Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 211422 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 1022 AM EDT Thu Sep 21 2017 .SYNOPSIS... A mid level ridge of high pressure will set up over the Great Lakes and remain stagnant into early next week. This high will offer dry weather and very warm temperatures. Daytime highs are expected to be 10 to 15 degrees above normal through the weekend. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Very few changes were needed to the forecast this morning, but the main concern for today involves the very slight chance of showers. The previous forecast decided to hold off on including showers, owing to an expected lack in coverage and some capping. None of this has changed, but a few showers have already developed (and dissipated) this morning near Dayton. Again, the best course of action appears to keep a silent 10% chance, with the expectation that almost all locations will remain dry today. With almost full sun over the ILN CWA, max temps were increased by a degree or so for this afternoon. Previous discussion > Mid level ridge to build from the lower MS VLY into the Eastern Great Lakes. Surface high pressure to remain centered over the Upper Ohio Valley today. High level debris clouds from upstream convection will spill over the ridge into the region today. Latest nighttime microphysics satellite channel depicts fog in the river valleys. Clouds spilling into the nw should mitigate widespread fog over West Central Ohio. Have issued a special weather statement for the southeast, highlighting reduced visibilities in valley locations. Some of the earlier model solutions and the latest GFS soln continues to generate some light qpf over our western counties. Upon inspection of the forecast soundings, expect a cap in place and without significant forcing do not expect widespread convection. Therefore, have maintained a dry forecast today. 850mb thermal ridge to our west nudges a little east today. Based on this slight warming expect highs a little warmer than yesterday. Expect highs 10 to 13 degrees above normal today and generally in the mid and upper 80s. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/... Given a quasi-steady state weather pattern tonight should be close to this morning. Temperatures will drop to lows from the lower 60s east to the mid 60s west. Valley fog, especially in eastern locations is again likely tonight. With placement of the mid level ridge and 8H temperatures, Friday/Saturday look to the be the warmest days during this warm weather period. Therefore, expect highs on Friday to be a little warmer than today with most locations topping out in the upper 80s under mostly sunny sky conditions. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... Ridge building at the surface and aloft will dictate weather conditions through most of this period. Latest models continue to indicate 1020 mb surface high pressure over New England in conjunction with a 5900 meter 500mb high extending from the Gulf Coast to Southern Canada. The surface high is shown to retrograde under the upper high to the Great Lakes and Ohio Valley by Sunday, with the system then exhibiting modest height and pressure falls by Tuesday. A large, high amplitude upper trough pushing a surface cold front toward the area on Wednesday will bring additional height falls, signaling a change in pattern for late next week. The absence of forcing and deep moisture in the anticyclonic circulation around the high will allow dry weather and mostly clear skies to persist from Friday night through Tuesday. Cooler air aloft riding above the surface cold front will produce enough instability for increasing clouds and a chance of showers and thunderstorms Wednesday afternoon and evening. Under anomalously high geopotential heights, temperatures will be up to 15 degrees above normal for late September. High temperatures reaching the middle and upper 80s Friday through Tuesday are forecast to slip to around 80 on Wednesday under clouds and cold advection. && .AVIATION /14Z THURSDAY THROUGH MONDAY/... Mid level ridge to build from the Lower MS VLY through the Eastern Great Lakes. Surface high pressure will remain centered just to our east over the Upper Ohio Valley. Subsidence over the area has led to clear skies through the first part of the night. The clear skies, light winds and a moist boundary layer created favorable conditions for fog development mainly in the river valleys Latest IR satellite imagery shows high level debris clouds from upstream convection spilling over the ridge into western Ohio. Have IFR VSBY restrictions at favored KLUK and KILN sites with mainly MVFR restrictions at remainder of the TAF sites. Moisture is shallow, so the fog will burn off quickly after sunrise. Expect some scattered cu development along with continued high level clouds from upstream convection. Radiation fog development likely again tonight with IFR restrictions limited to the favored valley location at KLUK. Through 06Z have limited the restriction to the MVFR category. OUTLOOK...No significant weather is expected at this time. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...AR NEAR TERM...Hatzos/AR SHORT TERM...AR LONG TERM...Coniglio AVIATION...AR

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