Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 260543 AFDJKL Area Forecast Discussion National Weather Service Jackson KY 143 AM EDT TUE JUL 26 2016 .UPDATE... Issued at 1135 PM EDT MON JUL 25 2016 WSR-88D radar shows much of the activity that plagued the southern portions of the CWA this evening has finally moved south or died off. Think most the rest of the night we will be met with drier conditions in terms of rain. That said we still have a moist environment in place and this will lead to potential for fog overnight into the morning. At this point not confident on coverage so will limit it to the valleys for now. Updated grids to lessen pops and update WX grids. Also trended grids toward obs and trends. UPDATE Issued at 930 PM EDT MON JUL 25 2016 WSR-88D radar showing best convection residing in locations generally south of the Hal Rogers Parkway this hour. Otherwise more in the way of scattered to isolated showers will be the story. In term of models trended toward the short term blend at this point which seemed to handle convection across the south this later evening hour. Also updated temps/dews/winds with latest obs and trends. UPDATE Issued at 603 PM EDT MON JUL 25 2016 WSR-88D radar shows convection continuing mainly south of a line from Pikeville, to Jackson, to McKee this hour. Expanded pops for a short period of time, but much of this will be diurnally driven and should continue a downward trend. Also locations north of this have been scoured out by earlier convection and outflow boundaries. CAMS have about as good of a handle on the convection, as one would expect and therefore no preference on any one model. Temperature curve has been difficult to pin down given the coverage of storms and outflow boundaries. Mostly went toward a blend approach with current obs and trended into the evening. The GLAMP seems to have the overall best curve at the moment in terms of guidance. Otherwise no major changes needed at this point. && .SHORT TERM...(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. && .AVIATION...(For the 06Z TAFS through 06Z Tuesday night) ISSUED AT 143 AM EDT TUE JUL 26 2016 With loss of best diurnal heating/lift, all precip has ceased across eastern KY. Only some sct to bkn high level clouds remain as of 5Z. Unfortunately, given the heavy rainfall at most of the TAF sites yesterday, lingering moisture has remained intact. Still expecting the combination of light winds, mostly clear skies, and this low level moisture and produce fog in many locations. Kept with alternate minimums late tonight for visibility with the anticipated fog development, though this may need to be adjusted as we actually see the fog form. Kept SJS within the MVFR category, however, since they saw the least amount of rain. A frontal boundary will stall out north of the state through the period, leading to additional sct convection for Tuesday afternoon. Kept with mention of VCTS at all sites during this time, since confidence is still low on the exact timing and placement of any of developing storms. Winds should remain generally light and variable at all sites during the TAF period, but those sites that happen to see a storm Tuesday afternoon could experience some brief gusty winds. && .JKL Watches/Warnings/Advisories... None. && $$ UPDATE...DJ SHORT TERM...ABE LONG TERM...RAY AVIATION...JMW is the U.S. government's official web portal to all federal, state and local government web resources and services.