plans for the upcoming weekend should monitor the forecast closely.

DISCUSSION

As of 238 PM EDT Tuesday...

KEY MESSAGE 1: A quasi-stationary front has with continuous moisture convergence and low level frontogenesis on its northern flank has brought us quite a bit of welcomed rainfall. As of this writing, uniform amounts just over 1.5" has been observed across northern portions of northern New York and northwestern Vermont, tapering to closer to 1" a bit farther south. Overall, amounts through tonight should range widely as heaviest rainfall will exceed 2" and lightest amounts in southern portions of Vermont will be more like 0.5".

A plume of elevated convection over southeastern Ontario is extending eastward and will be the focus of heavier rain through this evening as it crosses the middle of the forecast area. This is a narrow axis so it is hard to pin down exactly where it will track, but radar trends suggest it will be roughly across the central part of our region. However, large scale lift due to the aforementioned front will keep enhancing rainfall regardless of instability, which should be sufficient for broad coverage of thunderstorms. Most unstable CAPE will likely approach 500 J/kg as very warm and moist air to the south of the boundary continues advecting in ahead of the system's cold front still well to our west. Forecast soundings show the greatest instability may be in the hail CAPE layer, supporting possibilityof small hail but otherwise rumbles of thunder and additional downpours can be expected tonight.

Because of extended long term dry weather, much of today's rain is being absorbed by the soil. However, enough runoff is expected to lead to some small rises in area rivers and streams. Flashier basins such as the Mad River has already seen some response today, but no adverse impacts are expected.

KEY MESSAGE 2: Following a couple days of quiet weather with abundant cloud cover but little if any rain, another certain rainfall event is on the way for Friday. Model agreement is exceptional for a large swath of rain to overspread the region during the morning out ahead of a strengthening low pressure system. A vigorous shortwave will dig over the western Great Lakes, merging with a frontal system over the Midwest to help intensify low pressure to our west. This storm will rapidly move northeastward, passing near or right over our region (most likely along the St. Lawrence Valley) Friday afternoon and crossing into northern Maine Friday evening. The ECMWF extreme forecast index is less excited about rainfall amounts compared to the current event, but still shows a signal towards substantial rainfall. The latest blend of models shows storm totals largely in the 0.6" to 1" range through Friday evening.

Precipitation may be impacted by some our topography. A strong southwesterly low level jet will produce downsloping in the northern Champlain Valley, while our western slopes have a little bit of a boost in rainfall amounts. The near surface winds will also likely be strong out of the south with some similarities to today where ongoing rain will limit mixing, while any breaks in precipitation should support seasonably strong (30-40 MPH) localized gusts. At this time, the potential for hazardous winds aside from recreational interests looks low during this period.

KEY MESSAGE 3: A cold front will sweep through the area Friday night sharply lowering temperatures 10 to 15 degrees from Friday evening to Saturday morning. Temperatures will likely dip below freezing for most if not all locations across the area with only those near Lake Champlain and immediately near the St. Lawrence River staying just above freezing. As temperatures fall, snow levels during the day Saturday will also lower to 500-1000ft agl, with a transition from rain to snow above 1500ft agl, and a rain, wet snow mix, in elevations between 1000-1500ft agl. A few mixed in flurries cannot be ruled out even in the Champlain Valley, though temperatures will be marginal in the mid to upper 30s. Some snowliage appears likely with ensembles denoting nearly 100% chances for purely snowfall in the Adirondacks and Northeast Kingdom. Snowfall impacts will be minimal with road and ground temperatures well above freezing, and with only marginal surface temperatures, snow will likely be of a wet character, with minor accumulation only on the highest elevations and mainly on vegetation only. Most locations will not see any accumulations at this point. Current ensembles depict a 70- 90% chance of 1-2 inches of positive snow depth change in the heart of the Adirondacks and locations in the Northeast Kingdom near the International Border. Additionally, slightly higher amounts to a few inches will be likely on the mountain summits of the central and northern Greens and the Adirondacks, to include Whiteface and Lyon Mountain in NY, and Mount Mansfield, Burke, and Killington in Vermont.

