Area Forecast Discussion
Issued by NWS Jackson, KY

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609 FXUS63 KJKL 031732 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 1232 PM EST Sat Dec 3 2016 .UPDATE... Issued at 945 AM EST SAT DEC 3 2016 Updated the forecast to better reflect the current cloud cover across the area. Based on the latest satellite obs, most of eastern Kentucky has been under overcast skies for the past few hours, and it appears this trend will not change anytime soon. Therefore, the sky cover grids were updated to reflect cloud skies for most locations for the rest of the day. The updated zones have already been sent. UPDATE Issued at 656 AM EST SAT DEC 3 2016 Low stratocu continues to encompass much of eastern KY. This has allowed for more regulated temperatures through the early morning hours, and reduced any ridge valley split from earlier in the evening. Expect temperatures to begin rising over the next hour as the sun rises. These clouds will likely hold on through much of the morning, and will finally start breaking apart this afternoon in the south, eventually making its way to the northern CWA by late this evening. The remainder of the near-term forecast seems to be well on track with current conditions. All changes have been published and sent to NDFD/web. && .SHORT TERM...(Today through Sunday) Issued at 356 AM EST SAT DEC 3 2016 Surface high pressure will continue to overspread the state throughout the day today, passing just to our east by 6Z tonight. Overall this will result in light winds at the surface with llvl stratus clouds continuing to pull into the region from the NE through at least mid day in many locations. Llvl winds will begin to lighten and become more variable as the center of the high passes to our north and then heads east, allowing the llvl clouds to begin breaking up throughout the afternoon. Meanwhile, aloft, a shortwave will begin digging across the northern plains throughout the day, shifting eastward. This shortwave is expected to reach the Mississippi River Valley by Sunday, then move across the Ohio River Valley and points to the north by 0Z Monday. The upper level wind pattern will feature a jet streak across the Ohio River Valley ahead of the shortwave, increasing in strength as the shortwave nears. Mid/upper level winds will be westerly across KY and then SW just to our east. This will effectively pull moisture from the Gulf of Mexico northward and then eastward into the state. As such, this will result in high clouds expected to push northward into the CWA by later this afternoon. Moisture and clouds will continue to build this evening with the nearing mid/upper level wave, however it will have a hard time overcoming the bubble of dry air at the surface with the surface high pressure center still in place just to our east. Latest forecast soundings show moisture finally overcoming the drier air between 6 and 9Z at KSME and KLOZ in our southern CWA, between 6 and 12Z in the mid sections, and a few hours later in the northern CWA. Despite W to SW flow aloft, temperatures in the mid and upper levels will still be on the cooler side as precip moves into the region overnight Saturday, below freezing through much of the column. As such, even as temperatures at the surface may be at or above freezing at precip onset, rain may still mix with snow for the first couple of hours. However, temperatures will quickly warm as we head into the daytime hours, with the surface high continuing eastward and allowing warmer return flow at the surface. All precip will change over to rain during this time, with generally no snow accumulation or impacts expected. Rain is expected to continue through the day Sunday as the mid/upper level shortwave closes in on the region. This will produce generally between 0.10 and 0.20 inches or rain across the CWA, an overall light system but much needed none the less. .LONG TERM...(Sunday night through Friday) Issued at 503 AM EST SAT DEC 3 2016 Challenging extended package this morning. Models are in good agreement for DYS 3-4 but diverge significantly beyond that both with the details of the mid/upper level pattern as well as with sensible weather. Mid/Upper level cut off low moving out of Texas Monday opens up into a wave by Tuesday as it transits the MS/TN/OH valleys. This feature will provide another soaking rain to the area with models spitting out around an inch of rainfall on average, mainly from Monday night through Tuesday. Forecast gets complicated thereafter as a series of disturbances rotate around a low pressure system residing along the Northern Tier and southern Canada. Models appear to have difficulty with the strength and timing of several lobes of energy rounding this parent low. The GFS presents a quicker solution with weaker disturbances. The ECMWF advertises stronger disturbances which dig a bit further south resulting in an overall slower solution and correspondingly stronger surface features. The Canadian generally provides partial support for both solutions. For sensible weather we can expect a seasonably warm start to the extended but cool significantly through the period after Tuesday. Rain will be tapering off Sunday night before redeveloping across the region Monday night into Tuesday. There is very low confidence with respect to precipitation types and amounts beyond that. Depending on your model of choice we could see anything from rain to snow from Wednesday night through Friday. At this time felt the best approach was to stay close to the blend of model solutions and guidance which suggest that a wintry mix of precipitation will be possible through that time frame depending on the time of day/night. && .AVIATION...
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(For the 18Z TAFS through 18Z Sunday afternoon) ISSUED AT 1232 PM EST SAT DEC 3 2016 Low and middle level cloud cover will continue to plague the airports of eastern Kentucky through early this evening. The result will be a fluctuation between MVFR and VFR CIGS through between 5 and 8Z tonight. Conditions will likely worsen by between 12 and 13Z Sunday, as an area low pressure moves by just to our south, with MVFR to IFR conditions possible at the TAF sites due to low cloud cover and incoming rain showers. The first rain should begin moving into eastern Kentucky between 1 and 2Z this evening. The precipitation will gradually further and further north overnight, with some snow perhaps even mixing with the rain by 6Z. The northern edge of the precipitation shield is expected to push through our northernmost counties by 13Z Sunday.
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&& .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...AR SHORT TERM...JMW LONG TERM...RAY AVIATION...AR

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