textproduct: Burlington

WHAT HAS CHANGED

As of 147 PM EDT Thursday...

The Freezing Warning has been expanded across the rest of the Northeast Kingdom and portions of north-central Vermont.

KEY MESSAGES

As of 147 PM EDT Thursday...

1. Widespread frost and freeze expected tonight, with Saranac Lake and Montpelier's climate sites within reach of record lows, and then temperatures will gradually moderate through the remainder of the week.

2. Rain expected Saturday night into Sunday.

3. Somewhat unsettled for Memorial Day and into the middle of the work week, with seasonable temperatures expected. Drying trend in the long term looking likely.

DISCUSSION

As of 147 PM EDT Thursday...

KEY MESSAGE 1: Cool, dry weather is present over the region as a strong surface high slides across the northern latitudes. It'll be directly overhead tonight. Although there are some high clouds present, it appears likely to thin out, and they may not have too much of an impact on radiational cooling. The latest MET guidance has 22 for SLK and 29 for MPV. If we meet or exceed this, we could experience daily record lows. Blended guidance like the NBM can really struggle on these kind of nights and generously utilized MOS and high res guidance capable of capturing some of the cool drainage in drainage basins. Freeze warnings have been expanded in central Vermont given proximity to the freezing point. For now, the only hard freeze potential seems to be localized to some of the coldest locations, like the perennial cold possible at the Adirondack Airport/SLK. The only area without any frost headlines remains the northern Champlain Valley, which appears to hover near or over 36F . There could be some frost within some of the colder pockets within the northern Champlain Valley. NBM probabilities less than 36 F suggest a 15% chance or less away from Lake Champlain and a 5% chance near Lake Champlain, but if you don't want to even risk the low end possibility, then it never hurts to cover or bring in tender plants.

Friday will observe some moderation, and then with the slowing of precipitation and clouds Saturday evening into Sunday, we will have the potential for another cold night on Friday into Saturday, but with mid 30s to mid 40s allowing only localized frost. Then temperatures will climb towards seasonal norms with mid 60s to lower 70s on Saturday afternoon. Dry weather is expected with nil PoPs and low RHs. Today will be the windiest day before high pressure allows for only light winds.

KEY MESSAGE 2: Surface high pressure off the Canadian maritimes will be around 1035mb, which is quite strong for this point of the year. Forecast soundings show such dry air in place that precipitation will really struggle to lift northeast. Some have 850-500mb dewpoints at or below -20 C across that entire layer. We may see returns on the radar in the mid to upper levels, but it will all be virga. Increasingly confluent flow and an increasingly strong LLJ will begin to increase moisture fluxes and mix out the dry air in place. The degree to which we see rainfall across the region varies between a trace or a few hundredth up to a half inch. The brief tap of moisture is rather thin, and it will be relatively progressive. So the alignment of favorable moisture with dynamical support may be relatively short-lived. Ensemble guidance is at least somewhat optimistic, and despite the NAM12's impressive 70kt 850mb jet, it shows little terrain shadowing. There will be some orographic influence to rainfall, but it may not be everything given the efficiency of moisture transport and forcing. There are some timing differences that remain amongst various model scenarios as well. A cool, cloudy, and breezy Sunday with a 3-9 hour block of stratiform rainfall is expected. The general consensus for amounts is about a tenth to a third inch.

KEY MESSAGE 3: High pressure will attempt to nudge into the region from the west to start off next week, but a lingering coastal system over southern New England could keep some chance of rain for Memorial Day. While not a washout by any means, trends have moved towards not a fully dry Memorial Day with some wrap around moisture. Likely, there will be some isolated to scattered showers across the region, primarily in the morning, becoming more confined to the higher terrain into the afternoon on Memorial Day. Showers do look to be relatively weak given lower PWATs and decent flow aloft with 50 knots at 500mb. Drier air does look to take hold for Monday night through most of Tuesday. Temperatures for the early to mid week next week will be seasonable with highs in the 70s and overnight lows in the 40s. Shower chances return late Tuesday into Wednesday as an upper shortwave over eastern Quebec swings into the Canadian Maritimes with a trailing cold front over our region. As the system drops south, ensemble guidance is somewhat depicting a weak coastal low which may keep some moisture and shower chances into Wednesday night and perhaps Thursday morning. Regardless, as shower chances drop off by late next week, prolonged drier air is forecasted through much of the remainder of May in the long term. Broad strong high pressure is expected to build in over the Great Lakes with ridging across the Mid-Atlantic and Northeast bringing more dry air and rising temperatures.

AVIATION /00Z FRIDAY THROUGH TUESDAY/

Through 00Z Saturday...High pressure building into the region will provide all 7 of our taf sites with VFR conditions for the next 24 hours. North to northeast winds 5 to 10 knots this evening will become light 2 to 6 knots overnight into Friday. A few-scattered high clouds are possible from time to time.

Outlook...

Friday Night: VFR. NO SIG WX. Saturday: VFR. NO SIG WX. Saturday Night: VFR. Chance SHRA. Sunday: Mainly VFR, with local MVFR possible. Likely SHRA. Sunday Night: MVFR/IFR conditions possible. Chance SHRA. Memorial Day: Mainly MVFR, with areas IFR possible. Chance SHRA. Monday Night: Mainly VFR, with areas MVFR possible. NO SIG WX. Tuesday: VFR. Slight chance SHRA, Slight chance TSRA.

CLIMATE

Montpelier, VT (KMPV) and Saranac Lake, NY (KSLK) are expected to fall within 3 degrees of their record low. Below are the daily record values under threat for May 22nd, and the present forecast.

Record | Year | Forecast Temperature KMPV: 29 | 2002 | 31 KSLK: 22 | 1935 | 24

BTV WATCHES/WARNINGS/ADVISORIES

VT...Frost Advisory from 11 PM this evening to 8 AM EDT Friday for VTZ009-011-016>021. Freeze Warning from 11 PM this evening to 8 AM EDT Friday for VTZ003-004-006>008-010. NY...Frost Advisory from 11 PM this evening to 8 AM EDT Friday for NYZ026-027-087. Freeze Warning from 11 PM this evening to 8 AM EDT Friday for NYZ029>031-034.