Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 231436 AAB AFDJKL AREA FORECAST DISCUSSION...UPDATED National Weather Service Jackson KY 1036 AM EDT Wed May 23 2018 .UPDATE...
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Issued at 1036 AM EDT WED MAY 23 2018 Mid level heights continue to rise across the region as a ridge builds into the TN Valley and portions of the MS Valley. At the surface, high pressure has built into the region from the north behind a cold front that continues to sag south of the area. Visibilities have improved across the region as solar insolation and some drier air advecting into the area has led to fog lifting into low clouds and stratus. Drier air will continue to advect into the region on northerly flow, with some cumulus clouds anticipated into the afternoon, particularly in the southern third to half of the area. These will tend to diminish through the afternoon. Hourly grids have been updated based on recent satellite as well as observation trends, with the HWO having been updated to remove fog references from this morning. UPDATE Issued at 626 AM EDT WED MAY 23 2018 Issued an update to the forecast to input the latest observations and trend through the mid morning hours. Adjusted pops slightly as well to account for the few showers remaining. The changes at this time weren`t enough to warrant a new zfp.
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&& .SHORT TERM...(Today through Thursday) Issued at 330 AM EDT WED MAY 23 2018 Current conditions across the area feature a few showers and thunderstorms slowly pushing southeast across eastern Kentucky along a weakened cold front. The little lift through the night associated with the front will keep the few isolated showers and storms going through the predawn hours. In addition to this, ample rainfall during the day and some clearing spots overnight has allowed fog to develop in the river valleys and other locations. This has been highlighted and will likely keep the SPS for fog going through the mid morning hours. Heading into the day, the last of the showers will exit the area by mid morning allowing high pressure to push into the area allowing for clearing skies from the northwest. Skied overnight tonight will remain mostly clear with subsidence in place. This will also allow for a ridge to valley temperature difference with dry air in place. This may be skewed as well with the development of valley fog tonight. The mentioned boundary will remain largely weakened and quite vague but the presence will be seen by Thursday afternoon with a new surge of moisture across the Appalachian range with some shower and thunderstorm development along the VA and TN border. This activity will remain brief for Thursday afternoon. Overall, high pressure moving into the area will keep the weather quiet with the exception of some fog each morning. .LONG TERM...(Thursday night through Tuesday) Issued at 420 AM EDT WED MAY 23 2018 While the latest cycle of models are in slightly better agreement aloft during the extended portion of the forecast compared to last night, they still suffer from similar differences through the holiday weekend. They all depict a weak ridge over the Deep South and Tennessee Valley at the start of the period breaking down under increasing influence of a more active northern stream that will brings a weak trough and more energy to the area on Friday. At the same time, a developing upper low (and perhaps more) in the Gulf of Mexico will start to push onto the central Gulf Coast. It is this feature that will be a predominant factor in our forecast for the Memorial Day weekend and beyond. The northern stream trough passes through the Ohio Valley on Saturday and Saturday night with the ECMWF a tad faster than the GFS. This trough will have the tropical connection to the south and depending on its development could help to pull it north quicker than currently modeled. The GFS maintains a more eastward and weaker upper low down there through the weekend while the ECMWF is a notch stronger and more westerly. At the same time the Canadian seems to be picking up on the potential for the low to develop into a tropical system and deepen more significantly than the other medium range models with a placement in between their centers. This low and whatever remains of it will maintain lower heights through the region well into Monday and Tuesday along with a band of energy lifting into Kentucky per the ECMWF early on Monday and a tad later in the GFS. Given the considerable uncertainty with a potential tropical system looming will favor a blended solution, though a lean toward the ECMWF appears warranted given the recent GFS trends of slightly to the west with its low. Sensible weather will feature a return of humid and diurnally stormy conditions for the area through the Memorial Day weekend as moisture lifts into the state in conjunction with low pressure throughout the Deep South under a scenario where tropical development is rather weak. Should the low to the south break toward an evolving tropical storm Kentucky may be spared the days of high PoPs in lieu of a more contained area of highest PoPs and QPF with the core remnants of this system. For now, though, will stick with the idea of more of an amorphous low to our south resulting in mainly diurnally driven showers and storms with highest PoPs south - lingering through the end of the period as the low and moisture will be slow to clear out with time. Temperatures will be on the warm side of normal - especially at night given the high moisture content of the air. Did not deviate much from the common starting point guidance load except to add in some terrain effects for lows Thursday night before the dewpoints come up more significantly making for more uniform lows. As for PoPs, did brush them with more of a gradient from north to south through the period while smoothing out some of the timing details from the blend in favor of more of a diurnal and north to south influence. && .AVIATION...(For the 12Z TAFS through 12Z Thursday morning) ISSUED AT 626 AM EDT WED MAY 23 2018 Expect IFR and below conditions to persist across the area this morning as some lingering low clouds will be at the TAF sites south of the Mt Parkway as well as some lingering dense fog, especially locations that received rainfall. This fog and low cigs will burn off today by 15Z and with the cold front moving south, skies will clear out by the late afternoon. Expect clear skies heading into tonight with dense fog being confined to the deeper valleys and the river valleys. Winds will be light and variable through the period. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...JP SHORT TERM...SHALLENBERGER LONG TERM...GREIF AVIATION...SHALLENBERGER

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