Area Forecast Discussion
Issued by NWS Cleveland, OH
Issued by NWS Cleveland, OH
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032 FXUS61 KCLE 240059 AFDCLE Area Forecast Discussion National Weather Service Cleveland OH 859 PM EDT Mon Sep 23 2024 .SYNOPSIS... Low pressure will lift out of the Mid Mississippi Valley tonight and through the southern Great Lakes late Tuesday and Tuesday night. This will lift a warm front through the region Tuesday morning before a cold front sweeps through Tuesday night. A trough will linger across the region Wednesday before high pressure builds in from the north Thursday into Friday. && .NEAR TERM /THROUGH TUESDAY NIGHT/... 900 PM Update... Warm front/surface low pressure continues to push northeastward from the mid Mississippi Valley with mid level isentropic lift bringing the next round of rain in to the CWA. POPs ramp up overnight, temperatures to the upper 50s/lower 60s. Should be another round of decent soaking rain for the area in the next 24 hours. Previous Discussion... Unsettled weather will continue into mid week bringing pockets of beneficial rainfall to the region along with abundant cloud cover. The latest visible satellite loops show the spin associated with weak surface low pressure lingering over eastern Lake Erie near Buffalo, NY. Light northerly flow on the backside of this low across the unseasonably warm lake (water temps in the mid 70s F) combined with wraparound moisture and weak PVA is generating persistent light showers and drizzle. This is mainly occurring from north central Ohio and the central highlands through NE Ohio and NW PA where upsloping is locally enhancing the showers. QPF through early evening will only be a trace to few hundredths of an inch, but the dreary skies and damp conditions will continue. A break in the showers/drizzle is expected from mid evening through the first half of the night as the surface low drifts slightly farther east and becomes absorbed by a newly developing surface low lifting out of the Mid Mississippi Valley. Weak mid/upper shortwave ridging building across the southern Great Lakes region early tonight ahead of this system combined with weak surface ridging from the north will bring mainly dry conditions for the 00-06Z time period before the next system moves in. More on that below. Late tonight and Tuesday, the mid/upper shortwave trough over the Mississippi Valley driving the aforementioned surface cyclogenesis will phase with a stronger mid/upper trough dropping through the Plains and Upper Midwest. This will result in a deep mid/upper trough axis pushing into the western Great Lakes Tuesday and Tuesday night, with a slightly deepening surface low lifting from the St. Louis, MO region Tuesday morning through SE Lower Michigan and SW Ontario by Tuesday night. As this developing surface low organizes, a warm front will lift north across the region late tonight and Tuesday morning. Warm/moist advection and isentropic ascent driven by a developing 20-30 knot low-level jet will generate widespread showers spreading from SW to NE in the pre-dawn hours Tuesday, so have PoPs quickly increasing after 06Z tonight. That is where the forecast becomes challenging. Yes, everyone will see rain late tonight and Tuesday morning, but as the surface low lifts toward SE Lower Michigan in the afternoon and evening, redevelopment of showers and thunderstorms will occur ahead of the trailing cold front as the left exit of a 70-90 knot H3 jet streak impinges on the region and aids with increased frontogenetic forcing. HREF CAMS continue to show great variability the past two runs with how long of a dry slot there will be Tuesday afternoon behind the warm front, and that affects how much heating and destabilization can occur. The theme seems to be that at least scattered showers and widespread clouds will stick around through mid afternoon, and with the low late September sun angle, that makes us believe that instability will be greatly limited. The NAM only suggests 400 to 700 joules of surface based CAPE in the afternoon with HREF suggesting less, especially if the showers hang around through mid afternoon. The best chance for sunshine and higher CAPE appears to be south of the region. Nevertheless, with the surface low passing near the region and the aforementioned jet streak, shear will be sufficient for isolated strong to severe storms in the late afternoon and early evening before sunset. Deep layer shear looks to average 30-40 knots, and this could lead to gusty winds if any organized cores can develop. Low-level shear nearing 20 knots along with veering with height as the surface low passes nearby and low LCL heights of 500- 1000m could