Area Forecast Discussion
Issued by NWS Jackson, KY

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598 FXUS63 KJKL 251917 AFDJKL Area Forecast Discussion National Weather Service Jackson KY 317 PM EDT MON JUL 25 2016 .SHORT TERM...
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(This evening through Tuesday night) Issued at 317 PM EDT MON JUL 25 2016 Showers and thunderstorms continue to erupt this afternoon, with the best concentration occurring over our northern counties closer to a weak frontal boundary paralleling the Ohio River. This boundary will remain fairly stationary just to our north and remain a focusing mechanism for scattered to numerous showers and thunderstorms. While the storms should exhibit a diurnal trend, with coverage peaking in the afternoon hours, cannot rule out a storm at any time over the next 36 hours. The main threat with storms will remain heavy rainfall and lightning in the high CAPE but low shear environment. Storms seem to want to move along fairly well at 10 to 15 mph and that is a good thing considering PWATS are approaching 2 inches. However, there will be a minor threat for flash flooding in areas that see repeating rounds of thunderstorms. We are also seeing storms today gust out pretty easily and an isolated severe storm remains possible this afternoon with DCAPE exceeding 1000 J/kg. With the front remaining to our north through the period, the airmass over our region will remain very muggy with dewpoints staying well into the 70s. Increased clouds and showers during the day tomorrow should keep temperatures below 90 for most areas, and heat indices below 100 for a change. .LONG TERM...(Wednesday through Monday) Issued at 317 PM EDT MON JUL 25 2016 Models are in reasonably good agreement with general mid/upper level flow and larger scale synoptic features through the period. But significant differences are beginning to crop up with respect to details of embedded disturbances within the general flow pattern and corresponding sfc features thereby lowering overall confidence of the extended package, particularly with respect to sensible weather. Somewhat zonal flow quickly amplifies with a mean trough forming over the Great Lakes and Mid-West which remains in place across the region through the period. Rather significant ridging does develop aloft and replaces this eastern CONUS trough as it lifts northeast out of the region just beyond the end of the extended window. At the surface, it appears that a nearly stationary frontal boundary will exist somewhere across the northern portions of the Commonwealth. This feature will provide a focus for the bulk of our sensible weather through the extended in the form of showers and thunderstorms. However, main concern revolves around a sfc wave tracking through the region Thursday into Thursday evening. The last three runs of the GFS have been quite consistent with this wave that develops and moves across the Commonwealth. The GFS advertises PWATs increasing to between 2 and 2.25 inches during this window. In addition, freezing levels increase to between 14 kft and 15 kft AGL with moderately high CAPEs of 1000-1500 K/kg and LCLs between 500 and 1000 ft AGL. Should this scenario pan out there is a potential for some warm water processes. And while storm motions are considerable at 15-25 kts, flow aloft would be favorable for training along the sfc boundary wherever it eventually sets up. Consequently hydro issues may become a concern by Thursday. The 0Z ECMWF suggest a similar potential but carries the surface wave further north and west of our forecast area thereby keeping the heavy rain threat north of the Ohio River. A quick look at the 12Z ECMWF shows that it has trended slightly towards the GFS solution. With a mean trough over the eastern CONUS and expected rounds of mainly diurnal precipitation, daily high temperatures should be cooler than we have been experiencing, much closer to the mid 80 norms for this time of year. However, conditions will also be quite muggy keeping overnight lows in the upper 60s to near 70. Thus diurnal swings will be limited as well.
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&& .AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon) ISSUED AT 138 PM EDT MON JUL 25 2016 Scattered thunderstorms continue to erupt in a sultry airmass. These will likely remain rather hit and miss and will maintain no more than a VCTS mention in the TAFs for now. Expect these storms to exhibit a diurnal trend and diminish in coverage slowly after sunset, although there will be a small threat for a shower or storm anytime through the night and into tomorrow morning due to a frontal boundary sagging southward toward our area. Fog is another concern but it should remain patchy and is likely to only affect TAF sites that are hit directly by a thunderstorm this afternoon. With that in mind, will go with VFR TAFs for now through 18z Tuesday and let later shifts fine tune. && .JKL Watches/Warnings/Advisories... None. && $$ SHORT TERM...ABE LONG TERM...RAY AVIATION...ABE

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