Area Forecast Discussion
Issued by NWS Wilmington, OH

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556 FXUS61 KILN 220106 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 906 PM EDT THU JUL 21 2016 .SYNOPSIS... A large ridge of high pressure over the central portion of the United States will bring hot and humid conditions to the Ohio Valley through the weekend. A weak front will bring scattered showers and storms as it lays across the region. A strong cold front will bring more showers and storms for Monday with slightly cooler air for the first half of next week. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... A few lingering light showers will completely dissipate over the next hour, but expansive cirrus from earlier convection will likely keep skies mostly cloudy for the rest of tonight. Another MCS currently over southern WI will also add to our cloud cover later tonight. Models continue to struggle with ongoing convective activity across the region, though the HRRR has handled the short term fairly well today. Recent HRRR runs show the WI MCS diving south overnight and staying west of the ILN forecast area, which lines up well with current radar loop and upper level winds. However, the shortwave that triggered this activity will be riding the mid level ridge into Indiana and western Ohio by Friday morning and may generate some additional showers and storms further east. This activity could impact the northern CWA by daybreak, as suggested by the HRRR, RAP, ARW, and NMM. Synoptic models are of course more muddled, but they do also support the chance for showers and storms across our north late tonight. Have increased cloud cover overnight and introduced chance POPs across our north late. Also nudged up dewpoints a tad based on latest trends, which will make for muggy overnight lows in the upper 60s to lower 70s. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/... Heat and humidity will be the main focus through Friday and the weekend, but a challenging forecast for potential convection is also a part of the situation. Temps and dewpoints on the rise and fairly confident that at least most of fcst area will see heat indices reaching the 100 degree mark in the afternoon both Friday and Saturday. With 2 consecutive days of 100 have issued heat warnings for Hamilton and Montgomery counties and advisory for rest of fcst area. Biggest question mark is convection coverage and timing. Difficult to pinpoint timing and coverage through fcst period. Have opted to keep pops in the chance category for now but a bit higher than previous fcst. SPC has marginal outlook which looks reasonable as any widespread significant outbreak would not be expected in this pattern. Any storms would be slow moving with mainly strong wind gusts and heavy rain. Temps generally close to guidance through period. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... Sunday morning the long term will open up with mid-level ridging stretching across the entire center of the central United States from the west coast to the east coast. Over the next couple of days several shortwaves will traverse the region bringing on and off chances of showers and thunderstorms. This pattern will continue through most of the extended with a slightly lower heights and temperatures possible by the end of next week. The main story for the beginning of the extended will be the heat and humidity. 850 mb temperatures will again be around 20 degrees C with high temperatures in the lower 90s forecasted. This working in combination with dewpoints in the lower to mid 70s will put heat index values in the lower 100s. During the day Sunday a weak shortwave will move overhead bringing a chance of rain to the area with the GFS and ECMWF being pretty similar with the strength and position of the wave. During the day Sunday PWATs are forecasted to rise above 2.00" at times and given widespread instability have nudged PoPs upwards slightly. On Monday an upper level low will swing east across the Hudson Bay bringing a weak front across the area. Surface convergence is weak along the front and timing between the GFS and ECMWF is slightly out of phase. The ECMWF is slightly faster than the GFS with the GFS bringing the front through Tuesday morning. The ECMWF bring the front through Monday evening. Have leaned towards the ECMWF here. Behind the front much drier air will filter in with PWATs less than 1.00". This will help to bring a temporary end in the precip until Thursday. At the end of extended Thursday another shortwave will approach the area bringing the chance of rain back to the area. && .AVIATION /01Z FRIDAY THROUGH TUESDAY/... Weakening band of convection continues to progress SSE across far western Ohio. Cincinnati terminals may yet see a rumble or two of thunder, but otherwise expect any remaining showers to dissipate over the next hour or so. Expansive cirrus will likely keep skies overcast for most of the night, with another shield of cirrus currently over WI expected to spill into the Ohio Valley later on tonight. These storms over WI should dive south and remain west of our area, but the upper level disturbance that triggered them will move into IN and western OH towards daybreak Friday. This may trigger some additional convective activity that could affect the western terminals through midday Friday. However, with models not presently having a good handle on convective activity, there is low confidence in this possibility as well as potential timing of any showers/storms. There will likely be visibility restrictions at KLUK again tonight. A weak front dropping south from the Great Lakes will provide a small chance of storms Friday afternoon, but this will be contingent on possible morning convection and subsequent chances for destabilization. Expect SCT to BKN mid/upper level clouds Friday afternoon and slightly stronger southwesterly winds. OUTLOOK...Thunderstorms possible Friday through Monday. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...Heat Advisory from 10 AM Friday to 8 PM EDT Saturday for OHZ026-034-035-042>046-051>056-060-062>065-070>074- 078>082-088. Excessive Heat Warning from 10 AM Friday to 8 PM EDT Saturday for OHZ061-077. KY...Heat Advisory from 10 AM Friday to 8 PM EDT Saturday for KYZ089>100. IN...Heat Advisory from 10 AM Friday to 8 PM EDT Saturday for INZ050-058-059-066-073>075-080. && $$ SYNOPSIS...Padgett NEAR TERM...Kurz SHORT TERM...Padgett LONG TERM...Haines AVIATION...Kurz

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