Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 172359 AAA AFDJKL AREA FORECAST DISCUSSION...UPDATED National Weather Service Jackson KY 659 PM EST Tue Jan 17 2017 .UPDATE...
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Issued at 659 PM EST TUE JAN 17 2017 The surface cold front is slowly dropping southeast across our area early this evening. Plenty of light shower activity is ongoing across the southeastern half of the area. This looks to continue over the next few hours, as a low level jet continues to pump in moisture out ahead the passing surface boundary. The current forecast has this well in hand, and have only freshened up the hourly temperatures and dew points into tonight. This did slow the drop off somewhat into tonight, as winds behind the cold front remain more westerly, rather than northwesterly. Will take a better look at the overnight lows in the next update.
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&& .SHORT TERM...(This evening through Wednesday night) Issued at 315 PM EST TUE JAN 17 2017 As of mid afternoon, an upper level ridge extended from the Caribbean and Eastern Gulf of Mexico the north to off the Eastern Seaboard. Meanwhile, a general area of troughing extended from Ontario southwest to the Mid MS Valley Region and then southwest and then south into the Four Corners Region and Northwestern Mexico. Within this trough, a lead shortwave in southwest flow was currently moving across the Lower OH Valley Region with a more significant shortwave trough moving across the MS Valley Region and nearing the Great Lakes and Lower OH Valley region. Another upper level low was currently centered over the Southern Rockies and Norther Mexico. At the surface, low pressure was centered over the Great Lakes region with the trailing cold front nearing Eastern KY. This evening and tonight, the mid level shortwave trough should progress across the Great Lakes and OH valley area with the axis of this trough nearing the WV and VA borders by around dawn. The cold front meanwhile should move into VA this evening. Scattered to possibly numerous showers will remain possible until the cold front moves through. Sfc high pressure will begin building into the area. However, some low level moisture will persist even behind the cold front and with the shortwave trough axis yet to cross the area clouds, and isolated to scattered showers or light drizzle will be possible as the low level flow becomes more upslope. Behind the front some stratus build down fog will also be possible. The moisture depth is a bit in question so confidence in timing or extent of any drizzle is not all that high. The shortwave trough axis should depart during the morning hours, and with this so should the threat for any isolated showers or drizzle. Any stratus build down fog should also diminish. The upper level ridge axis should approach tomorrow afternoon with rising heights in the afternoon and evening. However, the ridge axis will be shifting east of the area Wednesday night. At the same time, the upper level low will have meandered into the Central and Southern Plains. Low pressure and an associated warm front at the surface will begin to approach late and moisture and isentropic lift will increase across the OH and TN Valley late. An increase in high clouds is expected late and mid clouds may move into the Lake Cumberland Region. However, the threat for showers should hold off until sometime on Thursday. This should allow some valley locations to experience lows in the low to mid 30s on Wednesday night, which would be warmer than average for late January but colder than the past several mornings outside of the northern counties. Valley fog should also develop, but the extent is uncertain due to the increase in clouds late. .LONG TERM...(Thursday through Tuesday) Issued at 258 PM EST TUE JAN 17 2017 Good model agreement continues into the upcoming weekend. An active pattern will continue into early next week with several rounds of showers expected. The added rainfall, combined with rivers already running high could lead to some high water issues as we head into early next week. However, confidence on actual amounts remains low, so will continue to leave out any flooding concerns into next week. The first round of rain will move in on Thursday and Thursday night as a shortwave trough pushes northeast across the region. Good forcing and lift will yield widespread showers. As the trough exits north on Friday, conditions will temporarily dry out, especially by Friday afternoon. Looks like dry weather should last through Saturday, although models are showing some support for a few widely isolated showers on Saturday. Moisture is fairly limited and lack of any significant forcing will keep the chance of rain out of the forecast for now. If a shower were to pop up, best shot would be somewhere across central Kentucky. As we head late into the weekend, chances are increasing of a large cut off low developing across the deep south, then slowly pinwheeling up the spine of the Appalachians. This slow moving system could bring an extended period of rainfall to the area late Saturday night through Monday night. Depending on the exact track of this system will determine exactly how much rain we receive. If southeast downsloping flow prevails through much of the time, it would eat away at potential rainfall. For now, going to go high on the rain chances through this period with more of the uncertainty falling on actual amounts. It certainly looks like it will be a mild and damp period which has been the theme lately. It looks like a brief shot of more normal temperatures for January will drop in by Tuesday, but again this may just be a quick shot before we start to warm again. Right now, no threat of any wintry weather for eastern Kentucky through Tuesday. && .AVIATION...
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(For the 00Z TAFS through 00Z Wednesday evening) ISSUED AT 659 PM EST TUE JAN 17 2017 A passing cold front will bring numerous showers to southeastern Kentucky over the next few hours. Most of the more concentrated activity will stay to the east and southeast of the TAF sites. MVFR ceilings will temporarily raise up to VFR for most locations following the frontal passage, before ceilings then return to MVFR and eventually IFR through the overnight. An approaching upper level disturbance towards dawn, may reinforce a few light rain showers or drizzle across the area. IFR ceilings will then gradually improve to MVFR, and eventually VFR from southwest to northeast, as high pressure builds in. West southwest winds of near 10 kts, will become more out of the west as the cold front exits to the southeast. Winds will diminish to around 5 kts or less by the end of the period.
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&& .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...GEOGERIAN SHORT TERM...JP LONG TERM...KAS AVIATION...GEOGERIAN is the U.S. government's official web portal to all federal, state and local government web resources and services.