908 FXUS61 KCLE 211045 AFDCLE Area Forecast Discussion National Weather Service Cleveland OH 645 AM EDT Sun Jun 21 2020 .SYNOPSIS... Low pressure will move northeast across the Upper Great Lakes region on Sunday. Another shortwave trough will move northeast out of the central Great Plains on Tuesday. An associated area of low pressure will move across the area on Tuesday, moving a cold front across the area Tuesday night. High pressure will build across the area for Thursday and Friday. && .NEAR TERM /THROUGH MONDAY/... Previous forecast discussion is on track with no changes made. Hi-res models still have little agreement on timing and location of convective development today. Some isolated storms have begun to pop up upstream of the area in parts of Indiana and Illinois which will continue to be monitored as they move towards the forecast area. Previous Discussion... Low pressure centered over Nebraska will move over the Upper Great Lakes region today. The placement of the track of this low will allow a southerly wind to usher in moist air across the area which will make high temperatures in the upper 80s feel increasingly uncomfortable. Thunderstorms are expected to develop, although the exact timing is still uncertain. Growing instability with the diurnal cycle and ample moisture will play two key factors in development timing. The most likely area for initial development will be along the lake breeze convergent boundary, similar to the past couple days, with a few isolated storms elsewhere. By the evening hours, a short wave will progress across Ohio, which will act as an additional driving factor to maintain convection into the evening and early overnight hours. The convection that develops today will be heavy rain produces with PW ranging from 1.5 to 1.75 inches according to the current RAP and NAM models and current forecasted storm motions will only be 10-20 mph. Warm, muggy conditions will continue into tonight as low temperatures will be in the mid to low 60s. On Monday, a shortwave disturbance associated with a surface low located northeast of Iowa will begin to impact the area. Southerly winds will continue to usher in ample moisture making for muggy conditions with highs in the low to mid 80s. This period on Monday has a lot of uncertainty with precipitation timing and location as model guidance is not resolving the setup very well. Kept chance PoPs in the forecast across the area for the Monday forecast as the diurnal cycle coupled with energy from the shortwave moving over the area will likely be enough for storms to develop. && .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/... A pre-frontal trough supported by a lead shortwave will bring a round of showers and likely thunderstorms across the area late Monday night and through midday Tuesday. The atmosphere recovers for Tuesday afternoon for the advancement of the surface cold front. Marginal to fair instability and marginal lapse rates may be enough for strong to possibly severe storms depending on how the morning plays out. The cold front reaches the OH/PA border around midnight. We retain the upper trough into mid week and with shortwave energy rotating through it, will have a diurnal uptick in shower/thunderstorms for Wednesday afternoon (scattered). Temperatures will be seasonable. The cold front will take the mugginess down a notch. && .LONG TERM /THURSDAY THROUGH SATURDAY/... Have a slight chance to chance mention of afternoon showers/thunderstorms Thursday and Friday as we will still be under the influence of broad upper trough across the Great Lakes. Surface ridging will attempt to extend up the Ohio Valley. After a brief break Friday evening, a possibly active warm front will lift across the IN/MI/OH region toward Saturday morning. As of now, a cold frontal passage is targeted for Sunday. Broadly speaking guidance is similar with the mid level pattern to support this. For now through, precip chances are broad brushed over the weekend until finer details can be extracted. Temperatures will nudge warmer Thursday into Friday with lower and mid 80s common across the area. Dewpoints will be on the rise too. && .AVIATION /12Z Sunday THROUGH Thursday/... VFR conditions are expected to persist for the majority of this TAF period. A weakening system will approach the area from the southwest today, bringing a warm, moist airmass with it. Cloud cover will increase throughout the period along with the chance of precipitation. Confidence in location and timing of thunderstorms is rather low as the hi-res models are not in agreement. Storms will likely develop with the diurnal cycle and along the lake breeze convergent boundary this afternoon. Opted for TEMPO of TSRA for all TAF sites this afternoon. Sites impacted by convection may temporarily drop to MVFR conditions and experience gusty winds. Aside from convection, winds will be light and from the west-southwest. CLE and ERI will be impacted by a lake breeze this afternoon around 17Z which will shift winds to be from the north. Outlook...Periods of non-VFR possible Sunday afternoon and through Tuesday with scattered thunderstorms. && .MARINE... Will get another lake breeze to develop today and Monday so expect onshore flow during the afternoons across the nearshore waters. Winds will still remain at 10 knots or less. Tuesday winds will increase with and behind a cold front to cross the lake and will likely average around 15 knots. This will bring waves up, but still not expecting Small Craft Advisory conditions. West-southwest flow continues through Thursday with waves of 3 feet or less. A couple rounds of widespread thunderstorms are expected; one for Monday and another round Tuesday. && .CLE WATCHES/WARNINGS/ADVISORIES... OH...None. PA...None. MARINE...None. && $$ SYNOPSIS...Campbell NEAR TERM...Campbell SHORT TERM...Oudeman LONG TERM...Oudeman AVIATION...Campbell MARINE...Oudeman