Area Forecast Discussion
Issued by NWS Cleveland, OH
Issued by NWS Cleveland, OH
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222 FXUS61 KCLE 271334 AFDCLE Area Forecast Discussion National Weather Service Cleveland OH 934 AM EDT Fri Sep 27 2024 .SYNOPSIS... The tropical remnants of Helene will lift into the Ohio Valley by tonight while rapidly weakening. Weak low pressure associated with the remnants of Helene will then drift across the Ohio Valley through the weekend before dissipating early next week. && .NEAR TERM /THROUGH SATURDAY/... 930 AM Update... Winds have begun to ramp up across the area this morning with gusts up to 30 mph observed across the western tier of counties. Opted to delay the onset of showers, especially across the northern tier of counties, as general progression of the showers seems to have slowed compared to the previous forecast. Aside from that, there were no other changes needed with this update. Previous Discussion... Tropical Storm Helene currently located over northern Georgia as of 10Z will continue to rapidly dissipate as it moves north across the state and then northwest towards the Ohio Valley where it will become "absorbed" into an upper- level low later today and tonight. This upper-level low is expected to remain across the Ohio Valley through Saturday (and beyond), and will be the primary driver for the local weather patten for the time being. Regional radar observations reveal an expansive area of rain across the southeast CONUS extending northward into the Ohio Valley with the northern extent of the precipitation shield just now entering the southern part of the forecast area (i.e. Marion to Knox County). This precipitation will make very minimal northward progress, maybe another tier of counties this morning before there is a more substantial northward surge of precipitation later this afternoon through tonight as the remnants of Helene approach. There should be a fairly expansive area of rain between 18-22Z before becoming more scattered this evening into tonight. In addition to the rain, northeast winds will be on the rise today, peaking during the afternoon/evening hours. The strongest wind gusts of 35-45 mph are expected in parts of Northwest Ohio and Central Ohio. A dry slot wrapped around the upper-low and behind the main area of moisture associated with Helene will result in a ~12 hour period late tonight into Saturday morning where most areas become relatively rain-free. However, additional moisture moves back in with scattered rain showers likely by Saturday afternoon/evening. && .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/... A trough at the surface and aloft affects our CWA through the short- term period as the vertically-stacked remnant low of Helene wobbles ENE`ward from the Lower OH Valley toward the Middle OH Valley Saturday night through Monday night, In addition, the remnant low is expected to devolve into a trough at the surface and aloft Monday night. Simultaneously, a warm front is expected to sweep generally N`ward through our region Monday night in association with a potent shortwave trough aloft progged to approach our CWA from the Canadian Prairies and the northern Great Plains. This weather pattern evolution will allow moist isentropic ascent aloft to generate abundant cloud cover and periodic rain showers in northern OH and NW PA through the short-term period. The moist isentropic ascent may release enough elevated instability to trigger a few thunderstorms, especially during the afternoon and evening hours of Sunday and Monday. Overnight lows are expected to reach mainly the lower to mid 60`s Saturday night and then mainly the mid 50`s to lower 60`s Sunday night and Monday night, respectively. Daytime highs are expected to reach the 70`s on Sunday and Monday. && .LONG TERM /TUESDAY THROUGH THURSDAY/... The aforementioned shortwave trough aloft is expected to approach from the Upper Midwest on Tuesday and then traverse the Lake Erie region and Upper OH Valley generally from west to east Tuesday night. Simultaneously, the attendant surface cold front sweeps SE`ward through our CWA Tuesday through Tuesday night and will be followed by a surface ridge building from the north-central U.S. Scattered showers are expected along and ahead of the cold front courtesy of low-level convergence/moist ascent along the front and pre-front low-level moist isentropic ascent aloft. In addition, the convergence/ascent along the surface cold front may trigger weak, yet sufficient boundary layer CAPE to trigger a few thunderstorms. Behind the front Tuesday night, a sufficiently-moist NW`erly to N`erly mean low-level flow associated with strong CAA and accompanied by 850 mb temperatures dropping to near 3C over ~22C Lake Erie will allow scattered lake-effect rain showers to occur over and generally southeast or south of the lake. Daytime highs are expected to reach the 70`s on Tuesday, before the cold front passage. Lows are expected to reach mainly the upper 40`s to mid 50`s around daybreak Wednesday. High pressure at the surface and aloft is expected to build from the Upper Midwest and vicinity on Wednesday