Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 171900 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 300 PM EDT Sat Mar 17 2018 .UPDATE...
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Issued at 300 PM EDT SAT MAR 17 2018 There is a 30+ deg F temperature spread across the forecast area due to the cold front sinking south. The forecast has been updated to account for the latest temperature trends. Showers have started to develop near the frontal boundary over western KY, being the start of activity to expand during the afternoon. However, dew points have dropped off to 45-50 in a pocket over the southern portion of the JKL forecast area. Unless they can recover, this would cut into the severe wx potential for late today. UPDATE Issued at 1231 PM EDT SAT MAR 17 2018 Forecast is largely on track, and this update primarily blends latest obs into the afternoon`s forecast. UPDATE Issued at 956 AM EDT SAT MAR 17 2018 There is a large hole in the clouds passing over the southern portion of the forecast area this morning, and a complete break in precip area wide. Have updated the forecast to include this. Development of additional showers/thunderstorms is still anticipated this afternoon. UPDATE Issued at 800 AM EDT SAT MAR 17 2018 Forecast in pretty good shape this morning. Continuing to monitor precip associated with a warm front across the region, which is quickly dissipating as we head into the 8am hour. Adjusted pops to better reflect the ongoing trends of less coverage, but forecast might still be a bit high. Will continue to monitor and adjust as needed. Regardless, any precip that does occur this morning will be light and all thunder potential should be gone through this afternoon. Also loaded in the latest observations to make sure the near term forecast for temps, dew points, and winds was on track with the current conditions. All grids have been published and sent to NDFD/web.
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&& .SHORT TERM...(Today through Sunday) Issued at 530 AM EDT SAT MAR 17 2018 A warm front is currently pushing into the state, and will continue to drift northward through around 12 to 15Z, making it as far north as the Mountain Parkway. From 15Z, the warm front will start to shift eastward, as a surface low pressure system begins to traverse the state from the NW, riding along the southern extent of the CWA through the afternoon, and exiting SE of the state after 0Z tonight. Behind this system, winds will become northerly as broad high pressure to our NW begins to take control. This area of high pressure will continue to make its way into the region through the day Sunday to round out the forecast period. As for sensible weather... The warm front nosing into the region will lead to an influx of warm and moist air, resulting in rain chances (and possibly an isolated rumble of thunder) across eastern Kentucky through this morning, with best chances exiting east of the CWA between 13 and 15Z. Lingering chances will remain across the northern half of the CWA through the first part of the afternoon, however some drying may occur in the southern CWA due to the dry slotting on the SW side of the approaching low pressure system. This dry slotting will be key in the possibility of afternoon convection, as any clearing in the skies could send temps well into the 70s and effectively increase instability. Forecasted temperatures were raised from the given model blends for us and neighboring CWAs given the potential for localized heating during any clearing that takes place. As the low pressure system continues to progress southeast, and moisture starts to mix back in with this warm air in the late afternoon, scattered storms will begin to develop. Based on the latest soundings, still looking at decent speed shear throughout the day. However, the jet is actually well into the mid levels, so expect any storms that develop to be fast movers, tapping into these higher wind speeds. While higher wind gusts could still translate to the surface, the best wind gusts will be in the tallest storms able to tap into these higher winds. Freezing levels, steep lapse rates, and dry air aloft also look conducive to a hail threat. Forecasted storm total rainfall is only between a quarter and a half of an inch, so not expecting much of a flash flood threat. This is further deterred by the fact that the storms will be so progressive, not allowing for any long duration heavy rainfall in any one location. The storm threat will quickly diminish between 0 and 3Z as the low pressure system shifts SE of the area and northerly flow at the surface creates a llvl inversion, preventing lift. Meanwhile...for the northern portion of the CWA...the warm front will never make it far enough northward during the day to allow for the southerly flow and WAA to take hold and influence the weather. As such, temperatures generally north of the Mountain Parkway will only reach the low 40s to low 50s, which is not warm enough to produce enough instability to instigate any storm potential. Furthermore, the northern CWA will find itself on the NE side of the passing low pressure system, which is more conducive to colder NE flow and less storm threat. Left thunder wording out of the northern CWA throughout the afternoon and evening as a result, however rain will still occur. Once the low pressure system exits to our SE this evening, wrap around moisture will keep precip chances in place across the CWA through much of the night, slowly tapering off from W to E by Sunday morning. Llvl clouds will also remain in place through the first part of the day on Sunday, clearing out by Sunday afternoon as a drier airmass moves in overhead under the influence of high pressure. Temperatures will be able to rebound back into the mid and upper 50s for highs. .LONG TERM...(Sunday night through Friday) Issued at 426 AM EDT SAT MAR 17 2018 The long wave pattern looks to be fairly amplified as well as progressive next week. The model agreement with regards to the smaller scale features is pretty good early next week, but then lowers through the rest of the period. A southern stream system will be moving quickly east out of the Four Corners region, reaching the mid-Atlantic by early Tuesday morning. A developing warm front will bring a return of showers to the area late Sunday night. Surface low pressure will be developing and moving east into the Tennessee Valley Monday into Monday night, bringing widespread showers to the area, with at least a small threat of thunder. Northwest flow will linger behind the departed low pressure on Tuesday, with the northern stream lending energy, and carving out a deeper trough across the eastern CONUS through mid-week. Precipitation will linger across eastern Kentucky, with colder air allowing for a snow threat, particularly across the higher terrain by Tuesday night. There remains a bit too much uncertainty at this point to play up any more specific impacts. Drier conditions will work in by Wednesday evening, as ridging moves in from the west. Dry weather will continue through early Friday, before the next potential system moves in by late in the day. Favored a slower arrival of the precipitation, given the disagreement this far out. Near normal temperatures initially will cool to well below normal by Wednesday, before gradually warming once again towards the end of the work week. && .AVIATION...
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(For the 18Z TAFS through 18Z Sunday afternoon) ISSUED AT 300 PM EDT SAT MAR 17 2018 A slow moving cold front was located near the Mountain Parkway and was dropping south through the forecast area at the start of the period. Most places were VFR with scattered to broken cu. The northern edge of the forecast area was likely IFR due to ceilings in portions of Fleming, Rowan, and Elliott counties. The front will continue to sink southward today. Showers and thunderstorms are expected to develop near and ahead of the front late this afternoon and early this evening, but will taper off after frontal passage tonight. IFR and MVFR ceilings are forecast to develop southward over the region behind the front late today and tonight, affecting the entire region by about 02z. Ceilings are forecast to break up and give way to VFR conditions from north to south between about 09Z and 18Z.
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&& .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...HAL SHORT TERM...JMW LONG TERM...GEOGERIAN AVIATION...HAL is the U.S. government's official web portal to all federal, state and local government web resources and services.