Area Forecast Discussion
Issued by NWS Albany, NY

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274 FXUS61 KALY 170530 AFDALY Area Forecast Discussion National Weather Service Albany NY 1230 AM EST Wed Jan 17 2018 .SYNOPSIS... A developing coastal low pressure system will form southeast of the Delmarva region overnight and track northeast to near Cape Cod late Wednesday morning. This system is expected to bring a moderate to heavy snowfall to much of the region overnight into Wednesday. Seasonably cold and mainly dry weather is expected Thursday with some lake effect snowfall northwest of the Capital District. && .NEAR TERM /THROUGH TODAY/...
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As of 1230 AM EST...Monitoring radar/satellite trends and surface observations for ongoing snow event. A fairly large mesoscale band has set up across eastern Ulster, Dutchess, northern Litchfield and southern Berkshire counties. Based on reflectivity values of around 25 dBZ, snowfall rates of around one inch per hour occurring. These areas are all in a Winter Storm Warning. Farther north and west, snowfall rates are lighter but snow is still accumulating. Snowfall reports from the evening revealed generally 1-4 inches, with a few to several more inches expected overnight through this morning. The latest RAP guidance with the GOES-16 Clean IR /10.35 micron band/ satellite imagery overlaid continues to show cloud tops cooling over much of the forecast area with the a positively tilted mid and upper level trough centered over the central- eastern Great Lakes Region. A decaying primary sfc low has drifted over the central NY-PA border. A secondary sfc/coastal low is continuing to form southeast of the Delmarva corridor. Over running moisture ahead of the coastal low continues to spill into the region with a baroclinic zone set-up over eastern NY and western New England. The current headlines look good with Warning for 5-10" of snow from the Mid-Hudson Valley of Dutchess Co., the Taconics into eastern Rensselaer County eastward into western New England. West of the warning area, advisories remain up for 4-8" in the Capital Region, eastern Catskills, Schoharie Valley, and the Lake George Region northern Saratoga Region, and 2-6" further west. With the approaching mid and upper level trough and a strong mid and upper left front quadrant of a jet-streak nearby, recent Northeast CSTAR research would suggest the potential for a quasi-stationary mesoscale band of snowfall on the northwestern side of this developing low pressure area especially after midnight to continue. The latest mesoscale models, including the 3-km HRRR and NAM do suggest the heaviest snowfall amounts extending from the Poconos northeast across the Catskills, mid Hudson Valley and into NW CT/Berkshires overnight. The morning commute will likely be fairly difficult across much of the area this morning due to the snow covered roadways and low visibility. As the low pressure lifts up towards eastern New England, snowfall will start to taper off from west to east during the day. We will have to monitor for a brief period of Mohawk-Hudson Convergence /MHC/ in the late morning into early afternoon based on some of the mesoscale model trends including the latest 3km NAM. Based on the track of the cyclone, and the local flow patterns in the adjoining valley, it is possible referring to the MHC CSTAR conceptual model. Winds will switch to the northwest behind the storm, but shouldn`t be too strong since the surface low is fairly weak, so blowing/drifting doesn`t look like a concern with this event. Temps today will generally be in the 20s, with a few spots in the mid-Hudson Valley and NW CT reaching the low 30s. Clouds should be breaking for some sun during the afternoon from west to east as well.
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&& .SHORT TERM /TONIGHT THROUGH FRIDAY/... A 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. Highs on Thursday will be in the upper teens to lower 30s with lows Thursday night in the mid teens to lower 20s. On Friday, any lingering lake effect should end during the morning with dry conditions expected Friday afternoon. Highs on Friday will be in the mid 20s to mid 30s. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... This period will mark a turn toward much above normal temperatures...with highs mainly in the 30s and 40s each day, and lows stating out mostly around 20 degrees Friday night, with mostly upper 20s and lower 30s by Sunday and Monday nights. With mid- January being Albany`s coldest time of the year, on average, lows there are normally in the mid teens, with highs around 30 degrees. High pressure centered over the deep south will build up into the mid-Atlantic region. An east-west frontal boundary will stay just north of our zones as low pressure over the center of the contiguous U.S. develops and tracks across the Great Lakes and into southern Quebec through Monday night, displacing the high pressure and bringing a good chance of rain showers throughout the area as early as Sunday night, which could start as snow. By midday Monday, all areas outside of the high peaks of the Adirondacks will likely experience pure rain shower activity ahead of a cold front which will move quickly east across our zones Monday night. It will be overcast with low instability. Only a modest decline in temperatures will be experienced behind the front...to as low as near normal. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... A double barrel low pressure system will impact eastern NY and western New England tonight into tomorrow with snow. The primary low over upstate NY will weaken tonight, as the secondary coastal low moves along the Atlantic Coast towards eastern Long Island by daybreak tomorrow. The coastal low will quickly move northeast of Cape Cod by the afternoon with the snow tapering to snow showers and flurries. In the developing snow shield conditions will continue to lower from MVFR/IFR levels in terms of cigs/vsbys. Expect the cigs/vsbys to lower to widespread IFR and some LIFR levels with vsbys down to 1/2SM to 3/4SM with moderate snow between 04Z- 08Z. The best chance for sustained moderate snow with vsbys a 1/2SM will be from KALB/KGFL/KPSF/KPOU from 07Z-13Z/WED. The snow will begin to taper and lighten prior to 16Z/WED with lingering MVFR cigs/vsbys thereafter. As the system moves northeast expect widespread VFR conditions after 18Z/WED with cigs BKN-OVC 3.5-4.0 kft AGL. The winds will be calm tonight or light and variable at 4 kts or less. The winds will increase from the N to NW at around 5 kts after 12Z/WED, and will continue to strengthen from the northwest at around 10 kts by the afternoon with some gusts 16-20 kts at KPOU/KALB/KPSF. Outlook... Wednesday Night to Saturday: No Operational Impact. NO SIG WX. Saturday Night to Sunday: Moderate Operational Impact. Chance of SHRA...SHSN. && .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 mid Hudson Valley and 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...
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CT...Winter Storm Warning until 3 PM EST this afternoon for CTZ001- 013. NY...Winter Weather Advisory until 3 PM EST this afternoon for NYZ032-033-038>043-047>053-058>060-063-082>084. Winter Storm Warning until 3 PM EST this afternoon for NYZ054- 061-064>066. MA...Winter Storm Warning until 3 PM EST this afternoon for MAZ001- 025. VT...Winter Storm Warning until 3 PM EST this afternoon for VTZ013>015.
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&& $$ SYNOPSIS...JPV/Wasula NEAR TERM...Frugis/JPV/Wasula SHORT TERM...11/JPV LONG TERM...ELH AVIATION...Wasula HYDROLOGY...11/JPV

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