721 FXUS61 KBTV 061529 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 1029 AM EST Sat Feb 6 2021 .SYNOPSIS... Scattered to numerous snow showers expected for today, most prevalent to the lee of Lake Ontario where localized significant accumulations are expected. An active weather pattern continues across the area for next week with additional systems bringing periods of light snows on Sunday evening, Tuesday, and again by next Friday. Forecast temperatures will be near to below seasonal normals. && .NEAR TERM /THROUGH SUNDAY/... As of 1029 AM EST Saturday...Forecast remains in good shape as of late morning with no changes needed. Have a great day! Prior discusison... A Lake Effect Snow Warning continues for southern St. Lawrence County in northern New York through 10 PM Saturday. Additional snowfall amounts of 3 to 11 inches expected with the potential for blowing and drifting snow and sharply reduced visibilities within the lake effect snow band. The highest snowfall totals will be possible near Edwards, Fowler, Fullerville in St. Lawrence County. Much of Vermont and portions of the New York side of the Champlain Valley have cleared out nicely. West of the Adirondacks, heavy lake effect snow is underway. Based on surface precipitation measurements of around 0.10 of liquid, 1"/hr snowfall rates are likely occurring in the heaviest activity. The band continues to waver with periodic breaks as well. We shall see how things fare as we get more reports rolling in this morning. The forecast is on track this morning with minimal changes needed. Across the rest of the region, we should see near dry adiabatic low- level lapse rates develop this afternoon with sufficient moisture in the DGZ, that along with any lake effect snow showers may produce additional areas of convective snow this afternoon. Anticipate breezy southwest winds throughout the day at 10 to 15 mph with gusts up to 30 mph in the afternoon. High temperatures should reach the mid 20s to near freezing. Becoming quieter this evening, as ridging builds in tonight with lake effect activity coming to an end. We may actually see clouds briefly scatter out, but we will hold on to some south to southeast winds overnight. Forecast lows are expected to hold in the teens, with some single digits in the Adirondacks and Northeast Kingdom. We should see that break last into the morning with some high clouds coming in. Perhaps we will get a repeat of the nice sunrise from the other day. Then clouds move in as a pair of shortwaves troughs approach our forecast area. Surface low pressure will develop offshore with the bulk of the dynamics to our south. Conditions should be favorable enough that most areas experience light snow Sunday afternoon. Forecast highs will be in the mid to upper 20s on Sunday. && .SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/... As of 337 AM EST Saturday...A period of accumulating light upslope snow showers likely through 06z Sunday, followed by building high pres for Monday/Monday Night. Synoptic and mesoscale features still support lingering snow showers on Sunday evening, with several ingredients available for continued light snowfall. First a modified arctic boundary will be moving thru the CPV around 00z and moderately strong llvl caa will help to squeeze out remaining moisture in developing upslope flow. Second, a pretty potent 5h vort at the same time is moving acrs northern NY/VT and third moisture is still available with 850 to 500mb progs > 80%. These parameters all support the idea of likely to cat pops, especially northern dacks and central/northern Greens from Mt Allen to Mansfield to Jay Peak. Also, quick investigation of soundings support falling snow growth zone, under llvl caa, with good moisture/omega cross section, so ratios wl be at least in the 20 to 1 range. Thinking an addition 1 to 3 with localized 4 to 5 inches possible at summits. Temps will be falling quickly on Sunday Night as progged 925mb values are btwn -16c and -18c by 12z Monday. Lows generally single digits to lower teens, highs Monday with some breaks in the overcast mainly teens to lower 20s. Also, a period of breezy/gusty winds likely with boundary on Sunday evening. Weak high pres ridge for Monday Night, quickly shifts to the east by 12z Tues, as some mid lvl moisture increases. Tricky temp fcst as values drop quickly earlier with clear skies/calm winds, but increase aft 06z Tues, with developing clouds/southerly winds. Have kept temps single digits above zero, but could