Area Forecast Discussion
Issued by NWS Cleveland, OH

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000 FXUS61 KCLE 210744 AFDCLE Area Forecast Discussion National Weather Service Cleveland OH 344 AM EDT Mon Aug 21 2017 .SYNOPSIS... High pressure over the region will continue to move east of the area today. Low pressure will move northeast across the Great Lakes Tuesday, forcing a cold front across the region Tuesday evening. High pressure will build east across the region Wednesday through the first half of the weekend. && .NEAR TERM /THROUGH TUESDAY/... Nearly zonal flow will persist across the country today as a weak shortwave trough moves east across the region. This feature along with some limited moisture and day time heating will support increasing CAPE through the afternoon. Can`t rule out the possibility for scattered showers and thunderstorms this afternoon. So, the threat for showers and thunderstorms could mess up viewing of the long awaited solar eclipse this afternoon. I am thinking it will be a 50/50 shot at actually having a good view of the moon/sun combo. The convective activity will begin to wane later this evening after sunset as shortwave pulls out to the east. The next threat for showers and thunderstorms will increase through the day Tuesday when the next cold front approaches the area. There are some indications that a pre-frontal trough will develop ahead of the cold front and could become the leading focusing mechanism to produce the convection. This could mess up the timing of the precipitation for a severe weather threat by stabilizing the atmosphere through the morning and preventing any day time heating from becoming dramatic. Now, if the GFS is correct with the later timing of the front and pre-frontal trough, then, we should see some heating in the east to aid in destabilization. CAPE values will be approaching 2000 J/Kg mainly in the east during the afternoon. The storm prediction center already has the eastern two thirds of the area in a slight risk for severe thunderstorms for tomorrow. Will hold off on mentioning any severe threat in the forecast at this time due to the issues mentioned above. Would rather use that terminology when threat is imminent. Otherwise, temperatures will be on the warm side again today. Highs will be between 86 and 88 degrees across the area except 82 to 84 in the east. The other issue is we will see dewpoint temperatures begin to climb into the upper 60s to lower 70s later today and stay there overnight. This will make for another muggy and sticky night. Highs on Tuesday will be slightly cooler as pre-frontal convection develops in the west. If we get sun in the east, then I think temperatures will be warmer than currently forecast. && .SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/... As is often the case this time of year, not sure exactly where the front will be located come Tuesday evening. The prefrontal trough will certainly be well east of the area but the front could be hanging back or perhaps the 850 mb front might not have crossed all of northeast OH and northwest PA. Will keep a chance of showers/storms over the eastern half of the forecast area, mainly before midnight. High pressure is progged to build in quickly on Wednesday. H8 temps are progged to drop to about +9C but the inversion is progged to be low with plenty of subsidence. Not expecting any lake effect precip, probably some clouds though, mainly early. It will be noticeably cooler and less humid with highs in the 70s. Most of the models suggest a trailing short wave will drop through the trough aloft come Wednesday night into Thursday. Will have a small chance of showers, mainly in the snowbelt, both primary and secondary, given the shift to a north wind. Some areas may not get out of the 60s on Thursday. && .LONG TERM /FRIDAY THROUGH SUNDAY/... High pressure should build across the area late in the week. Unseasonably cool temperatures will continue Friday, again with some sections of extreme northeast OH and northwest PA not getting out of the 60s. The anticyclonic flow should discourage any precip although there may be some lake effect clouds on Friday. Saturday should be sunny/mostly sunny. The high will begin to shift east of the area on Sunday. With an east flow in the boundary layer, we will likely not warm up too quickly. High clouds may begin to spread in from the west. Highs in the 70s. && .AVIATION /06Z Monday THROUGH Friday/... A small area of convection moved quickly along the shore of Lake Erie and will arrive near Erie in the next hour or so. Another area moving east out of Indiana is expected to weaken before it arrives in Findlay. Otherwise, there is the possibility for some widely scattered thunderstorm activity across the area today. Will leave TAFs dry through the day since there is a low probability that any site will see the activity. May need to adjust with the 12Z TAFs later this morning. Expecting mainly middle and high clouds through the rest of the day into tonight. Winds should shift around to a south to southwest direction for today and become light and variable again tonight. OUTLOOK...Non-VFR likely in scattered showers and thunderstorms on Tuesday and Tuesday night. && .MARINE... High pressure will drift off to the east today with a light south flow on Lake Erie. A few thunderstorms will continue to develop today into early tonight and mariners will have to be alert for thunderstorm wind gusts and wind shifts in the vicinity of the storms. A strong cold front will cross Lake Erie later Tuesday. The southwest flow will increase tonight and Tuesday morning ahead of the front. Thunderstorms will be likely Tuesday. A small craft advisory may be needed up the east lakeshore on Tuesday east of Cleveland, especially from around Ashtabula and Erie, PA eastward. Winds should begin to diminish on Wednesday but with colder air aloft and efficient mixing, the lake may remain stirred up on Wednesday. High pressure and lighter winds are expected late in the week. && .CLE WATCHES/WARNINGS/ADVISORIES... OH...None. PA...None. MARINE...None. && $$ SYNOPSIS...Lombardy NEAR TERM...Lombardy SHORT TERM...Kosarik LONG TERM...Kosarik AVIATION...Lombardy MARINE...Kosarik is the U.S. government's official web portal to all federal, state and local government web resources and services.