Area Forecast Discussion
Issued by NWS Albany, NY

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000 FXUS61 KALY 292110 AFDALY Area Forecast Discussion National Weather Service Albany NY 510 PM EDT Mon May 29 2017 .SYNOPSIS... Coverage of showers will diminish this evening, but more clouds and showers are likely Tuesday and Wednesday, with thunderstorms also possible as additional upper level disturbances move through the region. A dry day is finally in store Thursday. Temperatures will remain near to below normal. && .NEAR TERM /THROUGH TUESDAY NIGHT/... Tonight, after the initial surge of QG forcing/isentropic lift moves this afternoon, there appears to be little in the way of additional forcing through tonight. Will keep slight chance PoPs in case some remnant convection from central/western NYS can migrate eastward, and also for some patchy drizzle that may develop. Otherwise, just isolated showers with mostly cloudy skies expected. Lows should mainly fall into the upper 40s to mid 50s. Tuesday, another shortwave is expected to approach in the afternoon/evening. Models suggest some destabilization across central/western NYS in the afternoon, with perhaps some instability developing across the western Mohawk Valley/Adirondacks and eastern Catskills/Schoharie Valley if a few breaks in the clouds develop. There will be increasing 0-6 km bulk shear potentially exceeding 50 kt, esp across the southern Adirondacks and Mohawk Valley by later in the day, so if some convection migrates into western areas, some gusty winds may occur. In addition, MLMUCAPES reach 500-1000 J/KG acrs this region Tuesday afternoon. Latest SPC Day 2 Outlooks has the region in a Marginal Risk for severe wind gusts with convection late Tuesday afternoon/evening, but remains highly conditional on how much destabilization, from any breaks in the clouds that develop, late in the day. Current forecast highs are in the upper 50s to upper 60s. Tuesday night, remnant convection may still be ongoing across the region through midnight, especially from the Capital Region and points N and W. Convective trends should weaken through the night, esp S and E of the Capital Region where a deeper stable marine layer may reside. So, gradually decreasing chances for showers/storms through the night, with lows mainly in the upper 40s to mid 50s. && .SHORT TERM /WEDNESDAY/... The flow pattern will be dictated by a nearly-stationary upper low over northern Ontario. Upper trough axis extending southward from the low will swing through on Wednesday, resulting in the likelihood of another batch of diurnally-enhanced showers and thunderstorms. Potential for severe weather is intriguing with fast midlevel flow resulting in deep-layer shear values around 50 kt. The limiting factor will again be instability. However, there does appear to be a window for partial clearing Wednesday morning (depending on the departure of any Tuesday night activity) which would boost surface-based instability values. Midlevel lapse rates are progged to be solid at around 6.5-7 C/km as 500 mb temps drop to near -20C. Model surface dewpoints from the GFS/NAM in the upper 50s to low 60s may be a bit overdone, but even with MOS values in the mid-50s combined with highs in the 70s in the valleys, could still generate AOA 500 J/kg MLCAPE. Combined with deep-layer shear values, this could be enough for organized convection. Low wet bulb zero heights around 7500 feet suggest hail will be a threat with any organized convection, along with gusty winds. Given uncertainty with instability, SPC day 3 marginal risk looks good for now. Wednesday night into Thursday, midlevel flow will become more northwesterly in the wake of the trough passage as the Ontario upper low elongates in a west-east fashion. Subsidence spreading across the area looks to finally result in a dry day Thursday, although somewhat cooler than normal with 850 mb temps dropping to around 3C. Clouds may increase somewhat late Thursday night ahead of the next system. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
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The very active pattern continues into early June as a large upper level trough influences the Northeast for the end of the work week into the first weekend of the month bringing is multiple precipitation threats and cooler temperatures. We start the extended period with a cold front dropping out of southern Canada into the Northeast on Friday. While uncertainties exist with the front`s arrival time, have put the highest POPS in for the daytime Friday and lingered low chance POPS into the evening, especially for south/eastern zones. With WAA out ahead of the front bringing 850mb isotherms up to 8C - 11C, high temperatures Friday should reach into the mid 70s for southern areas. Further north/west highs may only reach mid 60s where the front should arrive earlier in the day. Included