textproduct: Cleveland

WHAT HAS CHANGED

Trends are for multiple rounds of thunderstorms this afternoon and evening, with scattered storms mainly in NE OH and NW PA between 2 and 4 PM, then another more widespread round of thunderstorms crossing west to east between 4 and 8 PM.

KEY MESSAGES

1) Scattered thunderstorms will develop and impact NE Ohio and NW PA between roughly 2 and 4 PM followed by a more widespread line between 4 and 8 PM. The main hazard is damaging winds, but isolated tornadoes and localized flooding are possible.

2) Showers linger mainly south of I-80 Thursday before high pressure brings dry, cooler, and less humid weather the rest of the week.

3) Warm, humid, and unsettled weather returns Saturday into next week.

DISCUSSION

KEY MESSAGE 1... Following the theme of summer and now early Meteorological Fall of 2026, yet another severe weather event is expected across NE Ohio and NW PA this afternoon and evening. Afternoon visible satellite and water vapor loops show a strong mid/upper shortwave trough progressing from the Upper Midwest into the Great Lakes. This is eroding the northern periphery of an unseasonably strong mid/upper ridge centered over the SE CONUS. The surface low associated with the mid/upper shortwave is near Hudson Bay and will progress east into northern Quebec tonight, dragging a cold front across our region. Despite the surface low being displaced so far north, plenty of jet dynamics will accompany the mid/upper shortwave this evening to enhance height falls and large scale ascent as well as to increase deep layer shear. This forcing coupled with moderate instability (MLCAPE of 1000-1500 J/Kg) will support a healthy line of convection.

In terms of timing and details, dying convection from last night has left a band of showers over Lower Michigan, Indiana, and extreme NW Ohio early this afternoon. This is setting up a differential heating boundary/pre-frontal trough over NW Ohio, which will act as the main trigger to ignite the main line of convection this evening as the shortwave and associated forcing overspread the area. Out ahead of this pre-frontal trough, a lake breeze boundary may set up east of Cleveland this afternoon. Forecast soundings do not have much of a cap to erode since mid-level lapse rates are weak ( 5 to 5.5 C/Km) and the atmosphere is quite warm through the entire boundary layer, so expect initial scattered convection to develop between 18 and 20Z along the lake breeze and impact NE Ohio and NW PA. A few of these storms could produce damaging winds since strong surface heating has created steep low-level lapse rates and resultant high DCAPE over 800 J/Kg. However, the main show will be with the line of convection that develops on the pre-frontal trough this evening. Consensus among HREF CAMS and the RRFS is for this line to develop from roughly the Lake Erie Islands to Marion after 20 or 21Z then propagate east through the Cleveland and Akron areas around 23Z and through NW PA by 01Z. The aforementioned instability coupled with deep layer effective shear increasing to 40-50 knots will support bowing segments capable of damaging winds. Any bowing segments will also need to be watched for isolated QLCS tornadoes since 0-3 Km shear will be over 30 knots and will try to orient normal to the line at times. Surface to 1 Km shear of 20-25 knots also supports the isolated tornado threat. Finally, storm cell movement will be fast (generally over 40 knots to the E and SE), but any repeated rounds of convection could result in locally excessive rainfall and flash flooding since PWATS are running unseasonably high (1.7 to 2 inches) and soundings show a deep warm cloud layer. This will mainly occur if parts of NE Ohio and NW PA see heavy rain from the initial scattered convection late this afternoon before the main line crosses the region this evening.

KEY MESSAGE 2... There will be a break in the rain showers most of tonight behind the line of convection, but a second mid/upper shortwave will progress across the Great Lakes and Upper Ohio Valley Thursday. The right entrance region of the mid/upper jet will lead to a weak surface wave that will ride along the front, causing the frontal boundary to briefly stall over northern or central Ohio Thursday morning. This wave and right entrance ascent should generate additional showers north of the boundary Thursday morning into the afternoon, especially along and south of I-80 and I-76. CAMS are in agreement with this, so increase POPS from 12 to 18Z. The front will finally push south behind this wave late Thursday afternoon and Thursday night allowing a large Canadian high at the surface to build down across the Great Lakes. This will bring dry and cooler, much more seasonable weather for Thursday night and Friday.

KEY MESSAGE 3... Unfortunately, the more typical mid September weather will not last long as a warm, humid, and unsettled pattern looks to quickly return this weekend. A couple of mid/upper troughs and associated closed lows progressing into the Pacific Northwest between Saturday and Wednesday will build an elongated mid/upper ridge across the south central and SE CONUS. This will allow temperatures well into the 80s and dew points in the upper 60s to around 70 to build back into the region Saturday and largely remain through Wednesday. Active quasi-zonal mid/upper flow across the Great Lakes on the northern periphery of the elongated ridge will send shortwave energy near or north of the region at times interacting with a wavering frontal boundary, and this will lead to at least scattered showers and thunderstorms. At this time, the greatest chances for rain appear to be Saturday and Tuesday, but timing individual chances is low confidence in this pattern, so the main message is very warm and humid with periodic showers/storms.

AVIATION /18Z Wednesday THROUGH Monday/

VFR across the TAF sites at 17z. However, ceiling will lower from northwest to southeast this afternoon and evening. In addition, showers and thunderstorms are possible near and round KTOL and will start this TAF withe a tempo group for TS at 18z and VCTS KFDY and KMFD this afternoon. Slightly bumped up by an hour or two for timing for TSRA impacts at TAF sites this afternoon. Still some uncertainty in TSRA coverage and intensity today, though strong wind gusts (around 30 knots) are likely with any storms that impact TAF sites east of KCLE. Targeted higher wind gusts in the 40 to 50-knot range may be needed in future amendments if confidence in direct impacts increases.

Confidence is also increasing for a period of non-VFR vsbys/ceilings following the convection overnight into Thursday morning. Have introduced MVFR vsbys/ceilings at most sites in a tempo group around 12z Thursday.

Winds will generally favor a south to southwest direction today, increasing into the 10 to 15 knot range with periodic gusts of 20 to 25 knots possible later this afternoon.

Outlook...Additional scattered showers are possible through Thursday, generally along and south of the US-30 corridor. Non- VFR may return for the weekend in isolated to scattered showers and thunderstorms.

MARINE

WSW winds will increase ahead of a cold front this evening and tonight, and may near Small Craft criteria in the eastern basin as winds approach 20 knots. The offshore component will build the highest waves in the open waters, but could see over 3 feet at times from Conneaut to Ripley. Winds will become NNW and rapidly decrease to 5-10 knots Thursday morning, with light and variable winds Thursday night becoming NE at 5-10 knots Friday as high pressure builds overhead. Variable wind speeds and directions are then expected Saturday through early next week as a frontal boundary sets up and wavers near Lake Erie.

CLE WATCHES/WARNINGS/ADVISORIES

OH...None. PA...None. MARINE...None.