Area Forecast Discussion
Issued by NWS Albany, NY

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000 FXUS61 KALY 151730 AFDALY Area Forecast Discussion National Weather Service Albany NY 1230 PM EST Wed Nov 15 2017 .SYNOPSIS... High pressure will be over New York and New England today with some sunshine and seasonable temperatures. The surface high will drift east of New England tonight, as a warm front associated with low pressure moving east of the northern Great Lakes Region will bring some light rain and snow to the region. A cold front will move through the area on Thursday with a coastal low pressure system forming south and east of Long Island, as rain showers will transition to snow showers with some accumulating snowfall over the higher terrain and north and west of the Capital Region into Thursday night. Cold and brisk conditions will close the work week with high pressure building back in. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Low clouds have eroded and high clouds are beginning to stream in from the west. Sunshine has helped temperatures get into the 40s and temperatures should rise a few more degrees this afternoon. Light south winds will also help temperatures to rise. Just minor adjustments to temperatures and sky cover through this afternoon. High temps today will range from the mid 30s to lower 40s over the mountains, and be in the mid to upper 40s in many of the valley locations. && .SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/... Tonight...Clouds will rapidly thicken and lower across the forecast area from the west to southwest to the east to northeast. As the warm front lifts through, the isentropic lift increases on the 290K/295K surfaces with an H850 low-level jet of 35-50 kts. The low-level jet is the strongest over central NY extending into the eastern Catskills, western Mohawk Valley, and the southern Adirondacks. Have slowed down the timing for the warm advection pcpn until close to 02Z to 05Z west of the Hudson River Valley, and then spread it eastward after midnight. Critical partial thickness and BUFKIT soundings indicate an onset of rain/snow across the forecast area, as wet bulb or evaporative cooling supports snow over the higher terrain initially, before temps rise above freezing. Actually min temps will occur shortly before or just after midnight, and then start to rise. H850 temps are 0 to +2C from southern VT, and the Mohawk Valley, Capital Region south and west by 12Z. Locations such as the southern Adirondacks/Lake George Region hover around 0C to -1C. The 00Z GFS/NAM 925 hPa temps are generally +0.5C to +4C. The valley areas will likely see little or no snow, except over portions of the west-central Mohawk, Upper Hudson Valley, and the eastern Windham County VT, where a coating to less than a half inch is possible. The southern Adirondacks may receive 1-2", with an inch or so over the eastern Catskills, and the southern Greens. Less than an inch for the Berkshires, northern Taconics, and Litchfield Hills. Low temps will likely be in the mid to upper 30s in most of the valley areas. The exception will be for the Upper Hudson River Valley, and eastern Windham County near the CT River Valley, where some lower 30s are possible. Expect lows in the upper 20s to lower 30s over the mountains. Thursday...The mid and upper level short-wave trough becomes negatively tilted with the cold or occluded front moving across the region in the morning. A secondary or coastal low forms just south and east of Long Island and races northeast toward southeast New England based on the majority of the deterministic and ensemble guidance in the late morning and early pm. The coastal low is fast moving that quickly draws in colder air across the region as the mid and upper level low moves overhead. The 00Z ECMWF continues to be on the western end of the envelope of solutions with the quick moving secondary or coastal low. The 00Z NAM and GFS are slightly further east with more of an impact across central and eastern New England. Low and mid level thicknesses will be lowering, and a transition to wet snow is possible across the western New England higher terrain during the afternoon. The boundary layer looks too warm for snow in many of the valley areas especially westward into the Hudson River Valley. It will continue to be monitored, as the strength of the upward vertical motion or omega profiles in the northwest quadrant of the cyclone could cool the column down enough for wet snow in eastern Windham County, and the rest of western New England. If this occurs, we may have to increase snow amounts. For now, we have some light snow accums over the southern Greens and northern Berkshires of an inch or less. Further west, under