Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 191050 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 650 AM EDT Wed Apr 19 2017 .UPDATE...
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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 12Z TAFS through 12Z Thursday morning) ISSUED AT 650 AM EDT WED APR 19 2017 Scattered to numerous showers are moving across the region this morning. While most of the TAF sites should remain VFR you could see temporary MVFR VIS in heavier showers. Overall think the coverage at the TAF sites will wane through the day, but a few thunderstorms can not be ruled out in the afternoon. Given less confidence could not see going anymore than VCTS at this point. Overall would expect ceilings to improve through the evening, as disturbance moves east. In general winds will remain light out of the south to southwest.
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&& .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...DJ SHORT TERM...DJ LONG TERM...HAL AVIATION...DJ

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