Area Forecast Discussion
Issued by NWS Cleveland, OH

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000 FXUS61 KCLE 170808 AFDCLE Area Forecast Discussion National Weather Service Cleveland OH 408 AM EDT Thu Aug 17 2017 .SYNOPSIS...
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Low pressure over the upper midwest will cross the northern Great Lakes today and tonight, then slide across eastern Canada. A weak warm front will lift north across the area today followed by a cold front late tonight and Friday morning. A short wave trough aloft will cross the eastern Great Lakes on Saturday. High pressure will build across the area by Sunday.
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&& .NEAR TERM /THROUGH FRIDAY/...
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A relatively strong surface low pressure and short wave energy will track across the Great Lakes with a broad area of warm/moisture advection ahead of the system. Coverage of showers and storms will increase across the midwest and spread into northwest Ohio early this morning. The eastward movement will fight the dry atmosphere and downslope flow for a while this morning and it may take until afternoon to get the activity to extreme NE Oh and northwest PA. Once the atmosphere has moistened up, additional thunderstorms will develop as the trough approaches. Wind fields aloft will be strong for this time of year. These storms should have both shear and cape available but mid level lapse rates are progged to be weak. Drying aloft is progged to increase from the west this afternoon which will steepen lapse rates but may ultimately cap the development. I suspect there will be a sweet spot where severe storms develop and it could be in northwest or north central OH during the mid/late afternoon. Will include the threat in the Hazardous Weather Outlook. Forecast high temperatures today will be on the high end of guidance since the showers and thunderstorms will likely not be persistent and the air mass is warm. Unsure how far east the stronger storms will push this evening as the sweet spot gets pinched off. Will keep higher pops across northeast OH and northwest PA the first part of tonight. The showers and storms could reach a point tonight across extreme NE OH and NW PA where there is redevelopment with the potential for heavy rain for a while. PW is progged to remain above 2 inches across extreme NE OH and NW PA through the evening. The weak cold front may take until late tonight or Friday morning to push across the forecast area. Model soundings suggest that the drying aloft and subsidence will increase Friday as the leading shortwave lifts out. Will keep a small pop across extreme northeast OH and northwest PA through midday Friday since there may be just enough upward motion and convergence to pop a shower a two until the front is through. Cooler tomorrow as cold advection will be steady through the day behind the front. High temps not too far from normal.
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&& .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
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Shortwave energy enhancing the upper trough across the Ohio Valley for Saturday will likely be enough to produce a few scattered showers/thunderstorms across the area. Hopefully that this threat will push east of the area by evening with the bulk of the trough through, but there is the possibility that a few showers linger into the evening across the far east. High pressure overspreads the area for Sunday.
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&& .LONG TERM /MONDAY THROUGH WEDNESDAY/...
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The high shifts east for Monday. We will have a touch of good summer heat Monday with highs in the mid and upper 80s with subtle ridging overhead and H8 temperatures getting close to +20C. For now leaned toward the warmer ECMWF guidance, but it is possible a few locations could touch 90. We return back to a longwave western U.S. ridge/eastern U.S. trough by midweek. The warm and muggy airmass for Monday night and into Tuesday will be replaced with highs in the 70s and a more comfortable night for Wednesday night with lows back into the 50s. Showers and thunderstorms look to be a good bet sometime on Tuesday, but have limited precip chances to 50/50 until the timing is more firmly set. Right now the major shortwave player across the northern Plains phases quickly with more minor impulses across the southern Plains which may not hold. Behind this frontal system, high pressure builds southward from south- central Canada/upper Midwest for mid week.
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&& .AVIATION /06Z Thursday THROUGH Monday/... South becoming southwest low level jet will spread across the area this morning with deep Gulf moisture and increasing upward motion. Showers and thunderstorms will increase in coverage with MVFR visibility in showers. The first round of showers/storms will moisten up the atmosphere this morning across northwest and north central OH and MVFR ceilings will develop, especially in the vicinity of showers by mid/late morning. Additional showers and storms will develop this afternoon although the timing and location becomes more difficult to pin down. By this evening, the majority of showers/storms should have ended across NW OH with activity continuing across NE OH and NW PA. OUTLOOK...Areas of Non-VFR possible Saturday. && .MARINE...
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A warm front will be pushing northeast across the lake today into this evening bringing the east-southeast winds around to the south- southwest. The cold front will follow late tonight with winds shifting to the west. The winds in the warm sector today/this evening will be brisk, but with the offshore flow will likely not need a small craft advisory just yet. For Friday, though, a small craft advisory looks to be a good bet with the west flow east of the Islands. Thunderstorms that develop this afternoon primarily across the western basin may be strong to severe. Winds diminish with time Saturday backing and then veering as a weak upper disturbance moves a trough across the lake. Winds settle further as high pressure passes over the lake Sunday, shifting east of the lake for Monday.
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&& .CLE WATCHES/WARNINGS/ADVISORIES... OH...None. PA...None. MARINE...None. && $$ SYNOPSIS...Kosarik NEAR TERM...Kosarik SHORT TERM...Oudeman LONG TERM...Oudeman AVIATION...Kosarik MARINE...Oudeman

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