the chilly H500 upper level low with temps lowering to -28C to -30C, we expect some accumulating snowfall over the southern Adirondacks, eastern Catskills, and the western Mohawk Valley in the mid and upper level deformation zone, and due to the cyclonic vorticity advection. The WPC Probabilistic guidance indicates high chc probs for a few inches (2" or greater) of snow over the southern Adirondacks THU-THU night, with lower chances over the southern Greens. We are expecting an additional inch or perhaps two before nightfall in parts of the southern Adirondacks. Highs temps will be in the mid 40s to around 50 in the Hudson River Valley, southern Berkshires south into NW CT with upper 30s to lower 40s over southern VT, especially east of western Bennington Co., the southern Adirondacks, and the eastern Catskills. Thu night...A brief lake connection in the northwest flow is likely. Also, some west/northwest upslope rain to snow showers are possible along the spine of the southern Greens, northern and central Taconics, and the Berkshires. 925 hPa temps fall -3C to -7C across the region. Lows fall into the 20s to lower 30s with a few teens over the southern Adirondacks. Additional snow accums will range from a few tenths in the Taconics, Schoharie Valley and Lake George Region to up to an inch or two over the southern Adirondacks, southern Greens, western Mohawk Valley, and eastern Catskills. Little or no snow is expected in the Capital District, mid- Hudson Valley, and southern Litchfield County. It will be blustery Thu night in the wake of the coastal low with northwest winds of 15 to 25 mph with a few gusts in the 35 mph or so range. Fri-Fri night...The low and mid-level flow quickly turns anticyclonic and northerly with high pressure building in from southeastern Ontario and the eastern Great Lakes Region. The lake effect and upslope snow showers will end by day break. The winds will gradually diminish during the day, as the sfc pressure gradient between the departing storm into the Canadian Maritimes and the sfc anticyclone building in weakens. Max temps will run about 5 degrees below normal with generally upper 30s to lower to mid 40s in the lower elevations, and upper 20s to upper 30s over the hills and mtns. High pressure slowly shifts eastward, and the onset of the warm advection pcpn with the next storm system approaching from the Great Lakes Region will likely hold off until the late morning on Saturday based on the latest deterministic and ensemble guidance trends. Low temps will likely fall into the 20s with some teens over the southern Dacks and southern Greens. && .LONG TERM /SATURDAY THROUGH TUESDAY/... The period starts out on Saturday with the likelihood of precipitation increasing as isentropic lift on the 290K surface develops in response to a frontal system approaching from the lower Great Lakes. Temperature profiles initially look to be cold enough for precip to start as a period of snow or a rain/snow mix in valleys. However, as the parent cyclone tracks northeastward into southern Quebec, low-level warming due to a strengthening S-SW flow will result in a rather quick changeover to plain rain by Saturday afternoon. The higher elevations will experience a slightly slower transition to rain, where some minor accumulations of less than an inch area possible mainly over the Adirondacks/Catskills. Will maintain high pops through much of Saturday night, as the system`s cold front crosses the region with additional rainfall. Minimum temps will occur close to sunrise Sunday morning, as temps will likely stay relatively warm much of the night ahead of the cold front. There are still some timing differences among various sources of model guidance, but overall trend has been for a slower evolution. Still, it is possible that temps cool off enough before the steady precip ends for a changeover back to snow across the higher terrain early Sunday morning. Winds will rapidly shift to the west behind the cold front an increase Saturday night. Wind gusts around 30-40 mph possible by Sunday morning. Sunday will feature breezy conditions with lake effect/upslope snow showers across the higher terrain as colder air aloft settles in. At this time based on expected west-northwest flow trajectory, lake effect snow will be most likely across the southwest Adirondacks and Mohawk Valley. However, it is too early to pinpoint exact locations and snow amounts. Light to moderate accumulations are possible. Lighter upslope snow showers possible across the southern Greens and Berkshires. Dry and blustery conditions will occur outside of the lake effect/upslope areas. It will remain breezy in the westerly/cold advection regime, with occasional gusts possibly exceeding 40 mph in spots. Lake effect snow to persist into Sunday night, but shift southward towards the Schoharie Valley and eastern Catskills as the flow is expected to become more northwesterly. GFS/ECMWF indicating surface ridging to occur on Monday, with just a few leftover lake effect snow showers. Dry and cool conditions expected Monday night into Tuesday. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
