Area Forecast Discussion
Issued by NWS Jackson, KY

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207 FXUS63 KJKL 210624 AAA AFDJKL AREA FORECAST DISCUSSION...UPDATED National Weather Service Jackson KY 224 AM EDT Sun May 21 2017 .UPDATE... Issued at 224 AM EDT SUN MAY 21 2017 The last of the better convection will be exiting into southern Ohio in the next hour. The latest IR satellite reveals generally warming cloud tops upstream, with only some scattered showers moving in from Tennessee. The models have been struggling with initialization, given that the mesoscale has been the dominant player thus far. Still, with moist flow out of the south and southwest, and the models hinting at an uptick in a low level jet through dawn, can not rule out at least scattered coverage through the rest of the overnight. Weak instability remains in place, keeping the threat of at least isolated thunder. Updates have been sent. UPDATE Issued at 1056 PM EDT SAT MAY 20 2017 Had some convection develop along left over outflow boundaries as mentioned earlier. Stuff has been avoiding southwest areas. However, widespread rain is now working into our southwest zones associated with a mid level wave pushing northward. This rain will continue to overspread the area overnight setting up a damp night and a damp start to Sunday for most of the area. Thunderstorm chances will be slowly diminishing overnight as instability diminishes with the widespread rain moving into the area. A few isolated storms will remain possible however. Updated temperature grids based on the rain cooled air in the east. Also, receiving numerous reports of significant flash flooding in Magoffin county associated with the ongoing flash flood warning. We may need to consider a flash flood watch if more significant rain threatens the area again. UPDATE Issued at 645 PM EDT SAT MAY 20 2017 All convection has shifted off to the north and east of the area with a lull expected through the early evening hours. A modest moisture gradient is in place across the area with areas near the Cumberland river in the southwest seeing dewpoints into the mid 50s, while dewpoints reside near 70 or higher to the north and northeast. With the dry air in the southwest, have removed any thunderstorm chances for the evening. Left some isolated pops in the areas with better moisture, but confidence is low if we will see new development. However, some left over boundaries have been noted in the area, so it wouldn`t take much to see some new development towards sunset. In fact, both the RAP and HRRR show this potential, so will leave some low end pops in over the next few hours. Also with the rain moving in tonight, models are fairly consistent with this idea, so have bumped pops up to categorical. && .SHORT TERM...(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. && .AVIATION...(For the 06Z TAFS through 06Z Sunday night) ISSUED AT 224 AM EDT SUN MAY 21 2017 VFR conditions will rule initially, as a cold front remains well to our west. Through dawn, an increasing low level jet will likely bring some MVFR ceilings in from the west. Scattered showers will become more numerous during the day on Sunday as a cold front gradually advances east across the Commonwealth. Thunderstorms will likely be more scattered in nature. The front will move through after 00z, with winds becoming more southwest behind the frontal passage, and showers diminishing from west to east. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...GEOGERIAN SHORT TERM...JMW LONG TERM...GREIF AVIATION...GEOGERIAN is the U.S. government's official web portal to all federal, state and local government web resources and services.