Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 151422 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 1022 AM EDT Tue Aug 15 2017 .UPDATE...
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Issued at 1022 AM EDT TUE AUG 15 2017 Showers continue to affect our southern zones this morning. However, the bulk of current activity will gradually move east out of the area by early afternoon. HRRR does suggest that there will be enough moisture in place across the area for some diurnal convection to refire through the afternoon. Tweaked PoPs for this line of thinking with the morning update. While we still expect the potential of thunder, we have yet to see anything today. Therefore, reigned in thunder just a bit and focused that potential for mainly this afternoon and early evening. UPDATE Issued at 800 AM EDT TUE AUG 15 2017 Did a quick update to touch up the PoP and Wx grids per the latest radar trends and the most recent HRRR guidance. Also tweaked the T and Td grids to account for the current obs. These grids have been sent to the NDFD and web servers.
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&& .SHORT TERM...(Today through Wednesday) Issued at 410 AM EDT TUE AUG 15 2017 07z sfc analysis shows general low pressure through the area with high dewpoint air in place. This is prompting light to moderate showers to traipse across eastern Kentucky this night as well as encouraging the development of fog despite the cloudy conditions. Winds are light with temperatures fairly uniform in the lower 70s most places along with dewpoints in the upper 60s to lower 70s. The models are in good agreement with the long wave pattern over the area through the short term portion of the forecast. They all depict slight troughing in place along with broad southwest flow through today with embedded shortwave impulses running nearly zonal from west to east across Kentucky. Heights will be on a slowly increasing trends ahead of the next main trough developing over the Pacific Northwest and inland to the Northern Plains. Given the model similarities and the small scale nature of the key features for sensible weather will favor a general model blend with a strong lean toward the HRRR and NAM12 for specifics. No well defined boundary nearby and high pw air in place will keep confidence rather low in timing and exact locations of the best pcpn/heavy rain threats. Have hit the southeast section of the area a little harder than the rest of the CWA per the guidance agreement on this tendency - along with the best chance for heavy rains there. The clouds and convection today will limit the warm up, but low 80s are still expected. Drier air will settle into this part of the state later today and overnight decreasing our shower and thunderstorm chances, but not down to below 20% for much of the area. High dewpoints tonight will mean a repeat with mild temperatures, not much ridge to valley distinctions, and more patchy/areas of non-terrain discriminating fog. The next batch of rain should be moving into the area on Wednesday, as similar conditions will be in place with some enhancement expected from energy packets aloft. Used the CONSShort as the starting point for the grids through the short term portion of the forecast with only minor, point-based adjustments to temperatures. As for PoPs, did enhance them diurnally and kept them more focused in the southeast parts of the area through Wednesday. .LONG TERM...(Wednesday night through Monday) Issued at 314 AM EDT TUE AUG 15 2017 The extended portion of the forecast begins on Wednesday night with an active pattern on tap across the CONUS. The period will begin with a strong trough tracking over the northern Plains and into the Great Lakes as it drags a cold front over the OH Valley region during the day on Thursday. Model profiles for Thursday afternoon show quite a bit of instability and good directional shear. This will definitely be a set up to monitor as SPC has issued a Day 3 Marginal severe risk. At this point, models so suggest that the bulk of the dynamics and instability will be north of the Ohio River where the greater risk will likely be. Thursday night and into the weekend, the mid level ridge will set up again over the Southeastern CONUS bringing return flow into the area. This will be combined with several shortwaves passing through the OH Valley with the next front passing through late Saturday. At this time, this feature does not seem to have the amount of instability and shear as the previous front. With the return flow continuing into next week, the threat of afternoon showers and thunderstorms will persist through the end of the extended forecast period. Overall, a wet extended forecast is expected through next week. && .AVIATION...(For the 12Z TAFS through 12Z Wednesday morning) ISSUED AT 745 AM EDT TUE AUG 15 2017 Scattered showers and a stray thunderstorm or two continue to affect eastern Kentucky this morning. Coverage will be highest in the south through the day. More instability around today will likely result in additional thunderstorm development by afternoon, but given uncertainty whether any particular TAF site will be impacted, kept them with just VCTS, at this time. Winds will remain light and variable throughout the period. Aside from the storm threats for the afternoon, the main concern for this TAF cycle is the ongoing flight categories due to fog and low stratus clouds through mid morning. Conditions should begin improving shortly by 14z, but expected no better than BKN cloud cover in the low end VFR range through the afternoon with any convection lowering the cigs/vis into the MVFR or lower range. cigs should lift heading into the evening, but there is a potential for more low cigs and fog later tonight. && .JKL WATCHES/WARNINGS/ADVISORIES...NONE. && $$ UPDATE...RAY SHORT TERM...GREIF LONG TERM...SHALLENBERGER AVIATION...GREIF

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