textproduct: Cleveland

WHAT HAS CHANGED

No major changes to the ongoing forecast.

KEY MESSAGES

1) Cooler and less humid the rest of the week with occasional widely scattered showers in far NE Ohio and NW PA through tonight.

2) Turning warmer and more humid this weekend into the start of next week with scattered showers and thunderstorms, but confidence in coverage is low.

DISCUSSION

KEY MESSAGE 1... Afternoon satellite and water vapor loops show the mid/upper trough deepening and becoming negatively tilted across the Great Lakes and Northeast CONUS. Current RAP analysis places the surface low over western New York, with the trailing cold front approaching the U.S. 30 corridor. A band of scattered showers along and ahead of the front driven by weak instability and low-level convergence is exiting a Mahoning to Knox County line. Expect most of the showers to be done by the time the front exits late this afternoon, but lingered some slight chance POPS through late afternoon due to diurnal heating and progressively cooler air aloft that could trigger an isolated shower or two. Dew points remain elevated this afternoon, but a secondary surface trough currently crossing the lake will start to bring in the true airmass change this evening.

For tonight, most areas will stay dry as the drier airmass continues to advect in, but the surface low will become vertically stacked beneath the closing off mid-level low over upstate New York. This will lead to a deepening cyclonic flow cold air advection pattern which should produce scattered lake enhanced rain showers in far NE Ohio and NW PA. Wraparound moisture supports the idea of some showers, but RAP forecast soundings show lake to 850 mb Delta T's only averaging about 10 C along with shallow moisture profiles confined below 800 mb. An inversion will also be present around 800 mb, so this shallow moisture and low inversion environment will keep the rain showers light and disorganized. With this all being said, limited POPS to slight chance in far NE Ohio and NW PA tonight.

By Wednesday, the drier air should win out and allow any lake showers to end as the closed low gradually drifts farther east and Canadian high pressure builds in from the Upper Midwest. This high will settle over the Lower Great Lakes and Ohio Valley Thursday into Friday allowing the pleasant temperatures and low humidity to continue through the end of the week. Lows in the mid 50s away from the lake both Thursday and Friday mornings will give the air conditioners a nice break.

KEY MESSAGE 2... The Canadian high will shift into the Mid Atlantic region this weekend allowing return southerly flow to develop as the old closed low over the NE U.S weakens and lifts out. At the same time, another northern stream mid/upper shortwave trough will drop out of the Upper Midwest Saturday and evolve into a closed low over the Ohio and Tennessee Valleys by Sunday. Deterministic and ensemble guidance is struggling with the exact evolution and ultimate track of this closed low and how long it will linger, which is common in these set ups. Confidence is highest in a return to warmer and more humid conditions given the enhanced warm air advection between the high to the east and closed low diving to the west, but coverage of convection in this airmass is much lower confidence. Kept NBM chance POPS Saturday through Tuesday at this time, with the greatest coverage during daytime heating. Some areas that have missed out on rain the past couple of weeks may see some with the scattered convection between this weekend and early next week as we turn the calendar to August.

AVIATION /00Z Wednesday THROUGH Sunday/

Widespread VFR ceilings remain in place this afternoon with pockets of lake effect showers across western portions of the forecast area. Ceilings will scatter out this evening, with lake effect/enhanced clouds redeveloping overnight. MVFR ceilings are expected in parts of Northeast Ohio and Northwest Pennsylvania, improving shortly after sunrise. VFR conditions with FEW/SCT cumulus clouds continue through the day Wednesday.

Gusty northerly winds will diminish below 10 knots after sunset, with sustained winds 10-12 knots and gusts to 20 knots expected from the northwest tomorrow. A persistent VFR forecast is expected through the end of the week, with gusty winds ending Thursday afternoon.

Outlook...Non-VFR conditions in scattered showers and thunderstorms are expected Saturday afternoon through Sunday.

MARINE

Northerly at 15-25 knots are expected to continue through early Wednesday night before gradually diminishing as high pressure builds in from the west. Onshore flow will allow for wave heights in the central and eastern basins to build to 4-7 feet. Small Craft Advisories and Beach Hazards Statements remain in effect to highlight the timeframe of highest risk to small craft and beach goers through early Wednesday night.

Light and calm winds expected by Friday as high pressure becomes centered overhead, generally becoming easterly over the weekend as low pressure passes to the south.

CLE WATCHES/WARNINGS/ADVISORIES

OH...Beach Hazards Statement through late Wednesday night for OHZ009>012-089. PA...Beach Hazards Statement through Wednesday evening for PAZ001. MARINE...Small Craft Advisory until 4 AM EDT Thursday for LEZ144>148. Small Craft Advisory until 8 PM EDT Wednesday for LEZ149.