Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 240738 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 338 AM EDT WED AUG 24 2016 .SYNOPSIS... With upper level ridging over the southeastern states, warm and moist air will begin to flow into the region today. Embedded waves in the mid-level flow will bring chances for showers and storms today and Thursday, in the northern Ohio Valley and southern Great Lakes. High pressure over the Great Lakes will bring drier conditions for Friday and Saturday, before chances for storms increase slightly on Sunday and into the new week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... As surface high pressure continues to move away to the east, an increasing gradient is setting up over the Ohio Valley. Ridging over the southeastern states is centered due south of the Ohio Valley, meaning that the mid-level flow is more westerly than southwesterly. Nonetheless, flow from 850mb and lower will have a significant southwesterly (theta-e advection) component, with both temperatures and dewpoints forecast to increase today. The atmosphere will be increasingly moist (precipitable water of around 1.8-1.9 inches) and unstable (MLCAPE of 750-1250 J/kg). Forcing is the clear limiting factor in terms of convective potential today. Warm frontal processes are failing to generate much upstream activity early this morning, though a few showers may still be possible in the northwestern CWA between 09Z-15Z. With no discernible surface features in the area today, attention will turn toward forcing slightly further aloft, though notably focused to the north and west of the ILN forecast area. A shortwave is forecast to move across southern Michigan during the late afternoon, with convergence in an area of enhanced 925mb-850mb flow pushing across northern Indiana. This should spark convection upstream of the region, which may eventually propagate into the forecast area toward the greater instability. With storms following this pattern ending up separated from the stronger flow and the source of lift, it is not surprising that high-resolution models have been fairly sparse in forecast coverage this far south. Will keep PoPs in a similar range as the previous forecast -- 20 percent in the south to 40 percent in the north. In terms of hazards, hard to see more than perhaps a threat for some gusty winds as the isolated/scattered storms propagate forward, but the severe threat over the ILN CWA appears pretty low without higher-end instability or a better-organized source of forcing. GFS/NAM projections indicate a 3C-4C rise in 925mb/850mb temperatures from yesterday to today, and max temps have been adjusted accordingly. This should allow for rises from yesterday of a few degrees in the northern CWA (where clouds will be a little more prevalent) and as much as 4-6 degrees in the south (where temps are likely to top out in the upper 80s). && .SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY/... The short term forecast discussion will be updated shortly. Previous discussion > Wednesday night the better pcpn chances remain across the nrn counties as upper level energy works through the flow. By Thursday, a cdfnt begins to approach the fa. It still looks like the northern half of the CWA will be most likely to be affected by storms on Thursday, but kept a slight chance for the srn counties. High temperatures will be a few degrees warmer ranging from 85 to 90. Forcing is very weak Thursday night, so washed out pcpn chances as the night progressed. && .LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/... A few showers and thunderstorms may linger on Friday in residual moisture and forcing near a weakening frontal boundary along and south of the Ohio River, including the Cincinnati metro area. Locations to the north including Dayton and Columbus should remain dry. High pressure and a dry airmass are expected for Saturday. For Sunday, moisture and energy spilling southeastward from Great Lakes low pressure will provide a chance of thunderstorms. Additional thunderstorms will be possible Monday when the low is forecast to drag a cold front across Ohio. A few thunderstorms may persist on Tuesday as the boundary sags gradually south to Kentucky. With a large and slow moving high in the upper atmosphere centered from the Central Appalachians to the Mid-Atlantic coast, and with mainly warm advection in the lower levels, a return to mid-summer heat is indicated. High temperatures ranging from the mid 80s to the low 90s will couple with dew points near 70 to make outdoor activities uncomfortable at best. && .AVIATION /07Z WEDNESDAY THROUGH SUNDAY/... A mid level ridge over the lower Gulf Coast states will slowly build northward through the TAF period. At the same time, embedded disturbances will rotate eastward through the Great Lakes. Return moist flow, along with the proximity of the disturbances, will bring at least a chance of showers and thunderstorms to the terminals today. Chances do not appear high at this time, with the best chance likely occurring near the KDAY terminal this afternoon. Have maintained a VCTS/CB at this location. Southeast to south surface flow will become south later this morning around 10 to 12 knots with some local gusts in the 15 to 20 knot range by afternoon. For tonight, the latest high resolution/convection allowing models indicate that the threat for showers/storms overnight will likely be closer to the lower Great Lakes, or mainly north or northwest of the terminals. As a result, have just VFR conditions at this time. OUTLOOK...Thunderstorms possible from Thursday into Thursday night, mainly near the northern terminals. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...Hatzos NEAR TERM...Hatzos SHORT TERM...Sites LONG TERM...Coniglio AVIATION...Hickman

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