Area Forecast Discussion
Issued by NWS Jackson, KY

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331 FXUS63 KJKL 230805 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 405 AM EDT Mon Apr 23 2018 .UPDATE...
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Issued at 240 AM EDT MON APR 23 2018 Despite east to southeast flow with a downslope component a band of showers continues to progress north across the area. Dewpoints across southern sections of the area have climbed into the 40s with light measurable rain having fallen in many locations out of a mid level deck from around SME to Bell and Knox counties per KY Mesonet observations and regional RAWS, HADS, and IFLOWS. This band will continue to move to the northeast with additional showers upstream. Pops will be updated to account for timing of this with hourly temperatures and dewpoints also freshened up based on recent observations. UPDATE Issued at 1120 PM EDT SUN APR 22 2018 Updated the forecast to remove outdated wording from the text forecast product and to speed up precipitation onset in our southwest and southern counties by a couple of hours per current trends in model data and obs. UPDATE Issued at 740 PM EDT SUN APR 22 2018 The forecast remains on track so far this evening. Mostly to cloudy skies will persist overnight, with rain showers expected to move into the area from the southwest late tonight into early tomorrow morning. Will leave the forecast as is for now, but will need to update later in the shift to make other small adjustments and to remove outdated wording form the zone forecast text product. Ingested the latest obs into the hourly forecast to establish new trends.
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(This evening through Monday night) Issued at 351 PM EDT SUN APR 22 2018 The latest surface analysis shows an area of surface high pressure continue to retreat northward. The east to southeast winds continue to lead to downslope flow and drier conditions across the region this afternoon. The latest scans of the regional WSR-88D radars suggest some of the rain shower activity is just now creeping into Wayne County. Given the continued slower trend, did opt to lower POPs for the afternoon. This upper level low to our south will continue to rotate east and eventually divergence aloft will lead to best chances of rain showers early Monday. Then a lull in activity is expected later in the day mainly in the far east, as 1000 to 850 mb winds increase leading to increased downsloping. The 00Z NAEFS standard anomaly tables show the 850mb winds are going to be oriented southeast and running greater than 3 standard deviations above normal. There is some weak instability in the Lake Cumberland region Monday afternoon and did lean toward slight chance thunder. The upper level divergence becomes broad Monday night, but the surface low and trough will come east. This will lead to increasing chances of POPs once again Monday night. .LONG TERM...(Tuesday night through Sunday) Issued at 405 AM EDT MON APR 23 2018 A 500mb low will be collocated with a surface low pressure system across Kentucky starting out at 0Z Wednesday. This will continue to shift eastward out of the state throughout Tuesday night and into the day Wednesday, with pops/rain chances expected to be on a decreasing trend during this time. Upslope flow will keep some chance pops in place through the day Wednesday, especially across the SE, but additional QPF will be under a tenth of an inch through 0Z Thursday. Models then lose considerable agreement by 0Z Thursday, with the NAM and GFS planting a developing closed low over the south/central Plains, and the ECMWF showing a strong closed low over the northern Ohio Valley and southern Great Lakes region with a shortwave trough over the central/southern Plains instead. The ECMWF shows this closed low shifting SE across Ohio Wednesday night and into the day Thursday, while both the GFS and ECMWF show the other shortwave/low system tracking just south of Kentucky into the deep south during this time. Surprisingly, which ever model pans out, neither actually pulls precip from either system into the state, so will keep Thursday dry in the forecast. Models then come into much better agreement for another system which will affect the region to end out the workweek. A 500mb shortwave will follow deep troughing across the region, deepening the trough as the axis moves through Kentucky Friday night into Saturday morning. At the surface a cold front is expected to shift from west to east across the state during the day Friday and into Friday night, bringing with it a swath of chance pops. Instability is still lacking, so will not include any mention of thunder at this time. In fact soundings are actually quite dry, so not expecting much QPF from this either. Even after tweaking QPF up slightly from the Superblend, still only have well under a tenth of an inch for the duration of the system. During much of the extended period, temperatures will actually remain relatively uniform, with highs in the low to mid 60s and lows in the 40s. However, if clearing occurs overnight Friday night and Saturday night (coupled with light winds), some sheltered valleys may fall into the upper 30s. Ridging will slowly take hold throughout the day Sunday and continue into Monday. This will allow temperatures to climb into the low 70s both days.
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&& .AVIATION...(For the 06Z TAFS through 06Z Monday night) ISSUED AT 235 AM EDT MON APR 23 2018 An upper level low will meander into western TN through the period. For much of the period the region will maintain a downslope component of the flow with lower levels slow to saturate. Thus mainly mid level clouds are expected through about 12Z with some low clouds thereafter but still in the VFR range. Some brief MVFR is possible in showers or any thunderstorms across western and northwestern sections of the area after 12Z, but vis should remain 6SM or higher through the period. Winds should increase to near or in excess of 10KT at the TAF sites during the first 6 hours of the period out of the east southeast to southeast. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...JP SHORT TERM...DJ LONG TERM...JMW AVIATION...JP is the U.S. government's official web portal to all federal, state and local government web resources and services.