textproduct: Burlington

SYNOPSIS

A dynamic low pressure system to our west will spread widespread, and occasionally heavy, precipitation along with areas of strong winds tonight into Thursday. As temperatures climb, snow will quickly become a wintry mix and then all rain by the daytime hours for most locations. Much warmer conditions during the afternoon will give way to a cold front, bringing temperatures back down to more seasonable values to end the week ahead of another wet period over the weekend.

NEAR TERM /THROUGH FRIDAY/

As of 120 AM EDT Wednesday...Winter weather and wind headlines are unchanged as a potent warm air advection scenario unfolds tonight through tomorrow morning.

Fcst remains in decent shape given the complexity acrs our cwa. Winds have increased with Lake Placid gusting to 45 mph last hour. Band of moderate precip is at our doorstep with some embedded heavier convective elements, so a rumble or two of thunder looks good thru 12z this morning. Greatest potential for additional ice accumulation wl be acrs central/eastern VT where temps are holding in the 28-32F range. Meanwhile, most obs are at or above freezing acrs the CPV and northern NY, so not anticipating much additional ice. Previous discussion below...

All winter weather types are expected across the region tonight before temperatures warm well above freezing tomorrow amidst impressive dramatic warming aloft; 850 millibar temperatures will surge from roughly -5 Celsius to 10 Celsius within 6 hours in much of the area (about 25 degrees Fahrenheit of warming up to a few thousand feet above the ground). Generally as the cold air erodes, precipitation type should trend from snow to sleet to freezing rain and plain rain. Unusually high probabilities of sleet as the primary weather type amongst model guidance exists for a substantial period of time tonight. This precipitation type is consistent with how high aloft the strong warm nose is expected to be and the resulting large refreeze layer with our antecedent cold air. That being said, as that refreeze layer shrinks with continuing low level south winds, precipitation will go over to freezing rain and rain overnight.

Given how strong the southwest jet is, even the more vulnerable eastern mid-slope locations in the Greens should warm above freezing within a few hours of that wintry mix period. Before that happens though, the precipitation rates associated with convection, and pre-dawn timing, are looking significant in terms of frozen precipitation. Higher elevations will have a shallower cold layer such that ice will accumulate in some of the same areas that saw significant ice last weekend. With this forecast, we did bump up ice accretions a bit in these areas for this forecast although confidence in sub-warning levels is high (under 0.5" flat ice). So while the duration of freezing rain looks brief, potential for icy conditions is high in much of the Winter Weather Advisory area through daybreak.

In addition to winter weather, we also have an unusually high probability of thunderstorms through the overnight period associated with rich moisture at the top of an elevated mixed layer several thousand feet above the ground. The timeframe continues to look largely in the early morning hours, roughly between 2 AM and 8 AM, and this could be overlapping with precipitation in the form of snow, sleet, and/or freezing rain as surface temperatures remain marginally cold. Given the strong inversion, don't be surprised to be woken up to loud thunder as convection may be rather widespread overnight.

After the winter weather, we will move into a period of strong winds. Peak south winds still look to be coincident with rain showers early in the morning, which will limit the spatial extent of the gusts outside of the northern Champlain Valley and northern slopes of the Adirondacks. Winds will be unusually strong for this time of year on Lake Champlain with sustained 40 40 MPH winds possible, especially around or a bit before daybreak. Then the potential for strong wind southwesterly wind gusts throughout northern New York through the afternoon hours remains high as cooler and drier air aloft moves into the region. Mean mixed layer winds will easily be in excess of 45 MPH and upwards of 55 MPH in northwestern portions of northern New York, especially in the late afternoon, given 60 to 65 knots at 850 millibars and steepening lapse rates.

Afternoon deep convection remains very unlikely due to warm and dry air aloft. So despite some steep lapse rates and warm and humid air at the surface ahead of the cold front, any showers that develop and shift south and east should not grow sufficiently tall to produce lightning. Post frontal west winds have trended a bit stronger with the latest data. However, even in eastern slopes winds do largely taper off after 8 PM so the end time of the wind advisory looks reasonable.

SHORT TERM /FRIDAY NIGHT/

As of 313 PM EDT Wednesday...The short term begins rather seasonable with dry conditions between weather systems this week. Friday will feature sunny skies with highs in the mid to upper 40s, with low 50s in the valleys. Winds will generally be light with some breezy conditions across the Northeast Kingdom. By Friday night, temperatures will fall into the upper 20s/low-to-mid 30s, with clouds increasing ahead of our next weather system tracking out of the Ohio Valley.

