Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 200822 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 422 AM EDT Thu Jul 20 2017 .SHORT TERM...(Today through Friday) Issued at 417 AM EDT THU JUL 20 2017 Upper level ridging will continue to build into the region today. It will dampen somewhat tomorrow in the northern portion of the state as a strong upper level low over Hudson bay allows for more WNW to ESE flow across the northern half of the U.S. to shift a bit southward into the northern Ohio Valley. That being said, even with this small shift, the upper level ridge will still have dominant control. At the surface, high pressure will also be large and in charge across the state today. The continued building heights will attribute to yet another day of well above normal temperatures, reaching 90 or maybe even topping it in most locations. A few fair weather cu will be possible during the afternoon, but otherwise conditions should remain dry under this regime. By Friday, however, a cold front will push towards the region from the north. Flow will become more S to SW, allowing more moisture to advect in from the south and boosting humidity levels a bit (though not a strong surge). This will cause two concerns. First, the presence of the frontal boundary just to our our north and a warm/more humid airmass in place, could spark isolated to scattered showers and thunderstorms during the day, especially in the afternoon. Best chances will be in the northern CWA and along the high terrain in the SE. Second, the S/SW flow will boost temps another degree or two, into the low 90s for highs. This will combine with the additional humidity in the atmosphere to produce heat indices just over 100 degrees in most locations. While we are still below heat advisory criteria based on the forecast, will go ahead and issue an SPS for heat concerns this day. .LONG TERM...(Friday night through Wednesday) Issued at 422 AM EDT THU JUL 20 2017 An upper level ridge will be over the Tennessee Valley, and surface high pressure over the lower Great Lakes and Appalachians at the start of the period. The high pressure at the surface and aloft will be weakening. In the upper levels, this will allow for slight cooling and a modest increase in wind as a northeast CONUS trough develops and the westerlies drop further south. At the surface, increased flow will help to bring Gulf of Mexico moisture into the area. The combined result will be an overall increase in shower/thunderstorm coverage as we move through the weekend. A cold front is expected to approach from the northwest Sunday and Monday, and this is when the highest POP will be carried. The GFS and ECMWF agree on the front passing through from northwest to southeast late Monday and Monday night, allowing for somewhat cooler and less humid air to move in to finish the period. Until then, conditions will be uncomfortably hot and humid. The hottest weather is expected on Friday, before an increase in clouds and precip starts to hold temperatures down. && .AVIATION...(For the 06Z TAFS through 06Z Thursday night) ISSUED AT 151 AM EDT THU JUL 20 2017 Surface high pressure and an upper level ridge building into the area will continue the rather stagnant weather pattern, with VFR conditions and light winds prevailing through the period. Fog will develop in the river valleys once again late tonight, dropping to MVFR or IFR restrictions by near daybreak. As fog lifts near daybreak, there is still a chance that SME could once again be affected, as has been the case for previous mornings. However, impacts have also shown a decreasing trend thanks to continued drying, so actually not confident enough of the fog being impactful enough to even include in the SME TAF. Once fog dissipates across east KY Thursday morning, expect mostly clear skies with mainly just diurnally driven CU developing in the afternoon, generally around 4k ft. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...JMW LONG TERM...HAL AVIATION...JMW is the U.S. government's official web portal to all federal, state and local government web resources and services.