textproduct: Burlington

WHAT HAS CHANGED

As of 243 PM EDT Sunday...

No significant changes.

KEY MESSAGES

As of 243 PM EDT Sunday...

1. An approaching cold front will keep temperatures mild through this evening with gusty south winds. It will bring a short period of showers Monday morning, gusty west winds, and chillier conditions through Tuesday.

2. Potential for widespread frost and freeze conditions primarily in eastern portions of Vermont for Wednesday morning. As winds increase out of the south, temperatures moderate back towards normal midweek.

3. Seasonable temperatures and periodic chances of light rain showers are expected for the second half of the week.

DISCUSSION

As of 243 PM EDT Sunday...

KEY MESSAGE 1: Through tonight, the system of interest which has helped produce breezy south winds and mild weather today is a pre-frontal trough, tied to a deepening low pressure system over James Bay, Canada. The trough is very well defined, with a ribbon of glaciated cloud tops and associated rain showers tracking eastward over the easternmost Great Lake this afternoon. These showers have produced only a trace to a hundredth of an inch of rain upstream as precipitation falls into a very dry layer of air. Would expect this type of rainfall to continue as it reaches northern New York later this afternoon before dwindling further as it pushes eastward.

A break in precipitation chances will follow tonight, then towards midnight as the system's cold front approaches the International Border from the west, a vigorous piece of spin aloft will help increase lift and force showers to blossom. These showers will organize along the cold front oriented from southwest to northeast, and track eastward through the morning hours. Showers will primarily fall during the predawn hours in northern New York, and across northern Vermont between about 6 and 9 AM. Following these showers, gusty west winds will mix to the surface with steepening near surface lapse rates.

Widespread gusts reaching the 30 to 40 MPH range will occur downwind of most mountain peaks across Clinton and Essex counties in New York and central and eastern Vermont, with otherwise 25 to 30 MPH gusts common across the region with efficient mixing in a strong cold air advection pattern. The strongest gusts, especially just behind the front when the top of the mixed layer could tap into >40 knot winds near summit layer, may result in some minor impacts as leaves fall in large numbers. However, these winds are unlikely to produce damage or warrant a wind advisory given the expected magnitude of winds.

Temperatures at 850 millibars, a proxy for our highest summit temperatures, will fall below freezing by tomorrow evening as moisture becomes very shallow. Would think some rime ice will be possible given this set up but it cloud ice and therefore snow is unlikely given the expected cloud temperatures and saturation. Continued breezes tomorrow night should prevent frost conditions and limit cooling at lower elevations, but lead to a biting cold for this time of year; wind chills will fall into the 20s for most locations by Tuesday morning.

Due to a reintensification of low pressure as it wraps up into eastern Canada Monday night and stalls out, Tuesday will remain blustery with persistent westerly breezes. While winds again will unlikely be hazardous, there are somewhat mixed signals at this time range as to how strong the gust potential is. The consensus offers a slight weakening trend through the day and peak magnitude at least 5 MPH lighter than on Monday as the low level winds gradually weaken.

KEY MESSAGE 2: It is a tricky low temperature forecast for Wednesday morning as guidance has trended southward and faster with the progression of the next trough, which introduces return flow earlier in the night. In general, it looks like from the Champlain Valley and points west, temperatures are likely to plummet after dark Tuesday and then stabilize or rise by midnight or so. Meanwhile, in much of Vermont the surface should decouple from the milder air aloft, and this should persist such that low temperatures continue falling through the night and drop back to near or below freezing. As such, while widespread frost/freeze is indicated, would not expect any Frost/Freeze products as the growing season from our perspective only remains in the Champlain Valley where it is looking less likely to see frost conditions develop.

Breezy south winds will probably necessitate another Lake Wind Advisory with trends towards a deeper low passing closer to our region on Wednesday, not too dissimilar to today with a warm front pushing through our region with plentiful dry air. Only small chances of rain, and mainly towards the evening and primarily in western portions of northern New York, are being offered. These probabilities increase after sunset, although have noted the ECMWF and its ensembles have about a six hour earlier arrival of showers than the GEFS; timing of showers are fairly uncertain. Most likely high temperatures are in the upper 50s to low 60s, or roughly 10 degrees higher than the early week highs.

KEY MESSAGE 3: Heading into the latter half of the week, high pressure will shift eastward, with southerly flow allowing for more seasonable temperatures. Daytime high temperatures will climb into the upper 50s to mid 60s, with overnight lows in the 30s to mid 40s. Throughout the week, several north stream systems will skirt across the region, allowing for some periods of light rain showers, although nothing looks significant at this time. The best chances for some light rain showers will be further north towards the border, with drier conditions further south. Although there will be several chances for showers, drier conditions look to return towards the weekend as ridging builds back into the region, although trends will need to be monitored as we get closer.

AVIATION /18Z SUNDAY THROUGH FRIDAY/

Through 18Z Monday...VFR conditions currently prevail across the region, with increasing cloud cover expected throughout the afternoon and evening. Some periods of MVFR conditions will be possible overnight with some light rain showers possible, primarily after 06Z through about 15Z or so. The main concern for aviators will be the breezy winds expected throughout the forecast period. Strong southerly winds currently prevail across the region, with winds generally 8 to 15 knots and gusts in excess of 20 knots. A brief lull in winds is expected this evening, before picking back up later in the night. By morning, winds will shift to become more westerly, remaining quite breezy throughout the day. Some pockets of LLWS will be possible, especially across northern New York.

Outlook...

Monday Night: VFR. NO SIG WX. Tuesday: VFR. NO SIG WX. Tuesday Night: VFR. NO SIG WX. Wednesday: VFR. NO SIG WX. Wednesday Night: VFR. Slight chance SHRA. Thursday: VFR. Slight chance SHRA. Thursday Night: Mainly VFR, with local MVFR possible. Slight chance SHRA. Friday: Mainly VFR, with local MVFR possible. Slight chance SHRA.

MARINE

Southerly channeled flow this morning has already resulted in observed sustained winds at Colchester Reef up to 25 knots, and low level flow will remain strong through tonight before finally relaxing around daybreak Monday. This extended period of southerly flow ahead of a cold front will result in a seiche effect on the broad lake, as well. Wave heights in the 2 to 4 foot range are likely during this period on the broad and northern waters, peaking overnight.

BTV WATCHES/WARNINGS/ADVISORIES

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