Area Forecast Discussion
Issued by NWS Cleveland, OH

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000 FXUS61 KCLE 161046 AFDCLE Area Forecast Discussion National Weather Service Cleveland OH 646 AM EDT Wed Aug 16 2017 .SYNOPSIS... High pressure will build east across the Great Lakes region today. A warm front will lift north toward the region tonight, lifting through the area on Thursday as low pressure deepens and tracks into the Great Lakes. A cold front will push east through the region on Friday, with high pressure building in behind the front through the weekend. && .NEAR TERM /THROUGH THURSDAY/...
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No major changes to the forecast with the early morning update. Went ahead and bumped highs up another degree at some locations. Starting to sour a bit on precip chances this afternoon. Hi-res models have backed off a bit, with minimal instability and some capping per model soundings. Will leave low slight chance mention in for now. Original discussion... Surface high pressure will dominate the area today, with little weather concerns through early afternoon across the area, aside from some early morning patchy fog. Expanded slight chance pops across the southwest CWA a bit this afternoon, as guidance continues to indicated isolated convection focused along a 925mb theta-e gradient. Went a couple degrees warmer with highs today compared to previous forecast, in line with the warmest MOS guidance. Surface warm front near the Ohio River will lift north toward the area tonight, as upper trough/cutoff low and attendant deepening surface cyclone over the northern Plains tracks east towards the Great Lakes. Precip chances will slowly increase from the west tonight as low level jet inches towards the region and pieces of energy eject east/northeast out of the upstream trough. Have slowed the arrival of pops from previous forecast considerably, with chance pops not arriving across the western part of the area until 09Z. This may need to be slowed even further over the next forecast cycle, with most of the area possibly remaining dry through 12Z Thursday. Pops will increase through the day Thursday as the warm front lifts north through the area and the low tracks into the western Lakes. Again, have slowed down the pop trend from previous forecast, with likely pops not arriving until 15-18Z west, and expanding across the entire area by 22-00Z. Models have trended a little deeper/slower with the low and the attendant cold front, so the forecast may be too fast yet. Dewpoints will surge into the low 70s in the warm sector Thursday, with highs in the mid 80s. 1000-2500 j/kg of SBCAPE possible across the area, with deep layer bulk shear 35-40 kts may be enough to sustain organized convection late in the afternoon with damaging wind gusts the primary threat. Instability is likely overdone a bit in the models, with convective debris limiting overall isolation. Concur with the SPC Day 2 outlook with a widespread marginal risk.
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&& .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/... Most of the models show what is essentially a dry slot sweeping across the lower Great Lakes Thursday night with increasingly dry air aloft and some subsidence. Will start out with "likely" pops Thursday evening and then lower the forecast probabilities from west to east Thursday night. The front will arrive late, probably early Friday morning, and cannot rule out enough low level convergence and upward motion to generate a scattered to broken line of showers or thunderstorms but it does not appear worthy of more than a "slight chance/chance" pop Friday, mainly in the morning. The models have been consistent with a nice trailing short wave on Saturday. The better upward motion and precipitation will gravitate toward the better instability which will be well south of the area but the actual short wave may track across the lower Great Lakes and there would seem to be at least a chance or slight chance of a shower or perhaps a thunderstorm. The warm waters of Lake Erie could contribute some instability. Not sure whether Saturday may end up being mostly cloudy or partly cloudy. Will forecast high temperatures near guidance from the mid 70s to around 80. && .LONG TERM /SUNDAY THROUGH TUESDAY/... The pattern will become more amplified next week. Surface high pressure should build across the Great Lakes by Sunday and heights will rebound. The air mass will warm above normal early next week ahead of the next cold front which looks on track for sometime later Tuesday. && .AVIATION /12Z Wednesday THROUGH Sunday/...
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High pressure will build across the Great Lakes today. MVFR BR, and perhaps a localized brief IFR reduction, this morning will quickly lift by 13-14Z. Scattered cu expected during the day, otherwise little sensible weather concerns through most of the period. Clouds will increase, and perhaps precip chances, by the end of the period as low pressure moves into the Great Lakes. Winds will generally be light through the day, with a bit of a ENE-N lake breeze affecting KERI/KTOL/KCLE with some stronger 6-9 kt winds. Winds will veer around to the east southeast by the end of the period. OUTLOOK...Areas of Non-VFR possible Thursday through Thursday night with scattered storms.
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&& .MARINE... High pressure will slide across Ontario and Quebec today and the flow on the lake will remain northeast veering more easterly by tonight. As pressure falls to the west, the winds will pick up on the lake also enhanced by the onshore component this afternoon. Winds and waves will stay below small craft criteria but the lake will get a but choppy by late this afternoon and tonight, especially the west half of the lake. A deepening low pressure system will track across the northern Great Lakes Thursday into Friday. A warm font will cross Lake Erie o Thursday followed by a cold front Friday morning. The wind field will increase with this system as well as the threat for showers and thunderstorms. The southwest flow will become west and northwest on Friday and a small craft advisory may be needed. High pressure will quickly build east across the Great Lakes this weekend and winds and waves will settle down. && .CLE WATCHES/WARNINGS/ADVISORIES... OH...None. PA...None. MARINE...None. && $$ SYNOPSIS...Greenawalt NEAR TERM...Greenawalt SHORT TERM...Kosarik LONG TERM...Kosarik AVIATION...Greenawalt MARINE...Kosarik

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