Area Forecast Discussion
Issued by NWS Albany, NY

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000 FXUS61 KALY 170009 AFDALY AREA FORECAST DISCUSSION National Weather Service Albany NY 709 PM EST Wed Jan 16 2019 .SYNOPSIS... Cold and windy conditions are expected tonight with clearing skies. Fair and cold weather is expected tomorrow before light snow moves into the area for Thursday night into Friday morning. A significant winter storm is expected late Saturday into Sunday across the entire area. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... As of 709 PM EST...Cold front has crossed the forecast area and temperatures are falling over all the area except the extreme south. Blustery this evening with winds gusting up to 40 MPH. Radar shows light snow showers over about two thirds of the forecast area. A few locations may see a coating of additional snow, but for most locations just some flurries. 7PM balloon sounding showed well mixed boundary layer with dry adiabatic lapse rate to 810mb - hence the windy conditions. Still expecting skies to be mainly clear after midnight and with diminishing winds, temps should drop off quickly late tonight. Temps forecast to fall into the single digits to teens for lows. Some parts of the Adirondacks will be in the single digits below zero for tonight. Although winds will be decreasing by late tonight, some wind chill values could reach as low as -10 to -18 over the Adirondacks. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/... 1030 hpa surface high pressure area will be passing over the area for Thursday morning. This will allow for light winds and clear skies. After a cold morning, temps will only warm up into the teens and 20s for highs on Thursday. Some clouds will start increase by late in the day, as the high starts shifting offshore of eastern New England and the next system starts to approach from the Ohio Valley. A weak area of low pressure will be shifting from the Ohio Valley towards the mid-Atlantic coast for Thursday night into Friday. Weak warm air advection will allow some light precip in the form of snow to develop across the area for late Thursday night. It may take a little bit of time for this to occur, as the very dry air mass at low levels will need to moisten up, but most areas should see some light snow after midnight, lifting northeast across the region. Limited moisture and weak forcing will keep QPF rather low, generally just 0.05 to 0.20 of liquid equivalent. Still, this will allow for about one to two inches of snow across the whole area, which will make for a slick morning commute on Friday morning. Precip should taper off by the mid to late morning on Friday, as the best forcing shifts east of the region. Some clearing in the clouds is expected on Friday afternoon as temps rise into the mid 20s to mid 30s across the area. With zonal flow in place aloft, some lingering clouds are expected for Friday night, but it should be mainly dry. Some low-level cold advection should allow for some colder temps to push into the area once again, with lows falling into the single digits and teens across the area. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... Confidence continues to increase for a significant multi-hazard winter storm impacting eastern NY and western New England Saturday into Sunday. Main hazards include heavy snowfall amounts and rates, possible period of sleet/freezing rain leading to ice accumulations for some(mainly Catskills, mid-Hudson Valley, NW CT) followed by strong winds/blowing snow potential and an arctic air mass that may lead to dangerous wind chills Sunday night into Monday. Strong 1035hPa high pressure in Quebec noses builds southward into the Northeast during the day on Saturday with northwesterly flow advecting in a chilly air mass across eastern NY and western New England. High temperatures are expected to remain well below freezing through the region with most staying in the teens and 20s. As upper flow backs to the southwest, clouds continue thickening through the day. The 12z/16 global guidance has come into better agreement that for a stronger moisture rich southern stream wave originating from the Pacific Ocean will dig into the Gulf States and pick up additional moisture from the Gulf during the day Saturday. As it travels northeastward towards the Ohio Valley and warm air overruns the cold air wedge over the Northeast, snow will begin from southwest to northeast. Exact start time for snow is still uncertain but guidance continues to suggest some light snow is possible Saturday morning from weak isentropic lift before the more appreciable snowfall associated with our winter storm overspreads the region Saturday afternoon and especially after sunset. Overnight Saturday, our southern stream wave moves into Ohio Valley as a potent northern stream wave associated with a strong upper level low and a very cold air mass over the Hudson Bay drops into the Great Lakes. Global guidance has come into better agreement that the two do not phase until during the day Sunday and this delay would mean our intensifying storm tracks across the I-95 corridor with the associated 850hPa low tracking from eastern PA across the mid-Hudson Valley into eastern New England Saturday night into Sunday. This has implications on the northern extent of our wintry mix/snow line would keep it suppressed further snow to the mid- Hudson Valley/NW CT/Berkshires with areas north and west likely remaining all snow (perhaps brief period of