Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 260800 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 400 AM EDT Wed Jul 26 2017 .SHORT TERM...(Today through Thursday) Issued at 400 AM EDT WED JUL 26 2017 07z sfc analysis shows high pressure in control of the weather over eastern Kentucky. This has cleared the sky and brought in drier air. Despite this, patchy dense fog is developing the far eastern valleys as seen via the GOES16 Nighttime Microphysics channel. The obs are not very indicative of any fog with just the KBYL site, along the Cumberland River, reporting lower vis at this point. The dewpoints have come down from last night and current vary from the upper 50s north to the mid 60s south as the winds are light to calm. Temperatures meanwhile, are showing some ridge to valley distinctions ranging from the upper 50s in the most sheltered of eastern valleys to the mid 60s south and on the ridges. Expect a bit of an uptick in the fog towards dawn, but still mainly confined to the river valleys. The models are in good agreement aloft through the short term portion of the forecast. They all depict the Central U.S. ridge retreating to the southwest by Thursday morning as a series of identifiable shortwaves slide southeast in the mid level flow and into the heart of the Ohio Valley. These waves will promote height falls over eastern Kentucky into Thursday morning ahead of a larger and stronger wave dropping into the Great Lakes. This latter wave will bring a favorable wind pattern through the mid levels capable of supporting organized storm clusters and has the potential to contribute to severe weather through the region from Thursday afternoon into the first part of the night. The model agreement suggests that a blend is the way to go - though a strong lean toward the higher resolution models like the HRRR and NAM12 is also warranted due to the small scale nature of the features important to the forecast - especially on Thursday. Sensible weather will feature another rather nice day, once the river valley fog burns off, with mostly sunny skies and warm temperatures, but not as humid as we saw late last week. However, an increase in clouds and moisture will occur starting in the evening and continuing through the night. The approach of a sfc low from the northwest will bring a threat for storms to the area during the pre-dawn hours Thursday with greater chances seen later the day as the winds increasingly strengthen and veer with height through the afternoon along with likely a strong build up to the instability. Morning convection may limit this instability, but the other ingredients should be pretty solid for at least strong storms around the area starting in the afternoon. High PW air will also support heavy rains, but any individual cells should be progressive enough to limit excessive rainfall concerns - barring significant training of storms. Have beefed up the thunderstorm wording in the HWO for this and will also be sure and highlight it in the weather story. The CONSShort was again the basis for all short term forecast grids with only minor point adjustments made to lows tonight to impart more of a ridge to valley temperature split. Also fine tuned the PoPs for the convection potential late tonight and through the day Thursday. .LONG TERM...(Thursday night through Tuesday) Issued at 300 AM EDT WED JUL 26 2017 The extended will start off active and wet, as a cold front moves slowly across the region. Numerous showers and storms are on tap for Thursday night and Friday. The rain should steadily taper off during the day on Friday, especially during the afternoon, as a cold front moves through. The rain will likely last through Friday night, but should be out of eastern Kentucky by early Saturday morning. After that, a ridge of high pressure is forecast to settle over the region. This ridge should bring dry weather to eastern Kentucky from Saturday night through the middle of next week. Temperatures will start off well below normal, due to persistent cloud cover, widespread precipitation, and cooler air invading behind a departed front. Highs on Friday and Saturday are forecast to max out around 80 degrees. Conditions will slowly warm after that, with daily highs generally in the low to mid 80s from Sunday onward. After a warm Thursday night to begin the period, lows around 70, nightly lows should be below normal. The weekend may see temperatures fall into upper 50s and lower 60s as cooler air moves in. The cooler nighttime temperatures are expected to continue through the middle of the week, with nightly lows in the lower 60s expected. && .AVIATION...(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. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...GREIF LONG TERM...AR AVIATION...GUSEMAN/GREIF is the U.S. government's official web portal to all federal, state and local government web resources and services.