slight chance thunder with the frontal passage as well given the southwesterly flow out ahead of the front. This front looks to stall on Saturday with the Euro and Canadian showing it stalling in the NYC/coastal CT area and a cooler air mass associated with Canadian high pressure building in behind it. The GFS is the outlier with its solution showing the front stalling much further north and west well into our CWA. Have edited the forecast to be in line with the EURO/Canadian solution. The cooler Canadian air mass will lead to below normal temperatures for the first weekend of June with highs in the upper 60s/low 70s Saturday and even cooler Sunday with most places struggling to rise out of the 60s. There is decent packing of the isobars due to the stalled boundary in close proximity to incoming high pressure so breezy conditions can be expected as well. Uncertainty exist with the precipitation threat for Saturday as most of the guidance shows a disturbance riding along the stalled boundary. Just how far north the boundary stalls will determine which areas receive showers in our CWA, if any. Have left chance POPS for now with highest POPS for southern spots to keep in line with the Canadian/Euro consensus. The uncertainty continues into Sunday, unfortunately, as the Canadian shows the front sliding well to our south and thus a dry forecast while the Euro shows a disturbance from the Ohio Valley moving northward into our region. Left slight chance POPs in for now but it is a low confidence forecast. Increased POPS heading into Monday as a potentially potent disturbance from the Midwest should move eastward into the Northeast. There is uncertainty on timing of precipitation as the Canadian shows the upper level shortwave cutting off rapidly in the Midwest and thus a slower arrival time while the Euro shows a weaker shortwave that moves in quicker. Given the time of year, have leaned closer to the EURO`s solution of a weaker system and thus only have chance POPS.
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&& .AVIATION /21Z MONDAY THROUGH SATURDAY/... Rain will continue this afternoon across the TAF sites although it will decrease in intensity and becoming more intermittent later this afternoon. Expect VFR conditions mixed with MVFR, mainly for Cigs, but also occasionally for Vsbys through this afternoon as the steadier rain moves through. Later in the day, coverage of showers will become more scattered but with continued VFR/MVFR conditions. VFR/MVFR cigs are expected to continue into this evening, and may lower to IFR levels later tonight, esp at KPSF. On Tuesday MVFR conditions are expected with showers and a chance of thunderstorms especially during the afternoon. Winds will be southeast around 5-10 kts through tonight with south winds at 10-15 kts on Tuesday. Outlook... Tuesday Night: High Operational Impact. Likely SHRA...TSRA. Wednesday: High Operational Impact. Likely SHRA...TSRA. Wednesday Night: Moderate Operational Impact. Chance of SHRA. Thursday: No Operational Impact. NO SIG WX. Thursday Night: Slight Chance of SHRA. Friday: Moderate Operational Impact. Scattered SHRA...TSRA. Friday Night: Low Operational Impact. Isolated SHRA. Saturday: Low Operational Impact. Isolated SHRA. && .FIRE WEATHER... A series of upper level disturbances will continue to impact the region, with showers and thunderstorms likely Tuesday and Wednesday. Rainfall is not in the forecast for Thursday, but temperatures will be a bit cooler than normal with RH values bottoming out mainly in the 40s. Westerly winds gusting to near 20 mph may help to dry things out somewhat. && .HYDROLOGY... Steady rainfall continues to exit east, with reports and radar estimates suggesting 0.25" to up to 1.00" has fallen, with heaviest amounts over Herkimer County. Additional periods of showers and thunderstorms are likely late tonight into Tuesday. Rainfall totals are generally expected to remain at a half inch or below, but locally a half inch to an inch is possible over the Mohawk Valley and Western Adirondacks. Showers and thunderstorms are likely yet again on Wednesday, with an additional 0.25-0.75" expected. Widespread flooding is not expected, although some minor urban, small stream, and poor drainage flooding cannot be ruled out especially if storms train over the same area. 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. && .EQUIPMENT... The ASOS at the Pittsfield Municipal Airport, MA continues to experience outages with hourly METARS occasionally or continuously missing. This will persist until communications are fully restored. && .ALY WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. MA...None. VT...None. && $$ SYNOPSIS...KL/Thompson NEAR TERM...KL/11 SHORT TERM...Thompson LONG TERM...Speciale AVIATION...KL/11/JPV FIRE WEATHER...Thompson HYDROLOGY...Thompson EQUIPMENT...ALY Staff

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