be much colder if clouds and winds are delayed. && .LONG TERM /TUESDAY THROUGH FRIDAY/... As of 337 AM EST Saturday...Still anticipating a rather active period of weather with several systems expected to impact our fa. Tuesday's event still looks like a widespread light snow event, may approach near advisory level given fluff factor in a few areas, but overall positive impacts with building snow pack and improving conditions for local skiing, riding and snowmobiling acrs our cwa. Meanwhile a larger system with deeper moisture looks more likely on Friday. Bottom line, you may want to keep the snow removal equipment and fat powder skis on standby this upcoming week. For Tuesday, guidance in very good agreement with weak sfc low pres tracking just to our south, while 5h vort crosses directly overhead, along with good ribbon of enhanced 850 to 700mb moisture, under a general synoptic scale waa signature. This system will be fast moving, given westerly 500mb winds of 60 to 70 knots, but still with favorable moisture and good uvv's in the favorable DGZ, expect relatively high snow ratios in the 20 to 1 range. Taking a model blend for qpf indicates generally 0.15 to 0.30 with some isolated higher amounts possible southern sections near 0.40. Given snow ratios, a general 2 to 6 inches is possible on Tues/Tues Night acrs fa. Have bumped pops into the 70/80% range for Tues/Tue evening. Highs in the 20s on Tues, fall back into the teens Tues Night. On Weds 1040mb high pres over the northern Plains tries to nose into northern NY/VT, while weak mid/upper lvl ridge aloft develops. This wl result in a general dry period of wx for Weds into Thurs with slightly below average temps. Still some uncertainty if coldest core of air stays just to our north, or does enough llvl northerly flow from high pres anchored to our northwest push cold air south acrs our cwa. Have taken a conservative approach to cold air with highs generally upper teens to lower 20s with lows in the single digits. Overnight lows could be much colder on either Weds or Thurs Night, depending upon position of sfc high pres. A stronger system with deeper moisture from the Gulf of Mexico is expected to race our direction for Friday/Saturday. Most guidance in good agreement on a precip event for our fa, but still as expected some uncertainty on track of sfc low pres. The setup will feature deep closed mid/upper lvl cyclonic circulation over the northern Plains, while se conus ridge develops. This will help advect high pw values into the Ohio Valley/Mid Atlantic States, while sfc low pres develops along tighten thermal gradient. My initial thoughts would be we stay on the cooler side of low pres, with llvl thermal profiles support mostly all snow. However, last couple runs of the GFS have continued to shift north and west with sfc low pres and tracks primary acrs the eastern Great Lakes, with secondary developing over the Mid Atlantic Coast, which could provide warm nose aloft to support a mix. These finer details will become much clearer, along with trof evolution and sfc low pres track by early next week. For now have mentioned likely pops and kept precip as all snow. Still noticing some signal for additional arctic air to build behind this system for next weekend. Stay tuned. && .AVIATION /16Z SATURDAY THROUGH WEDNESDAY/... Through 12Z Sunday...Currently VFR with a narrow lake effect snow band stretching across northern New York. For the most part, have mentioned VCSH, but did use a TEMPO from 15Z to 18Z for 2SM visibilities in -SN at KSLK. Any other snow showers would produce locally MVFR to IFR visibilities. Prevailing conditions should be VFR, with ceilings around 3500-5000ft agl. After 14Z, anticipate increasing south to southwest winds up to 8 to 13 knots with gusts 18 to 24 knots at times. Winds subside to around 5 knots around 03Z, with lake effect diminishing and clouds thinning. Outlook... Sunday: Mainly VFR, with areas MVFR and IFR possible. Likely SN. Sunday Night: Mainly VFR, with local MVFR possible. Chance SHSN. Monday: VFR. NO SIG WX. Monday Night: VFR. NO SIG WX. Tuesday: Mainly VFR, with local MVFR possible. Chance SN. Tuesday Night: Mainly MVFR, with areas VFR possible. Chance SN, Chance SHSN. Wednesday: Mainly VFR, with local MVFR possible. NO SIG WX. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...Lake Effect Snow Warning until 10 PM EST this evening for NYZ029-087. && $$ SYNOPSIS...Haynes NEAR TERM...JMG/Haynes SHORT TERM...Taber LONG TERM...Taber AVIATION...Haynes