Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 191751 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 151 PM EDT Tue Sep 19 2017 .SYNOPSIS... A weak upper level disturbance will move through the area, offering a chance of showers and thunderstorms today into Wednesday. Drier conditions are expected for the end of the week into the weekend as upper level ridging builds into the Ohio Valley. Above normal temperatures will continue into the upcoming weekend. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Showers and thunderstorms continue to push in from the east this morning with PWATs around 1.70" (near max observed values for this time of year). This area of showers and thunderstorms is thanks to a shortwave pushing east through the region this morning. Overall, high res guidance shows a weakening trend of the complex this afternoon as LLJ convergence weakens and vorticity advection wanes. Have made minor adjustments to the forecast this morning due to current trends, but overall thinking remains unchanged. New zones already out. Prev Discussion-> Showers and thunderstorms have developed across portions of IL and IN ahead of a mid level shortwave over the Mid MS VLY. As this s/w moves east into the Ohio Valley scattered convection will develop across ILN/s FA. Marginal instability develops durg the day, so embedded thunderstorms will will also be possible, mainly during the late morning into this afternoon. The best coverage of showers and embedded thunderstorms will occur across the western counties. Precipitable water values increase with values up to 1.75 inches this afternoon. This high pw is close to record values for this time of year. Therefore, locally heavy rain will be possible in storms. Although clouds and pcpn will mute temperatures some today, warm conditions are expected to continue with highs from the upper 70s northwest to the lower 80s southeast. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/... As mid level shortwave weakens and instability is lost expect to see showers and embedded thunderstorms end early this evening. Expect some decrease in clouds with partly cloudy skies overnight. Light winds, low level moisture should lead to the development of patchy fog overnight. Expect lows in the lower and middle 60s. A few showers and perhaps a thunderstorm will be possible across the eastern counties early Wednesday as the weak s/w departs the area. Otherwise, mid level ridge builds across the west. This ridge will offer dry weather conditions and warm temperatures. Expect highs on Wednesday 7 to 10 degrees above normal, and generally in the lower and middle 80s. && .LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/... High pressure at the surface and aloft will dominate the weather through the period. Dry air and subsidence in the circulation around the high should keep any precipitation from occurring, and cloud cover will probably be lower than normal as well, suggesting ample sunshine. Geopotential heights will be well above average for late September. Models indicate a 5900 meter 500 mb high lifting gradually across the Ohio Valley to the Great Lakes. This warm regime will allow high temperatures to reach the mid 80s, about 10 degrees above normal. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... Mid level shortwave continues to slowly push east across the TAF sites this afternoon and can clearly be seen on water vapor. As the shortwave has slowly weakened this afternoon and lapse rates remain pitiful lightning has quickly decreased in coverage. Therefore have gone ahead and pulled thunder from the TAF sites even though an isolated strike can`t be ruled out. This evening the shortwave will slowly exit east with showers coming to an end from west to east. Overnight into Wednesday morning winds will quickly decouple thanks to the weak pressure gradient and with dewpoint depressions close to zero degrees fog looks likely. The main catch remains how much leftover cloud debris will be across the area. Overall have trended TAFs downward with visibilities and also brought in some cigs as well. Latest HRRR and NAM is also hinting at some MVFR/ IFR ceilings forming overnight which could delay fog formation as well. For now confidence is higher in fog formation compared to MVFR/ IFR ceiling formation. During the day Wednesday some weak shower and thunderstorm formation will be possible, but given that the TAF sites are on the back side of the shortwave have kept mention of precipitation out. OUTLOOK...No significant weather is expected at this time. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...Haines/AR NEAR TERM...Haines/AR SHORT TERM...AR LONG TERM...Coniglio AVIATION...Haines

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