Area Forecast Discussion
Issued by NWS Albany, NY

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000 FXUS61 KALY 160004 AFDALY Area Forecast Discussion National Weather Service Albany NY 704 PM EST Mon Jan 15 2018 .SYNOPSIS... A low pressure system will approach from the Great Lakes tonight into Tuesday, bringing increasing chances for snow. This system, combined with a developing coastal low pressure area, is expected to bring a moderate snowfall to much of the region Tuesday into Wednesday morning. && .NEAR TERM /THROUGH TUESDAY/...
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As of 650 pm, areas of mid and high level clouds were over much of the forecast area with areas of lower stratus east of the Hudson Valley due to moisture advection off the Atlantic. Expect variable coverage of clouds early this evening with an increasing trend after midnight. Overall, forecast is in good shape without any substantial changes needed. Previous discussion...As of 330 PM EST...Strong high pressure (around 1051 hpa) is located northeast of the region over eastern Quebec. This high pressure area has allowed for plenty of subsidence, resulting in mainly clear skies for northern areas. However, low-level stratus clouds have moved across much of western Mass, NW CT and across parts of the mid- Hudson Valley today, thanks to a moist flow off the Atlantic. Meanwhile, southerly flow aloft has also allowed mid level clouds to increase across western and central New York, and these are starting to spread eastward as well. Through the evening hours, clouds will gradually increase across the region, especially the mid and high level variety, as a large closed off 500 hpa low over the upper Midwest and Great Lakes starts to move eastward. Temperatures, which have been very chilly today thanks to the light northeast flow in place, will initially drop this evening into the teens, but then will likely hold steady for the remainder of the overnight as clouds fill in. As the upper level low starts to move eastward, it will open up and take on a positive tilt. Ahead of this feature, strong s-sw flow aloft within the mid levels will result in warm air advection for our area, producing some lift. This lift, aided by upslope flow across the southern Adirondacks, will start to produce some areas of light snowfall for late tonight (basically after midnight or 1 AM). This snow looks to mainly impact areas from the Mohawk Valley on north/northeastward, as downsloping and less forcing should help prevent too much from occurring for areas south of Albany. Most areas won`t see much more than just a coating to half inch overnight, as the snowfall will be light and fairly intermittent. As the trough continues to slide eastward, a weak surface low will be moving from the eastern Great Lakes and into upstate New York for during the day Tuesday. With the persistent isentropic lift and approaching upper level energy, light snowfall will gradually expand across the region for during the day. This should allow for a steady light snowfall to develop for most areas from about to mid to late morning onward. Snowfall doesn`t look overly heavy in intensity, but does look fairly continuous throughout the day, especially across the higher terrain. Most areas look to see at least 1 to 3 inches by evening and the evening rush will likely be slow and difficult in many areas, with more snow to come during the late evening into the overnight hours as well. Will include most of the area within a Winter Weather Advisory and continue Winter Storm Watch for far eastern areas. Temperatures through the day will mainly be in the 20s. A few spots in the mid-Hudson Valley may top out around 30. Light winds for tonight look to become southerly for during the day Tuesday at around 5 to 10 mph. Although the snow looks fairly light and fluffy, the relatively light winds should prevent much blowing and drifting from occurring.
