Area Forecast Discussion
Issued by NWS Jackson, KY

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444 FXUS63 KJKL 200812 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 312 AM EST Sat Jan 20 2018 .UPDATE... Issued at 630 PM EST FRI JAN 19 2018 Low clouds are quickly moving northeast into central Tennessee. Models handling this cloud cover poorly at best, but NAM bufkit soundings are picking up on the moisture associated with this cloud cover between 900 and 850 mb. Once the clouds move in, looks like they will be with us for the balance of the weekend. Thus, opted to go ahead and go with cloudy skies through Sunday evening. With the increased cloud cover tonight, have opted to put the lowest temperatures around 05z prior to the onset of clouds. The eastern valleys should still make a run at the teens, but we will see a modest temperature rise in these locations through the second half of the night as the clouds blanket the area. && .SHORT TERM...(This evening through Saturday night) Issued at 346 PM EST FRI JAN 19 2018 Current conditions across the area feature clear skies over the region as high pressure centered over the northeastern Gulf Coast continues to extend a ridge axis northward along the Appalachian Range. With high pressure shifted east, south to southwest winds brought some much needed warmer air into the region with temperatures warming into the low 40s across the area. Despite this warm up, mainly clear skies will hang on into tonight and will allow for once again significant radiational cooling the valleys with a weak southerly flow on the ridges. This will lead to another night of a significant ridge to valley temperature difference with valleys in the upper teens and ridges in the upper 20s. By dawn, some mid and upper level cloud cover will roll into the region as southerly flow increases. Despite the cloud cover, WAA will be strong enough for temps to warm into the low 50s on Saturday. Heading into Saturday night, an upper level wave deepens and ejects into the central Plains as southerly flow increases. By, late Saturday night a warm front develops and begins to lift northward. This will bring a chance of showers to the area Saturday night. Given the low chance, the forecast challenge will be the fact that forecast soundings are pretty shallow with the moisture depth. Thus the rainfall onset is certainly in question. .LONG TERM...(Sunday through Friday) Issued at 330 PM EST FRI JAN 19 2018 For the extended forecast, the overall pattern has remained fairly consistent with a zonal to ridging pattern over the weekend before a system moves in Monday afternoon. The models are coming into better agreement with timing, especially with the latest runs. However, the GFS is still ever so slightly faster with the arrival of the precipitation band. Although, the ECMWF shows a more stout precip line than the GFS. Furthermore, the ECMWF shows the incoming trough for early next week more amplified than the GFS. This could affect exactly how much cooler the temps will get after the front moves through mid-week. Will continue to monitor future model runs of the trough pattern in terms of the temps for later on next week. At the very end of the period, the pattern will start to shift for another system looking to make its way into the CWA. As for the surface, the period starts with an inverted trough to the east with a surface high pressure system to the south. By Sunday morning, the winds will become more southerly with a warm front to the north of eastern KY. This pattern will bring in WAA and an increase in temps for the weekend. The warm front will increase chances for some rain showers on Sunday, but the models are in disagreement on how much will fall. After the cold front moves through on Monday, surface high pressure will build in mid- week leading to cooler, drier weather. Towards the end of the forecast period on Thursday night and into Friday morning, there is potential for a ridge/valley temperature split due to light/calm southerly winds and little cloud cover. && .AVIATION...
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(For the 06Z TAFS through 06Z Saturday night) ISSUED AT 312 AM EST SAT JAN 20 2018 A cloud deck around 3K feet AGL is overspreading the area, and will be rather persistent during the period. It will continue to bring low end VFR and high end MVFR conditions. South to southwest winds will pick up to around 10 kts in most places during the day.
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&& .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...KAS SHORT TERM...SHALLENBERGER LONG TERM...CGAL AVIATION...HAL

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