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Area Forecast Discussion
Issued by NWS Cleveland, OH
Issued by NWS Cleveland, OH
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369 FXUS61 KCLE 160538 AFDCLE Area Forecast Discussion National Weather Service Cleveland OH 138 AM EDT Tue Jul 16 2024 .SYNOPSIS... A frontal boundary will settle across the Lower Great Lakes today before pushing southeast across the area as a cold front Tuesday night into early Wednesday. High pressure will build in from the west Wednesday night through the end of the week. && .NEAR TERM /THROUGH TONIGHT/... 1:30 AM Update... The severe thunderstorm watch has been expanded eastward to include several counties in Northwest Ohio and the western basin of Lake Erie. Mesoanalysis suggests there is a still a good plume of instability (as high as 3000 J/kg of MUCAPE) into the I-75 corridor. This core of instability is expected to advance eastward into the forecast area, which should provide a good amount of buoyancy to the MCV/QLCS that is approaching from the west. This line is still producing severe weather winds at the IN/OH state line with numerous reports of severe wind gusts and damaging winds (mainly tree damage at this point). Even so, we are generally expecting an overall weakening trend as this QLCS moves across the area. However, since there is still good instability and the MCV is likely producing enhanced lift/shear, it`s quite uncertain how long this QLCS progresses before truly weakening below severe limits. The current expectation is for sporadic/isolated severe-level wind gusts within the severe thunderstorm watch area, before it weakens to sub-severe levels. Previous discussion... An active near term period is expected with multiple chances for thunderstorms through Tuesday. Some storms may be strong to severe after midnight tonight with the primary threat being damaging wind gusts. As of 330 PM, a roughly west to east axis of cumulus exist along a pseudo warm front, extending from central IA towards Northwest Ohio. Strong to extreme instability resides along and just south of this axis, with MLCAPE as high as 4000 to 4500 J/kg in some spots across the Midwest with surface dew points in the mid to upper 70s. Water vapor imagery reveals a well- defined upper trough axis arriving across southern MN this afternoon, with storms beginning to develop along this instability axis across central IA. Thunderstorms are expected to increase in coverage across portions of IA/IL/southern WI through this afternoon, roughly following this instability axis east- southeastward. Anticipate this axis to slowly drift northwards through the rest of this afternoon and evening, reaching roughly the Lake Erie/southern MI vicinity ahead of the approaching complex which is expected to arrive just after midnight tonight. Given the overnight timing of the storms, confidence is on the lower side for widespread damaging wind gusts, although can`t rule out isolated instances of 60 to perhaps 70 mph gusts, particularly across NW OH where instability and DCAPE will be highest. Heavy rain and localized flooding is also possible, given PWATs around 2.0 inches and warm cloud depths exceeding 10kft. For Tuesday, a cold front will be beginning to sag south across the Great Lakes, though storm coverage may be more limited due to large-scale subsidence from the overnight thunderstorm complex, similar to what occurred this morning. It appears higher chances for storms may reside further to the south near the US-30 corridor along remnant outflow boundaries (i.e. pre- frontal). Any storms that do occur would bring a damaging wind and hail threat, in addition to heavy rain and localized flooding. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... The cold front will slowly make its way south through the region during the day Wednesday, ushering in a refreshing pattern change. However, the front`s progress will be slowed by the positively tilted mid/upper trough axis digging across the Upper Midwest and western Great Lakes. This will cause the boundary to hang near the southern CWA until Wednesday evening, and pooling low-level moisture along it combined with synoptic forcing from a 90-100 knot H3 jet streak rounding the base of the digging trough will lead to some additional shower and thunderstorm development. Cloud cover and morning showers should limit the instability, so expect the severe weather potential to largely be south of the region, but cannot rule out a strong storm or two with locally heavy rain and gusty winds given the forcing and lingering juicy airmass. The