Area Forecast Discussion
Issued by NWS Albany, NY

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000 FXUS61 KALY 201738 AFDALY Area Forecast Discussion National Weather Service Albany NY 138 PM EDT Fri Oct 20 2017 .SYNOPSIS... An area of high pressure will build in from near the Mid Atlantic States this afternoon into tonight for the upcoming weekend, resulting in continued dry weather and above normal temperatures. Unsettled weather returns late Monday into the midweek. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... As of 109 PM EDT, Strong subsidence in the wake of a dry cold front east of New England, and a sfc anticyclone building in from the Piedmont Region and the Mid Atlantic States has yielded sunny skies. The visible satellite picture is clear and there are very little changes to make to the ongoing forecast with a tweak upward for a few lower 70s over the mid-Hudson Valley. The 12Z KALY sounding shows the strong subsidence inversion with weak/modest cold advection and the strong northwest flow throughout the troposphere aiding in some downsloping. North to northwest winds of 10 to 15 mph with some gusts to 25 mph or so due to decent mixing will continue this afternoon before subsiding quickly. Highs will be in the mid 60s to around 70F in the valleys. Upper 50s to lower 60s will be common over the mountains. Some of the previous near terms... Winds have become breezy out of the north- northwest this morning behind the dry frontal passage last night with temperatures currently sitting in the 50s to near 60 degrees. This will allow for a sunny and dry day today, which remains on par with our current forecast. Further details regarding the forecast are below. There are indications that a boundary layer thermal gradient sets up right in the middle of our forecast area, implying high temperatures in northern areas could be considerably cooler than in southern areas. Differences in guidance as to where that gradient sets up result in some uncertainty but generally highs in the 60s today with a few lower 70s southern areas and around 60 southern Adirondacks. && .SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY NIGHT/... High pressure controls the weather through the period and builds east. Warm advection is expected to begin Saturday and continue Sunday but with the upper ridge and low level ridge axes so close to our region, winds should be quite light and it should be quite dry through a deep layer. Some thin high clouds will begin to filter into the region Sunday and Sunday night well ahead of the developing system to our west. How much warming we see Saturday and Sunday will depend on how much the boundary layer warms and how much mixing we can get with potentially such light south winds. Highs Saturday around 70 to lower 70s but some mid 60s southern areas. Highs Sunday in the lower to mid 70s. Nighttime lows look to be on the cooler side of guidance with the clear sky, near calm winds and such a dry atmosphere. && .LONG TERM /MONDAY THROUGH THURSDAY/... Large scale amplification of the upper pattern across North America will continue through this period, resulting in an increasingly active pattern featuring more rain chances, and a trend toward cooler temperatures for the local area. Models seem to have come into slightly better agreement regarding timing of initial PV anomaly along the Gulf Coast/Lower MS Valley region tracking north and deamplifying ahead of digging trough from northern Plains region, with height falls spreading across the northeast Tuesday-Wednesday. This suggests that chances for rain should increase, perhaps as early as late Monday or Monday night across southern/western areas, with the potential for a more widespread, soaking rainfall Tuesday-Tuesday night. Ample low level flow from the Gulf of Mexico and Atlantic Ocean, combined with the slow approach of the upper level trough suggest some locally heavy rainfall could occur. Model uncertainty increases for Wednesday-Thursday, as the 00Z/20 ECMWF suggests a formidable upper level impulse closes off and tracks north/northeast from Delmarva Thursday, with an attendant surface low developing and tracking north/northwest into New England. This would bring another bout of widespread rain to much of the region, especially for areas near and east of the Hudson River. The 00Z/20 GFS, GEFs, and GEM remain much more progressive with little indication of such a feature. For now, will keep chance PoPs for Wed night-Thu, but no higher at this time. As for temperatures, still remaining well above normal for Mon-Mon nt, with highs reaching 70-75 in valleys, and 65-70 across higher terrain, and overnight lows mainly in the 50s, although some areas may actually hold near or above 60 if clouds/wind persist. Still mild Tuesday-Tuesday night, with highs 65-70 in valleys, 60-65 across higher elevations, and lows Tuesday night ranging from the mid 40s across northwest areas, to the lower/mid 50s south and east. Cooling becomes more evident Wednesday, with highs mainly in the 50s and 60s, with highs Thursday only in the 50s, although some areas may only remain in the 40s if steady rain occurs. Overnight lows Wed nt/Thu am mainly in the upper 30s to mid 40s. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... High pressure will continue to build into the area today and tonight, resulting in clear skies and continued VFR conditions. North-northwest winds will continue to be gusty this afternoon, at around 15 to 20 kts, before lessening this evening. Winds will become light and variable at less than 5 kts tonight into tomorrow. Outlook... Saturday Night-Sunday Night: No Operational Impact. NO SIG WX. Monday: Low Operational Impact. Slight Chance of SHRA. Monday Night: Moderate Operational Impact. Chance of SHRA. Tuesday: High Operational Impact. Breezy Definite SHRA. Tuesday Night: High Operational Impact. Definite SHRA. Wednesday: Moderate Operational Impact. Chance of SHRA. && .FIRE WEATHER... Northwest to north wind gusts will approach 25 mph this afternoon... An area of high pressure will build in from the south and west today into the upcoming weekend, resulting in continued dry and mild conditions. RH values will fall to between 30 and 45 percent this afternoon and Saturday afternoon. Nighttime RH values will range between 75 and 100 percent. Northwest winds at 15 mph or less this morning will become north to northwest at 15 mph midday and gusts could approach 25 mph midday through this afternoon. Winds diminish to variable at less than 15 mph tonight them become west to south at less than 15 mph Saturday. && .HYDROLOGY... No precipitation is expected through at least the weekend thanks to persistent high pressure, with river/stream flows remaining at normal to below normal seasonal levels. The next chance of rainfall arrives early next week, as a widespread rainfall is possible associated with a slow-moving frontal system. It is much too early for specific details, but some heavy rain may occur in the Tuesday to Wednesday time frame. 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...NAS/Wasula NEAR TERM...NAS/JVM/Wasula SHORT TERM...NAS LONG TERM...KL AVIATION...KL/JVM FIRE WEATHER...NAS HYDROLOGY...NAS

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