also support a brief spin up tornado. Mid-level lapse rates will be fairly flat (5.5 to 6 C/Km), so do not expect hail. Any severe weather would be gusty winds and/or a brief tornado, and again, this is a very marginal, conditional threat depending on how much of a dry slot develops. If there is a severe storm, areas along and south of the US 30 corridor have the best potential since that area has a greater chance at a longer dry slot/sunshine. Will keep a mention in the HWO. Showers will gradually end from west to east Tuesday night as the cold front sweeps east across the region. Highs will range from the mid to upper 70s Tuesday, except upper 60s to low 70s in NW PA where showers are likely to hang on the longest. Lows tonight will generally be in the upper 50s to low 60s, with low to mid 60s Tuesday night. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... Showers and thunderstorms will be ongoing in the eastern half of the CWA throughout the day Wednesday. There is some fair instability on Wednesday as CAPE values will be approaching 1000j/kg in the southeast and eastern counties due to diurnal heating. The surface low will be occluding to the north, and with low lapse rates and minimal shear in place, only general thunderstorms are expected at this time. A cold front will push through the region Wednesday night into Thursday and with that PoPs will decrease. On Thursday a ridge will build in over the western Great Lakes as a cutoff low moves south over the mid-Mississippi Valley. Dry weather is expected through the end of the period as northeasterly flow sets up over the region. Highs for Wednesday will be in the mid to upper 70s with overnight lows down into the upper 50s. For Thursday, highs will reach the upper 70s and low 80s and lows in the upper 50s, low 60s for the night. && .LONG TERM /FRIDAY THROUGH MONDAY/... PoP chances will increase throughout the day on Friday as a potential tropical system makes its way north into the region. There is still some uncertainty as to the northern extent of the system and how it will interact with the upper-level cutoff low in the mid- Mississippi Valley. As of now, chance PoPs have been carried over for the western two-thirds of the CWA for Friday into the weekend. There will be an tightened pressure gradient as the system moves northward with winds gusting out of the northeast at 20-30 mph Friday afternoon into the overnight hours. Temperatures will be roughly 5 degrees above average through the weekend with highs in the mid 70s to lower 80s. Lows will be in the lower 60s before falling into the high 50s to start next week. && .AVIATION /00Z Tuesday THROUGH Saturday/... Deteriorating conditions once again with MVFR/IFR ceilings expected as the next wave of low pressure moves back into the region over the next few hour. Rain chances return largely after 09Z. Visibilities, which will likely begin coming down to MVFR prior to the rain arriving, could go IFR at times in the -SHRA/RA. The high probabilities for on/off showers with perhaps isolated thunder will be slow to exit, so unsettled weather should be expected for the bulk of the forecast period. Might see some slow flight category improvement for the western terminals towards the end of the TAF. Outlook...Non-VFR likely Tuesday in showers and thunderstorms and low ceilings. Non-VFR conditions may linger through Wednesday with residual rain and low ceilings in the region. && .MARINE... A northwesterly wind continues over Lake Erie at 10-15 knots with waves 1 to 3 feet this afternoon. Winds will become light and variable as a surface low pressure slows across the eastern Great Lakes overnight into Tuesday. On Tuesday, winds will shift to be out of the southeast at 10-15 knots as the low moves off eastward. Tuesday night, winds will increase in the eastern portion of Lake Erie to 20-25 knots. A Small Craft Advisory will be needed for Ashtabula, OH east to Ripley, NY for a short period of time during the overnight hours into Wednesday. Winds will veer to be southwesterly and lighter at 5-10 knots during the day Wednesday as a cold front crosses Lake Erie. The winds will start to veer throughout the day on Thursday ahead of the next low pressure system before settling in a east-northeasterly at 10-15 knots. The aforementioned low will approach from the south and winds will increase as a result to 20-25 knots over the central and western basins of Lake Erie. As a result, a Small Craft Advisory could be needed for those areas Friday. && .CLE WATCHES/WARNINGS/ADVISORIES... OH...None. PA...None. MARINE...None. && $$ SYNOPSIS...Garuckas NEAR TERM...Garuckas/26 SHORT TERM...Kennedy LONG TERM...Kennedy AVIATION...26 MARINE...Kennedy