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High pressure will continue moving off the northern New England coast this afternoon. Low pressure will approach from the Great Lakes region tonight, and move across the area during Thursday. A warm front associated with this system will approach from the southwest late tonight into Thursday morning, followed by a cold frontal passage early Thursday afternoon. VFR conditions are expected through this afternoon, as patchy lower clouds remain confined to higher elevations. High/mid level clouds will increase from west to east this evening. Later tonight, lower clouds will expand northward across the region, with MVFR Cigs developing. Also, light rain will develop after 08Z/Thu, with periods of light rain/rain showers expected through at least 16Z/Thu. Some wet snow could be mixed in initially at KPSF. Expect MVFR/IFR conditions to develop, both for Cigs and Vsby, from around 09Z/Thu through at least 16Z/Thu. Conditions could improve in some areas after 16Z/Thu, esp at KPOU, where MVFR/VFR conditions may develop. Winds will trend into the southeast to south at 5-10 KT this afternoon, then become light/variable after sunset. However, at KALB, south winds may actually increase later this afternoon into a good portion of tonight, as south winds increase to 8-12 KT, with some gusts of 15-20 KT possible. Winds may decrease shortly after the rain develops. On Thursday, expect south to southwest winds through 18Z/Thu at generally 5-10 KT, with some gustiness possibly developing toward and after 18Z/Thu. Low level wind shear is expected to develop at sites where surface winds decrease to less than 8 KT tonight, as winds around 2000 FT AGL increase from the south to 35-40 KT. So, have included mention of LLWS at KGFL/KPOU and KPSF for later tonight. Outlook... Wednesday Night: Moderate Operational Impact. Likely SHRA. Thursday: Moderate Operational Impact. Likely SHRA. Thursday Night: Low Operational Impact. Breezy Slight Chance of SHRA...SHSN. Friday: Low Operational Impact. Breezy NO SIG WX. Friday Night: No Operational Impact. NO SIG WX. Saturday: High Operational Impact. Definite RA...SN. Saturday Night: High Operational Impact. Breezy Definite RA. Sunday: Low Operational Impact. Breezy Slight Chance of SHRA.
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&& .FIRE WEATHER... High pressure will be over New York and New England today with some sunshine and seasonable temperatures. The surface high will drift east of New England tonight, as a warm front associated with low pressure moving east of the northern Great Lakes Region will bring some light rain and snow to the region. A cold front will move through the area on Thursday with a coastal low pressure system forming south and east of Long Island, as rain showers will transition to snow showers with some accumulating snowfall over the higher terrain and north and west of the Capital Region into Thursday night. && .HYDROLOGY... No major problems are expected on the main stem rivers the next 5 days ending Sunday. Dry weather is expected today with temperatures trending closer to normal. A warm front, and then a cold front will bring precipitation back to the Hydro Service Area, Wednesday night into Thursday morning. A coastal low and an upper level low will keep the precipitation going into Thu night. Total liquid equivalents will range from about two tenths to a half of an inch over the area. The higher totals will likely be across the southern Adirondacks and portions of western New England. Snow amounts may range form 2 to 4 inches or so over the southern Adirondacks and southern Greens late Wed night through Thu night. High pressure briefly builds in on Friday before strong low pressure approaches from the Great Lakes Region on Saturday. A bout of rain/snow to all rain is likely ahead of the warm front initially. A cold front will sweep through Saturday night into Sunday with additional precipitation. Right now, total QPF from the system will range from a half an inch to three quarters of an inch. 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...None. NY...None. MA...None. VT...None. && $$ SYNOPSIS...Wasula NEAR TERM...NAS/Wasula SHORT TERM...Wasula LONG TERM...JPV AVIATION...KL/JPV FIRE WEATHER...Wasula HYDROLOGY...Wasula

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