Area Forecast Discussion
Issued by NWS Wilmington, OH

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436 FXUS61 KILN 262359 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 759 PM EDT TUE JUL 26 2016 .SYNOPSIS... A stalled frontal boundary along or south of the Ohio River will continue to be the focus of thunderstorm activity through Wednesday night. On Thursday, an upper level wave will cross northeast and into south central Ohio, sparking more widespread activity. This upper level feature will cross east overnight and a trailing surface low on Friday will mark a slight decrease from this activity starting Friday night as high pressure builds north of the region. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
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Shower/thunderstorm activity that formed over parts of southern IN and northwestern KY is beginning to move into area. As this progresses ENE, expect a weakening trend as it moves into area that was worked over by convection earlier in the day. This activity will mostly be diurnally driven, so decreased PoPs after 03z leaving the FA dry through most of the overnight period. Despite rain-cooled air across southern third of CWA, temperatures are track with forecasted lows for tonight (upper 60s in north to lower 70s in south). Cloud debris from convection in the region will persist for the southern third of the FA for the first half of the night. Will need to monitor clearing trends through the overnight period for potential fog development for areas that received heavy rain earlier today (primarily along the Ohio River). As of right now, expect that mid/high level clouds should limit widespread fog development for southern parts of FA.
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&& .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/... Wednesday will see any ongoing convection from overnight storms decrease early given an expected unsupportive diurnal trend. There may however be lingering showers along and especially south of the Ohio River given the continued stalled surface boundary and continued influx of moist air from the low and mid atmospheric levels. All of the models are showing a marked decrease in coverage during the day Wednesday with the highest potential laying out over northern Kentucky. Overnight Wednesday may see an increase in storms but the feature initiating any overnight convection appears muddled and highly dependent on a more distinct surface feature which does not seem a likely scenario at this moment in time. Thursday will see a marked increase as most of the models are keying off of a vort max streaming ne ahead of an upper level s/w and combining with daytime insolation. Have increased pops Thursday and really ramped them up in the southeast where all indications show continued storms - similar to what is occurring at this moment in time. Given this, have lowered max temps in the southeast to just lower 80s, and could be even lower depending on where and how long rainfall occurs. Outside of the max temps being lower in the southeast on Thursday, numerical guidance were all within a degree or two of each other for the climatological stations for any given period. It did not appear to be a large change from what was already in the forecast. Storms for any period along and south of the Ohio River will have a potential to include very heavy rainfall and an increased threat for flooding given the continued feed of moisture to the region in question. Strong winds will remain a lesser yet still viable threat, and large hail chances appear minimal through this time. && .LONG TERM /FRIDAY THROUGH TUESDAY/... The long term will start with a series of upper level disturbances moving across the area along with a front stalled out. This will help to keep the chance of rain in the forecast almost through the entire extended until Tuesday when weak mid- level ridging moves into the region. Looking more into the details, Friday will open up with a shortwave moving across the region and the leftover frontal boundary from earlier in the week still across the area. Upper level lift is sufficient with weak PVA moving across and moisture values remain above average for this time of year with PWATs forecasted to be around 1.70". Instability is also present with ML CAPE values around 500 J/kg. As the shortwave exits Friday PoPs will slowly taper off due to weak subsidence behind the wave. Saturday through Sunday another weak shortwave trough will remain in close proximity to the area with a surface front located across the CWA. This will help to bring the chance of rain right back to the area. Given the weak upper level trough quickly pulling east the cold front stalling across the area seems likely. Given the chance of showers and thunderstorms during the day have kept high temperatures near climo. Monday into Tuesday as the shortwave trough exits weak mid-level ridging will then build overhead as mid-level high pressure builds over the central United States. There still remains timing differences on when the high will build and how far it will build east. For now have just trended PoPs down. && .AVIATION /23Z TUESDAY THROUGH SUNDAY/...
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A stalled frontal boundary will continue to linger across southern parts of the area through the TAF period. For this evening, SHRA/TS activity across southern IN and northwestern KY will move ENE and is expected to dissipate with loss of daytime heating. For overnight period, expect primary concern to be BR/FG development at southern sites of KCVG and KLUK. With calm winds and sct mid/high deck, expect that very moist low level environment should support BR development as far north as KILN. Expect MVFR VSBYs for KCVG and KILN and the potential for VLIFR VSBYs for KLUK. There exists some uncertainty as to how thick and persistent mid/high clouds will be for southern parts of area which will ultimately determine expanse of BR/FG development for aforementioned sites. Drier air should keep VFR VSBYs at KDAY, KCMH, and KLCK. For Wednesday, a weak sfc boundary will be oriented along and just south of the Ohio River, providing the possibility of SHRA/TS development during peak diurnal heating. CAMs continue to struggle in this weakly forced but unstable regime, and therefore, there is little confidence in coverage and timing of potential activity. While environment for KCVG and KLUK will be most supportive of SHRA/TS, confidence remains limited enough to keep all sites dry through the remainder of the TAF period. Winds will remain light and variable for all terminals for Wednesday. OUTLOOK...Thunderstorms likely Thursday and possible again Friday and Saturday.
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&& .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...Franks NEAR TERM...KC SHORT TERM...Franks LONG TERM...Haines AVIATION...KC

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