####018013703#### FXUS61 KCLE 160215 AFDCLE Area Forecast Discussion National Weather Service Cleveland OH 1015 PM EDT Thu May 15 2025 .SYNOPSIS... Low pressure over the Northern Plains will lift a warm front northeast across the region into tonight. Another low pressure system will cross the Upper Great Lakes Friday night, dragging a cold front east across the area on Saturday. High pressure will build south across the area Sunday through Monday. && .NEAR TERM /THROUGH FRIDAY NIGHT/... 9:50 PM... Latest model guidance continues to show the severe QLCS passing to the north of our forecast area, with the southern portion of it clipping our northern forecast area. It seems the lack of forcing to the south and some dry mid-level air has been the result of this. It's still possible that some additional development along the southern edge continue, especially along the warm front and adjacent instability gradient that currently crosses our forecast area. Previous Discussion... For this afternoon, it does appear that we have a window of time with 1000-2000 J/kg of ML CAPE with continued theta-e advection. Not much of a focus to kick off convection, but one shower has recently developed near Toledo. Otherwise we will be waiting for later tonight for the potential of strong to severe thunderstorms to arrive in the area. Low pressure is located over eastern North Dakota with an occluded front extending southeast towards Lake Michigan. Thunderstorms have been filling in along this boundary and will continue to do so tonight as a negatively tilted upper level trough lifts into the Upper Great Lakes. A strongly unstable environment has developed upstream with 2500-3500 J/kg of ML CAPE across Indiana and Illinois. A capping inversion is likely in place for now but 12Z high resolution models are pretty aggressive with convection continuing to expand in coverage as it pushes east of Lake Michigan this evening into Southwest Lower Michigan and northern Indiana. It is possible that somewhat discrete cells merge into an MCS as the evening progresses and approaches the Toledo area towards 11 PM. Models show some spread overnight with how this system evolves tracking into northern Ohio with some models keeping activity focused closer to Lake Erie and Cleveland with other models showing activity moving southeast along the instability gradient towards Mansfield and Canton. Even by midnight we could have 1000-2000 J/kg of surface based CAPE still in place extending from Toledo southeast towards Canton. Severe weather is a possibility with either option. There is a low end chance the thunderstorms pass north of Lake Erie but with northwesterly flow in the mid-levels of the atmosphere, preference is for convection to move east or southeast ahead of the building ridge aloft. The Storm Prediction Center has expanded the Enhanced risk of severe thunderstorms along the I-75 corridor with the Slight Risk of severe thunderstorms extending all the way into NW Pennsylvania. The primary severe weather hazards are both wind gusts to 70 mph and large hail. Heavy rain is also a concern, especially if training of thunderstorms occurs. Most areas will see between half inch to an inch of rain although a swath of 1-2 inches is possible where the bulk of the thunderstorms track. In addition there is a threat of tornadoes tonight. Low level flow will be backed both ahead of the trough and also near Lake Erie. These could be either with discrete cells or along some type of line of storms. The southwesterly flow ahead of the storms will help to maintain surface based instability or a shallow near surface inversion that could be overcome well into the overnight hours. Activity will exit to the east by morning with clouds expected to clear as we reside beneath an expansive dry slot aloft. Southerly flow will allow for good recovery of the airmass with temperatures reaching the low to mid 80s again. Dewpoints mix out into the low 50s but start to creep back up towards 60 degrees by evening. The broad upper level low over the Upper Midwest rotates northeast towards the Great Lakes during the evening as a 75 knot jet at 500mb moves around the south side of the upper low. Thunderstorms are likely to develop across southern Illinois and Indiana and move east through the Ohio Valley with a high wind threat as indicated by the moderate risk issued by the Storm Prediction Center. Farther north, ML CAPE values creep up to 1000-1500 J/kg in NW Ohio. Thunderstorms moving into northern Indiana and NW Ohio are more likely to be scattered in nature with less deep layer moisture to work with. Shear will be strong with 40-50 knots after 8 PM and there will be another risk of severe thunderstorms Friday evening. THis threat appears more conditional based on how thunderstorms evolve both tonight and tomorrow. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... A nearly vertically-stacked low at the surface and aloft is expected to move generally E'ward from the northern Great Lakes to southern QC between daybreak Saturday and daybreak Sunday. This low track should allow the trailing surface cold front to sweep E'ward through our CWA late Saturday morning through the afternoon. Behind the nearly vertically-stacked low, a shortwave ridge aloft builds gradually from the north-central United States as net surface troughing lingers over Lake Erie and vicinity, including our CWA. Ahead of the cold front, low-level WAA and peeks of sunshine should allow Saturday's daytime highs to reach the mid 60's to mid 70's. Strengthening low-level CAA behind the cold front will allow temperatures to tumble and contribute to overnight lows reaching the upper 40's to mid 50's around daybreak Sunday. Scattered showers and thunderstorms should occur along and ahead of the cold front, amidst weak to moderate boundary layer instability and strong deep-layer bulk shear in the warm/relatively-moist sector. This thermodynamic and kinematic environment may support strong to severe thunderstorms, especially in NE OH and NW PA, where greater diurnal heating/boundary layer destabilization should occur prior to the cold front passage. Any lingering rain showers associated with forcing for ascent amidst sufficient moisture along the upper- reaches of the cold front should exit generally E'ward by sunset Saturday evening. However, the seeder-feeder process amidst a sufficiently-cold/moist low/mid-level atmospheric column may allow periodic and isolated lake-enhanced rain showers to stream