Area Forecast Discussion
Issued by NWS Albany, NY

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000 FXUS61 KALY 120540 AFDALY AREA FORECAST DISCUSSION National Weather Service Albany NY 140 AM EDT Wed Aug 12 2020 .SYNOPSIS... A cold front will stall near New York City Wednesday through Friday, resulting in some possible showers and thunderstorms each day across the mid-Hudson Valley into northwest Connecticut. Elsewhere, it will be mainly dry. Temperatures and humidity levels will be slightly lower for the rest of the week. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... As of 1259 AM EDT...Still seeing renewed convection along old outflow boundary across parts of Dutchess, southern Berkshire and Litchfield Counties. Downpours and some lightning will continue over the next few hours before moving out of the area. Additional rainfall amounts could still reach 0.50 to 1.00 inches in the most persistent storms. Still enough MLCAPE around 500-1000 J/Kg to support convection overnight, although DCAPE has diminished due to stabilization of the boundary layer. Increased pops across the southern part of the area for the convection moving through. In the wake of the showers and thunderstorms, clouds will partially break with the potential for some patchy fog in some valley locations. Lows will drop into the 60s to lower 70s, with muggy conditions persisting. && .SHORT TERM /6 AM THIS MORNING THROUGH THURSDAY NIGHT/... Wednesday and Thursday will feature mostly dry and slightly cooler and less humid weather across the region. The cold front which moved across the region on Tuesday night will continue to push farther south and east and eventually stall near New York City. Along this front, additional showers and thunderstorms will be possible each day. Most of the activity should stay south of the region during this time period but an isolated shower or thunderstorm cannot be ruled out across the mid- Hudson Valley into northwestern Connecticut, as they will be the closest to the front. Pops were lowered significantly from the previous forecast and in collaboration with surrounding offices. Farther north, a large area of high pressure will slowly build over the region and bring a cooler, less humid and drier air mass. Dew points will drop into the 50s to lower 60s, making it feel a bit more comfortable. Highs both days will range from the upper 70s in the higher terrain to the low to mid-80s elsewhere with lows in the 50s to lower 60s. && .LONG TERM /FRIDAY THROUGH TUESDAY/... The long-term forecast period looks to feature a downtrend in temperatures from warmer than normal levels at the period`s onset to closer to normal or even slightly cooler than normal values late in the period. As far as precipitation, the period is expected to be mostly dry particularly through the first half of the extended before chances increase late Sunday through Tuesday. This is all part of a potential large-scale pattern change where the heat ridge, which has been so vast and intense across much of the country for much of this season, focuses more on the western U.S. (with the closed 594+ dam heat dome parked over the Southwest U.S.). This will allow the potential for weakness (in the form of upper troughiness) in the H500 pattern to develop over the eastern U.S. In fact, global ensembles all indicate an upper trough to track from western Canada into central Canada and dig over the central United States. By Monday, forecast models are showing the mean trough axis to be established from the Hudson Bay into the Great Lakes and Appalachia. At the surface, a cold front will approach the FA from the west late Sunday night into Monday with showers and thunderstorms along and ahead of it. This coupled with mid to upper impulses associated with the aforementioned upper trough will support the potential for showers and thunderstorms Monday across eastern New York and western New England. Broad cyclonic flow aloft associated with mid to upper impulses still hanging over the region could support in another bout of some diurnal shower and thunderstorm development across the FA on Tuesday. Friday through Sunday, the deterministic models (particularly the ECMWF and Canadian-NH) shows surface high pressure over the area providing for plenty of subsidence and thus dry/tranquil weather. Temperatures as touched on earlier, will undergo a downtrend through the extended. Daytime high temperatures on Friday are expected to reach the mid 80s in the valleys decreasing to the upper 70s to near 80 by Tuesday (cooler higher elevations). Nighttime lows are expected to be mainly in the 60s through the extended (50s higher elevations). && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... A line of showers and storms has moved through the region and is currently exiting the southeastern zones of the forecast area as of 0530Z. A few showers may linger at KPOU for the next hour or two but all other TAF sites should remain dry. Some clearing is expected behind the line, which should promote some BR/FG development, especially since all TAF sites did receive rain. Will have to monitor as skies clear and winds lighten further over the next couple of hours. After daybreak, flying conditions will return to VFR for the remainder of the day. Winds will be light and variable overnight, becoming mainly westerly around 5-10 kts during the day. Outlook... 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: No Operational Impact. NO SIG WX. Saturday Night: No Operational Impact. NO SIG WX. Sunday: No Operational Impact. NO SIG WX. && .FIRE WEATHER... Isolated showers and thunderstorms are expected into this evening before a line of showers and thunderstorms push from west to east across the region tonight. This will result in RH values increasing to between 90 to 100 percent. A drier and slightly cooler and less humid air mass slowly builds across the region on Wednesday and Thursday. Any shower/thunderstorm chances will be across the mid-Hudson Valley into northwestern Connecticut. RH values will drop to around 40-55 percent during the day and rebound to between 85 and 100 percent at night. Winds will decrease to around 5 mph tonight. Winds both Wednesday and Thursday will be between 5-10 mph. && .HYDROLOGY... No widespread hydrological problems expected in the ALY Hydro Service Area over the next several days. A line of showers and thunderstorms are expected to move from west to east across the region tonight. On Wednesday and Thursday, only isolated shower or thunderstorm activity is expected across the mid- Hudson Valley into northwestern Connecticut with dry weather elsewhere. Locally heavy rainfall associated with thunderstorms may result in ponding of water or poor drainage flooding of low lying and urban areas. No river flooding is forecast at this time. 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/Rathbun NEAR TERM...SND/JPV/Rathbun SHORT TERM...Rathbun LONG TERM...Evbuoma AVIATION...JLV FIRE WEATHER...Rathbun HYDROLOGY...Rathbun

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