In addition to the precipitation Friday night into Saturday, winds will turn to the northwest with better confidence in stronger winds Saturday due to a lack of precipitation limitations that existed Friday. With an influx of cold northwest air, lapse rates will quickly steepen with strong mixing beginning early Saturday morning. Sustained winds will increase to 20 to 25 MPH, with 55-80% chance for gusts over 40 MPH from the Adirondacks eastward on Saturday. Recreators should also plan for mountain summit gusts as high as 40- 55 MPH, especially in the Adirondacks. While we don't anticipate needing a Wind Advisory (for gusts greater than 46 mph), trends will need to be watched closely going forward. Surface winds will slowly weaken back towards 10 MPH or less Saturday evening with gusts and mountain winds following suit by Sunday.

Rain and snow showers will also taper off Saturday evening as the system pulls away to the northeast. 850 mb temperatures Saturday night will be remarkably cold for this time of year in the -9 to - 11C range Saturday night supporting temperatures in the 20s for most of the area, including the entire Champlain Valley. Pockets of teens will be possible in the coldest hollows of the Adirondacks and Northeast Kingdom as surface temperatures anomalies will be 10 degrees below normal. Temperatures will slowly moderate back towards seasonable normals to start next week with highs Tuesday close to 60F.

AVIATION /18Z TUESDAY THROUGH SUNDAY/

Through 18Z Wednesday...Within this 24 hour TAF period, the first 8 hours will be the most complex. A stationary boundary remains across our area extending from St. Johnsbury in Vermont to Ogdensburg, NY. Widespread rain is ongoing and is expected to become more showery than stratiform rain in the coming hours. Showers will continue through 06Z, before tapering off with some mist potentially lingering at the latest to daybreak tomorrow. There is an outside chance of thunderstorms, particularly at MSS/BTV/SLK/PBG from 01-04Z from west to east. Thunderstorms may lower visibilities briefly towards IFR, with cigs remaining MVFR. In general, cigs will generally be 1000-1500ft agl through the next 6 hours, with high confidence in IFR at MSS through 00Z. Visibilities reductions should remain prevailing 4-6SM, with a few bouncing IFR conditions under heavier showers, mainly at MSS/PBG through 21Z. After 21Z, all terminals outside of RUT should see cigs trend towards IFR with probabilities of IFR at all sites increasing from 30-60% between 00-02Z. SLK/PBG will see trends towards IFR before BTV/MPV/EFK. RUT will likely remain MVFR through the period. IFR ceilings are expected to persist at terminals that get to IFR through at least 14Z, after which cigs will slowly improve towards VFR by the end of the TAF period.

In addition to cig and vis reductions, southerly winds, outside of MSS, will see continued intermittent gusts up to 20 knots or so between showers, though gusts will not be constant. Winds tonight will gradually turn southwest and then west to northwest by daybreak tomorrow, with weakening gusts. Beyond daybreak, northwest winds will turn terrain driven and breezy around 15-20 knots for the terrain terminals.

Outlook...

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

MARINE

Periods of rough lake conditions are anticipated this week into the weekend. Today, a low level jet is moving across the region, bringing periods of rough lake conditions. A Lake Wind Advisory remains in effect for Lake Champlain's broad waters. Southeast winds 20 to 30 knots, with gusts up to 40 knots, will gradually diminish this evening along with waves which are likely to subside from 3 to 5 feet down to closer to 1 foot tonight. As low pressure passes through, winds will sharply lower overnight before turning northerly at a more modest 10 to 15 knots.

Additional periods of concern will be Wednesday night and again Friday into Saturday as a couple of fronts move through the region. Overall, it will not be a pleasant week to venture out on Lake Champlain, especially in smaller watercraft.

CLIMATE

A preliminary daily record rainfall occurred at PBG (Plattsburgh area) today where the total has reached 1.28" as of this writing, exceeding the previous record of 1.03" set in 2022.

Looking ahead to Saturday, daily low maximum temperatures are likely. Current records are indicated below at some climate sites in our region:

Record Low Maximum Temperatures:

October 17: KBTV: 42/1970 KPBG: 44/2015 KSLK: 36/1970

BTV WATCHES/WARNINGS/ADVISORIES

VT...None. NY...None.