Area Forecast Discussion
Issued by NWS Wilmington, OH
Issued by NWS Wilmington, OH
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927 FXUS61 KILN 221729 AFDILN AREA FORECAST DISCUSSION National Weather Service Wilmington OH 129 PM EDT Sun Sep 22 2024 .SYNOPSIS... An upper level disturbance moving through the Ohio Valley will bring occasional chances for showers and a few thunderstorms tonight through Tuesday. Warm conditions are expected again today before more seasonable temperatures overspread the region for the start of the work week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Mostly clear skies this morning will soon be replaced by expansive cloud cover moving in from the W as a midlevel S/W approaches this afternoon into this evening. The drier air currently entrenched across the region will be shunted to the E into the afternoon, with a fairly pronounced dewpoint gradient expected to go along with it as some richer LL moisture advects in from the W through the daytime. But it will take some effort to truly moisten the profile, with an expectation that an approaching band of SHRA, with embedded TS, will erode with eastward extent. The SHRA may initially be falling from a deck at about 8-10kft, with quite a bit of dry air to overcome in the LL. This is shown well even on the typically more moisture- robust guidance, with a rather deep layer of dry air in the bottom 8-10kft to overcome, especially during the onset. So while there will most certainly be some virga and perhaps some sprinkles, the prospect of appreciable measurable rainfall drops off rather abruptly near/E of I-75 through at least midday. As we progress into early evening, enough saturation should occur that coverage of SHRA, with even some TS, should gradually increase toward sunset and beyond. But even then, rainfall amounts should be rather light (<0.1") in most spots E of I-75. The best chance for more appreciable rainfall will likely be after sunset W of I-75 as broken clusters of SHRA/TSRA attempt to move W before eroding again with eastward extent. Highs should again reach into the lower 90s in central/south- central OH and NE KY as the clouds and pcpn will be much more delayed in these areas. Further to the W, expect temps to top out in the mid to upper 80s. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/... West to southwest flow will continue aloft tonight into Tuesday with additional areas of mid level energy advecting across our area. This will help drag a frontal boundary slowly east into the region tonight and as we perhaps moisten up a bit more, we should see a somewhat better chance for showers and few thunderstorms to continue across the area tonight. Again though, given the overall dry pattern, will continue to limit pops to chance category for tonight. Lows tonight will be in the low to mid 60s. It looks like the frontal boundary may stall out across our area through the day on Monday. With additional waves of mid level energy moving through the Ohio Valley, a chance of showers and a few thunderstorms will continue through the day. The best chance for pcpn will be along and southeast of the boundary, generally across our southern forecast area. Temperatures will be more seasonable with highs on Monday ranging from the mid 70s northwest to the lower 80s in the southeast. && .LONG TERM /MONDAY NIGHT THROUGH SUNDAY/... Shortwave energy continues to dig into the Great Lakes and Ohio Valley to start the extended period Monday night and Tuesday. With an associated cold front just to our west, southwesterly flow will provide deep moisture, allowing for a good chance of widespread showers and storms. The latest guidance calls for a wave of surface low pressure to lift toward the Ohio Valley late Monday night, with showers increasing from southwest to northeast by morning. The cold front will then make it way through the area later on Tuesday. Guidance varies a bit, but QPF amounts appear to average half inch to an inch during this time. The low moves away on Wednesday... at which time uncertainty in the forecast increases significantly as a tropical system may be moving into the southeast United States. In general, we appear to be headed into more of a blocky pattern once again, with the northern stream retreating well north into Canada. This would make rainfall in our area depend upon the development and movement of the tropical system late in the week. For now, have a low chance of PoPs to allow for the uncertainty during this time. && .AVIATION /18Z SUNDAY THROUGH THURSDAY/... The river valley BR/FG has long dissipated, leaving mostly sunny skies through the morning hours. However, deeper-layer moisture is on the increase from the west as moisture advection works its way E into the region. This will promote ISO/SCT SHRA/TSRA through the first part of the TAF period, especially for wrn sites through this evening. Given the expected evolution of the activity, it is difficult to pinpoint one particular favored location or time window for the greatest coverage, although did attempt to highlight the afternoon round with TEMPOs as best possible. Do think there will be additional redevelopment near/after 00z, which will move back into the local area between about 00z and 06z. As such, decided to broad brush a VCSH, even recognizing that there will be large portions of the first 12 hours where there is not SHRA or TSRA particularly close to a specific terminal. There should be a decrease in overall coverage of pcpn locally by 06z, with MVFR, and even IFR, CIGs settling in during the predawn hours, especially for nrn sites. KDAY/KILN will have most favorable conditions for IFR CIGs, but certainly it may briefly be possible elsewhere, too. SW winds around 10-12kts this afternoon will go more westerly at around 5-7kts past 21z through the remainder of the period. CIGs will gradually lift/scatter toward/past 18z Monday. OUTLOOK...Thunderstorms possible Tuesday. MVFR CIGs possible Tuesday into Wednesday. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...JGL NEAR TERM...KC/JGL SHORT TERM...JGL LONG TERM... AVIATION...KC