greatest coverage of showers and thunderstorm will be from roughly Findlay to Youngstown. By Wednesday night, the mid/upper trough axis will swing into the central Great Lakes, pushing the front south of the region with broad Canadian high pressure ridging in from the Upper Midwest. This will bring dry conditions and the beginning of the true airmass change, setting up mostly sunny and beautiful weather for Thursday as the large surface high becomes elongated from the heart of the cornbelt through the Ohio Valley by Thursday night. Highs in the upper 70s/low 80s Wednesday will cool into the low/mid 70s Thursday with much lower humidity levels. Lows Wednesday night will fall into the upper 50s/low 60s, with impressive lows of 55 to 60 Thursday night given the clear skies and light winds. Open the windows! && .LONG TERM /FRIDAY THROUGH MONDAY/... An amplified pattern will remain in place through early next week characterized by broad mid/upper troughing over the Great Lakes and Northeast US downstream from strong mid/upper ridging over the Intermountain West. This will keep the major summer heat out West while below normal temperatures dominate the eastern US. At the surface, the broad Canadian high will remain elongated across the Midwest and Ohio Valley Friday and Saturday, gradually drifting into the eastern Great Lakes and New England by Sunday and Monday. This will keep pleasantly cool and dry conditions in place Friday through the weekend, with very slowly moderating temps as return flow develops by Sunday and Monday. Uncertainty increases for Monday with some guidance hinting and warm/moist advection north of an approaching warm front, so at this time, kept NBM slight chance PoPs. Highs will be in the mid/upper 70s Friday warming into the upper 70s/low 80s Saturday and Sunday and low/mid 80s Monday. && .AVIATION /06Z Tuesday THROUGH Saturday/... An organized line of thunderstorms located along the IN/OH continues to progress eastward, with recent reports of 60 mph wind gusts. However, latest radar structure appears to suggest that it`s weakening as it approaches the I-75 corridor. Did time out this line of thunderstorms across all TAF sites, with greater confidence in timing and impact for our western TAF sites, and much lower confidence for eastern TAF sites. There is a possibility that this dissipates quickly enough for little to not thunderstorms to occur at sites along and east of I-77. Will continue to monitor though. Brief lower ceilings and visibilities will be possible within thunderstorms. Thunderstorms should exit the area by 12Z. Additional scattered showers and thunderstorms should develop later this afternoon into early tonight. Timing and areal extent of these storms is very uncertain though, so started with VCSH/VCTS mentions for now. MVFR ceilings become Southwest to west winds 10-12 knots with occasional gusts 18-22 knots will diminish this evening to 5-8 knots while becoming south. Winds gradually turn southwest to west while increasing to 12-15 knots with gusts to 20-22 knots by mid Tuesday morning/early afternoon. Winds gradually weaken tonight. Outlook...Non-VFR possible in isolated to scattered showers and thunderstorms Tuesday afternoon and evening. Non-VFR possible in patchy fog Tuesday night into Wednesday morning. && .MARINE... The Small Craft Advisory for the western and central basins will expire at 20Z since winds and waves have subsided behind the exiting MCV/wake low. Winds are gradually subsiding in the eastern basin from Willowick to Ripley, but still seeing enough observed winds in the 20-25 knot range at buoys and lighthouses to keep the Small Craft Advisory and Beach Hazards statement going through 00Z. By tonight, winds will turn SSW and decrease to 5-10 knots for a few hours, but trends are increasing for another uptick in SW winds of 15-25 knots by Tuesday morning associated with another MCV/wake low. This will be leftover from a large convective complex that is expected to develop to the west this evening, so Small Craft headlines may be needed again Tuesday morning. WSW winds decrease to 10-15 knots Tuesday afternoon and evening, turning NNW Tuesday night and Wednesday behind a cold front. N winds of 10-15 knots are then generally expected Wednesday night through Thursday night as Canadian high pressure builds in from the west, decreasing to 5-10 knots Friday and Saturday. && .CLE WATCHES/WARNINGS/ADVISORIES... OH...None. PA...None. NY...None. MARINE...None. && $$ SYNOPSIS...Kahn NEAR TERM...Kahn/Saunders SHORT TERM...Garuckas LONG TERM...Garuckas AVIATION...Iverson MARINE...Garuckas