Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 262046 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 446 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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Updated to account for rapidly improving conditions and a decrease in shower threat this evening into the overnight. Temperatures were dropped significantly over the southern third of the CWA given the rain-cooled atmosphere present here. They will still fall in line with the forecasted low temperature overnight. Upstream convection currently situated west of Louisville appears to be sparked by the outflow from the system currently exiting our cWA and should not persist for any length of time this late day. Prev disc follows -> Widespread showers over southeastern CWA and a trailing chance of more stratiform rain with significantly less coverage to the north and west of it will continue to decrease this afternoon. This decreasing trend should persist into the evening and overnight hours, but given high pwat values being continually pumped into the region, we cannot in good conscience remove pops entirely from the overnight period for the southeastern half of the CWA. The high pwat values will remain over the surface boundary laid out along the Ohio River, and zonal H5 flow that will permit weak vorticity maxima to potentially continue ongoing convection or less likely help spark new isolated storms overnight. Temperature guidance has been consistent overnight with relatively steady mins within a degree or two of 70.
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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 /21Z TUESDAY THROUGH SUNDAY/... TSRA have developed over CVG/LUK near a stalled frontal boundary. Expect those 2 locations to be affected by the TSRA for the first couple of hours of the period with MVFR/IFR vsbys. After that TSRA will be scattered across srn OH and nrn KY, so transitioned to a VCTS. Up at KILN, a MVFR cigs on the nrn edge of the convection has worked in. As the convection works ne, it could brush ILN. Only went with VCTS for a few hours to cover the threat. DAY could get nicked by a VFR shower, but expect CMH/LCK to remain dry. Model trend is for the convection to weaken and dissipate with the loss of daytime heating, so have the tafs dry overnight. With lingering dewpoints in the 70s at the srn tafs, kept the mention of some fog overnight. Scattered convection should pop up again tomorrow, so have VCTS in the CVG 30 hour taf. OUTLOOK...Thunderstorms possible Thursday afternoon through Friday. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...Franks NEAR TERM...Franks SHORT TERM...Franks LONG TERM...Haines AVIATION...Sites

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