Area Forecast Discussion
Issued by NWS Jackson, KY

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640 FXUS63 KJKL 260620 AAA AFDJKL AREA FORECAST DISCUSSION...UPDATED National Weather Service Jackson KY 220 AM EDT Wed Jul 26 2017 .UPDATE...
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Issued at 155 AM EDT WED JUL 26 2017 Latest loop of the GOES16 Nighttime Microphysics channel shows the fog forming in the far eastern valleys, otherwise not much has been noted in the obs, despite the mostly clear skies, owing to the drier air in place. Have touched up the sky cover and fog through the rest of the night and also added in the latest obs and trends for the T/Td grids. These have been sent to the NDFD and web servers. UPDATE Issued at 717 PM EDT TUE JUL 25 2017 High pressure will make for an overall pleasant summer night across eastern Kentucky. Valley fog will develop late this evening into early Wednesday morning as clear skies prevail underneath subsidence and light winds. Should see this remain confined to mainly valley locales where greater cooling will occur since crossover temperatures may have a difficult time being reached on ridges.
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&& .SHORT TERM...(This evening through Wednesday night) Issued at 359 PM EDT TUE JUL 25 2017 High pressure was passing by to our north today behind the cold front which passed through. Drier air has struggle to make it into our area , but it succeeded to the point that the weather has been dry with only fair weather cu. Precip has been held to our south and west in TN and western KY. Dry weather is expected to hold through tonight and the day Wednesday. However, an upper level trough will begin to deepen over the Great Lakes and New England, allowing another cold front to drop south. Warm air advection will return to our area ahead of the front, bringing moisture return on Wednesday night. Models suggest this could result in some showers or thunderstorms Wednesday night, but there`s not much in the way of forcing/features outside of warm/moist advection and isentropic lift. Have used just a slight chance of precip late. .LONG TERM...(Thursday through Tuesday) Issued at 323 PM EDT TUE JUL 25 2017 The extended portion of the forecast begins on Thursday with an amplified upper level pattern for this time of year. With a stout ridge in place over the western CONUS, a shortwave will drop southeast through the Midwest into the OH valley for Thursday as a surface cold front will push southeast into the area. Good low level moisture and temps rising into the mid 80s, will mean a good chance for showers and thunderstorms by Thursday afternoon as the front approaches. In fact, instability will suggest a slight severe potential with the main threat being wind as the freezing level will likely be pretty high for any hail development. Model soundings would suggest more of a downburst threat with some DCAPE values preset. Thursdays activity will wane into the night. Renewed convection will be likely as well into the day on Friday with a slowed boundary draped over the area will be enough for another round of convection Friday afternoon. Less instability though for Friday afternoon will mean a lesser severe threat if any. After the last of the forcing or whats left of the boundary exits southeast and southern KY by Friday night, a period of dry weather will settle in. Aloft, the mid level ridge axis will shift east over the area in conjunction with a surface bubble of high pressure will keep eastern Kentucky dry for the rest of the extended. In addition to this pattern, the lack of a return flow in this pattern will allow for cooler temps and less muggy conditions than what we have seen heading into the start of next week. && .AVIATION...
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(For the 06Z TAFS through 06Z Wednesday night) ISSUED AT 220 AM EDT WED JUL 26 2017 VFR conditions will prevail for most sites as mainly valley fog develops through the early morning hours. SME should stand the best chance of an extended period of sub-VFR visibilities with a nearby water source, but SJS/SYM may see a period or two of degraded conditions through the night. LOZ saw drier air mix to the surface this afternoon, so this may limit the fog potential there, while any development at JKL would likely be brief early Wednesday morning as valley fog lifts past the ridgeline before dissipating. VFR conditions will return for all by mid morning with light west/southwest winds of less than 5 knots the rule through the day.
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&& .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...GREIF SHORT TERM...HAL LONG TERM...SHALLENBERGER AVIATION...GUSEMAN/GREIF

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