textproduct: Burlington

WHAT HAS CHANGED

As of 143 AM EST Saturday...

Confidence has continued to increase in a light snowfall Tuesday night.

KEY MESSAGES

As of 143 AM EST Saturday...

1. Gusty south winds and mild temperatures today along with scattered rain and higher elevation snow showers.

2. March will start off cold, with well below normal temperatures on Sunday and Monday. Light and fluffy snow still on track for Sunday with limited impacts.

3. Trending warmer through much of next week with several chances for precipitation.

DISCUSSION

As of 143 AM EST Saturday...

KEY MESSAGE 1: We're on track for very breezy conditions this morning as a pressure gradient increases. Aside from the mountain summits, the strongest winds will be in the northern Champlain Valley, especially the eastern side due to topography. A southerly low level jet will be channeled through the valley, with time-height cross sections of wind speeds show the jet maximizing between 7 and 11 AM in the 50 to 55 knot range just above the shallow inversion. High resolution model data shows 975 millibar winds in Burlington peaking around 41 knots, showing potential for winds to peak near 50 MPH. Given the time of year/cold surface conditions, not sold on maximizing this potential but localized gusts near Lake Champlain above Wind Advisory criteria will be possible.

As a well-defined cold front moves into northern New York and sweeps east of the area through this afternoon, there will be widespread showers that gradually diminish in coverage moving towards the east, likely due to decreased low level moisture. Precipitation along the front will not be particularly noteworthy even, with a cold rain possibly mixing with snow as temperatures aloft cool with time. Temperatures ahead of the front will largely be in the low to mid 40s during the day, with even mountain summits warming above freezing briefly, given a wedge of warm air pooling ahead of the cold front featuring 850 millibar temperatures rising above 1 degree Celsius. Somewhat deeper mixing than expected could lead to some spot 50 degree values today.

KEY MESSAGE 2: Much colder air will spill southeastward into the region tonight, with 925 millibar temperatures falling below the climatological 10th percentile per HREF mean in the St. Lawrence and northern Champlain Valleys Sunday morning. A lingering thermal gradient, with relatively mild air in the southern Champlain Valley and will support an area of snow primarily to the south of this coldest air; since there isn't much of a surface feature to organize the snow, it appears a narrow jet streak will be the primary forcing mechanism. With a lot of dry air filtering southward, the degree of saturation aloft will only be marginally sufficient for snow. As such, snowfall amounts and timing of snow remains highly uncertain. There is a strong consensus that southern areas remain on track to see potential for more substantial snow than farther north, but with a wide spread in potential precipitation indicated in these areas. As an example, in the latest REFS, the 25-75th percentile range for snowfall across just about all of Orange, Rutland, and Windsor counties is 4", with amounts ranging from 1-5" or 2-6". If and when the mid-levels saturate, the thermal profiles look extremely favorable for high snow to liquid ratios. Various algorithms to predict snow ratios point to values greater than 20:1.

Following the light snowfall on Sunday, modified Arctic high pressure will build eastward into the region and low level temperatures areawide will become anomalously cold. This sprawling high will lead to clear skies and light winds such that a bitterly cold night can be expected Sunday night. Temperatures will be below zero areawide by Monday morning. Plentiful sunshine and slightly modifying low level temperatures with weak warm air advection during the afternoon should help temperatures on Monday recover into the mid 10s to low 20s, or about 15 to 20 degrees below normal.

KEY MESSAGE 3: Confidence in warming conditions continues to increase as we make our way through the first week of March. We'll remain under an active pattern, so with an anticipated warming trend, we should also be trending toward more rain vs wintry precipitation. That being said though, there's still a variety of model solutions, between both deterministic and ensemble members, especially toward the latter half of the week.

High pressure starts to exit to our east on Tuesday, making way for low pressure approaching from the southern Great Lakes. Clouds will increase through the day ahead of this latter feature; there's still some uncertainty as to how much cloud cover we'll have early in the day for viewing of the "Blood Moon", though would expect any clouds that are around during the morning would be high and thin. Precipitation spreads into our region late in the day and overnight Tuesday night. Confidence continues to increase in snow being the predominant weather type, in spite of daytime temperatures in the low to mid 30s. South winds and a fast forward progression of the system would lend toward less overall QPF, especially in the Champlain Valley and along the northern slopes of the higher terrain.

This first system passes to our east by Wednesday morning, setting up a frontal boundary to our south while high pressure builds in to our north. Another wave of low pressure will ride along this front, pushing warmer air back north on southerly return flow. The question is how far the warm air is able to intrude on the cold air that will be entrenched across the north and east, especially along/east of the Greens and in the northern St Lawrence/Champlain Valleys. The concern is, of course, the potential for freezing rain where cold air is slower to scour out. Plenty of uncertainty with this second system and the associated precip types as a result, as it will depend heavily on the strength/positioning of the high and the track of low pressure. The forecast remains just rain/snow at this time given the uncertainty, but we'll have to continue to monitor for the potential for wintry mix/freezing rain, especially since it could coincide with the Thursday or Friday morning commutes (timing differences in model solutions are as much as 12-24 hours for bulk of precip). Regardless, with daytime temperatures looking to warm into the 40s for the latter portion of the week, any wintry precip would change over to plain rain.

AVIATION /06Z SATURDAY THROUGH WEDNESDAY/

Through 06Z Sunday...Primary aviation concern will be developing strong and gusty south/southwest winds after midnight into Saturday morning, along with areas of moderate turbulence and enhanced low level wind shear. As surface cold front approaches overnight gusty south to southwest winds of 15 to 25 knots with localized gusts 25 to 35 knots are expected, especially between 09z-16z Saturday. As front sweeps across our region a wind shift to the west/northwest is expected by Sat afternoon with a chance of a few light rain/snow showers at SLK and brief MVFR cigs/vis. Mostly VFR conditions are expected at our other sites thru the next 6 to 12 hours, with just brief MVFR cigs possible with passage of cold front.

Outlook...

Sunday: VFR. Chance SN. Sunday Night: VFR. NO SIG WX. Monday: VFR. NO SIG WX. Monday Night: VFR. NO SIG WX. Tuesday: VFR. Chance SN. Tuesday Night: Mainly MVFR, with areas IFR possible. Chance SN. Wednesday: MVFR/IFR conditions possible. NO SIG WX.

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 have diagnosed the problem, but repairs will likely not be able to occur for quite some time due to circumstances beyond our control. Therefore, the time of return to service is currently unknown. The following NOAA Weather Radio transmitters may be able to provide service during this 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...None. NY...None.