Area Forecast Discussion
Issued by NWS Albany, NY

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000 FXUS61 KALY 140156 AFDALY AREA FORECAST DISCUSSION National Weather Service Albany NY 956 PM EDT Sun Oct 13 2019 .SYNOPSIS... The stretch of tranquil weather will continue through Tuesday. A widespread rainfall appears likely on Wednesday with chilly and blustery conditions by Thursday. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... As of 1015 PM EDT, temps have already dropped into the upper 30s/lower 40s across portions of the southern Adirondacks and Lake George region, where patchy high clouds are gradually thinning. However, low clouds were noted on IR satellite imagery across eastern PA and northern NJ, with some expansion noted to the N and E. Near-term models suggest these clouds may continue expanding northeast through midnight across the mid Hudson Valley, southern Taconics and NW CT, so have increased cloud coverage in these areas from earlier forecast. There could be a few breaks in these areas after midnight, before additional low clouds potentially redevelop and/or expand northward closer to daybreak as an upper level disturbance tracks south and east of the region. The northwest edge of these lower clouds should also extend into portions of the central/southern Berkshires around daybreak as well. Otherwise, mainly clear skies are expected farther north and west. Winds are expected to be light to nearly calm, so temperatures should be able to fall to the lower/mid 30s to lower 40s. However, milder min temps are expected across the mid Hudson Valley/NW CT region where more clouds are expected, where mins may only drop into the mid/upper 40s. && .SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY/... Upper low will retreat into eastern Canada and a weakening cold front with very little moisture will track through our region. Boundary layer southwest flow along with a partly to mostly sunny sky should help temperatures warm into the mid 60s to around 70 but 50s to lower 60s northern areas. Any isolated showers would be in northern areas Monday afternoon. Cooling and clearing expected Monday night but with some steady boundary layer winds from the west to northwest and boundary layer temperatures cooling considerably, some lake effect clouds could extend into the southern Adirondacks and parts of the western and central Mohawk Valley. Guidance is not showing much cloud cover as winds will not be strong and will be more west than northwest but any clouds off the lakes could prevent temperatures from falling as much as they could into early Tuesday morning. The core of coldest air is over our region Tuesday with very light winds expected. Based on mixing potential and the potential for some scattered to broken clouds in some areas, highs in the mid 50s to around 60 but lower 50s higher terrain. Wednesday morning should be tranquil and dry as warm advection strengthens. Upper energy diving out of Canada will approach through Wednesday afternoon and rapid warm advection along with deep moisture advection ahead of the upper energy should result in clouds and precipitation arriving in western areas perhaps by midday and the rest of our region through the afternoon. Most areas will see the start of a period of soaking rain by late afternoon, that will continue into Wednesday night. Highs Wednesday in the upper 50s to lower 60s. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... Our intensifying parent trough over the Great Lakes within the northern jet stream looks to phase with a southern stream shortwave and become negatively tilted Wednesday night. Strong consensus between the NCEP model suite and the ECMWF and CMC-NH continues with guidance suggesting this interaction results in rapid cyclogenesis of a coastal low off the Carolinas. Strong isentropic lift ahead of the advancing coastal low continues into Wednesday evening with the south-southeast 850mb jet strengthening to 40-50kts. This should allow widespread rainfall to continue and expand into western New England. Guidance generally shows the coastal low tracking northward overnight and moving into eastern New England which would spare most of eastern NY/western New England from the brunt of this "bomb" cyclone. The cold front from the parent trough looks to quickly advance eastward through NY Wednesday night which should push widespread/steady rain out of area with just some lingering showers in its wake. However, guidance continues to hint that the advancing cold front could enter into New England in time to meet up with the coastal low which could tighten the baroclinic zone over western New England and enhance rainfall amounts there. The latest WPC QPF guidance also hints at this enhancement as well. Still too early to give specifics but it`s something worth monitoring. Otherwise, most of