Area Forecast Discussion
Issued by NWS Jackson, KY

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404 FXUS63 KJKL 192035 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 435 PM EDT Tue Sep 19 2017 .SHORT TERM...(This evening through Wednesday night) Issued at 435 PM EDT TUE SEP 19 2017 20z sfc analysis shows a bland sfc pattern in place over Kentucky while a mid level disturbance is passing through the Ohio Valley. This has activated the moist and humid air in place over the area to generate showers and a few thunderstorms that continue to move through eastern Kentucky this afternoon. The convection also brought plenty of clouds to the area limiting the sunshine by early afternoon. However, outside of any storm, temperatures had little trouble climbing into the low and mid 80s while dewpoints were in the mid 60s most places and winds light/variable. The models are in good agreement aloft with the longwave pattern through the short term portion of the forecast. However, some of the smaller scale, but important, features are handled just a little differently by each model. In general, though, they all depict the mini trough moving through the region tonight into Wednesday ahead of the ridge rebuilding from the southwest. The energy associated with the troughing feature will temporarily suppress heights and provide some impetus to any convection that manages to develop on Wednesday. Given the model agreement have favored a general blend updated with the latest guidance from the CAMS and higher resolution models. Sensible weather will feature convection dieing out this evening with some subsidence overnight clearing the clouds - probably leading to areas of dense fog developing in the river valleys, at the least, by dawn. The fog will burn off in the morning on Wednesday with isolated convection developing by afternoon - propelled by the energy aloft. Similar conditions as tonight will set up for Wednesday night with any convection fading out early in the evening followed by some clearing and then areas of fog developing - likely becoming locally dense in the river valleys again. The CONSShort and ShortBlend were used again as the starting point for all the grids. Did make some adjustments to the temperature ones each night based on terrain due to at least a small ridge to valley split setting up. As for PoPs, did again tweak them for the diurnal cycle peaking late in the afternoon and then diminishing after sunset on Wednesday. .LONG TERM...(Thursday through Tuesday) Issued at 349 PM EDT TUE SEP 19 2017 Models continue to display good agreement with a highly amplified long wave pattern developing across the CONUS into the weekend. Deep troughing will establish itself throughout the West. In the east, a seasonably strong ridge will build from the lower Mississippi Valley into New England. By early next week, the western trough and tropical activity in the western Atlantic pinches off the ridge, forcing the center to lift into the Great Lakes while the south end gradually dampens off. Sensible weather for eastern Kentucky remains uneventful and warm through most of the period. Thursday looks to be the only day when a few showers may threaten the area, before ridging becomes the dominant influence in our weather. Forecast soundings suggest enough surface based instability to warrant the mention of some thunder on Thursday. However, do question this after considering the rapid height rises taking place across the region through the day. For now, went ahead and included a slight chance of thunder, which actually helps to match up better with neighboring offices. After Thursday, the start of autumn looks to be dry and warm. Temperatures will run around 5 degrees above normal but will gradually drop closer to normal as heights slowly fall off with time. Highs will run in the mid 80s through the weekend, dropping off to the lower 80s by the end of the extended. Daily lows will start out rather warm as well, generally in the mid 60s but will drop closer into the lower 60s with time. Drier air settling into the area will allow for some cooler 50s in the valleys through the latter portion of the forecast. && .AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon) ISSUED AT 230 PM EDT TUE SEP 19 2017 Showers and a few thunderstorms are crossing the area this afternoon as a disturbance moves in aloft. While convection will be rather scattered it is already impacting the JKL and SYM TAF sites with the SME and LOZ ones skating by at the moment. Have allowed for some VCTS in the south, but went prevailing at JKL. SYM and SJS are be more questionable for seeing a direct hit from a storm so have also gone with VCTS there for a few hours. After the convection diminishes this evening, skies may clear off again, leading to another night of likely valley fog. Indications are that the fog tonight could be a little worse than it was this morning with dewpoints running a tad higher. Any fog burns off by 14z with VFR conditions returning. Winds, outside of any storm, will be light and variable through the period. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...GREIF LONG TERM...GEOGERIAN/RAY AVIATION...GREIF is the U.S. government's official web portal to all federal, state and local government web resources and services.