Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 210023 AFDJKL Area Forecast Discussion National Weather Service Jackson KY 823 PM EDT FRI MAY 20 2016 .UPDATE...
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Issued at 823 PM EDT FRI MAY 20 2016 After some thunder in our southwest counties late this afternoon, lightning has dried up. Although models still show weak elevated instability present this evening, they don`t show any meaningful increase. That being the case, have removed thunder.
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&& .SHORT TERM...(This evening through Saturday night) Issued at 355 PM EDT FRI MAY 20 2016 19z SFC analysis shows an inverted trough developing and lifting into the Tennessee Valley. This is spreading showers and a few thunderstorms into East Kentucky from southwest to northeast. The rain is also bringing a potential for heavy rains with PWATs around 1.5 inches into the evening, but so far the worst of the rain has stayed west of the CWA. Thin clouds in the east and north allowed temperatures there to climb into the lower 70s while readings are holding in the mid 60s to the southwest where the steadier showers moved in a bit earlier in the afternoon. Dewpoints rose into the low 60s in the southwest while they have made it to the mid 50s north and east. Winds, meanwhile, have been generally light and variable through the day. The models are in good agreement aloft through the short term portion of the forecast. They all depict a trough rolling into the Ohio Valley tonight and spreading its core of energy through the region. This low will deepen just to the northeast of Kentucky on Saturday, but in a switch from 24 hours ago, is keeping this fairly deep tough as just an open wave and moving it off to the east of the area by Sunday morning. Have favored a general model blend for forecast specifics with a strong lean toward the HRRR and the NAM12, though did adjust the NAM`s heavy rain position more easterly - closer to where the other models clustered for tonight`s forecast. Sensible weather will feature a wet evening of soaking rains for the CWA as the southern SFC low lifts through western parts our area with storms and heavy rain a potential. The highest QPF is expected to be over our northwest counties in line with the deformation zone of the low as it passes. Yet, the precipitation should be progressive enough that any high water issues should be in the urban and small stream advisory category, at worse. The showers will eventually become more scattered later tonight from southwest to northeast but low clouds and some fog is left behind through the rest of the night and into Saturday morning. As the low spins into eastern Ohio, low clouds and showers will remain through much of the area starting in the north and spreading south with the system`s cold front during the day. Some upslope flow in the wake of the low and front will likely keep a few light showers around into Saturday night. Again used the ShortBlend as a starting point for most elements of the forecast with only limited terrain adjustments for temperatures through the period. During the latter part of the forecast the SuperBlend was used to initialize the forecast with adjustments made mainly to increase the PoPs later in the period due to the models under doing the upslope potential. .LONG TERM...(Sunday through Friday) Issued at 400 PM EDT FRI MAY 20 2016 Model agreement is good through Wed. Thereafter differences crop up as a result of models struggling with timing and strength of minor impulses embedded in nearly zonal mid level flow. These features are responsible for uncertainty through the latter half of the extended. Felt best approach was to stay close to the blend of solutions and guidance, especially through the latter portion of the period. Shortwave dropping through the base of easter CONUS mid/upper level trough will pass through the Ohio Valley-Tennessee Valley Region Sunday. Mid and upper level ridging will build into the region by Monday and then flatten out into a more zonal flow regime for the remainder of the extended. For sensible weather, Sunday`s shortwave appears strong enough to generate some isold to sct shower activity with the help of diurnal heating Sunday afternoon. NAM/GFS both have come more in line with what has been a consistent ECMWF. Decent lift/cooling around 10 kft associated with the aforementioned shortwave will combine with diurnal sfc heating to create steep boundary layer lapse rates. However, model guidance does not seem to be as impressed. For now maintained inherited slight pops for Sunday but would not be surprised if that has to be increased in the future, especially over the higher terrain to our south and east. High pressure at the sfc/ridging aloft will provide generally fair weather through the start of the week. Thereafter tendency was to broad brush pops to handle inconsistencies among the models in timing and strength of impulses in zonal flow through the region. The end result was a general chance pop, sct showers and thunderstorms through the entire latter half of the extended window. Attm not seeing anything in the fcst soundings that would indicate any type of widespread hydro or severe weather issues. Hard to tell how much convection, debris clouds, and rain cooled air may have on temps through the period, but continue to see a slight upward trend in highs, into the lower 80s each day. Not seeing as much change in overnight lows, running near normal until mid week when they also warm to above normal level, generally in the 60s. && .AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon) ISSUED AT 215 PM EDT FRI MAY 20 2016 A low pressure system lifting into the Tennessee Valley is spreading showers and a few thunderstorms up into Kentucky and just now starting to enter the Cumberland Valley. Ahead of this, VFR conditions will hold for a few more hours, but fall quickly from southwest to northeast through the late afternoon and early evening hours. For the TAFs: have spread VCTS northeast along with the prevailing showers. MVFR vis and cigs follow shortly late this afternoon and continue through the night with cigs likely dropping into the IFR or lower category after midnight as the SFC wave passes. Look for the showers to scatter out later tonight from southwest to northeast, though they may continue at SJS and SYM into the day Saturday. Do expect some improvement in the cigs, perhaps up to MVFR, later in the day, Saturday. Winds will be mainly light and variable through the period as the SFC low lifts right through East Kentucky. && .JKL Watches/Warnings/Advisories... None. && $$ UPDATE...HAL SHORT TERM...GREIF LONG TERM...RAY AVIATION...HAL

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