Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 220600 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 100 AM EST Sun Jan 22 2017 .UPDATE... Issued at 100 AM EST SUN JAN 22 2017 Made a minor update to the forecast for the remainder of the night. Based on direct visual observations and surface obs, beefed up fog in the grids and the forecast text product to areas of dense from patchy dense. The hazardous weather outlook was also updated to included mention of reduced visibility due to fog for the rest of the night. The rest of the forecast was in good shape as is with no other changes necessary. UPDATE Issued at 1022 PM EST SAT JAN 21 2017 Have begun to see some patchy dense fog develop in the valleys as some partial low level clearing combines with temperatures nearing their crossover point. May still see a few sprinkles across the Big Sandy region through early tonight before more widespread rain moves in from the south later tonight into early Sunday morning. UPDATE Issued at 724 PM EST SAT JAN 21 2017 Have seen a recent uptick in developing rainfall across northeast Kentucky back to along and south of Mountain Parkway. May continue to see some light shower/sprinkle activity from here north this evening as a subtle lead shortwave trough traverses the Bluegrass region. Still expecting a more widespread swath of rainfall to arrive later tonight into Sunday morning across the Lake Cumberland region, moving north through the morning. && .SHORT TERM...(This evening through Sunday night) Issued at 432 PM EST SAT JAN 21 2017 A large and deep low pressure system will track east across Kentucky during the period, bringing wet weather and possibly thunder. Models have had trouble honing in on the details of what`s going to happen. Although runs from 24 hours ago seemed to back off on heavy rain threats, recent runs from last night and today have again pointed to a heavy rainfall potential, especially near the Virginia border. An ESF statement is issued for this. The matter was chatted about with MRX, and the decision was made to hold off on any flood watch until there was more certainty. In terms of synoptics and forecast details- the surface low is being largely driven by a powerful upper level system moving east out of the southwest CONUS. There is actually not much baroclinicity present considering how strong the surface system will be. A warm front being drawn north by the system should reach KY before being overtaken an occlusion and the low itself moving eastward. A band of overrunning precip along/north of the front is expected to move north over KY on Sunday. A relative lull should arrive from south to north once this passes by. Models show weak instability, largely after the deep moisture has passed by. Can`t rule out some thunder during this time, but have kept it at only a slight chance. On Sunday night, deep moisture returns under the upper low and comma head. This is when models contain the heaviest precip. Forecast soundings are nearly moist adiabatic but mostly stable. This coincides with persistent strong upward vertical motion. if models persist and show better convergence on a wet solution, a flood watch may still be needed. .LONG TERM...(Monday through Saturday) Issued at 330 PM EST SAT JAN 21 2017 The extended forecast period begins on Monday with a deep closed upper low tracking northeast through the spine of the Appalachians. As this feature tracks northeast, blocking over the New England and Canadian Maritime region will hinder the exit of the back edge precip moving through eastern Kentucky. This slow exit followed with the approach of the colder air in behind on Monday night into Tuesday may lead to a brief mix of rain and snow on top of Black Mountain. In addition to this, models have been coming into more agreement of a prolonged heavy rainfall event coming to an end Monday evening into Monday night across eastern Kentucky. Some lingering minor flood problems may be possible, if not just some rivers running full. Both the Euro and GFS seem to have come to an agreement on this with the Euro being slightly wetter. Will keep this mention in the HWO. Heading into the midweek time frame, a brief period of ridging moves into the OH valley with a period of drying as southwest flow increases ahead of the next incoming cold front. High temps on Wednesday will climb into the upper 50s to low 60s with SW 10 to 20 knot winds bringing in an unseasonably warm airmass. In fact, models are suggesting an overall drying trend to the approaching front with the bulk of the moisture to the north over the Midwest and into Ohio. Little if any precip is expected with this feature. Passage of the front on Wednesday night will bring in a colder airmass to the region by Thursday with a possible prolonged upslope event taking shape for Thursday and Friday. At this point the pattern brings in a longwave trough across the eastern CONUS into the weekend. The northwest flow then brings a series of disturbances in an upslope scenario. At this point, while the models hint at temps being warm enough for rainfall during the day and snow showers overnight, an upslope event with the correct wind component would mean some convection and snowfall at warmer temps. For now, went with a general snowfall at 34 degrees and below due to the uncertainties in the models but this may need reevaluated. The general trend is cooler towards the end of the extended but models have backed off from the depth of the cold air. Due to this, will leave any mention of snow out of the HWO as none is expected to be impactful at this point. && .AVIATION...(For the 06Z TAFS through 06Z Sunday night) ISSUED AT 100 AM EST SUN JAN 22 2017 VFR conditions will prevail through much of the night, before an incoming batch of lower ceilings and light rain approaching from the south introduce MVFR ceilings by early Sunday morning at SME/LOZ. LOZ and SME have also been experiencing low visibility due to fog over the past few hours, and the TAFs have been modified to reflect. LOZ has seen conditions as bad as VLIFR VSBY and LIFR CIGS due to fog. The fog should thin out once rain showers begin affect SME and LOZ early Sunday morning. Visibilities may also deteriorate to MVFR criteria or possibly lower in heavier showers through the morning. Rain showers will spread north and east through the morning, with SJS perhaps seeing the rain hold off until later morning due to more of a downslope (southeasterly) wind component. A lull in the rain looks to occur around late morning into a portion of the afternoon, before another batch moves through later in the day into the evening, complete with a chance for some thunder. High- end MVFR/low-end VFR ceilings should result through much of the day with south/southeasterly winds generally near 5 to 10 mph. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...AR SHORT TERM...HAL LONG TERM...SHALLENBERGER AVIATION...AR

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