Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 201046 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 646 AM EDT FRI MAY 20 2016 .SYNOPSIS... A low pressure system will lift out the Tennessee Valley and into the Upper Ohio Valley through tonight. This will bring widespread showers to the region later this afternoon and overnight. Scattered showers will linger into Saturday as the low pressure system moves off to the east. && .NEAR TERM /THROUGH TONIGHT/... Mid level short wave energy rotating around the base of the upper level trough over the southern plains will eject northeastward into the Ohio Valley region through this evening. As it does, a developing surface low currently over the lower Mississippi Valley will lift northeast into the upper Ohio Valley today into tonight. An associated 30-40 knot 850 mb jet will pivot up across eastern Kentucky through this afternoon, nosing into southern portions of our FA by this evening. This will lead to shower development across our south through early afternoon, becoming more widespread and lifting up across our area this evening. Instability is marginal at best, but is more impressive just to our south. Think some of this may get advected up into our area so will allow for a chance of thunder later this afternoon into this evening across about the southeast third of our FA. Given the track of the surface low, low level shear profiles will be very impressive through this evening, but any severe threat should be limited by the overall lack of instability. PWs will push up around 1.5 inches late this afternoon/early this evening across our south before gradually dropping off through tonight. This could result in locally heavy rainfall, especially with any embedded thunderstorms. One and 3 hour ffg is running in the 1.5 to 2 inch range across our south and southeast and the 2 to 2.5 inch range for 6 hour ffg. The 00z nam is the most aggressive with the QPF, with a narrow axis of 2 to 2.5 inches nosing up into our northern Kentucky counties, and this does have a little bit of support from some of the convective allowing models like the nssl wrf. Meanwhile, the ECMWF, CMC and GFS are more in the 1.5 to 2 inch storm total range into our southern counties. With even the worst case scenario models just getting us close to ffg and some uncertainty between the models as to exactly where the heaviest axis will lineup, will hold off on an FFA at this point, but include locally heavy rain in the grids and a mention a flood potential in the HWO product. Temperatures today will be a little tricky given the increasing clouds and rain spreading into the south later this afternoon. Will go ahead and range highs from the upper 60s southwest to lower 70s in the northeast. && .SHORT TERM /SATURDAY THROUGH SUNDAY/... The surface low will be located somewhere across southern Ohio Saturday morning and is forecast to weaken as it drifts slowly off to the east southeast through the day. This will result in scattered lingering rain showers through the morning, before beginning to taper off from the west through the afternoon as some drier air tries to work in. Expect mainly dry conditions Saturday night, but a mid level short wave will drop quickly down across eastern Ohio on Sunday, resulting in the possibility of a few showers across our east. Expect highs on Saturday mainly in the upper 60s, warming into the lower 70s for Sunday. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... Sharp ridging over the Mississippi Valley region will move east and envelop the Ohio Valley by Monday morning, providing a period of dry weather and warming temperatures. Going into the new week, the pattern appears more typical of late spring -- with warmer southerly flow at the surface, and chances for precipitation as occasional waves move along the generally-westerly mid-level flow. Recent model runs have been slightly faster with the onset of the pattern change, and now suggest that precipitation chances could begin as early as Tuesday evening (in a regime of strong southwesterly 925mb-850mb theta-e advection). Pseudo-zonal flow beyond this time range will likely support occasional chances for showers and storms during the rest of the week, but timing the small-scale features out will be critical for specifics on this part of the forecast as it gets closer to the current time. Temperatures are expected to rise above normal through the long term forecast period, especially beginning on Tuesday, when the southerly near-surface flow becomes established. The occasional chances for precipitation during the middle of the week will keep these forecast numbers on the conservative side (upper 70s to around 80) for now, but these could need to be increased slightly on any given day if a brief dry / sunny period eventually becomes more certain to occur. && .AVIATION /10Z FRIDAY THROUGH TUESDAY/...
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All taf sites vfr this morning as widespread cirrus has moved into the area ahead of the next system. There are some light returns on the radar off to the southwest, but the atmosphere is currently relatively dry though (PWATs around 0.6") so these returns are likely evaporating before hitting the ground. By later this afternoon the atmosphere will quickly saturate as the upper level low approaches (PWATs on the GFS and NAM around 1.4"). The high res ARW, NMM, and RAP are in good agreement bringing rain into CVG/LUK between 18 and 21 Z while the latest run of the HRRR is about 3 hrs faster. Have followed the ARW, NMM, and RAP solutions when constructing the TAFs. The latest run of the NAM is now showing more instability than the previous run, but looks to ambitious in destabilizing the atmosphere. The GFS shows very little instability. Have kept the mention of thunder out of the TAFs as the GFS appears the more likely solution. For the most part this afternoon cigs will stay VFR until the surface low arrives later this evening. As the surface low moves overhead cigs will fall very quickly to IFR and then LIFR. GFS and NAM forecast soundings are in very good agreement with this along with SREF prob cig heights. Cigs will the likely stay down into Saturday morning as TAF sites remain in close proximity to the surface low. OUTLOOK...Thunderstorms possible Saturday.
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&& .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...JGL NEAR TERM...JGL SHORT TERM...JGL LONG TERM...Hatzos AVIATION...Haines

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