Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 051010 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 510 AM EST Mon Dec 5 2016 .SHORT TERM...
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(Today through Tuesday) Issued at 403 AM EST MON DEC 5 2016 As the mid/upper level wave that impacted the area yesterday continues to shift northeast of the region, more zonal flow is taking hold with surface high pressure moving eastward across the state. That being said, MVFR clouds continue to plague much of the region under a pretty steep inversion that has set up. Dry air will continue to filter in aloft and in the mid levels throughout the day, eventually working its way down to the surface and allowing the low cloud deck to mix out, generally after 15 to 18Z. Attention then turns to a strong upper level low positioned over southern TX this afternoon. At the surface, the center of low pressure will be located just off the TX/Louisiana coast, but will continue to push northeastward throughout the day following the upper level low, quickly reaching Mississippi by this evening, and TN late tonight, before traversing eastern KY and eastern TN during the day tomorrow. This will push the center of high pressure currently across the state to our northeast, and allow deeper moisture to quickly begin filling into the state from the south, reaching our southern CWA between 21Z and 0Z this afternoon/evening. That being said, upper level winds will continue to pull moisture into the region well ahead of this system, so even as the low clouds begin to mix out today, high clouds will already begin building in ahead of this system. Overall, it is not likely that we will see much of a break in the clouds throughout the day as a result. According to the latest forecast soundings from the NAM12, the transition from high clouds to moisture build down and precip will be very quick. Only slight chance pops are in the forecast along the TN border before 0Z, but widespread rain is expected to encompass the entire southern half of the CWA by 6Z, and and the entire eastern portion of the state by 12Z. A steady rain is expected to continue throughout the day Tuesday. Still not seeing enough support for instability, even aloft, to include thunder at this time. The upper level low is expected to decrease in strength, becoming an open wave by the time it moves over eastern KY. As the surface low pressure center moves across the CWA in the afternoon, drier air will be quick to filter in behind, weakening the surface low and cutting off best rain potential. As such, rain is likely to end just as quickly as it started, with only low end chances expected across far eastern KY by 0Z Tuesday. While temperatures today will be near seasonable normals despite cloud cover, the surge of warmer moist air into the region will actually boost temps well into the 50s for the day tomorrow. .LONG TERM...(Tuesday night through Sunday) Issued at 510 AM EST MON DEC 5 2016 Models are finally showing better agreement with mid/upper level features through the extended and have even seen some trends towards better agreement in sensible weather elements. A broad trough moving through the Intermountain west at the start of the period will reach the Ohio Valley Wednesday night, passing through during the day Thursday. The 0Z GFS and Canadian, having been the more consistent runs, are a bit stronger with the mid level features of this system than the 0Z ECMWF. Regardless the boundary layer and sfc features associated with this disturbance are quite weak. Timing is similar with all solutions now, with the ECMWF only slightly slower. Overall trends are for lower pops and less QPF potentials. However, this system will still usher in some very cold air into the region, with H850 temperatures bottoming out close to -15C. The high pressure system building in behind this disturbance will settle down directly over the Commonwealth by Saturday night, allowing temperatures to drop into the low to mid teens. Would not be surprised if morning lows flirted with some single digits Saturday morning in our typically colder valley spots. Thereafter return flow develops rather quickly, pulling plenty of moisture northward back through the MS valley and into the OH. If initial indications are correct, fairly strong isentropic lift will bring overspreading precipitation back into our area as early as Sunday. Too early to capture details at this time, but with the cold air in place imagine that precipitation will probably fall as a wintry mixture at the onset early Sunday morning before transitioning to just rain through the day.
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&& .AVIATION...(For the 06Z TAFS through 06Z Monday night) ISSUED AT 127 AM EST MON DEC 5 2016 Tricky TAFs for the period once again. Upper level wave is continuing to exit northeast of the region, with surface high pressure moving in across the state. In most situations the lingering moisture and high pressure center would suggest fog, however in this situation, we are still seeing thick llvl clouds across much of the region, including well upstream of the TAF sites. As such, redid TAFs to remove mention of fog, as this will likely be a low stratus event, with generally MVFR CIGS expected. Can`t rule out some IFR at times however, though it seems like the majority of the obs upstream are within the MVFR range. Tomorrow, low clouds will likely persist into the afternoon, before finally starting to scour out. About this time, another system will begin approaching from the southwest. This will allow for high clouds to enter back into the region, and quickly build down after 0Z, with rain chances soon to follow. Went ahead and included VCSH at most TAF sites between 3 and 4Z, except for the far northern KSYM, where chances will likely occur closer to the end of the forecast period. Overall winds should remain light and variable, though more gusty conditions may continue at KSYM through the next several hours before finally dissipating. && .JKL WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SHORT TERM...JMW LONG TERM...RAY AVIATION...JMW

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