Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 240841 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 341 AM EST Fri Feb 24 2017 .SHORT TERM...(Today through Saturday) Issued at 340 AM EST FRI FEB 24 2017 Early morning surface analysis shows an area of surface low pressure continues to track NE out of the Central Plains into Missouri and a warm front is now well north across the Upper Ohio Valley region. WV imagery this morning showing plenty of upper level moisture streaming into the region and this is leading to scattered high clouds across eastern KY. Given these have only been high clouds and the valleys have decoupled leading to decent temp splits from some of the cooler valley locales. A mix of high clouds and possible some diurnally driven CU will remain the story through the day. LLJ will continue to move east in response to strengthening system to our west. This will begin to mix down as we move into the afternoon hours with gust of 25 to 30 possible across the Bluegrass and Lake Cumberland region. The other issue will be downsloping flow across the far east could also mix down drier air, with RH values in the mid 30s to lower 40s possible. This will have to be monitored today given the gusty winds, but it will help that the gustier winds will be west of the drier downsloped air. All the focus shifts to strengthening system to the west as we move into the late evening and overnight period. Models remain in good agreement with trailing cold front approaching from the west through the day. Initially convection will fire out ahead of the front and track across portions of the Midwest. Some of these will be single cell type storms, but as the system progresses east storm mode will become more multicell/QLCS. Given the strength of the cold front, lapse rates will remain steep through the evening and into the overnight. Also models, specifically CAMS, are in good agreement with the trailing cold front catching up to the initial convection possibly providing further lift as it moves into the region. One issue will be how much instability remains in place at that point given the time of day and year. However, if we are able to maintain this, the speed shear environment will be substantial through a deep layer and low level shear is rather impressive with some directional shear possible. This seem to be picked up well by the SHERBE (that deals with high shear low CAPE environments) with values near 1 or higher. Overall storm mode will remain more QLCS in nature and therefore the tornado threat will be very isolated. Think the better threat for tornado will exist further north across the Ohio Valley where more boundary interactions will take place. The main threat across eastern KY will be damaging winds given the storm mode and strong jet, and an outside threat of marginal hail given the airmass cooling aloft causing freezing levels to drop to near 10 KFT. In terms of grids, did opt to slow the progression of POPs to better align with the CAMs and also added enhanced wording for damaging winds given the greater threat. Behind this front will be progressively cooler temperatures from west to east early Saturday into Saturday afternoon. That said, higher terrain locations could hit the freezing mark by the end of the period. Given some wrap around moisture is possible did keep some sprinkles and perhaps flurries across the higher terrain into the afternoon. Given the high temperature will occur at midnight the temp curve will be quite unorthodox, and therefore leaned away from blended diurnally driven curve. .LONG TERM...(Saturday night through Thursday) Issued at 340 AM EST FRI FEB 24 2017 The long term discussion will be issued shortly. && .AVIATION...(For the 06Z TAFS through 06Z Friday night) ISSUED AT 1240 AM EST FRI FEB 24 2017 A mix of high and even a narrow band of lower clouds are moving across eastern KY at this late night hour. The good news is we are looking at VFR conditions for the TAF sites, with lowest band of clouds staying at or around to 5 KFT level. Now some of the valley locales have decoupled this evening and therefore some will see patchy fog. The other concern is a increasing LLJ, as 850MB winds increase ahead of strengthening surface and upper level system progresses east. Therefore kept the LLWS in the forecast starting around 08Z to 12Z timeframe. Places that will have to best chance of seeing the stronger jet will be Lake Cumberland and Bluegrass regions. This will mix out by around 14Z and by tomorrow afternoon we will see some of these stronger winds mix down leading to gusty conditions. Think again the better mixing will occur across the Lake Cumberland and Bluegrass regions where 25 to 30 mph gusts are possible. We are continuing to monitor the potential for strong to severe thunderstorms to round out the TAF period. Right now a line of storms is expected to move into areas west of a line from Sandy Hook, to Jackson, to Middlesboro at or around 04Z to 06Z. The main threat with any stronger storms would be for damaging wind gusts. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...DJ LONG TERM...JP AVIATION...DJ

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