Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 191810 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 210 PM EDT Wed Apr 19 2017 .UPDATE...
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Issued at 210 PM EDT WED APR 19 2017 Scattered showers continue to develop across the area this afternoon. Am finally seeing a few strikes showing up as well. Temperatures, and grids in general were in good shape. Bottom line, few if any changes to the early afternoon update. UPDATE Issued at 957 AM EDT WED APR 19 2017 Forecast is in pretty good shape this morning. An area of scattered showers is slowly tracking off to the east. Additional activity is beginning to fire further west now that diurnal heating has begun to destabilize the boundary layer. A few thunderstorms can not be ruled out either. Updated the zones to freshen up wording and to remove morning fog. Grids have been updated as well to bring them in line with recent hourly trends. UPDATE Issued at 629 AM EDT WED APR 19 2017 Scattered to numerous showers continue to move ENE across the region this morning based on the latest WSR-88D scans. These are being provided to us by modest LLJ and dampening upper level short wave seen in the mesoanalysis. That said, did opt to raise POPs across portions of the region but still wane these through the afternoon. Otherwise more minor updates were needed to deal with latest obs and trends.
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&& .SHORT TERM...(Today through Thursday) Issued at 335 AM EDT WED APR 19 2017 Surface wise, what was left of the boundary that was south of the region yesterday has now lifted well north of the region. The is leading to southeast flow across the region. The satellite trends have showed the mid level deck that had eroded with some drier mid level air is filling back in. This is likely do to a developing LLJ at around the 850MB layer and dampening upper level wave, as LVX VAD Wind profile shows around 30 knots near this level bringing credence to the model guidance. Along with the cloud cover development the WSR-88D radars are showing mostly isolated showers across the eastern side of the state, while a more robust area of showers has developed across central portions of the state. The HRRR has been all over the place overnight into the morning in how this evolves and not much help has been gained from much of the other guidance. Therefore, took a middle of the road approach in the grids. This will keep most of the area in scattered coverage through the early afternoon and overall coverage in then expected to wane by around 22Z. That said, hold off thunder till this afternoon, as better instability will be possible with MUCAPE values climb into the 500 J/kg range, but the winds will be light aloft making this more garden variety activity. Tonight thinking many spots will see a break in the showers and possibly a break in the clouds. Did opt to lower the valley temps and keep patchy fog going given the possible clearing/low level moisture from afternoon convection. By Thursday do keep shower and even afternoon thunderstorms in the forecast, as we remain in the warm sector ahead of the next synoptic boundary. Given the lack of surface lifting keep the better coverage along the higher terrain near the VA border. Otherwise well above normal temperatures are on tap, with highs climbing into the upper 70s to lower 80s for most. .LONG TERM...(Thursday night through Tuesday) Issued at 447 AM EDT WED APR 19 2017 Overall, there is good model agreement during the period. At the onset, a cold front will be entering KY from the northwest, and crossing the JKL forecast area Thursday night. It is expected to bring at least scattered showers and thunderstorms. The front will stall to our south, and remain in close enough proximity for an ongoing potential of precip on Friday. During the day Friday, low pressure will be taking shape over the southern plains. This will be in response to an upper level wave (emanating from the upper low currently off the Pacific Northwest coast) moving southeast toward that region. The low pressure system will track eastward and draw the frontal boundary back north toward southeast KY Friday night and Saturday. The GFS has trended further south with the eventual low track since yesterday, and is similar to the ECMWF which has remained nearly steady. This track takes the low near the KY/TN border, resulting in a wet start to the weekend, with a temperature contrast across the JKL forecast area. Rain is a good bet everywhere on Saturday. Thunderstorms will also be possible near the passing low, with surface based instability possible in far southern KY, and elevated instability further north. Heavy rainfall could be a concern, with the GFS and ECMWF both showing some 2"+ amounts Saturday/Saturday night. Subsequent models runs should provide more confidence as to if and where an axis of excessive rainfall occurs. Significant rain should be pulling out with the departing low by Sunday, but some light rain could linger. Ridging at all levels then builds in on Sunday night and brings decreasing clouds, with fair weather lasting through the rest of the period. && .AVIATION...
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(For the 18Z TAFS through 18Z Thursday afternoon) ISSUED AT 210 PM EDT WED APR 19 2017 Scattered showers continue to develop across the area this afternoon. Am finally seeing a few strikes showing up as well. Went with a general VCTS at all of our terminals until early evening as activity should die down with loss of diurnal heating. Only restrictions might be a very temporary drop to MVFR VSBYS in any thunderstorms should they pass directly over a terminal. However, with such widespread coverage decided to keep VSBYS predominantly VFR. Guidance suggests we may see some light fog early morning Thursday with some high end MVFR VSBYS, but decided to keep more optimistic VFR VSBYS for now. Winds will generally be light and variable except in and nearby thunderstorms. Gradient winds pick up from the southwest Thursday around 10kts with higher gusts to about 18kts as a cold front approaches the region.
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&& .JKL WATCHES/WARNINGS/ADVISORIES...NONE. && $$ UPDATE...RAY SHORT TERM...DJ LONG TERM...HAL AVIATION...RAY is the U.S. government's official web portal to all federal, state and local government web resources and services.