038 FXUS61 KBTV 220000 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 700 PM EST Wed Dec 21 2022 .SYNOPSIS... A powerful storm system will develop across the central Plains and track toward the eastern Great Lakes by Friday. A significant high wind event is expected on Friday morning with gusts 50 to 75 mph across most of the region, along with scattered to widespread power outages anticipated. As much colder air races into the region on Friday afternoon and evening, a flash freeze is expected with temperatures quickly tumbling below freezing and any rain changing to snow by evening. The combination of snow melt and rainfall will produce sharp rises on waterways with several rivers potentially reaching minor flood by late Friday into Saturday. && .NEAR TERM /THROUGH THURSDAY/... As of 649 PM EST Wednesday...A tranquil evening is underway with just minor updates to account for low and mid-level cloud trends per satellite imagery and surface observations. The quiet period of wx overnight is courtesy of a 1035mb high pressure ridge over northern New England. Meanwhile, a weak sfc boundary is crossing northern NY this evening. This boundary, combined with favorable southwest flow advecting lake enhanced moisture into northern NY wl cont to produce intervals of clouds. However, as sfc high pres builds into the area and moisture in the 925mb to 850mb thins, expect some clearing skies overnight. These clearing skies makes for a challenging temp fcst with lows mainly in the teens to lower 20s. A flurry or light snow shower is possible over the dacks into northern VT mtns thru 06z. Thursday, mid/upper lvl moisture wl increase aft 18z ahead of our developing powerhouse of a system, with some light rain/snow expected toward 00z Friday. Not anticipating major impacts to the evening commute as precip should be light and mainly confined to the upslope regions of the dacks and southern Greens thru 00z, with temps warming into the 30s. && .SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/... As of 440 PM EST Wednesday...A lot of largely impactful weather continues to focus during this timeframe. Thursday evening strong overrunning of warm, moist air in the 700-850 millibar layer atop our seasonably cold air mass will cause widespread precipitation to spread northward through the region. Data has trended colder with marginally cold conditions to support all snow at the start in a larger region, including the northern St. Lawrence Valley where northeasterly winds will persist, and just about all locations above 1000 feet elevation, before gradually transitioning to rain showers after midnight as snow levels rise given the continued low level warming. The substantially easterly component to the near surface winds will make it hard to scour out the cold air east of the Green Mountains which could lead to a period of freezing rain in the transition to plain rain. At this time, the threat is small as the dominant precipitation type forecast does favor primarily snow and rain as temperatures in most locations warm well above freezing by Friday morning. Precipitation will tend to become more showery as the night wears on due to the effect of a powerful low level jet lifting northeastward through our region. The exception is upslope areas in the eastern Adirondacks and much of southern Vermont. Combination of storm total precipitation of around 2" in these areas plus snow melt as dew points rise above freezing leads to river flooding potential, highlighted in our Hydro section of the AFD. The main impactful weather is expected to be scattered to widespread downed tree limbs and power outages due to very strong wind gusts early Friday. Peak gusts comparable to a category 1 hurricane are forecast in the western slopes of the Green Mountains. We're increasingly concerned by the likelihood of populated areas well away from the mountains, including the populated Champlain Valley towns in Chittenden and Addison Counties, not accustomed to seeing winds of this magnitude. The low level jet will peak during the morning hours, most likely between 4 AM and 9 AM, which will likely be so strong that it will break through the mountain barrier regardless of stability. As a result, dangerous wind gusts will occur well away from the higher terrain. Looking at model data reveals very strong 925 east-southeast winds increasing into the 70 to perhaps 90 knot range along the corridor from Essex Junction to Middlebury, supporting surface peak winds in excess of 65 MPH. Multiple long-time forecasters have not seen winds at this pressure level at this magnitude in our region. While most areas will not see destructive winds, a favorable setup for widespread strong winds and consistent forecast data has led us to upgrade all High Wind Watches to High Wind Warnings. Areas not in the warning will still have potential for some 45 to 50 MPH winds such as in much of Orange and Windsor Counties in Vermont where a Wind Advisory is in effect for the same period. These winds will also usher in much warmer air with temperatures surging into the mid and upper 40s in most locations, with some low to mid 50s not out of the question given the drying effects of the downsloping winds. Following the wind event, we quickly shift gears to the impacts of a very sharp cold front that will push eastward through the region between noon and 5 PM. A low pressure area riding northward along this boundary midday Friday could slow its eastward progress, but the consensus has trended faster than previously indicated. The impacts will be roughly the same, with rapid temperature falls as winds turn abruptly from easterly to southerly/southwesterly. Given the remarkable surface convergence, heavy precipitation along the boundary will be accompanied by a little bit of instability and development of a fine