textproduct: Cleveland

WHAT HAS CHANGED

No significant changes to the previous forecast.

KEY MESSAGES

1) Dry with slowly warming temperatures through Tuesday.

2) A brief period of heat and humidity will arrive on Wednesday with showers and thunderstorms late Wednesday into Thursday.

3) Cooler end to the week, but heat and humidity build again next weekend.

DISCUSSION

KEY MESSAGE 1... An Omega Block will continue across the Lower 48 through the rest of the holiday weekend, characterized by mid/upper troughs over the Pacific Northwest and eastern Great Lakes/New England and a broad mid/upper ridge in between over the Plains. This will keep the southern Great Lakes and Ohio Valley under favorable upper level confluence to maintain a large surface high of Canadian origin overhead. As a result, the very pleasant temperatures and low humidity found across the area this afternoon will continue through Labor Day Monday. Expect another cool night tonight, with lows in the low/mid 50s inland from the lake and upper 50s to near 60 along the lakeshore. A slightly warmer day is expected Monday, but still comfortable with highs in the mid 70s to around 80.

The large Canadian high will drift east into the Mid Atlantic region Monday night and Tuesday as the central CONUS mid/upper ridge expands east into the Ohio and Tennessee Valleys in response to shortwave energy ejecting into the northern Plains. This will set up return southerly flow and resultant warm air advection, so temperatures and dew points will be noticeably higher Tuesday. Look for highs to get back into the low/mid 80s.

KEY MESSAGE 2... The mid/upper ridge will become firmly established across the Ohio and Tennessee Valleys (briefly) Tuesday night and Wednesday as the aforementioned shortwave progresses into the Great Lakes. Strong warm air advection ahead of the accompanying cold front and 850 mb temps warming to 17-18 C beneath the thermal ridge will support highs in the upper 80s to around 90 Wednesday, and dew points in the low 70s will yield heat indices in the low/mid 90s. The ridge will already be flattening Wednesday evening as the shortwave digs into the central Great Lakes. This will push the cold front through the region late Wednesday evening or Wednesday night. There will likely be a narrow ribbon of moderate to strong instability given the heat and humidity, and this coupled with the right entrance region of a 120-130 knot upper jet streak crossing Lower Michigan should support organized convection. Will need to monitor for strong to severe storms Wednesday evening into Wednesday night, but the main uncertainty continues to be convective coverage. A second mid/upper shortwave crossing the Great Lakes Thursday will likely stall the cold frontal boundary over northern or central Ohio in response to a surface wave tracking along it, and this will keep decent coverage of showers and thunderstorms over the area Thursday before drying out Thursday night.

KEY MESSAGE 3... Canadian high pressure will finally build into the southern Great Lakes and Ohio Valley Thursday night and Friday and push the boundary south of the area, supporting cooler and less humid conditions. However, renewed mid/upper troughing pushing into the western CONUS next weekend will build and expand the stubborn central CONUS mid/upper ridge back into the Great Lakes and Ohio Valley. This will cause heat and humidity to build back into the area next weekend, with highs in the 70s Friday warming into at least the mid 80s for the weekend.

AVIATION /18Z Sunday THROUGH Friday/

Some low VFR clouds have developed across the region with incoming high pressure into the region and cooler air over warm Lake Erie. There may be some intermittent ceilings around 3-5 kft but clouds should remain few/sct through the evening. Clouds will clear with the diurnal cycle ending. Clouds will return on Monday morning with cold air advection over the lake. Winds will largely be northeasterly through the period. A land breeze may develop tonight and allow for southeast flow at KERI.

Outlook...Non-VFR possible with showers and storms on Wednesday and lingering into Thursday.

MARINE

High pressure over the southern Great Lakes will keep a decent northeasterly gradient over the lake through Labor Day Monday, so kept NE winds in the 15-20 knot range the rest of this afternoon and again Monday afternoon. This will build wave heights to 2 to 3 feet in the central basin with a moderate risk of rip currents at times. Winds will become light E to SE Monday night and Tuesday then SW at 15-25 knots late Tuesday night and Wednesday ahead of a strong cold front. Small Craft Advisories may be needed Wednesday. Winds will turn W to NW and decrease to 15-20 knots behind the front Wednesday night and Thursday, going light by Friday as high pressure returns.

CLE WATCHES/WARNINGS/ADVISORIES

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