the rainfall should transition to showers late Wednesday night into Thursday morning with total QPF amounts ranging 0.75 to 1.50" with locally higher amounts on the eastern Catskills which tend to see terrain enhanced amounts in this flow regime. This should be a very progressive system with most of the rain falling between 18z Wednesday and 12z Thursday. As our coastal low continues to "bomb" out by Thursday morning (intensifying from ~1005mb 12z Wed to ~975mb by 12z Thurs), the upper level parent trough becomes a closed 500mb low over the Gulf of Maine with the coastal low becoming the dominant surface feature. Eastern NY and western New England on Thursday should experience a colder and windy day with wrap around showers. High temperatures should be 5-10 degrees cooler than normal, only rising a few degrees above the morning low temperatures into the low to mid 50s, thanks to a tightening pressure gradient between the departing coastal low and strengthening high pressure from the TN Valley. Deep boundary layer mixing in the cold air advection regime should lead to windy conditions with westerly sustained winds ranging 10-18mph and gusts up to 25-35mph (highest in the terrain). While some lake enhanced showers are possible, the wrap around cold air at 850mb, as per the GEFS, does not deviate from normal, so the delta-T between Lake Ontario and the 850mb isotherms only barely meets the ~13C criteria. Breezy conditions look to continue into Thursday night as sufficient pressure rises continue over our region behind the closed low in the Canadian Maritimes. While the strong west-northwest flow should maintain the cold air advection regime, overnight lows should be around normal, falling into the mid 30s to low 40s, due to breezy winds. A strengthening upper ridging should build into the Northeast on Friday with surface high pressure taking control of the region which should weaken winds. Even still, the cool air mass should remain in place with high temperatures once again about 5 degrees below normal in the 50s. The upper level ridge axis moves overhead Friday night leading to clearing skies and a good radiational cooling set-up. Expecting Saturday morning lows should be quite chilly with all areas falling into the 30s with upper 20s for parts of the Adirondacks, Greens sand Catskills. Temperatures quickly moderate back towards and even a bit above normal for the weekend as southwest return flow returns and high pressure maintains control. The next chance for showers looks to hold off until early next week. && .AVIATION /02Z MONDAY THROUGH FRIDAY/... A weak ridge of high pressure will shift east of the region overnight, while a cold front passes east across the TAF sites Monday afternoon. Moisture will be limited, so only a few clouds and a wind shift are expected to accompany the frontal passage. Patchy ground fog is expected to develop at KGFL after 02Z/Mon, and may intermittently drop Vsbys to IFR levels through daybreak. Elsewhere, mainly VFR conditions are expected through around 10Z/Mon. However, some lower clouds may drift northward and produce MVFR Cigs at KPOU and KPSF between 10Z-16Z/Mon. VFR conditions should otherwise prevail into Monday evening. Winds will be light/variable overnight, then become south to southwest at 5-10 KT Monday morning through early afternoon. Winds will shift into the west in the wake of the cold front later Monday afternoon, and increase to 8-12 KT, with some gusts up to 20 KT possible. Outlook... Monday Night: No Operational Impact. NO SIG WX. Tuesday: No Operational Impact. NO SIG WX. Tuesday Night: No Operational Impact. NO SIG WX. Wednesday: High Operational Impact. Definite RA. Wednesday Night: High Operational Impact. Definite SHRA. Thursday: Moderate Operational Impact. Breezy Chance of SHRA. Thursday Night: Low Operational Impact. Breezy Slight Chance of SHRA. Friday: No Operational Impact. NO SIG WX. && .FIRE WEATHER... The stretch of tranquil weather will continue through Tuesday. A widespread rainfall appears likely on Wednesday with chilly and blustery conditions by Thursday. RH values will be 50 to 70 percent Monday afternoon and 45 to 60 percent Tuesday afternoon with 80 to 100 percent at night. Winds will be light tonight, then south at 15 mph or less Monday morning shifting to west. West winds at less than15 mph Monday night become light south to southeast late Tuesday afternoon. && .HYDROLOGY... The forecast area is expected to remain mainly dry through Tuesday night with any precipitation being spotty and hydrologically insignificant. A widespread soaking rainfall appears likely by Wednesday into Wednesday night. 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 NEAR TERM...KL/NAS SHORT TERM...NAS LONG TERM...Speciale AVIATION...KL FIRE WEATHER...NAS HYDROLOGY...NAS

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