line. While low topped convection will be possible at the leading edge of the front, additional heavy precipitation changing from rain to snow is expected, with perhaps some sleet briefly as temperatures cooling aloft out paces the surface temperatures. Flash freeze still looks like a real problem given the widespread precipitation coinciding with a rapid drop of temperatures well below freezing during the late afternoon and evening. The duration of the heavy precipitation will tend to be brief as much drier air works into the region. The one exception may be southern St. Lawrence County, where strong southwesterly flow will keep low level moisture off of Lake Ontario going and accumulating snowfall will persist. Snow will briefly be blowing across the higher terrain before winds taper off, while again in the lake- effect snow zone blowing snow will likely be an issue through Friday night. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... As of 353 PM EST Wednesday...As low pressure continues to pull north away from the region, impacts will continue to be felt across parts the forecast area through the weekend. The main focus will be over the St. Lawrence Valley where southwesterly winds will continue to gust up to 50 mph through mid-morning and lake effect will be ongoing across southern portions of the Valley. Lake Ontario remains warm, and the incoming air mass will be quite cold favoring a long duration light lake effect snow event. While the exact location of where banding sets up remain uncertain, confidence is moderate to high that southern parts of St. Lawrence County could reasonably see 6 to 12 inches of snow through Sunday before the band shifts south of the area. Elsewhere, dry conditions and seasonably cool temperatures are expected with highs only in the teens to mid 20s and lows in the single digits to teens. Winds remain brisk across the rest of the region as well, especially Saturday where gusts will be in the 25 to 35 mph range supporting wind chill values in the single digits above and below zero. Winds abate slightly to 15 to 25 mph on Sunday, and wind chills won't be as bad in the single digit to low teens. By Sunday night into next week high pressure will return to the region allowing winds to finally slacken. Despite some sunshine returning the air mass remains on the colder side of normal with highs ranging through the 20s and lows continuing in the single digits to teens. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... Through 00Z Friday...A weak surface boundary will bring intervals of MVFR ceilings thru 05Z with HIR TRRN OBSCD. Thereafter, expecting lower clouds will dissipate, and a higher cloud ceiling overspreads the region during the pre-dawn hours at 12-15kft. These mid-level clouds will generally remain in place through the daylight hours Thursday. Should see MVFR ceilings redevelop after 21Z Thursday at RUT and MPV. Light and variable winds overnight will become S-SE at 5-10kts during the daylight hours Thursday. Winds locally NE around 10kts at KMSS on Thursday. A period of very strong winds, extreme turbulence and wind shear is expected late Thurs into Friday acrs our taf sites, beginning just after the current TAF period, which ends at 00Z Friday. Outlook... Thursday: VFR. Slight chance SHSN. Thursday Night: Mainly MVFR, with areas VFR possible. Strong winds with gusts to 40 kt. Likely RA, Chance SN. Friday: Mainly MVFR, with local IFR possible. Strong winds with gusts to 50 kt. Definite RA, Definite SHRA. Friday Night: Mainly VFR, with local MVFR possible. Windy with gusts to 30 kt. Chance SN, Slight chance SHSN. Saturday: Mainly VFR, with local MVFR possible. Windy with gusts to 35 kt. Slight chance SHSN. Saturday Night: Mainly VFR, with local MVFR possible. Chance SHSN. Christmas Day: Mainly VFR, with local MVFR possible. Slight chance SHSN. && .HYDROLOGY... FLOOD WATCH in effect from Friday afternoon through Saturday evening due to a combination of snowmelt and rain. Basin average rainfall of 1.5" to 2" and about 1" of liquid equivalent from snowmelt is likely. The highest rainfall totals are expected in eastern facing slopes of the Adirondacks in Essex County, New York and across the southern Greens in Windsor County, Vermont, which could have locally higher totals to 2.5". Minor flood stage is expected to be reached on the Otter Creek at Center Rutland, the Mad River at Moretown, and the East Branch of the Ausable River which are of the highest concern at this time. Uncertainty exists on the Winooski River at Essex Junction, with minor flooding not out of the question. Elsewhere, significant river rises are expected, and minor poor drainage and urban street flooding is possible. For details on specific area rivers and lakes, including observed and forecast river stages and lake elevations, please visit the Advanced Hydrologic Prediction Service /AHPS/ graphs on our website. && .EQUIPMENT... NOAA Weather Radio WXM-44 atop Mount Ascutney is currently off the air due to a suspected problem with the RF transmission cable/jumper at the antenna. A site visit will be necessary to isolate the issue and, unfortunately, a return to service is unknown at this time. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...High Wind Warning from 4 AM to 7 PM EST Friday for VTZ002>009- 011-016>019. Flood Watch from Friday afternoon through Saturday evening for VTZ005-008>011-017>021. Wind Advisory from 4 AM to 7 PM EST Friday for VTZ010-020-021. NY...Wind Advisory from 4 AM to 1 PM EST Saturday for NYZ026-027- 087. High Wind Warning from 4 AM to 7 PM EST Friday for NYZ029>031- 034. Flood Watch from Friday afternoon through Saturday evening for NYZ031-034. && $$ SYNOPSIS...Taber NEAR TERM...Banacos/Taber SHORT TERM...Kutikoff LONG TERM...Lahiff AVIATION...Banacos HYDROLOGY...WFO BTV EQUIPMENT...BTV