Area Forecast Discussion
Issued by NWS Jackson, KY

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635 FXUS63 KJKL 150810 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 410 AM EDT Tue Aug 15 2017 .SHORT TERM...
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(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.
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&& .AVIATION...(For the 06Z TAFS through 06Z Tuesday night) ISSUED AT 200 AM EDT TUE AUG 15 2017 Scattered showers and a stray thunderstorm or two continue to affect eastern Kentucky early this morning. Coverage will be highest in the south, but even SYM could see a shower, with some increase in areal extent expected toward dawn in the far SE portion of the state. Limited instability should keep the thunder chances low, so just went with VCSH for all TAF sites. For Tuesday, though, there will be more instability around likely resulting in additional thunderstorm development in the afternoon, but given uncertainty whether any particular TAF site will be impacted, kept with VCTS, at this time. Winds will remain light and variable throughout the period. Aside from the storm threats for Tuesday afternoon, the main concern for this TAF is the potential for low flight categories due to fog and low stratus clouds through mid morning. With abundant moisture across the region, we have the potential for LIFR conditions. However, can`t rule out some brief drops below this category. Conditions should begin improving shortly after daybreak, 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. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...GREIF LONG TERM...SHALLENBERGER AVIATION...JMW/GREIF

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