Area Forecast Discussion
Issued by NWS Albany, NY

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000 FXUS61 KALY 160226 AFDALY AREA FORECAST DISCUSSION National Weather Service Albany NY 926 PM EST Fri Feb 15 2019 .SYNOPSIS... Showers are likely along an approaching cold front this evening, with some light snow over the higher terrain. Temperatures will return to seasonable values for the weekend behind the front with mainly dry weather expected. A weak system has the potential to bring light accumulating snow Sunday night into Washington`s Birthday. && .NEAR TERM /THROUGH SATURDAY/... Showers have exited and the cold front is through all areas. There is a zone of clearing in central and eastern NY but clouds still lingering from just east of the Capital District to points south through the Taconics and the mid Hudson valley into western New England. The clearing should linger through this evening but as low level flow turns more NW, some of the lake effect clouds and moisture should build east and close off the zone of clearing. West to northwest surface winds will likely stay steady through the night, slowing the cooling of temperatures overnight. Some lake effect snows should extend into the southern Adirondacks by daybreak, too. Just some minor adjustments to temperatures, sky cover and chances for snow showers through the night. Previous AFD below... Expecting little more than a few hundredths of an inch to around a tenth of an inch of QPF with this front, although there could be some brief downpours as forecast soundings suggest steep lapse rates and weak shallow instability. The rain could briefly end as snow showers but accumulation is not expected outside of the southern Adirondacks and perhaps the southern Greens and Berkshires where less than an inch is expected. Ahead of the front, gusty southerly winds to around 25 kt will continue. Temperatures will continue to drop in steady cold advection behind the front, with westerly winds gusting 20-30 kt at times. A steep temperature drop has been observed at KRME/KSYR of about 7F in an hour. The NYS Mesonet site at Herkimer dropped 9F in about 15 minutes. Lake effect snow will begin over the western Adirondacks, but accumulations look limited due to the shallow inversion heights barely over 1 km, and marginal surface to 850 mb delta- Ts of around 15C. Could pick up 1 to 3 inches tonight into early tomorrow over northern Herkimer and Hamilton Counties, with a few tenths of an inch possible closer to the Thruway corridor late tonight into Saturday morning. Will need to watch for the potential for moisture to freeze on surfaces with the cold advection, although gusty winds should dry things out a bit. Lows will be in the upper teens to upper 20s with at least partial coverage of postfrontal stratus. Saturday, midlevel troughing will remain overhead early with height rises occurring in the afternoon as a surface ridge builds in. This will allow any remaining lake effect activity to dissipate. Partial sunshine is expected with highs near seasonal normal values in the mid-20s to upper 30s. && .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/... Saturday night into Sunday, a mainly tranquil period of weather is expected with zonal midlevel flow trending southwesterly with time. At the surface, a ridge of high pressure will continue to nose into the region from the northwest, resulting in good radiational cooling conditions Saturday night. Lows in the single digits and teens are expected, near normal for this time of year. With the cold high remaining to the north and low pressure organizing to our southwest, expect seasonably cold conditions to continue Sunday. Morning sunshine should give way to increasing high and mid clouds by the afternoon and evening. Some light precip may creep into the Catskills late in the day, but the majority of the day should remain dry. Sunday night into Monday, a flat midlevel wave tracks into the region in fast west-southwest flow. At the surface, weak low will move up the upper Ohio Valley before reforming offshore of NJ. Broad isentropic lift will begin spreading into the region after 00Z Mon, and may take a bit of time to saturate the column. Some weak frontogenesis is depicted by the 12Z GFS in the 850 to 700 mb layer as well. The ECMWF, which had kept the precipitation mainly to our south, has trended back north a bit for the 12Z run. There are a majority of GEFS plumes that result in measurable precipitation for much of our area, so have increased PoPs to the likely range for 06-12Z Mon for all but the northernmost tier of zones. Some lingering weak Fgen is depicted 12-18Z Monday even after the low goes well offshore, so we could wring out additional light accumulations. At this point, appears a 1-3 inch snowfall is possible over much of the forecast area. There is still some uncertainty to be worked out regarding timing and track of the system, but trends have been a bit wetter. Lows are expected to range from the upper single digits to the mid-20s, so any snowfall that occurs should stick readily to most surfaces. Timing could impact the Monday morning commute (to the extent that one exists on a federal holiday). Any lingering snowfall should taper off Monday afternoon and evening. Highs are expected to reach the mid-20s to mid-30s, a bit below seasonal normals. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... This period will be dry on the ends with snow at mid-week. High pressure builds across the forecast area with plenty of sunshine on Tuesday. The high breaks down in response to weak low pressure expected to materialize with great ambiguity somewhere over the mid- Atlantic and affect our area with snow, with the height of the activity being Wednesday night. The Canadian and European models hint at light snowfall amounts, with the GFS being slightly more generous. This situation will have to be monitored over the course of this weekend to see if models could be evolving things into a more concise system, but right now it looks like nothing more than a minor event...mainly snow. Flows look to be somewhat weak through a large column from the surface on up, which may allow sufficient-enough diurnal warming to change some central and southern zone locations over to a rain or mix as the system begins to pull away on Thursday. Sprawling Upper Midwest high pressure tries to work its way in, but a low pressure wave across the mid South will at least limit the availability of sunshine initially. However...for now the high is expected to win out for the start of the following weekend. High temperatures will range from the upper teens to mid 30s on Tuesday, the lower 20s to lower 30s on Wednesday, the upper 20s to upper 30s on Thursday, and from around 30 degrees to around 40 degrees on Friday. Lows will range from around zero degrees to the mid teens Monday night, the lower single digits to around 20 degrees Tuesday night, and the lower teens to mid 20s Wednesday night. Only very slightly colder readings are expected for Thursday night. && .AVIATION /03Z SATURDAY THROUGH WEDNESDAY/... A cold front is tracking through the region and winds have shifted at KALB and KGFL but will shift from south to west at KPOU and KPSF by about 02Z-04Z. There are scattered showers in the region but mainly north of KPOU. So, including VCSH at KALB, KGFL and KPSF with TEMPO for MVFR visibilities and ceilings between 00Z-04Z in any scattered showers. Just including VCSH at KPOU but no TEMPO for any reduced ceilings or visibilities because any showers are more isolated. Once the cold front exits the entire region, there will be some intervals of breaks in the clouds but moisture off the great lakes will result in a mostly cloudy sky through tonight. Ceilings should be just above 3000 feet but could be at or just below 3000 feet at KPSF for a time between 06Z-14Z. All ceilings rise to or above 3500 feet after about 14Z Saturday. Visibilities will be predominantly VFR through Saturday afternoon. Winds will shift to west this evening at around 10 Kt with some gusts over 20 Kt, maybe approaching 30 Kt at KALB. West winds continue through tonight, gusty at times, then shift to northwest after about 14Z Saturday, and continuing gusty through Saturday afternoon. Outlook... Saturday Night: No Operational Impact. NO SIG WX. Sunday: No Operational Impact. NO SIG WX. Sunday Night: Moderate Operational Impact. Likely SN. Washingtons Birthday: Moderate Operational Impact. Chance of SHSN...SN. Monday Night: No Operational Impact. NO SIG WX. Tuesday: No Operational Impact. NO SIG WX. Tuesday Night: No Operational Impact. NO SIG WX. Wednesday: Moderate Operational Impact. Chance of SN. && .HYDROLOGY... No hydrologically significant precipitation is expected through the weekend. Some light rain and snow showers will occur along a passing cold front this afternoon and evening, with light lake effect snow in its wake. Temperatures will return to seasonable values this weekend. A weak system will bring the potential for light accumulating snow Sunday night into Monday, but QPF totals are expected to be a quarter inch or less. 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...Thompson NEAR TERM...NAS/Thompson SHORT TERM...Thompson LONG TERM...ELH AVIATION...NAS HYDROLOGY...Thompson is the U.S. government's official web portal to all federal, state and local government web resources and services.