Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 241946 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 346 PM EDT Wed May 24 2017 .UPDATE... Issued at 300 PM EDT WED MAY 24 2017 Updated the near term grids with the issuance of the tornado watch. Added severe wording to the wx grids and timed the storms via radar trends and latest from the HRRR. Also tweaked sky cover and the hourly T/Td based on obs and trends. These have been sent to the NDFD and web servers along with an updated set of ZFPs and HWO for the tor watch. UPDATE Issued at 1140 AM EDT WED MAY 24 2017 15z sfc analysis shows a seasonably deep, and stacked, low moving through the Tennessee Valley. The warm frontal structure with this is lifting northeast into eastern Kentucky with an associated cluster of showers and embedded thunderstorms. This first batch should go through relatively benign, but any `dry slotting` behind this initial band would open up the opportunity for increasing instability and the development on more organized and potentially severe storms given the favorable wind profile and cold pool aloft. We will monitor the situation through the early afternoon with a particular focus on clearing and thinning potential in the cloud cover. Temperatures currently are in the upper 50s to lower 60s with the rain and closer to the mid 60s outside of it with dewpoints nearly the same. Winds are light and variable away from any thunderstorm. Have updated the forecast to fine tune the PoPs, QPF, and wx through the afternoon per radar trends and the latest HRRR. Also, touched up the T and Td per the latest obs and trends. These have been sent to the NDFD and web servers along with an updated ZFP. UPDATE Issued at 644 AM EDT WED MAY 24 2017 The latest surface analysis shows that the deepening surface low near the TN/OH Valley will track NNE through the day. The HRRR suggest there will be multiple rounds of showers and thunderstorms, but differing solutions are offered up by other CAMs. Given will leave the POPs as is until better overall consistency and trends are seen. Based on the radar trends the lead shield of showers and thunderstorms will progress into the Lake Cumberland region by around 13Z and far east by 16Z. Severe risk concern is still in place owing seeing destabilization this afternoon. && .SHORT TERM...
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(Today through Thursday) Issued at 410 AM EDT WED MAY 24 2017 Surface analysis shows an area of surface low pressure continues to deepen across Middle TN this morning. This as an upper level wave in the lower MS Valley based on WV SAT rides NE providing plenty of forcing for ascent across the TN and OH Valley. This will also drive the aforementioned surface low pressure NNE likely just NW of the CWA. This will probably drive a more occluded front across the region and lead to a solid chance of showers and thunderstorms from late morning into this afternoon. The low track certainly has our attention, as it would favor backed winds near the surface. The real issue at hand will be the large scale forcing could inhibit building any instability this afternoon with more debris clouds streaming into the region. However, despite the caveat if we do see clearing and subsequently more instability organized convection would be likely given ample shear, with effective values running in the 30 to 40-knot range. Also the low level backing mentioned above would combine with low LCLs and effective SRH approaching 200 m^2/s^2 leading to a isolated tornado risk. However, the main risks with any stronger storms that could get going would be damaging winds and large hail given the potential for rotating updrafts. The CAMs remain complicated and solutions continue to differ probably owing to the large scale ascent. The HRRR TLE does offer a shot of seeing severe hail, but the CIPS are lack luster when it comes to climo for this setup. Also given the deep moisture also can not rule out the potential for isolated instances of flash flooding. This upper level closed low will continue to wrap up today and deepen across the Ohio Valley. The low pressure will track north and this will lead to a lull in the precipitation this evening. Did not go no POPs tonight but would not be surprised if that is the case. However, this system will become vertically stacked across the Ohio Valley. This will send an area of PVA and low level convergence SE toward the region by dawn Thursday. An area of showers will accompany this area of lift and ride across the region on Thursday. Then surface pressure and height rises are left in the wake. Temperatures today will be dependent on clearing, but lower 70s will probably be the story. Did hedge below the blended guidance Thursday given the lowering 850mb temps and cloud cover. .LONG TERM...(Friday through Wednesday) Issued at 346 PM EDT WED MAY 24 2017 The blended model data was suggesting that after a dry day on Friday, eastern Kentucky will be in for a period of wet weather from Friday night through Monday, with another period of rain possible on Tuesday and Tuesday night. The wettest period looks to be from Saturday afternoon through Sunday evening, when it appears that a frontal boundary will stall across the area. Scattered to numerous showers and storms will possible during this time. Temperatures during the extended should be running at or slightly above normal, with daily highs ranging from the upper 70s to lower 80s, and nightly lows in the mid to upper 50s.
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&& .AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon) ISSUED AT 230 PM EDT WED MAY 24 2017 It looks like multiple bands of convection will be crossing the area through the evening with thunderstorms possible at all the TAF sites. Initially the eastern ones will see storms with the west having a round between 19 and 22z. Some of these western ones may make it east into the JKL/SJS sites toward sunset, but uncertainty is high with the evolution and progression of this next band for the CWA. Following the convection later this evening, cigs will fall to MVFR or lower through the night with more scattered showers and less organized convective development. Outside of any storms winds will be light and variable. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...GREIF SHORT TERM...DJ LONG TERM...AR AVIATION...GREIF

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