Area Forecast Discussion
Issued by NWS Jackson, KY

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085 FXUS63 KJKL 241815 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 215 PM EDT Tue Apr 24 2018 .UPDATE... Issued at 215 PM EDT TUE APR 24 2018 Just a few tweaks to the grids for the early afternoon update. Band of showers is beginning to take shape over the far east as expected. No update to the zones ATTM. UPDATE Issued at 1208 PM EDT TUE APR 24 2018 Forecast is pretty much on track. Updated the zone package to freshen up wording. Also increased PoPs across the far east a bit. Last few hours HRRR has been consistently developing a band of more moderate shower activity generally along and northeast of U.S. Highway 460. Can not rule out a few rumbles of thunder either, especially with some areas getting a peak at the sun from time to time. Rain has dissipated and is moving out of areas within the Flood Advisory. Will let the advisory run its course to allow for excessive runoff to subside as well. UPDATE Issued at 1000 AM EDT TUE APR 24 2018 Grid are in good shape and forecast is on track. Only had minor tweaks to hourly temps and dew points. Will plan on a late morning update to remove morning wording from the zone package. Otherwise, did issue a flood advisory for portions of our southwest. Twenty- four hour rainfall totals have been around 1.5 inches. Training of moderate showers through the area will lay out about another half inch by mid-day. As a result suspected there could be some minor flooding, especially in poor drainage areas. UPDATE Issued at 642 AM EDT TUE APR 24 2018 Forecast seems to be in pretty good shape so far this morning. Near term POP forecast is matching quite well with the current radar. Latest HRRR and NAM 12 are trying to show a dry slot working its way in across a portion of the CWA through the early afternoon, however this is not being mimicked by the Hi-res ARW or NMM. Confidence wasn`t great enough to warrant a changing of the forecast, but this will be something to keep an eye out for as we head through the day. Also made sure the near term forecast was on track with the latest observations for temps, dew points, and winds. All updates have been published and sent to NDFD/web. && .SHORT TERM...(Today through Wednesday) Issued at 414 AM EDT TUE APR 24 2018 A strong 500mb low is currently making its way across western Kentucky and Tennessee, while the associated surface low is just slightly farther SE, moving into the Carolinas. The surface low is quite expansive, encompassing much of eastern TN as well at 12Z. This surface low will continue to strengthen throughout the day and into tonight as it moves NE across the Carolinas, reaching Virginia by 12Z Wednesday. The upper level low will shift just east of Kentucky by this point as well. After 12Z, the system will continue to ride up the eastern Atlantic seaboard, with the upper level low losing considerable strength as it becomes absorbed into a larger system over the lower Great Lakes. Meanwhile, broad high pressure will move southeastward, taking hold across Kentucky for the day Wednesday. As for sensible weather, despite light easterly winds at the surface, winds in the mid and upper levels will be due south, pulling ample moisture into the region and resulting in widespread rainfall through much of the day. There still looks to be a brief period in the late afternoon where soundings show enough instability during peak heating to produce a few rumbles of thunder. Ingredients are not overwhelming, however, especially as you head northward through the CWA, so did not go any higher than an isolated mention. QPF should generally be a half inch or lower through the day, but any heavier showers/thunderstorms could easily surpass this. Heading into the overnight, we start to see the system shift eastward and winds quickly transition to a more northward direction in the mid and upper levels, and NW in the lower levels. This will cut off some of the influx of moisture, however we will still be able to tap into wrap around moisture from the system, so expect continued scattered but light rain shower potential throughout the night. Did keep mention of numerous showers in the far SE portion of the state where upslope flow will play a large factor. By Wednesday, the system will continue to drift away from the region as drier high pressure takes hold from the west. Pops are expected to slowly diminish from west to east throughout the day, once again holding on the longest in the far SE with continued favored NW flow. Given the abundance of clouds and rain across the region, temperatures will be fairly uniform and mild. Highs both today and tomorrow will be in the low 60s, with overnight lows in the low 50s. .LONG TERM...(Wednesday night through Monday) Issued at 437 AM EDT TUE APR 24 2018 Whatever active weather there is during the period looks like it will be in the first few days. Light rain on the trailing edge of a storm system moving up the east coast could still be affecting our far eastern counties Wednesday evening, but will be on the way out. At least a brief break in precip is then expected into the day Thursday. By late Thursday, rain could again be in the picture from another upper low moving slowly across the southeast CONUS (the system currently over MT, WY, and the Dakotas). It`s uncertain how far north the rain will occur. The GFS and NAM both have light precip in our southern counties late Thursday into Thursday night, while the ECMWF keeps it to our south. Considering a similar model scenario played out in advance of the system currently bringing us rain, the American models will be given consideration and a chance POP will be carried near the TN border. Whatever plays out, the system is expected to depart Thursday night. After only a brief break, a cold front is expected to arrive Friday evening (supported by an upper level trough currently offshore of British Columbia). Moisture looks to be very meager, and the ECMWF is dry and the GFS only has very light precip in our far north. The situation does not seem to justify anything more than a slight chance of showers at the northern edge of the forecast area. After this, ridging at the surface and aloft is forecast to build into the area, resulting in dry weather Saturday through Monday, with highs nearing 80 by Monday. && .AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon) ISSUED AT 215 PM EDT TUE APR 24 2018 Storm system over the TN and OH valley continues to rotate to the east, at present centered roughly over south central Kentucky. As expected there is a band of showers beginning to take shape across the east. HRRR seems to have had a good handle on this feature. As such did include a VCTS for SJS for a few hours early in the period, especially with a bit more sunshine in the east. However, convection is expected to be isolated and widespread enough to exclude any mention of thunder at other terminals. Flight conditions will generally deteriorate through the evening and overnight, mainly for CIGS as they drop into IFR/LIFR territory. Winds will generally be light and variably but will gradually turn out of the northwest as the storm center continues to push eastward. && .JKL WATCHES/WARNINGS/ADVISORIES...NONE. && $$ UPDATE...RAY SHORT TERM...JMW LONG TERM...HAL AVIATION...RAY

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