Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 172340 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 640 PM EST Sat Feb 17 2018 .SYNOPSIS... High pressure sliding off the New England coast this afternoon is making way for a low pressure system passing south of Long Island and outside the benchmark. Light snowfall is expected across Southern Vermont and along the spine of the Greens, generally 1 to 4 inches. A significant warming trend is expected Monday through Wednesday of next week, along with increasing chances for rain. Near record high temperatures are possible Tuesday into Wednesday, with highs well into the 50s and possibly lower 60s. && .NEAR TERM /THROUGH SUNDAY NIGHT/...
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As of 634 PM EST Saturday...Radar imagery shows the first wave of precipitation moving into southern New York ahead of a surface low currently crossing the Appalachian Mountains in West Virginia. Currently over Vermont, enough dry air is in place to keep us dry for a few more hours before the lower levels are saturated and we start to see some snow at the surface. Overall, forecast is on track for a quick shot of snow to start this evening with the best accumulations over southern and eastern Vermont and along the spine of the Green Mountains. Made some minor adjustments to the near term forecast to match obs, but no major changes needed. Previous Discussion...As high pressure moves away from the region this evening, a low pressure system will be skimming the New England coast to the South. Some light snow will spread into Vermont after about 11pm. Very progressive mid-level flow is in place, and will push this system east of the region pretty quickly. All snow should fall by about 8am. Snowfall totals will range from around an inch or less across Northern New York to two to five inches in Southern Vermont. There may be some higher totals along the spine of the Greens as well. Clouds and snow will keep overnight temps mild, ranging through the 20s. Another ridge of surface high pressure will build into the area Sunday and Sunday night from the South. Will take a bit to push the rest of the moisture eastwards on Sunday, but we should see some sunshine by the afternoon, especially in the Champlain valley. We may also see some upslope snow showers lingering through the morning hours in the NW facing slopes of the Greens. Temperatures will be above normal again on Sunday with some upper 30s in the Champlain and Saint Lawrence valleys with lower to mid 30s elsewhere. Gusty NW winds upwards of 20 mph at times during the afternoon. Sunday night high pressure center drifts eastward and pressure gradient will be increasing with a southerly return flow developing. Sunday night will also feature temperatures well above seasonal normals with mid 20s in the valleys and teens in the higher elevations.
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&& .SHORT TERM /MONDAY THROUGH MONDAY NIGHT/... As of 347 PM EST Saturday...High pressure will continue to exit to our east on Monday, placing the region under deep southwest flow. Hence we`ll see increasing warm advection and moisture, leading to a period of precipitation Monday and Monday night. It`ll take a bit for the dry air at the surface to saturate, so precipitation will mostly hold off until Monday afternoon, and temperatures will be above freezing in most areas by then. So expect most locations will see the precipitation start out as rain, though a bit of snow may mix in across the higher terrain of the Adirondacks and northern Greens at the onset. The rain will be steadiest overnight Monday night as a warm front lifts across the region. This will also allow temperatures to rise much of the night after a brief drop in the evening east of the Greens. Overall, 24 hour rainfall amounts will be about a quarter to a half inch, with the Champlain and Connecticut River valleys seeing the least due to shadowing in the southwest flow. && .LONG TERM /TUESDAY THROUGH SATURDAY/... As of 347 PM EST Saturday...The focus for this term becomes very warm, near record warm temperatures, along with potential rainfall placement. The warm front looks to become nearly stationary north of the Saint Lawrence Valley through Wednesday morning, with waves of low pressure traveling along it. This will bring periods of rain, particularly across northern sections. There are still some model differences in frontal placement and the extent of the associated precipitation, but the consensus of the guidance shows 0.50-1.50 inches will be possible through Wednesday with the heaviest amounts along the border. In addition, temperatures will warm considerably through the period, approaching record highs on Tuesday and Wednesday. With temperatures well into the 50s to around 60, and Tuesday night`s low staying well above freezing, runoff from snowmelt and rainfall will be a concern. See the hydrology section for more details. The mild spell comes to an end later Wednesday with a cold front quickly crossing the region. Cooler and drier air will return under high pressure through Friday. However, temperatures will remain above seasonal normals, with highs remaining in the 30s to around 40 both Thursday and Friday. The threat of precipitation returns Friday night and Saturday with another surge of warmer air, though not nearly as mild as what we`ll see earlier in the week. Note that there are considerable differences in model solutions for next weekend, so have stayed close to a model blend to account for the uncertainty. && .AVIATION /00Z SUNDAY THROUGH THURSDAY/... Through 18Z Sunday...Increasing cirrus from west to east through the day continues. After 00Z Sunday, low clouds and snow will advance from the south associated with coastal low pressure, lowering ceilings to MVFR at all sites except KPBG and KMSS, and vsby to IFR at KMPV and KRUT. Snow exits after 09-10Z with vsby lifting to VFR, but MVFR ceilings remain. Winds trend southerly after 14Z at 5-15 knots. Outlook... Sunday Night: VFR. NO SIG WX. Washingtons Birthday: Mainly VFR, with local MVFR possible. Chance SHRA. Monday Night: MVFR. Definite RA. Tuesday: Mainly MVFR, with local IFR possible. Likely RA. Tuesday Night: Mainly MVFR, with local IFR possible. Likely RA, Chance SHRA. Wednesday: Mainly MVFR, with local IFR possible. Likely RA, Chance SHRA. Wednesday Night: Mainly MVFR, with areas VFR possible. Chance SHRA, Chance SHSN. Thursday: Mainly VFR, with local MVFR possible. NO SIG WX. && .HYDROLOGY... As of 355 AM EST Saturday...A 48-hour period of anomalously warm temperatures will affect the region from Monday through Wednesday. Periods of rainfall, modest winds and dewpoint temperatures climbing into the 40s to lower 50s will foster rapid snowmelt across the entire area. Still some variability shown with this afternoon`s modeled 48-hr QPF, though the general consensus is for two day totals averaging from 0.5 to 1.5 inches, heaviest north. Taking this all into account, modest to substantial river rises look highly probable starting Monday night and continuing through Wednesday, supported by NAEFS/SREF MMEFS hydrograph data. While widespread open water flooding is not expected, several rivers may approach minor flood. Given the numerous ice jams in place from the substantial thaw this past January, localized high water/flood concerns near these features will also remain a concern. As future data helps hone the forecast in the coming 36-hours, a Flood Watch will likely be necessary for most if not all of the forecast area during this period. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Neiles NEAR TERM...Neiles/RSD SHORT TERM...Hastings LONG TERM...Hastings AVIATION...Neiles HYDROLOGY...JMG is the U.S. government's official web portal to all federal, state and local government web resources and services.