373 FXUS61 KCLE 220456 AFDCLE Area Forecast Discussion National Weather Service Cleveland OH 1256 AM EDT Mon Aug 22 2022 .SYNOPSIS... A slow moving low pressure system will move to the eastern Great Lakes through Monday and maintain an unsettled weather pattern. High pressure will build overhead through the mid-week period. The next trough will approach from the north by Friday. && .NEAR TERM /THROUGH TODAY/... 12:30 AM Update... The heavy thunderstorms have ended with just leftover light rain occurring from Ashtabula County into Erie and Crawford Counties in PA. This area of rain will move out and dissipate over the next 2 hours. Watching isolated showers and thunderstorms slowly cross Lake Erie at this time. This activity should reach the lakeshore from Cleveland east after 08 or 09Z, so increased PoPs back to chance in those areas after that time. Otherwise, expect a mild and muggy night with patchy fog possible where heavy rain occurred. We should see a diurnal flare up again Monday starting by mid morning and continuing through the afternoon, but coverage should be less as the upper low/trough pulls away. A lingering surface trough over far eastern Ohio and NW PA combined with the diurnal heating will lead to the greatest potential for showers/storms to be east of I-77. Previous Discussion... Very heavy rain continues along the lakeshore from Geauga County through eastern Lake County, Ashtabula County, into Erie. The storms have been producing rainfall amounts between 1 and 2 inches an hour based on ground observations. Locally higher amounts occurring in the heaviest rain. Activity is expected to move slowly northeast out of the area. Another round of showers continues to rotate southeast out of Michigan in a weakened state at this time. Short term models suggest this band will move southeast across Lake Erie and produce more showers and thunderstorms over the northeast overnight. Will have to monitor trends due to ongoing flooding across the area. Otherwise, patchy dense fog is expected across the area during the night. Original Discussion... Surface analysis has a broad 1015mb low extending across eastern Indiana/western Ohio with an upper level low nearly vertically stacked overhead. Sufficient clearing earlier this afternoon allowed the airmass to destabilize with ML CAPE values of around 1500 J/kg. However convection over Central Ohio has produced a lot of cirrus debris which has limited further destabilization across central Ohio. Convection continues to fill-in across NW Ohio and closer to the lakeshore and will continue to shift east through the evening. In addition, the HRRR suggests additional convection will fill in across SW Ohio where heating continues and may drift towards the Central Highlands with time. As the upper trough continues to slowly pivot eastward tonight, storm motion will continue to the northeast. The one area where pops may end up being to high could be across inland NE Ohio but will adjust with future updates as needed. Broad rotation associated with the upper level system, especially co-located near the better surface convergence, has led to the development of several funnel clouds in NW Ohio. While funnel clouds may occur, the overall tornado threat remains low given the lack of stronger shear and storm organization. Thunderstorms have maintained a relatively low centroid making heavy rain a concern, especially where training occurs with southwest to northeast storm motion. Pockets of rainfall in excess of 2 inches is possible and flood products may be needed, especially where heavy rain has occurred over the last 24 hours. Will continue to monitor severe weather potential but the threat remains fairly isolated given effective shear values of only 20-30 knots. Most likely case would be if a storm with a stronger core collapses. Coverage of precipitation will decrease considerably as we move past peak heating and mid-level dry-slot wraps in from the west. Where breaks develop in the clouds overnight, patchy fog may develop with light winds and a moist boundary layer. As the 850-700mb trough pivots across eastern Lakes Erie towards dawn, we expect to see lake enhanced showers move in off the lake. Fairly good coverage is expected across the eastern forecast area again on Monday, with coverage increasing with daytime heating. Both temperatures and instability will be a little lower with the cooler airmass overhead on Monday. Chances for showers will become increasingly confined to just off the far east end of Lake Erie on Monday night. && .SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/... Upper level trough moves eastward very slowly through Wednesday night. A surface trough should linger over/near Lake Erie through at least Wednesday morning. This may assist with shower/thunderstorm development through Tuesday afternoon, especially across the eastern half of the CWA. Models then attempt to move everything eastward with the upper level trough. Still slightly concerned we will add some rain chances to Wednesday with later updates as some jet energy moves across southern Ontario. Temperatures look to be near seasonal averages through the short term period. && .LONG TERM /THURSDAY THROUGH SUNDAY/... A broad surface trough will linger over the area through Friday night as a surface high pressure gradually shift southeast. On Friday, a weak cold front associated with a low pressure near the Gulf of St. Lawrence is forecast to move southeast across. This boundary will bring a brief chance of precipitation, unless it stalls across the area. Opted to maintain a front that stalls to the southeast of the area for now, keeping chance PoPs in the forecast. There is a non-zero chance of thunder with this system, although it will be highly dependent on instability developing and any upper level support present. Late Friday into Saturday, an upper level ridge, and associated surface high pressure, will build over over the Eastern U.S. and persist through the remainder of the period. On Sunday, an increase in southerly winds will mark an increase in high temperatures, reaching into the mid 80s, which is expected to be the warmest day for the period. Dewpoints on Saturday and Sunday will climb into the low to mid 60s, marking a return of humid, muggy conditions across the area. && .AVIATION /06Z Monday THROUGH Friday/... Thunderstorms with locally heavy rain across the area continue to move east across the region. Expecting activity to be scattered in nature with a possible round moving into the area later tonight. Then, as day time heating picks up again tomorrow, expecting more showers and thunderstorms to develop again. Ceilings will be on the low side overnight down to IFR and visibilities down to IFR/MVFR at times due to fog developing across the area. Winds should be light through the period. Outlook...Non-VFR possible with scattered rain showers and thunderstorms through early Tuesday, with the best chance Saturday afternoon through Monday. && .MARINE... Low pressure is expected to track eastward near the south shore of the lake tonight into Monday morning. In the lows wake a cold front crosses the lake with winds becoming northwest to north. Speeds generally remain under 15 knots which typically wont build waves above the 2 to 4 foot range. These northerly winds persist into Monday night with maybe a slight increase in the speed. A short small craft advisory may be needed Monday evening into the overnight. Will definitely need to mention a moderate risk of rip currents in the HWO for a decent portion of the lake east of the Islands Monday into Monday night. Will also need to monitor for waterspouts along the frontal boundary. A surface trough then lingers on/near the lake into Wednesday. Just cool enough air aloft and the convergence along the trough axis may be enough to produce some waterspouts. Confidence not as high with this potential to mention in the forecast at this time. If conditions look more favorable over the next couple days we will add them. && .CLE WATCHES/WARNINGS/ADVISORIES... OH...None. PA...None. MARINE...None. && $$ SYNOPSIS...KEC NEAR TERM...KEC/Garuckas/Lombardy SHORT TERM...MM LONG TERM...Campbell AVIATION...Lombardy MARINE...MM