Area Forecast Discussion
Issued by NWS Albany, NY

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000 FXUS61 KALY 161748 AFDALY Area Forecast Discussion National Weather Service Albany NY 1248 PM EST Tue Jan 16 2018 .SYNOPSIS... A weak area of low pressure will move into our region from the Great Lakes today, bringing some light snow. Then, a developing coastal low pressure system will emerge off the Delmarva this evening and track northeast to near Cape Cod Wednesday morning. This system is expected to bring a moderate to heavy snowfall to much of the region tonight into Wednesday. && .NEAR TERM /THROUGH WEDNESDAY/...
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Winter Storm Warning remains in effect for the northern and central Taconics, southern Vermont, Berkshires and Litchfield Hills this evening into Wednesday afternoon... Winter Weather Advisory remains in effect for the rest of eastern New York today into Wednesday afternoon... As of 1248 PM EST...Areas of light snow will continue across the area through this afternoon, as weak low pressure approaches from the Lower Great Lakes. This light snowfall is occurring thanks to persistent warm air advection within the broad sw flow aloft ahead of an approaching positively tilted trough. The snow is fairly spotty in nature and hasn`t brought much accumulation to the region so far, with most areas seeing an inch or less, although there have been some localized higher totals in the upslope favored areas on the northside of the Mohawk Valley into the Sacandaga area of about 2-3 inches. The light snow will be more prevalent for areas south and east of Albany during the afternoon/early evening, due to the SW to NE orientation of the upper trough and forcing associated with the thermal advection. Additional accumulation this afternoon will continue to be fairly light (an additional inch or less for most). Still, this light snow will affect the evening commutes with some slippery travel on untreated roads with temperatures in the 20s to near 30. More substantial snowfall is then expected starting this evening into tonight, as a coastal low pressure system is forecast to emerge off the Delmarva and track northeast along a baroclinic zone close to the NJ/Long Island coast. At the same time, the positive tilt mid/upper level trough will migrate eastward across the lower Great Lakes and Ohio/Tennessee Valleys. Model QPF varies, but are in generally good agreement with the track of the coastal low. The ECMWF continues to indicate greater widespread QPF compared to other sources of guidance, but details due to terrain enhancement and shadowing are more apparent in higher-resolution guidance such as the 3km NAM and HREF. So the highest confidence in warning level snows are across western New England into the north/central Taconics of NY, thus we will continue with the Winter Storm Watch Warning. We are also expecting some mesoscale banding to potentially develop overnight into early Wednesday morning with the pattern closely resembling a laterally quasi-stationary band from recent CSTAR research. NAM/GFS continue to depict the area of greatest 850-700mb F-Gen along coastal areas, which would imply banding to set up to the north and west of the F-Gen based on the CSTAR research. Hi-res guidance not overly apparent in forecasting mesoscale banding, but this will be something to keep an eye on. For now, we will mention up to 1 inch per hour snowfall rates in the warning area with 6-9 inches total snow in a 12-18 hour time frame, but these totals would have to be raised should a quasi-stationary band develop. Outside of the warning area, we will maintain the Winter Weather Advisories for totals of 4 to 8 inches of snow from around the Capital District south and east across the Catskills, mid Hudson Valley and southern Taconics. Light snowfall from today included in these amounts, thus these totals will occur over a 24-30 hour duration so we will hold with the Advisory. Generally 3-6 inches is forecast for areas north and west of the Capital District. The morning commute Wednesday will be affected by the snow, as moderate to heavy snow will still be falling, especially from around the Capital District south and east as the coastal low approaches the Cape Cod area. Again, we will have to watch for potential mesoscale banding, which would enhance snowfall rates and storm totals. The Warning/Advisory will go through mid- afternoon Wednesday with the snow expected to end from west to east. The steady snow should end before the evening commute Wednesday, with just a few leftover snow showers possible.
