Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 042000 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 300 PM EST Sun Dec 4 2016 .SHORT TERM...
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(This evening through Monday night) Issued at 300 PM EST SUN DEC 4 2016 Active pattern on tap in the short term. The initial weather maker for eastern Kentucky will be an area of low pressure aloft, that is expected to move across the region this afternoon through the overnight period. Scattered to at times numerous light rain showers will move across eastern Kentucky through early this evening. The rain should finally begin to taper off after 4Z tonight, as the upper low moves off to our east. Eastern Kentucky should be precipitation free by around 11Z Monday. Rainfall amounts with this first system should be very light across eastern KY tonight, generally a tenth of an inch or less. After several hours of quiet weather, another area of low pressure is forecast to approach the region from the southwest Monday afternoon and evening. Rain showers associated with this second weather system should have overspread the entire area by around 6Z Tuesday. This second weather system will provide a more robust shot of rain. We could see rainfall amounts Monday night into early Tuesday morning rain from around 0.4 inches in our far north, to between 0.5 and 0.8 inches in our far south. Temperatures should be running at or slightly below normal during the day on Monday, with highs ranging from the mid 40s in our northern areas to around 50 in our southern areas. Tonights lows should bottom out with above normal values in the mid to upper 30s, due to the influence of cloud cover and precipitation. Tomorrow nights lows look to be even warmer, as winds shift from the east to south and increase in strength and cloud cover and precipitation also increase in coverage. Monday nights lows are expected to fall into the low to mid 40s, with a non diurnal hourly temperature pattern also expected due to cloud cover and wind influences. .LONG TERM...(Monday night through Saturday) Issued at 518 AM EST SUN DEC 4 2016 Models solutions are in reasonably good agreement with the general mid/upper level pattern through the extended but continue to differ significantly with details in the strength and timing of several features embedded within an overall progressive flow. This results in even larger differences in sensible weather later in the forecast. Mid/upper level cut off low moving out of Texas early in the period opens up into a wave as it passes through the region Tuesday. The GFS is slightly slower and stronger with this first disturbance compared to the more similar ECMWF and Canadian. This system will provide a soaking rain to the area with models spitting out about an inch of rainfall on average, mainly from Monday night through Tuesday. Forecast soundings do hint at some marginal, very elevated instability Monday night. Mid/upper level lapse rates do steepen a bit between about 10k and 22k feet. In general CAPE remains below 100 J/kg. But there is substantial shear within this layer as well, on the order of 30 to 50 kts. So while one could not totally rule out a faint rumble of thunder, feel the overall threat is low enough that any mention of thunder was left out of the forecast for now. However, will pass on to upcoming shifts for monitoring. Forecast gets quite tricky thereafter as a series of disturbances rotate around a low pressure system residing along the Northern Tier and southern Canada. A shortwave trough swings through the region sometime towards the end of the week, most likely Thursday, as models present a range of possibilities with respect to the timing and strength of this trough. Details of sensible weather are not any clearer but the GFS and Canadian continue to advertise a more similar solution with the ECMWF a much warmer and wetter outlier, bringing a surface low and heavier precipitation in the form of rain across the Commonwealth. The faster GFS solution ushers colder air into the area at a much quicker pace and hints at the possibility of some light isold to scattered snow shower activity. The Canadian, being a colder solution similar to the GFS keeps our weather dry. Until models begin to show better agreement and/or show some solid trends will continue to rely heavily on the model/guidance blends which suggest that a wintry mix of precipitation will be possible through that time frame depending on the time of day/night. On a more certain note, much colder air does eventually move into the area for Friday and next weekend. Thus any precipitation that does fall will transition to just snow Thursday night into Friday with the potential of some lingering upslope snow shower activity into early Friday morning. Wouldn`t be surprised if future forecasts extend the snow shower activity into Friday proper or even Friday night, as this is type of scenario is typically handled poorly by the larger scale synoptic models. At this point do not expect anything more significant than minor snow accumulations at best, and if that.
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&& .AVIATION...(For the 18Z TAFS through 18Z Monday afternoon) ISSUED AT 1227 PM EST SUN DEC 4 2016 Look for VFR conditions through around 21Z today as we see a lull from the rain for a few hours. Conditions are expected to deteriorate to MVFR as low clouds and rain showers move back into the area from the west between 22 and 23Z today. CIGS should fluctuate between 2.5 and 3K. Conditions will worsen slightly between 0 and 1Z, as an approaching cold front brings more widespread showers and lower level cloud cover to eastern Kentucky. That MVFR conditions should persist between 0 and 3Z this evening. After that, we can expected a period of IFR CIGS as rain showers and even lower level cloud cover invade the area. These conditions should last until roughly 12Z tomorrow, before things gradually improve through out the morning. MVFR conditions should once again be in place as the rain departs and cloud levels rise a bit from 12Z onward. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...AR LONG TERM...RAY AVIATION...AR

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