Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 250233 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 1033 PM EDT Sat Sep 24 2016 .UPDATE...
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Issued at 1033 PM EDT SAT SEP 24 2016 The forecast remains on track so far tonight. Anticipate that no major departure from the current will occur overnight. Therefore, no major changes to the forecast are planned at this time. Did ingest the latest obs into the hourly grids to establish new trends. Aside from that, the forecast will remain as is. UPDATE Issued at 735 PM EDT SAT SEP 24 2016 The forecast is looking good so far this evening, with near calm winds, mostly clear skies and valley fog still on tap for tonight. Ingested the latest obs data into the hourly grids to establish new trends, but made no other changes to the forecast as of yet.
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&& .SHORT TERM...(This evening through Sunday night) Issued at 309 PM EDT SAT SEP 24 2016 A strong upper level ridge is in place across across much of the lower Mississippi and Ohio River valleys early this afternoon, caught between two upper level closed lows... one off the eastern Canadian coast, and another more progressive low moving northward across the Dakotas. Meanwhile another disturbance remains positioned across much of Florida and the southern extent of the SE gulf states. This will show little progression through the remainder of the weekend, staying well to our south and with little impact on the region`s weather. However, the closed low over the Dakotas will continue to track northeast today, pushing the associated troughing pattern eastward toward the Upper Great Lakes by Sunday evening. This will work to break down the high pressure ridging over time, though is should still have general control of the Ohio River Valley during this time. At the surface, a very weak boundary is pushing southward across the state this afternoon. This is connected to a surface low pressure center currently in the Dakotas, being driven by the upper level low. However with such strong upper level ridging in place, this frontal passage is dry and overall benign. The only change will be a deeper northerly post frontal wind component and some continued diurnal CU through this evening. Strong surface high pressure to our NE will push into the state behind this frontal passage overnight, with light winds and strong subsidence expected once more. This pattern will lead to temperature differences between the ridges the valleys overnight. Also, any lingering moisture, especially in the deeper valleys and near bodies of water, will likely lead to more fog development overnight, with some locally dense spots possible. High pressure will be in control once again during the day tomorrow (Sunday). Temperatures will only be a degree or two lower than today at best, despite the weak cold frontal passage, with such strong ridging and dry air in place. Meanwhile, the strong surface low will push into south-central Canada Sunday morning, and continue an eastward track throughout the day. This will pull with it a stronger cold front, moving eastward and into the Mississippi River Valley by Sunday evening, then eventually into central KY to end out the forecast period Sunday night. Weak southerly flow just ahead of this line will do little to increase moisture across the region, keeping best POPs and QPF at bay, especially for eastern KY, through the end of the forecast period. However, can`t rule out some low end pops making it into portions of the CWA late in the night. Clouds will be slow to develop as well, allowing temperatures to be very similar to that of tonight, with a ridge valley split likely to occur as well. .LONG TERM...(Monday through Saturday) Issued at 436 PM EDT SAT SEP 24 2016 The period starts out with models in fairly good agreement, but ends much differently. A cold front will move through from NW to SE on Monday and Monday evening. There are differences between models regarding the QPF and POP, but there is a general agreement that the greater precip and highest POP will be southeast of the JKL forecast area. Have used just a chance pop area wide for our forecast area at this point. With the high temperatures expected, there should also be instability to fuel some thunder ahead of the front. High pressure builds in from the west with fair and cooler weather behind the front for Tuesday into at least early Wednesday. For the later part of the week, the ECMWF and GFS part ways regarding the evolution of the upper trough which initially supports the cold fropa. In the GFS, the trough axis passes on Wednesday and it remains progressive, lifting NE off the New England coast by Friday, with upper level ridging again building into our area from the SW. This would mean mainly fair weather and moderating temperatures. Meanwhile, the ECMWF closes off an upper low (nearly cutting it off for a time) over our area, with the system lingering into the weekend. There are some members of the GFS ensemble which lend support to this, but the spread of solutions takes in a wide range regarding the upper trough/low. An GFS ensemble mean solution is preferred, which does not linger an upper low for a long period, but does hold onto troughiness longer than the operational GFS. This would mean a few showers possible (mainly east) on Wednesday as the upper trough passes, and dry weather with a subdued warm-up late the week. However, considering the range of possibilities, confidence is not high. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) ISSUED AT 735 PM EDT SAT SEP 24 2016 High pressure will remain in control of our weather through the weekend resulting in VFR conditions for most areas with light and variable winds. Some diurnal CU is expected to develop across the forecast area Sunday afternoon, with bases mainly between 4.5 and 6k ft. These clouds should dissipate with loss of daytime heating tomorrow evening. Patchy valley fog will form again overnight, possibly affecting LOZ and SME with some MVFR BR for a couple of hours late in the night into early Sunday morning. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...AR SHORT TERM...JMW LONG TERM...HAL AVIATION...AR

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