Sandwiched between a sub-tropical high off the Carolinas, and another high centered over the northern Plains, a stationary front will set up from the Gulf into our region. Rounds of precipitation over the weekend look likely as moisture and repeated lows track northeastward. Precipitation will move in by Saturday morning as mainly rain for most locations. Higher elevations in the Adirondacks and along the spine of the Greens could start off as a wintry mix of freezing rain and sleet before changing over to all rain. Little to no snow is currently expected, but the Adirondacks and the spine of the Greens could see a glaze of ice from freezing rain Saturday morning. Temperatures on Saturday will rise into the mid to upper 40s which will see precipitation change completely over to rain areawide. The Northeast Kingdom could see wintry mix conditions return by late Saturday afternoon from potential wet-bulbing and normal diurnal cooling towards the evening. A low-level jet looks to accompany the moisture which could mix down to the surface gusty winds with 30 to 40 knots winds at the top of the boundary layer.

LONG TERM /SATURDAY THROUGH WEDNESDAY/

As of 313 PM EDT Wednesday...A pair of blocking highs looks to keep the remainder of the weekend and start of next week on the wet side. Rain will continue Saturday night with some locations still holding on to a wintry mix, especially in the Northeast Kingdom. Rain will continue throughout the day Sunday becoming more showery by Sunday afternoon. The uncertainty in precipitation amounts lies in the location of where the boundary sets up. The GFS, which is running cooler than consensus firstly, is more progressive with the system, becoming more showery with less overall QPF. Whereas the ECMWF is slower in its progression yielding more precipitation, and given the typical slowing trend for these large-scale systems, this solution looks more favorable. Temperatures on Sunday will be fairly persistent from Saturday with highs in the upper 40s to low 50s, and lows overnight in the upper 20s to mid 30s in the valleys.

By Monday, the main weekend storm finally is able to move eastward as steering flow aloft increases. The upper-level trough associated with this unsettled weather will slowly begin to traverse across Canada with high pressure building in behind across the northern Plains. A cold front will pass through the region Monday morning with some back-end snow showers possible as temperatures Monday morning hover near freezing. Behind the front, temperatures look to remain below average for the start of the work week as a broad area of high pressure builds in across the eastern third of the country Tuesday.

AVIATION /05Z THURSDAY THROUGH MONDAY/

Through 06Z Friday...A wide range of precipitation types and associated flight categories currently across our taf sites with a mix of VFR/MVFR. Light freezing rain continues at KMSS with on and off snow at MPV, while other sites have limited impacts from precip attm. However, a band of moderate to locally heavy precip wl lift from south to north over our taf sites in the next 1 to 3 hours with vis trending toward MVFR and a mix of MVFR/IFR cigs, especially MPV/SLK. A rumble or two of thunder is likely given upstream lightning activity thru 12z. Precip wl fall mostly in the form of rain, except some freezing rain/sleet possible at EFK/MPV and MSS, before changing to all rain by 12z. Winds continue to strengthen at 2500 to 4500 ft agl with values in the 45 to 55 knots range, per latest TYX and CXX VAD profiles. These winds wl result in areas of moderate turbulence and wind shear thru this morning, with localized gusts up to 35 knots likely at BTV btwn 10z-15z. As mixing improves this aftn, especially northern NY taf sites, expect localized gusts 35 to 45 knots at MSS/SLK and 25 to 35 knots at PBG/BTV/MPV and EFK. The mix of MVFR/IFR should trend toward VFR by 18z as drier air aloft mixes toward the sfc. Winds decrease after sunset with VFR conditions prevailing.

Outlook...

Friday: VFR. NO SIG WX. Friday Night: VFR. Slight chance FZRA. Saturday: Mainly MVFR, with areas VFR possible. Definite RA, Slight chance FZRA. Saturday Night: Mainly MVFR, with areas IFR possible. Definite RA. Sunday: Mainly MVFR, with areas IFR possible. Chance SHRA. Sunday Night: MVFR/IFR conditions possible. Chance SHRA. Monday: Mainly VFR, with local MVFR possible. Slight chance SHRA, Slight chance SHSN.

BTV WATCHES/WARNINGS/ADVISORIES

VT...Wind Advisory until 8 PM EDT this evening for VTZ001-002-005. Winter Weather Advisory until 11 AM EDT this morning for VTZ003-004-006>008-010-018>021. NY...Wind Advisory until 8 PM EDT this evening for NYZ026>031-034- 035-087. Winter Weather Advisory until 11 AM EDT this morning for NYZ029>031-034.