Area Forecast Discussion
Issued by NWS Jackson, KY

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373 FXUS63 KJKL 212030 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 330 PM EST Sat Jan 21 2017 .UPDATE... Issued at 1255 PM EST SAT JAN 21 2017 Mid/high level clouds have been rather thick today, and have slowed the temperature rise. This is especially the case in valleys which chilled very effectively before dawn, before the clouds arrived. Thick that most valleys will eventually catch up, but the hourly trends needed to be adjusted to account for it. Some very light rain has been reported by the KLOZ ASOS, and have left 20% pops in the forecast in the southeast part of the area this afternoon. Radar is also showing returns near the northwest edge of the forecast area. Have added a 20% pop there for this afternoon, but it`s uncertain if precip can make it through the drier air beneath where it`s originating. UPDATE Issued at 940 AM EST SAT JAN 21 2017 The update only blends mid morning obs into the forecast grids, with no substantive changes. UPDATE Issued at 643 AM EST SAT JAN 21 2017 Forecast still on track early this morning. Middle and high level cloud cover will continue to stream over the area today as a weather system approaches from the southwest. Ingested the latest obs into the hourly grids to establish new trends. No major update to the forecast is required at this time. && .SHORT TERM...
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(Today through Sunday) Issued at 302 AM EST SAT JAN 21 2017 The models are suggesting that most of eastern Kentucky should experience dry weather today, due to progressively southeasterly flow and the downslope warming and drying that will occur across the area as a result. It appears that the best moisture associated with an approaching weather system will remain just off to the south of our area today. This, combined with the downslope warming and therefore drying mentioned above, should be enough to keep precipitation at bay for all but our southernmost and easternmost counties today. After a brief lull, widespread rainfall is expected to move in from the south and southwest this evening through the end of the day on Sunday. An area of low pressure is forecast to move out of the southern Mississippi valley and across the Ohio and Tennessee valleys tonight and tomorrow. As this system moves east, it is forecast to strengthen, and therefore slow down, as it moves across our area. The slow movement of this system, combined with a steady flow of warm moist air off the Gulf of Mexico, will lead to widespread rain showers across eastern Kentucky to finish out the weekend. We may even see a few thunderstorms tonight and tomorrow due to the strength of the passing low and the presence of weak elevated instability. Rain could be locally heavy at times. Temperatures will remain well above normal this weekend, with highs expected to top out in the mid to upper 60s today, and the lower 60s on Sunday. Overnight lows should be in the lower 50s. Mostly cloudy to cloudy skies will be on tap as well. Winds should generally be out of the south or southeast at around 5 mph during the period .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.
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&& .AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon) ISSUED AT 1255 PM EST SAT JAN 21 2017 VFR conditions are expected to prevail until late tonight, with mainly mid/high level ceilings. A bit of light rain will affect far southeast KY this afternoon, and possibly near/north of I-64, but it should not offer up much in the way of restrictions. The next round of more significant weather will not arrive until late tonight. Showers and lower ceilings are expected to spread into the JKL forecast area from the southwest before dawn on Sunday. The worst conditions should be in the far west and southwest, with at least MVFR if not IFR occurring on Sunday morning. Further east, drying downslope flow will work to erode the lowest clouds, and the eastern tip of the state should remain VFR. However, there still could be some showers even in the far east before the end of the period. A few thunderstorms can`t be ruled out in the southern part of the area by mid day on Sunday. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...HAL SHORT TERM...AR LONG TERM...SHALLENBERGER AVIATION...HAL

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