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&& .SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/... A small ridge of high pressure will build in Wednesday night providing mainly dry conditions. However, due to well aligned westerly flow and borderline conditional lake induced instability, there will be some lake effect snow showers across the western Adirondacks. Any accumulations should be light, with shallow inversion heights of only around 850 mb are expected. Temperatures will be near normal, with lows in the single digits and teens. Similar conditions should prevail on Thursday, with a flat ridge in place and a westerly flow continuing. Again, some light lake effect snow showers may affect the western Adirondacks, but dry conditions should prevail elsewhere. Snow showers may be a bit more enhanced with greater coverage Thursday night across the western/southern Adirondacks, as a fast-moving short wave trough is expected to move through. Still, only minor accumulations are forecast with mainly dry conditions elsewhere. Temperatures will remain near normal during this time. && .LONG TERM /FRIDAY THROUGH MONDAY/... Gradual upper ridging building into the region into the beginning of next week. Intervals of clouds Friday trending to mostly cloudy by Sunday as warm advection strengthens. Strong upper energy approaches Monday with rain moving in Sunday night, expanding in coverage Monday. Temperatures are a bit uncertain as some guidance has stronger upper ridging than other guidance, which will determine where a west-east oriented boundary layer thermal gradient sets up, just north, across or just south of our region. Too far out in time to know for sure, so blending guidance temperatures until we get closer to next week. There could be some mixed precipitation Sunday night before the strongest warm advection spreads into the region Monday. Highs Friday in the 30s with some mid to upper 20s northern areas. Highs Saturday and Sunday in the 40s but mid to upper 30s northern areas. Highs Monday in the 40s with upper 40s south and lower 40s north. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/...
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As a weak storm approaches from the Great Lakes, light snow has been intermittent across the region so far today, which has allowed for variable flying conditions. Periods of light snowfallhave dropped visibility to 2 to 5 miles at times, otherwise, it has been P6SM. Ceilings generally have been 3000 to 5000 ft for most sites, although lower ceilings have been occurring at KPSF due to the interaction of the southwest flow with the higher terrain. Winds will be calm or very light from a southerly direction through the remainder of the day. Will continue to allow TEMPOs through this afternoon for IFR conditions, but it will probably be VFR/MVFR for much of the time. By this evening, snowfall will become steadier and more widespread, allowing for IFR conditions to become predominate after 22z-00z, as a coastal storm starts to take shape. All sites will see snowfall through the overnight hours, with the heaviest snowfall after midnight through about sunrise, allowing for visibility as low as 3/4SM (especially at KPOU/KPSF). Winds will continue to be fairly light and variable overnight, eventually become westerly towards sunrise. Snowfall will be tapering off by the mid-morning hours, allowing for visibility to improve. However, some lingering clouds could still allow for MVFR cigs through the late morning hours. Winds will switch to the northwest and increase to around 5-10 kts. Outlook... Wednesday Night: No Operational Impact. NO SIG WX. Thursday: No Operational Impact. NO SIG WX. Thursday Night: No Operational Impact. NO SIG WX. Friday: No Operational Impact. NO SIG WX. Friday Night: No Operational Impact. NO SIG WX. Saturday: No Operational Impact. NO SIG WX.
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&& .HYDROLOGY... Ongoing flooding due to ice jams will continue to be addressed with areal flood warnings. There could still be some lingering issues as any existing ice jams may tend to become frozen in place due to the continued cold temperatures expected over the next few days. Warmer weather is not expected until the weekend. In terms of precipitation, a moderate snowfall is expected for much of the area from today into Wednesday, with heavy snowfall from the northern and central Taconics eastward across western New England. 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. && .ALY WATCHES/WARNINGS/ADVISORIES... CT...Winter Storm Warning from 5 PM this afternoon to 3 PM EST Wednesday for CTZ001-013. NY...Winter Weather Advisory until 3 PM EST Wednesday for NYZ032- 033-038>043-047>053-058>060-063>066-082>084. Winter Storm Warning from 5 PM this afternoon to 3 PM EST Wednesday for NYZ054-061. MA...Winter Storm Warning from 5 PM this afternoon to 3 PM EST Wednesday for MAZ001-025. VT...Winter Storm Warning from 5 PM this afternoon to 3 PM EST Wednesday for VTZ013>015. && $$ SYNOPSIS...JPV NEAR TERM...Frugis/JPV SHORT TERM...JPV LONG TERM...NAS AVIATION...Frugis HYDROLOGY...11/JPV

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