generally ESE'ward over/downwind of ~13C (i.e. ~55F) Lake Erie and impact far- NE OH and NW PA Saturday evening into the first couple predawn hours of Sunday morning. Otherwise, fair weather is expected as dry air advection at the surface and aloft, and stabilizing subsidence accompanying the shortwave ridge aloft, take-hold in our CWA. Current odds favor fair weather this Sunday through Sunday night as stabilizing subsidence accompanies the aforementioned ridge at the surface and aloft, which should continue to build from the north- central United States and eventually the western Great Lakes. Despite intervals of sunshine, continued synoptic-scale low-level CAA will contribute to highs reaching the upper 50's to lower 60's in NW PA and mainly the lower 60's to near 70F in northern OH during the late afternoon on Sunday. Additional pockets of clear sky and continued low-level CAA should allow overnight lows to reach the lower to upper 40's in NW PA and the mid 40's to lower 50's in northern OH around daybreak Monday. && .LONG TERM /MONDAY THROUGH THURSDAY/... On Monday, fair weather should persist in our CWA as the aforementioned ridge at the surface and aloft continues to build from the western Great Lakes and stabilizing subsidence continues to impact northern OH and NW PA. Afternoon highs should reach the upper 50's to near 70F amidst intervals of sunshine and continued low- level CAA on the synoptic scale. The potential for periodic rain should increase gradually and generally from west to east overnight Monday night through daybreak Wednesday as the ridge axis aloft drifts from the western Great Lakes to the eastern Great Lakes and Upper OH Valley, a low aloft wobbles E'ward across the northern Great Plains toward the Upper MS Valley while becoming vertically-stacked with its attendant surface low, and the surface ridge exits E'ward as a surface trough enters our CWA from the northern and central Great Plains. This weather pattern evolution at the surface and aloft should allow a warm conveyor belt to undergo moist isentropic ascent aloft and exhibit frontogenetical convergence, allowing for the aforementioned increase in rain potential. Our region should remain within the relatively-cold sector at the surface. Lows should reach mainly the 40's to lower 50's around daybreak on Tuesday and Wednesday, respectively. Daytime highs on Tuesday should reach the upper 50's to upper 60's. Aloft, the aforementioned ridge axis should shift E'ward from the eastern Great Lakes and Upper OH Valley to near the Canadian Maritimes and Bermuda between daybreak Wednesday morning and sunset Thursday evening. Simultaneously, the aforementioned vertically- stacked low at the surface and aloft should wobble ESE'ward from the Upper MS Valley to the Upper OH Valley as the attendant surface trough continues to affect our region. Northern OH and NW PA should remain within the relatively-cold sector at the surface. Additional periods of rain are expected as the low pressure system's warm conveyor belt continues to undergo moist isentropic ascent aloft. Weak diurnal destabilization of a sufficiently-moist boundary layer should permit low-level convergence/resulting ascent associated with the low's cyclonic circulation to trigger additional rain showers during the late morning through afternoon hours of Wednesday and Thursday, respectively. These lifting mechanisms may release sufficient CAPE, especially elevated CAPE, to generate a few thunderstorms Wednesday afternoon through the predawn hours of Thursday morning. Daytime highs should reach the 60's on Wednesday and Thursday, respectively. Overnight lows should reach mainly the upper 40's to lower 50's around daybreak Thursday. && .AVIATION /00Z Friday THROUGH Tuesday/... VFR conditions will be in place this afternoon with thunderstorms expected overnight. We are watching for a complex of severe thunderstorms that has developed over WI/IL, and will move across MI/IN over the next several hours, approaching KTOL towards 04Z. These storms are likely to continue eastward overnight, although there is still a great deal of uncertainty regarding coverage and intensity of storms as they move across the area. Latest model guidance has trended downward with storm coverage and intensity, especially for the southern portion of our forecast area, including KFDY and KMFD. Thunderstorms will have the potential for heavy rain with IFR conditions and may also have strong winds of 30-50 knots or small hail. South to southeast winds this evening into tonight of around 10 knots becomes westerly behind thunderstorms late tonight into Friday morning. Winds become southerly around 6-12 knots Friday afternoon/evening. Outlook...Periodic showers and thunderstorms with non-VFR are possible through Saturday. && .MARINE... Mainly NE'erly to E'erly winds around 5 to 10 knots, augmented by a lake breeze, and waves of 2 feet or less are expected through this early evening as a very weak ridge persists over Lake Erie. The ridge exits ENE'ward tonight as a warm front moves NE'ward across Lake Erie. E'erly to SE'erly winds around 5 to 15 knots ahead of the front veer to S'erly to SW'erly behind the front. Waves of 3 feet or less are expected. On Friday through Friday night, winds around 10 to nearly 20 knots are expected to vary between SE'erly and SW'erly as multiple trough axes sweep E'ward across the lake. Waves should remain 3 feet or less in U.S. waters. On Saturday, SW'erly winds around 10 to nearly 20 knots veer to W'erly and freshen to 15 to 25 knots as a cold front sweeps E'ward across Lake Erie. Waves build to as large as 4 to 8 feet, especially east of The Islands, and a Small Craft Advisory will likely be needed. Behind the cold front, a trough lingers over Lake Erie through Sunday. WSW'erly to NW'erly winds around 15 to 25 knots and waves as large as 4 to 8 feet Saturday night should be followed by mainly W'erly to N'erly winds easing to around 10 to 15 knots on Sunday. Accordingly, waves should subside to 3 feet or less by nightfall Sunday evening. NW'erly to NE'erly winds around 5 to 15 knots Sunday night through Monday should become mainly N'erly to NE'erly Monday night through Tuesday as a ridge builds slowly from the west. Waves should be mainly 3 feet or less, but occasional 4 footers are possible. && .CLE WATCHES/WARNINGS/ADVISORIES... OH...None. PA...None. MARINE...None. && $$ SYNOPSIS...10 NEAR TERM...10/Saunders SHORT TERM...Jaszka LONG TERM...Jaszka AVIATION...Saunders MARINE...Jaszka