Area Forecast Discussion
Issued by NWS Jackson, KY

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492 FXUS63 KJKL 171958 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 258 PM EST Tue Jan 17 2017 .UPDATE... Issued at 100 PM EST TUE JAN 17 2017 Hourly grids have been updated for recent radar, satellite, and observation trends. A cold front is still approaching the area from the west and a shortwave trough is approaching the Lower OH Valley. Thus, although showers are currently more numerous across the south, some redevelopment will be possible from mid to late afternoon with some limited heating and instability ahead of the front. Higher pops have been carried across the south today while recent radar trends and short term models supported lowering pops in the norht. Moisture should be deeper and instability a bit greater in the south this afternoon so have hold onto isolated thunder chances there for a few more hours although no lightning has been observed for several hours in the region. Confidence in any thunder is low. Enough heating should also take place for the record at JKL to be broken. It has already been tied through 1 PM EST. UPDATE Issued at 1040 AM EST TUE JAN 17 2017 Radar trends and many of the short term model runs were in good agreement bringing an area of showers across the Lake Cumberland Region and across the Cumberland Valley and Ky Cumberland Mountains area. Pops in this area were raised to categorical for a couple of hours with those transiting out by early afternoon. However, with the cold front an a shortwave trough still upstream, chance to low end likely pops were held onto for a few hours into the afternoon as some redevelopment seems probable. Temperatures behind this band are in the low to mid 60s and even warm air advection ahead of the front without much in the way of sunshine the CWA should experience similar temperatures during the early to mid afternoon and this will be enough to break the record high for the 17th at JKL. The current record is 62 from 1990. UPDATE Issued at 640 AM EST TUE JAN 17 2017 Did a quick update to the grids early this morning primarily to fine tune the PoPs and Wx through the next few hours based on the latest RADAR trends and HRRR guidance. Also tweaked the T and Td grids per the current obs and trends. These have been sent to the NDFD and web servers. && .SHORT TERM...
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(Today through Wednesday) Issued at 345 AM EST TUE JAN 17 2017 08z sfc analysis shows a well defined area of low pressure lifting northeast into the Great Lakes. This is dragging a cold front slowly east through the Mid Mississippi Valley and toward Kentucky. Additionally a northward moving warm front is currently lying across eastern Kentucky with a large area of convection rolling east along it. This cluster of showers, with a potential for embedded thunderstorms will continue to press deeper into eastern Kentucky from the west with a healthy dose of soaking rains expected for most places by dawn. The clouds and arriving showers, along with south stirring winds, have mostly mixed out the colder valleys, but there remain a few in the east that did manage to get into the upper 40s while most of the rest of the area reside in the mid to upper 50s with lower 60s found in several places south of Jackson. Dewpoints, meanwhile are running in the low to mid 50s most places. This is making for another quite mild mid January night - sitting at or near record max minimum temperatures - across the area. The models are in only fair agreement aloft through the short term as the southeast ridge holds fast no matter what troughs move by to the northwest. This will mean deep level southwest flow will continue supporting our current spate of mild and wet conditions through the near term. Specifically, an opening, southern stream, wave will shift off to the north of Kentucky today. This is followed by a fairly strong northern stream trough digging through the Ohio Valley tonight - only briefly dampening the heights over the region. The model spread is rather large for this feature particularly given that it is only 24 to 36 hours out. The ECMWF is a tad sharper and slower with this when compared to the GFS - but not as slow as the NAM. This wave will be driven in part by a 300 mb jet streak passing to our north with sustained upper level divergence over Kentucky today and tonight on its right entrance region. Ridging rapidly builds back over Kentucky later Wednesday in all models in the wake of the northern stream wave. Given the lowered confidence with that second wave tonight have favored a blended solution along with a lean toward the higher resolution HRRR for the near term. Sensible weather will feature a wet start to the day as a leading band of showers moves through eastern Kentucky followed by a brief lull around midday. By late afternoon another round of showers and potential thunderstorms will seep northeast into the area just ahead of a weakening cold front that pushes through during the first part of the night. Cooler and drier conditions follow into Wednesday morning, but readings will still be well above normal, as well as freezing, through the short term with a small rebound by the afternoon as high pressure quickly moves into the Ohio Valley. Started with the CONSShort and ShortBlend for most elements through the short term portion of the forecast - making only minor adjustments to temps and winds today. Also, adjusted PoPs more toward the HRRR in the near term. .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.
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&& .AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon) ISSUED AT 115 PM EST TUE JAN 17 2017 MVFR is currently observed across the area with some IFR locally in showers near the VA border. MVFR and possibly brief periods of VFR in breaks in the clouds should prevail through the 21Z to 3Z period in norther section with showers possible. Shower and perhaps a stray thunderstorm near JKL, SME, and LOZ are also possible during this period. Some IFR will also be possible during that time near the TN and VA borders. Otherwise, low level moisture should return from the north and west behind the front and MVFR or IFR expected to return and generally persist through the end of the period. Some stratus build down fog and mist will also be possible 3Z to 15Z especially on ridges. Southwest winds will be gusty initially sustained generally 10 to 15 kts, with gusts up to 25 KT or so. These should diminish and become more west during the 21Z to 0Z period. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...JP SHORT TERM...GREIF LONG TERM...KAS AVIATION...JP

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