through Thursday. Low-level dry air advection and a lowering subsidence inversion accompanying the ridge are expected to cause lake-induced CAPE to wane and lingering lake-effect rain showers over/generally southeast or south of Lake Erie to end by Wednesday evening. Otherwise, fair weather is expected through Thursday as stabilizing subsidence accompanies the ridge. Limited daytime heating amidst net low-level CAA will allow highs to reach the 60`s to near 70F Wednesday. Considerable clearing, easing surface winds, and low humidity at/near the surface are expected to allow lows to reach the 40`s to lower 50`s around daybreak Thursday. During the day on Thursday, our CWA is forecast to become located along the western flank of the surface ridge and begin to be impacted by net low-level WAA. This net low-level WAA regime and daytime heating should allow late afternoon highs to reach the upper 60`s to mid 70`s. && .AVIATION /12Z Friday THROUGH Tuesday/... Overcast skies are observed areawide with mostly high cirrus, though a few pockets of clouds around 4-7kft. Impacts from the remnants of Helene will begin to occur later this morning with low ceilings, rain, and wind. Rain and thickening clouds will build in from the south this morning through the day and into this evening and tonight. Initially, a steady rainfall is expected, especially west of I-77 but rain will become more scattered this evening into tonight. A gradual lowering of ceilings to the 1-3kft range is expected late this afternoon into tonight at most TAF sites with a few hours of IFR ceilings possible late tonight. Low visibilities are possible with heavier rain, especially towards the south and west. KFDY has the best chance with visibilities as low as 1 SM, with the chance for brief IFR visibilities also possible at KTOL, KMFD, KCLE, and KCAK. Northeast winds will also be on the rise late this morning, with gusts of 20-30 knots possible this afternoon through this evening. Strongest wind gusts are expected towards the south and west (e.g. TAF sites such as KTOL, KFDY, and KFDY) where gusts of 25-30 knots will be more persistent and max isolated gusts of 35 knots will be possible. Winds should gradually subside tonight. Outlook...Periods of non-VFR are possible with scattered rain showers and low ceilings through Tuesday. && .MARINE... The Small Craft Advisory and Beach Hazards Statement from Maumee Bay to Willowick take effect at 5 AM today, while the Small Craft Advisory and Beach Hazards Statement from Willowick to Ripley take effect at 8 AM today. All of these alerts will be in effect until 8 AM EDT Saturday. Fairly-strong ENE`erly winds on Lake Erie may allow the water level at/near Toledo to peak near 5.5 feet to nearly 6 feet above low water datum late this afternoon through early evening. Flood stage at Toledo is 6 feet above low water datum. We will continue to monitor the latest lake level forecast and observations closely for the potential need for a Lakeshore Flood Warning. Helene`s low wobbles generally N`ward and then NW`ward from GA to the Lower OH Valley through this evening. Thereafter, this low is expected to remain nearly-stationary through Sunday night before drifting ENE`ward toward the Middle OH Valley on Monday and weaken steadily. Simultaneously, a trough extending from Helene`s low is expected to impact Lake Erie and interact with a high pressure ridge focused over/near the northern Great Lakes. The interaction between the trough and ridge will allow NE`erly to E`erly winds around 10 to 20 knots early this morning to freshen to around 20 to 30 knots by daybreak and remain around 20 to 30 knots through this evening. Waves of 4 feet or less early this morning build to as large as 5 to 10 feet later this morning through evening. As Helene`s low weakens steadily and the attendant trough over Lake Erie does the same, the NE`erly to E`erly winds are expected to ease to around 15 to 25 knots between midnight and daybreak Saturday morning, ease further to 5 to 15 knots by daybreak Sunday, and then remain around 5 to 15 knots through Monday. Waves are expected to subside to 4 feet or less by nightfall Saturday evening and to 3 feet or less by daybreak Sunday. However, occasional 4 footers are possible in open U.S. waters on Sunday through Monday. E`erly to SE`erly winds around 5 to 15 knots veer to S`erly Monday night as Helene`s remnant low dissipates in vicinity of the Middle OH Valley and a warm front sweeps N`ward across Lake Erie. On Tuesday, S`erly to SW`erly winds around 10 to 20 knots veer to NW`erly as a cold front sweeps SE`ward across the lake. Waves are forecast to be mainly 3 feet or less, but occasional 4 footers are possible and the cold front passage may yield Small Craft Advisory conditions. && .CLE WATCHES/WARNINGS/ADVISORIES... OH...Beach Hazards Statement through Saturday morning for OHZ003- 007-009>012-089. PA...Beach Hazards Statement through Saturday morning for PAZ001. MARINE...Small Craft Advisory until 8 AM EDT Saturday for LEZ142>149. && $$ SYNOPSIS...Saunders NEAR TERM...Campbell/Saunders SHORT TERM...Jaszka LONG TERM...Jaszka AVIATION...Saunders MARINE...Jaszka