752 FXUS61 KBUF 180228 AFDBUF Area Forecast Discussion National Weather Service Buffalo NY 1028 PM EDT Thu Oct 17 2019 .SYNOPSIS... Showers will gradually taper off overnight as low pressure across Maine weakens and moves northeastward. Dry weather will then return by Friday afternoon as high pressure builds back into the region, with fair weather and steadily warming temperatures then following for the weekend as the high slides off the east coast. && .NEAR TERM /THROUGH FRIDAY/... Radar imagery shows that steady showers have exited to the east of the forecast area, however there still are some scattered lake effect showers. A broad cyclonic flow will remain in place overnight, but low level moisture will start to wane with time as the low weakens and moves further away. A combination of lake enhancement and upsloping supports a chance of showers for most of the night, but additional rainfall amounts will be on the light side, less than a tenth of an inch. Abundant moisture trapped beneath the subsidence inversion will keep skies overcast across the region tonight. This will keep temperatures from dropping much, with lows in the lower 40s on the lake plains and upper 30s across higher terrain. Friday any remaining light lake effect showers or sprinkles southeast of the lakes will end by mid to late morning as inversion heights continue to lower, and moisture becomes too shallow to support rain. Clouds will be very stubborn to break however with ongoing shallow lake instability and northwest upslope flow beneath the steepening subsidence inversion. If there is any clearing across Western NY, it will likely not develop until late afternoon. The clouds and cool airmass will only support highs in the lower 50s on the lake plans and mid to upper 40s across higher terrain. && .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/... The upper level ridge currently east of the Rockies with a corresponding surface high pressure ridge will be directly overhead Friday night. With strong subsidence, any remaining inland stratocu should quickly dissipate with mostly clear or clear skies overnight. This should result in valley fog and areas of frost forecast over areas where the growing season is still considered active. Sheltered areas in lower terrain may reach the 32F mark, while other locations should hover in the lower to mid 30s. In higher terrain, many areas should be able to drop below 32F. Despite the cool start, Saturday should turn out to be a nice day with weak warm air advection on the back side of the ridge which should be moving toward and off the East Coast by the evening. Skies should remain mostly clear throughout the day and well into the evening. The slight warm advection together with abundant sunshine should allow temperatures to generally reach the 60F mark, with the usual variations by terrain and proximity to the lakes. Saturday night shouldn't be as cold as the previous night, but still expect some temperatures to dip into the 30s in sheltered/higher terrain, with ~40F readings elsewhere. The next system is currently traceable back to the Pacific Northwest. This system is forecast to remain fairly weak as it moves into the plains and then barely make it into the Great Lakes region by Sunday. This system will probably go unnoticed as it moves through. Can envision a mid/upper level cloud deck, but right now will continue to stay on the drier side with low (~15%) chance for measurable rain for Sunday. Otherwise, the region should see another day with temperatures creeping into the lower 60s, followed by another dry night with lows mostly in the 40s. && .LONG TERM /MONDAY THROUGH THURSDAY/... Warm air advection will increase Monday as a 40kt low-level jet moves north along the spine of the Appalachians. A southeast wind will increase across the region while surface high pressure retreats to the northeast. While a cold front will be approaching from the west, mostly dry and warm are expected Monday with highs in the upper 60s to near 70. A slowly deepening surface low will move north of Lake Superior Monday night-Tuesday morning. The associated cold front will track east across the eastern Great Lakes late Monday night through Tuesday. The 10/17 12z GFS is a smidge faster than the ECMWF with the timing of the cold front. Showers, possibly heavy at times will track east ahead and along the front. The strong low-level jet will mainly be on the stable side of the front as it moves by but gusty winds are possible when the front passes. The large scale trough will become negatively tilted by Wednesday and strong cold air advection is expected to move across the Great Lakes behind the cold front. Forecast guidance is depicting 850mb temperatures dropping to -3 to 0C. Lake induced instability will be present while the combination of westerly flow and upstream moisture will allow a lake response to form Tuesday night and end by Thursday east of Lake Erie and Lake Ontario. There may be a period Wednesday night where the boundary layer gets cold enough for snow showers across the higher terrain east of Lake Ontario and the western Southern Tier. They will be short-lived as high pressure moves into the region during this time. && .AVIATION /02Z FRIDAY THROUGH TUESDAY/... Although steadier showers have ended, there will continue to be extensive wrap around moisture from a strong coastal low over Maine. This combined with lake effect instability and upslope flow will produce scattered showers and maintain stratus overnight. This will result in mainly MVFR flight conditions with patchy IFR cigs across higher terrain overnight. CIGS will be mainly MVFR Friday morning, but should improve as clouds lift and begin to scatter out during the afternoon hours. Outlook... Friday night...VFR. Saturday through Monday...Mainly VFR. Tuesday...Areas of MVFR with a chance of showers. && .MARINE... Deep low pressure over Maine will begin to weaken before it reaches the Gulf of Saint Lawrence on Friday. Moderate northwest winds will continue overnight before gradually diminishing into Friday. Small Craft advisory conditions will persist through late tonight on Lake Erie, and through much of Friday on Lake Ontario. High pressure will then build into the eastern Great Lakes Friday night and Saturday before drifting off the east coast Sunday. This will bring a period of lighter winds to the eastern Great Lakes for the weekend. && .HYDROLOGY... 2-3 inches of rain fell in the Black River Basin yesterday and this has resulted in high levels. It will remain below flood stage, but forecast points are expected to reach action stage. Boonville and McKeever are expected to crest late tonight, with Boonville already slightly above action stage. There is little chance that either of these points will reach flood stage. Watertown is expected to reach action stage Saturday, and should crest below flood stage late Saturday or early Sunday. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...None. MARINE...Small Craft Advisory until 5 AM EDT Friday for LEZ040-041. Small Craft Advisory until 5 AM EDT Friday for LOZ030. Small Craft Advisory until 5 PM EDT Friday for LOZ043-044. Small Craft Advisory until 2 PM EDT Friday for LOZ042. Small Craft Advisory until 11 AM EDT Friday for LOZ045. && $$ SYNOPSIS...Apffel/Hitchcock NEAR TERM...Apffel/Hitchcock SHORT TERM...Zaff LONG TERM...HSK AVIATION...Apffel/Hitchcock MARINE...Apffel/Hitchcock HYDROLOGY...Apffel