snow/sleet). While the first half of Saturday night likely remains all snow across eastern NY and western New England with high snow ratios (dry/fluffy snow) and possibly high snowfall rates given strong lift extending through a deep column intercepting the dendritic snow growth zone, we could then see the warm nose inch northward towards our area. The second half of Saturday night looks to experience the strongest warm air advection as our 850hPa jet intensifies to 50-60kts which would warm the column and increase the fetch of Gulf/Atlantic moisture reaching the Northeast. This would then shrink our dendritic snow growth zone and even shift the "sweet spot" experiencing the best lift through the -12C to -18C zone to the Upper Hudson Valley and Adirondacks. While this would decrease snow ratios for areas from the Greater Capital District south and eastward, there is strong agreement amongst the global guidance that a copious amount of moisture advects into our area with potentially 0.50 - 0.75 inches of liquid from 06z - 12z Sunday. In fact, the snowfall band overnight Saturday resembles that of a quasi- stationary snowfall band as described in previous CSTAR research. Thus, even lower snowfall ratio closer to climatology (10 to 12:1) would not limit significant snowfall accumulations and high snowfall rates. Thus, our confidence for areas reaching warning criteria snowfall continues to increase from the Capital District north and west. For areas in the mid-Hudson Valley, NW CT, the Catskills and perhaps the Berkshires, the warm nose could inch close enough the mid levels warm close enough to or even higher than 0C that these areas mix with sleet and even freezing rain. This could lead to ice accumulations as the sfc-925 layer remains cold. Exact icing potential is still uncertain but should be ironed out this event draws closer. The ECMWF is the coldest solution limiting the wintry mix to the far southern mid-Hudson Valley and NW CT with the CMC-NH a bit farther north with the mixing potential while the GFS is the warm outlier. For this update, again went with a ECMWF and CMC-NH blend for precipitation type. By Sunday, our northern stream and southern stream wave phase over the Northeast allowing our positively tilted trough to become neutrally titled. Snowfall continues into Sunday morning with cold air quickly wrapping in behind our system with our warm nose quickly shifting into New England. Any wintry mix Sunday morning should then transition back to all snow during the day with snow ratios increasing again. Winds during the day Sunday look to also increase as the storm matures over New England with gusts up to 25-30 mph possible potentially leading to blowing snow. Snowfall should linger through most of the day Sunday before exiting from west to east late in the day into Sunday night. Total liquid equivalent for this event remains impressive with very good model agreement with 1 - 1.75 inches of liquid across the region which is why we continue to believe this event will lead to significant snowfall amounts. Very cold air continues advecting into eastern NY/western New England Sunday night with 850hPa isotherms dropping to -19C to -28C and surface lows falling into the single digits and even below zero from the Capital District north/west. Strong winds continue overnight as well with gusts 25 - 35mph possible which could lead to dangerous wind chills and necessitate wind chill headlines. Monday remains cold with temperatures likely only rising into the teens and single digits. Winds stay breezy and with such cold temperatures, it won`t take much for wind chills to reach dangerous levels (-5F to -20F). Some lake effect snow showers are possible for the terrain given arctic northwest flow over the lakes. We should moderate by Tuesday with high temperatures warming into the teens and 20s but the pattern turns active again by mid-week with another possible system. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... Mainly VFR conditions forecast for the next 24 hours. KGFL, KALB and KPSF could see a brief period of MVFR conditions in a light snow shower or flurry this evening before skies clear around midnight. Gusty northwest winds to 35 kts this evening diminish to around 10 kts towards daybreak Thursday. Winds on Thursday forecast to be light and variable. Outlook... Thursday Night: Moderate Operational Impact. Likely SN. Friday: Moderate Operational Impact. Chance of SHSN...SN. Friday Night: No Operational Impact. NO SIG WX. Saturday: Moderate Operational Impact. Chance of SN. Saturday Night: High Operational Impact. Definite SN. Sunday: High Operational Impact. Definite SN. Sunday Night: Moderate Operational Impact. Chance of SN. Martin Luther King Jr Day: Low Operational Impact. Breezy NO SIG WX. && .HYDROLOGY... No hydrologically significant precipitation is expected until the weekend. Temperatures will remain mainly below freezing, favoring continued ice formation/expansion on area waterways. A powerful winter storm is set to impact the region over the weekend. The precipitation type is expected to be mainly snow with a wintry mix possible across the Catskills, mid Hudson Valley, Taconics, Berkshires and NW CT. QPF could exceed an inch with the potential for up to two inches in some areas. 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...SND/Frugis NEAR TERM...SND/Frugis SHORT TERM...Frugis LONG TERM...Speciale AVIATION...NAS HYDROLOGY...Frugis/Thompson

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