909 FXUS61 KCLE 271138 AFDCLE Area Forecast Discussion National Weather Service Cleveland OH 738 AM EDT Tue Aug 27 2019 .SYNOPSIS... A low currently over western Ontario will deepen and track to Hudson Bay Tuesday into Wednesday, forcing a cold front east across the area this afternoon into tonight. High pressure will build northeast across the region Wednesday night through Thursday night. Another cold front will move across the region on Friday followed by high pressure building in from the northwest for the weekend. && .NEAR TERM /THROUGH WEDNESDAY/... Not many changes made with this update. Forecast is progressing as expected up to this point. There is little bit less certainty with this afternoons convection and the areal coverage of thunderstorms. Previous Discussion... Current radar observations show scattered light showers across northern Ohio and western Pennsylvania. These will linger through the night with the dissipating trend continuing through the night. Most showers will have dissipated by late morning as the upper level shortwave responsible for forcing these showers moves off to the northeast. The large-scale upper level trough currently situated over the western Ontario and Upper Midwest will slowly continue east today. A cold front extending from an elongated surface low over the Upper Midwest will continue east today and initiate a line of thunderstorms over western Ohio this afternoon. Though the the 500mb jet will be offset to the west, strong low level winds at 925mb and 850mb will provide effective wind shear of up to 25 to 35 knots, which will be enough to support organized convection this afternoon. Instability will be limited due to extensive cloud cover lingering through much of the day. Southerly flow will act to recover the atmosphere and advect warm, moist air, characterized by dew points near 70 and temperatures in the mid to upper 70s. Due to extensive cloud cover, SBCAPE is only expected to be around 1000 J/kg by 21Z this afternoon. If cloud cover clears out more than expected before thunderstorms develop this afternoon, then a severe threat in the form of wind damage may be present. Otherwise, if widespread cloud cover continues through the day, then severe weather will really be limited this afternoon. In addition to a wind threat, an isolated tornado may be possible. 0-1 km shear is expected to be around 20 knots with 0-1 km SRH around 100 to 150 m^2/s^2. when combined with very low LCL heights of only a couple hundred meters, we have a marginally favorable environment for a weak tornado. However, this is still dependent on the development of organized convection, for which there is still uncertainty due to marginal instability. Convection is expected to exit the area to our east by 06Z Wednesday, though there may be some residual showers in Northwest Pennsylvania into Wednesday morning. Humidity, temperatures, and cloud cover all decrease following the passage of the cold front, with mostly sunny skies, high temperatures in the mid to upper 70s and dew points in the upper 50s on Wednesday. && .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/... A cold front will move east across Lake Erie Wednesday night as an upper trough swings across the eastern Great Lakes. Partly to mostly cloudy skies expected with the front with temperatures at 850mb falling to around 7C across NW PA by Thursday morning. Sufficient convergence along the northeast shore of the lake for a chance of showers late Wednesday night into Thursday morning. The coolest air quickly shift east on Thursday with southwest flow returning so highs will only be 2 to 4 degrees cooler across eastern portions of the forecast area. High pressure will build east across the Ohio Valley Thursday with another weak cold front sliding south across Lake Erie Friday morning, bringing another low chance of showers. Southwest flow ahead of the front will still allow temperatures to approach 80 degrees on Friday across the south, before trending cooler again heading into the weekend. && .LONG TERM /SATURDAY THROUGH MONDAY/... Surface high pressure will build east across the Great Lakes Region Saturday and Saturday night, pushing the frontal boundary south to near the Ohio River. Saturday is expected to be dry aside from just a slight chance of rain near the I-75 corridor. Shortwave energy will move through the flow aloft Saturday night and Sunday bringing a chance of showers to all areas. Models still showing some spread with placement frontal forcing and this chance of rain so adjustments to timing and coverage are likely. High pressure will strengthen over the Central Great Lakes Monday, pushing any lingering chance of showers south of the area. && .AVIATION /12Z Tuesday THROUGH Saturday/... IFR and MVFR CIGs are currently present over much of northern Ohio. Radar observations show a line of disorganized showers near KTOL and KFDY that are just ahead of the cold front. These will continue east today. Additional development is expected along and ahead of the cold front in the form of showers and thunderstorms. Model guidance have been trending earlier for thunderstorms so have things an hour or two earlier and most TAF sites. VFR conditions should develop tonight over western Ohio and spread eastward overnight. OUTLOOK...Areas of Non-VFR today, lingering across eastern OH and northwest PA into tonight. && .MARINE... Unsettled weather expected through the mid-week period as a series of fronts cross Lake Erie. A Small Craft Advisory remains in effect with brisk southerly flow on the lake today. Winds of 15-25 knots expected this morning as a low level jet moves overhead, gradually decreasing into this afternoon. Given the offshore flow, will keep the swimming risk at moderate as higher waves will be focused offshore. Winds will be on the increase again on Wednesday ahead of a cold front that will cross Lake Erie Wednesday evening. A Small Craft Advisory will likely be needed again from Lorain County eastward. One more front is expected to cross the lake late Thursday night into Friday and will be accompanied by another period of winds in the 15-25 knot range. Winds will shift around to the northeast behind this last front heading into Saturday with winds of 5 to 15 knots. && .CLE WATCHES/WARNINGS/ADVISORIES... OH...None. PA...None. MARINE...Small Craft Advisory until 5 PM EDT this afternoon for LEZ142>149. && $$ SYNOPSIS...Saunders NEAR TERM...Saunders SHORT TERM...KEC LONG TERM...KEC AVIATION...Saunders MARINE...KEC