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&& .SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/... By Tuesday night, energy is expected to be transferred from the Clipper type system to an area of low pressure south and east of Long Island. A positive tilt trough aloft will be advancing eastward across the lower Great Lakes and Ohio Valley region. This set up looks to be conducive for some mesoscale banding to develop, and resembles a potential quasi-stationary band pattern from noted CSTAR research. Deterministic and ensemble model QPF has also increased from previous runs, which lends more confidence to a moderate snowfall event, especially for much of the area from the foothills of the southern Adirondacks south and east. Due to the best forecast 850-700mb F-Gen across SE NY into western New England, the most likely area for potential mesoscale banding looks to be across the southern Green Mountains of Vermont and the Berkshires of Massachusetts perhaps as far back as the Taconics in eastern New York based on the CSTAR research. The snow from the coastal low should persist through much of Wednesday morning, especially for areas east of the Hudson Valley. This system will likely impact the morning commute for much of the area. Wednesday afternoon, lake effect snow showers will start to develop downwind of Lake Ontario as westerly wind align with conditional lake-induced instability developing. So scattered snow showers will move back into the western Adirondacks before dark with some light accumulations possible. Lows Tuesday night will be in the upper single digits to upper 20s with highs on Wednesday in the upper teens to around 30. Lake effect snow showers will continue into Wednesday night across the western Adirondacks, but will be light due to lowering inversion heights. Otherwise, it will be mainly dry with near normal temperatures for the rest of the area. Lows will be in the single digits and teens. Mainly dry weather is expected on Thursday as high pressure builds into the region. Temperatures will be seasonable with highs in the upper teens to lower 30s. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... Mid-level ridging will be in place for the beginning of the weekend bringing mild temperatures along with it. Apart from the Adirondacks who could see an isolated snow shower on Friday, eastern New York and western New England look to remain dry through Saturday. There will be very weak forcing for ascent on Saturday over the region so there is a possibility some rain/snow showers may have to be added to the forecast as we approach the weekend. On Sunday a deep trough will be in place over the central CONUS. Negative PV advection resulting from the divergent outflow of low over the Midwest will support jet-o-genesis/ridging over the Northeast, further strengthening the WAA regime over our region. There will be increasing clouds during the day Sunday with rain pushing into the region late in the day as the low pressure center progresses northeastward over the Great Lakes region. Global guidance suggests an upper-level cut-off low developing with this system, so many more model runs will be needed to work out the details with this system. Highs will increase from the upper 20s (higher terrain) and low 30s (elsewhere) on Friday into the the low 40s (higher terrain) and high 40s (elsewhere) on Sunday. If the strong WAA regime materializes, temperatures will likely have to be increased. There could be some more snow melt and ice jam flood issues with the warming temperatures and rain next weekend. && .AVIATION /00Z TUESDAY THROUGH SATURDAY/...
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VFR conditions early this evening beneath a lingering ridge of high pressure, although MVFR stratus continues to impact KPSF due to moisture advection off the Atlantic. Some of this stratus is also getting into KALB/KPOU but at around 3.5kft. Expect this stratus to diminish somewhat around 03Z as low-level winds veer. Mid and high level clouds will continue to thicken and lower overnight ahead of an upper level trough tonight. Light snow is expected to begin, spotty at first, around 12Z and become steadier with IFR vsby expected around 14-15Z (except at KPOU where it could be around 3 hours later). Snowfall intensity may vary some during the day allowing vsby to improve to MVFR, but timing on that potential is unclear at this time. Winds tonight will be light and variable, becoming southerly at around 5 kt during the daylight hours on Tuesday. Outlook... Tuesday Night: Moderate Operational Impact. SN likely. Wednesday: No Operational Impact. NO SIG WX. 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: Low Operational Impact. Slight Chance of SHRA.
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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 very 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 Tuesday into Wednesday, with heavy snowfall possible from the northern and central Taconics east through 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 Watch from Tuesday afternoon through Wednesday morning for CTZ001-013. NY...Winter Weather Advisory from 7 AM Tuesday to 7 AM EST Wednesday for NYZ032-033-038>043-047>053-058>060-063>066- 082>084. Winter Storm Watch from Tuesday afternoon through Wednesday morning for NYZ054-061. MA...Winter Storm Watch from Tuesday afternoon through Wednesday morning for MAZ001-025. VT...Winter Storm Watch from Tuesday afternoon through Wednesday morning for VTZ013>015. && $$ SYNOPSIS...11/JPV NEAR TERM...Frugis/Thompson/JPV SHORT TERM...11/JPV LONG TERM...Cebulko AVIATION...Thompson HYDROLOGY...11/JPV

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