Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 202018 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 418 PM EDT Sat May 20 2017 .SHORT TERM...
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(This evening through Sunday night) Issued at 418 PM EDT SAT MAY 20 2017 A warm front located just north of the CWA has kept warm southerly flow across the region today, and has recently been the epicenter of which isolated to scattered convection has developed. While storms are generally located along our northern periphery and moving out of the CWA as of 4pm, the continued presence of this warm/moist/unstable airmass cannot rule out some continued isolated development through this evening. Latest CAMs aren`t in very good agreement, but all of them do show that a few more developing storms are not completely out the question through this evening, so kept isolated mentioned through the evening. By this evening the warm front will begin to lift northward as surface low pressure moves northeast towards the Upper Great Lakes region overnight and pulls it with it. This movement will also drag a surface cold front farther eastward into Western KY overnight. This cold front will be the main concern throughout the short term portion of the forecast as it continues its track eastward, reaching and then passing across the eastern portion of the state Sunday evening through Sunday night, exiting by 12Z Monday. A line of convection has already developed across the western portion of the ahead of this frontal feature, and is poised to continue eastward ahead of the approaching front. Models are all in good agreement that convection, potentially widespread, will begin impacting our CWA overnight, with scattered to numerous convection continuing throughout the day Sunday, before the front finally pushes through. Once the front does pass over a location, temperatures will quickly drop and dry air will fill in within the matter of a couple of hours. This will result in a defining line as to where the front is, with a cut off to clouds and precip just behind. In fact, the pops are likely too broadbrushed for the cut off that will likely occur, but will keep them as such just given some uncertainty on timing. Latest forecast soundings continue to support heavy raining cells for the convection that occurs overnight and tomorrow, with the entire forecast column saturated from the ground up, but not a lot of forcing otherwise. This will eliminate most hail concerns, and winds are not overly impressive, but can`t rule out a few higher gusts in the heaviest storms. Continued to hype up flooding warning in HWO, as any high precip producing cells could cause problems, especially if multiple storms pass over the same locations, or across areas which have already been saturated from rains over the previous days. .LONG TERM...(Monday through Saturday) Issued at 345 PM EDT SAT MAY 20 2017 The models are in fair, but steadily growing, agreement with the highly amplified pattern that will affect the region through the extended portion of the forecast. The models depict a relatively deep trough over the heart of the continent at the start of the extended with Kentucky in mostly fast zonal mid level flow just to the south. This upper low will then proceed to consolidate to the southwest and start to dig through the Plains Tuesday night into Wednesday. As this occurs, several energy batches will drift over eastern Kentucky While the core of the low moves into the Ohio Valley. At this point, the models diverge more with the GFS closing off the low and settling over Kentucky while the ECMWF is also starting to close off, but further north - over Lake Michigan. Either way, plenty of additional energy will pour through the area to end the work week with some better consensus on moving the upper low to the Mid Atlantic region on Friday - though the ECMWF is significantly stronger at this point than the GFS. Heights will then start to rebound for Kentucky that evening and early Saturday, though still some energy will probably be working its way across the state late in the period. Sensible weather will feature a brief respite from the heat and humidity Monday, but return flow will quickly brings PoPs, in the form of showers and thunderstorms, back in later that night and Tuesday as sfc low pressure takes shape to the southwest - though somewhat cooler conditions will continue through the rest of the week. This low will then likely move through the area with heavy rain a concern in the far east as it slowly passes Tuesday night and Wednesday. Cooler wx follows to end the work week, but the high pressure that pushes into the area will not be that strong and additional showers will be possible on Saturday. Did not deviate too far from the blend temps for the extended as conditions look too damp for much of any terrain differences of note. Also kept the PoPs similar as the blend came in pretty reasonable.
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&& .AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon) ISSUED AT 147 PM EDT SAT MAY 20 2017 While generally VFR conditions are in place to start out this afternoon, some scattered MVFR cigs are starting to build across the area. As the afternoon continues, showers and thunderstorms will begin developing and impacting portions of eastern KY, especially central and northern. As such, went ahead and included VCTS at KSYM, KSJS, and KJKL for the potential that one of these isolated to scattered storms impacts the TAF site throughout the afternoon. A lull will be possible in the evening and first part of the night as the afternoon convective activity subsides. However, a cold front approaching from the west will quickly ramp up clouds and precip chances once again as we head into the morning hours Sunday. Widespread showers and thunderstorms are expected throughout the day Sunday, with some of these storms expected to be heavy rain producers. That being said, went with predominate MVFR conditions Sunday, but expect that CIGS and especially VIS will be very variable throughout the day as storms move across the TAF sites. Winds will generally be light and variable, though any storms could produce some higher gusts today and tomorrow as well. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...JMW LONG TERM...GREIF AVIATION...JMW is the U.S. government's official web portal to all federal, state and local government web resources and services.