FXUS61 KBTV 081749 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 1249 PM EST Fri Dec 8 2023 .SYNOPSIS... Generally quiet weather is expected today into Saturday with dry weather and a gradual warming trend despite persistent clouds. A storm system will affect the entire region later Sunday into Monday with a variety of weather including heavy rainfall and some accumulating wet snowfall. Behind this system seasonably cool and mainly dry weather return for much of next week. && .NEAR TERM /THROUGH SATURDAY/... As of 1236 PM EST Friday...Satellite imagery showing erosion of cloud cover from south to north throughout the forecast area. Still on track for a few hours of filtered sunshine for most locations this afternoon, with just some mid and high clouds streaming overhead. High temperatures are on track for the upper 20s to upper 30s, which is very close to seasonable normals. Prior discussion... Surface ridging slides offshore today into Saturday while upper ridging builds into the region with mainly dry wx expected. Clouds are the most challenging portions of the forecast over the next 36 hours. Given the current synoptic inversion in place, weak sun angle and current extent of cloud cover, I've gone more pessimistic than guidance showing cloudy skies this morning to only gradually thin by this afternoon before partial clearing this evening is replaced by more mid/high cloud cover tonight into Saturday. Developing southerly flow over time should ensure a gradual moderation in temperatures through the period, with highs today in the 30s, and then 40s on Saturday. && .SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY/... As of 359 AM EST Friday...Saturday night's weather is relatively quiet compared to what is in store for the region later Sunday into Monday. Overnight lows on Saturday stay rather mild with continued warm air advection. Aside from a few scattered rain showers, most of the rain will come after daybreak on Sunday, especially into Sunday afternoon as a strong storm system approaches the Northeast US. Initially, the H5 trough is positively tilted with a weak low pressure developing near the St Lawrence valley. Temperatures on Sunday afternoon will be unseasonably mild in the mid 40s to low 50s. Southerly winds will also make for a breezy, if not blustery day with wind-driven rain. Expect 0.25 to 0.75 inch of rain to fall by early Sunday evening. With dew points surging into the 40s, there will be rather significant snowmelt leading to the loss of snowpack. The combination of rainfall and snowmelt runoff will eventually lead to area river rises by Sunday night into Monday. More details in the hydrology discussion. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... As of 359 AM EST Friday...Model guidance has come into better consensus that a coastal low would develop over the Mid Atlantic and track over central/eastern MA overnight Sunday into Monday morning, before deepening as it lifts northeastwards into Maine. Individual members of the 00z GFS and ECMWF are now showing remarkable consistency and clustering considering we are still over 72 hours out. While the overall upper level flow is still fairly progressive with a neutral to slightly positive NAO regime, models are indicating that the H5 trough does go negatively tilted for a time, greatly increasing the odds of colder air arriving in time for a 6 to 12 hour window of heavy, wet snow. While the threat for pre- frontal strong to damaging winds has diminished, concern is increasing for 35 to 40 mph post-front northwest winds leading to power outage concerns due to snow loading. Expect the sub-freezing 925mb isotherm to approach Champlain valley by the pre-dawn hours on Monday before sweeping across our entire CWA by early Monday afternoon. Expect surface temperatures to fall into the 32-34 range for points along and west of the Adirondacks through the pre-dawn hours, and then for areas east of the immediate Champlain Valley by the morning commute. Temperatures are expected to remain constant or fall slightly during the day as strong cold air advection continues, with 925mb temperatures falling to -6 to -8C range regionwide by sundown. Still thinking that the immediate Champlain valley could see a slushy inch or two of wet snow due to wet bulbing but temperatures should hold steady at 33-36 for locations like Burlington. On the other hand, locations along the spine of the Greens and the Adirondacks would be cold enough for most of the precipitation to fall as heavy, wet snow for most of Monday. With upwards of 1.5 inches of QPF and with a 8:1 SLR, jackpot locations could see in excess of over a foot of snow. Generally locations at or above 1000 ft could expect 6-12 inches of heavy, wet snow, with 500-1000 ft seeing 3-6 inches of snow and 1-3 inches for the broader valleys below 500 ft. In a nutshell, this is an elevation dependent storm in terms of wintry impacts. A silver lining is that given the thermal profiles, mixed precipitation is unlikely, outside of a brief period of sleet when the rain changes over to snow. By Monday late afternoon into evening, as the low pressure center lifts further north and east into northern Maine and maritime Canada, stratiform precipitation will quickly come to an end across northern NY and then VT, transitioning into upslope snow showers. But as mentioned earlier, with heavy wet snow clinging onto the trees and continued northwest gusts in the 25 to 35 mph range, expect lingering power outages and difficult recovery efforts by utility crew. As for rest of the week, weather pattern remains unsettled but overall no big storms are in the horizon with a couple of moisture- starved clipper systems keeping our high temperatures near or slightly below normal. For reference, typical highs for mid December are in the low to mid 30s. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... Through 18Z Saturday...Low stratus clouds will continue to erode from south to north, with flight conditions lifting from MVFR to VFR over the next few hours. Predominantly VFR conditions will continue through 12Z Saturday with just some mid and high clouds streaming overhead. Winds will be light and variable this afternoon, becoming south 5-10 knots after 00Z this evening. Outlook... Saturday Night: Mainly VFR, with local MVFR possible. Chance SHRA. Sunday: Mainly MVFR, with areas IFR possible. Definite RA. Sunday Night: Mainly IFR, with local MVFR possible. Windy with gusts to 30 kt. Definite RA, Definite SN. Monday: Mainly MVFR, with areas IFR possible. Windy with gusts to 30 kt. Definite SN, Definite RA. Monday Night: Mainly MVFR, with areas VFR possible. Slight chance SHSN. Tuesday: Mainly VFR, with local MVFR possible. NO SIG WX. Tuesday Night: Mainly VFR, with areas MVFR possible. Slight chance SHSN. Wednesday: Mainly VFR, with local MVFR possible. Slight chance SHSN. && .HYDROLOGY... A strong storm system will bring widespread 1.5 to 2.5 inches of precipitation, with locally over 3 inches of QPF Sunday into Monday. Dew points surging well into the 40s on Sunday afternoon into evening will lead to significant snowmelt. NOHRSC analysis shows widespread 1-3 inches of Snow Water Equivalent outside of the immediate valleys. The combination of rainfall and snowmelt runoff will lead to sharp river rises with minor flood stage possible for area rivers overnight Sunday into early Monday. Strong cold air advection will change rain into heavy, wet snow by Monday morning, with even the valleys changing to snow by mid day Monday. This will help mitigate the snowmelt runoff contribution, and with the overall progressive nature of this storm system, vulnerable basins including Winooski River, Ausable River, Mad River and Otter Creek have the best chance of exceeding bankfull and go into minor flood stage. At this time, moderate flood stage looks unlikely but we will continue to monitor the trends. Stay tuned. && .EQUIPMENT... The Burke Mountain NOAA Weather Radio Transmitter (Frequency 162.425, WWG-50) will unfortunately be down until further notice as we await parts. We apologize for the inconvenience. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...JMG NEAR TERM...Duell/JMG SHORT TERM...Chai LONG TERM...Chai AVIATION...Duell HYDROLOGY...Chai/JMG EQUIPMENT...