Area Forecast Discussion
Issued by NWS Albany, NY

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800 FXUS61 KALY 162329 AFDALY Area Forecast Discussion National Weather Service Albany NY 629 PM EST Tue Jan 16 2018 .SYNOPSIS...
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A developing coastal low pressure system will emerge off the Delmarva tonight 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.
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&& .NEAR TERM /THROUGH WEDNESDAY/...
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As of 629 PM EST...This update was to address the hourly POP trends for the developing snow shield with the inverted sfc trough with the double-barrel cyclone. The coastal low continues to develop southeast of the Delmarva region. We increased the POPS a bit from the Capital Region/Mohawk Valley south and east. Headlines remain the same. Previous near term... As of 330 PM EST...A sharp positively tilted trough over the central part of the CONUS will continue to dig southward as it progresses eastward this evening and into tonight. Ahead of this feature, a weak surface wave of low pressure is moving across the eastern Great Lakes towards the area. Persistent s-sw flow ahead of these features have been allowing for a period of warm air advection, which has brought some patchy light snowfall through the day. This snowfall has been very light and has been most persistent across upslope areas of the higher terrain, with most of the area seeing a light accumulation of a coating to an inch or two. During this evening, snowfall will start to become more widespread and steadier in coverage/intensity, as a weak wave of low pressure develops off the mid-Atlantic coastline. As this wave slowly lifts northeast, an inverted coastal trough will allow the snowfall to pick up in intensity for later tonight, especially for areas south/east of Albany. The heaviest snowfall looks to be for after midnight, especially for southern/eastern parts of the region. With the approaching upper level trough and a strong jet-streak nearby, 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. Mesoscale models, including the 3km HRRR and NAM do suggest some heavier snowfall amounts extending from the Poconos northeast across the Catskills, mid Hudson Valley and into NW CT/Berkshires. Considering this, will upgrade eastern Ulster/Dutchess counties into the existing Winter Storm Warning (which is in effect for the Taconics/western New England) with expected totals around 6-10 inches in this area. Elsewhere, additional snowfall will generally be 3 to 6 inches, with some locally higher amounts. The morning commute will probably be fairly difficult across much of the area on Wednesday 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 on Wednesday. Snowfall should be done in the Capital Region and mid-Hudson Valley by the mid to late morning and should be ending in western New England by the late morning or early afternoon hours. 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 on Wednesday 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 on Wednesday afternoon from west to east as well.
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&& .SHORT TERM /WEDNESDAY NIGHT 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 /00Z WEDNESDAY THROUGH SUNDAY/... 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 snowfall have 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. && .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... CT...Winter Storm Warning until 3 PM EST Wednesday for CTZ001-013. NY...Winter Weather Advisory until 3 PM EST Wednesday for NYZ032- 033-038>043-047>053-058>060-063-082>084. Winter Storm Warning until 3 PM EST Wednesday for NYZ054-061- 064>066. MA...Winter Storm Warning until 3 PM EST Wednesday for MAZ001-025. VT...Winter Storm Warning until 3 PM EST Wednesday for VTZ013>015. && $$ SYNOPSIS...11/JPV NEAR TERM...Frugis/Wasula SHORT TERM...11/JPV LONG TERM...ELH AVIATION...Frugis HYDROLOGY...11/JPV

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