Area Forecast Discussion
Issued by NWS Jackson, KY

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705 FXUS63 KJKL 240520 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 120 AM EDT Wed May 24 2017 .UPDATE... Issued at 101 AM EDT WED MAY 24 2017 A wave continues to move across the region with multiple waves riding through the flow seen on mesoanalysis and WV SAT. It does look like we will see a relative lull in showers until we move closer to dawn when the surface low deepens. Made some adjustments to POPs with the latest obs and trends otherwise a standard update of the obs was done. UPDATE Issued at 1055 PM EDT TUE MAY 23 2017 Hourly pops have been updated based on recent radar trends. Showers and even a rumble of thunder in the far southeast has occurred in the last hour as a mid level disturbance works through the area. The current round of showers should weaken and shift out of the area over the next couple of hours. However, another disturbance should bring another round of showers and perhaps a thunderstorm encroaching on the area around dawn. UPDATE Issued at 835 PM EDT TUE MAY 23 2017 Some late afternoon heating and a mid level disturbance have combined to bring some showers and thunderstorms to parts of Central KY and parts of Middle TN and the Cumberland Plateau of TN. Much of these have experienced a downward trend in intensity over the past hour or so with the exception of the convection in the Bluegrass Region of KY while showers persist across much of southeast KY. Thunder chances were added for the evening with the upstream thunder detected. Also, dewpoint depressions across much of the area are just a few degrees. With low level moisture lingering and some cooling in between the current shortwave and the next to approach late tonight and on Wednesday at least some patchy fog will be experienced possibly both on the ridges and int the valleys and this has been included. Otherwise, no substantial changes were needed at this time. && .SHORT TERM...(This evening through Wednesday night) Issued at 500 PM EDT TUE MAY 23 2017 20z sfc analysis shows a broad area of low pressure over the middle of the Tennessee Valley encompassing Kentucky. This has brought showers and sprinkles to eastern Kentucky as well as plenty of clouds. The rain has also kept temperatures in check and on the cool side through much of the JKL CWA with readings currently in the low 70s northwest and southwest where the clouds were thinnest to the mid 60s in the rain further east. Dewpoints are generally in the upper 50s to lower 60s while the winds are light and variable. The models are in good agreement aloft through the short term portion of the forecast. They all depict a deep and cut off closed low digging into the Deep South through Thursday morning along with ample energy swirling around. The core will roll down the backside of this larger trough and generally target locations to the south of Kentucky on Wednesday into Wednesday night. The good model agreement lends support to a blended model solution along with the use of the high res HRRR through the near term. Sensible weather will feature scattered showers departing to the northeast this evening - with a stray thunderstorm possible. This will be followed by a lull in the activity through midnight for most locations under cloudy skies before the next surge in moisture moves in late tonight with showers and thunderstorms increasingly possible toward dawn. The thick clouds should keep most of the fog at bay tonight, but for places that saw the rain late this afternoon and into the evening - should the clouds thin enough - patchy fog will be possible and will need to be monitored. Showers and thunderstorms will then sweep over all of eastern Kentucky on Wednesday with some gusty winds and a window of heavier rain possible should they manage to be more organized - perhaps helped from a mid level wave swinging through around midday. Have highlighted this time frame in the grids for the best shot at thunder, as well. Later in the day the thunder chances fade out from west to east as the main sfc low lifts past to the east. Lighter shower will linger, though, into the night. The CONSShort and ShortBlend were used as a starting point for the grids` with only minor adjustments to temps through the period. As for PoPs, made some significant adjustments to them to better represent the spatial and timing aspects of the rain shield moving into East Kentucky from late tonight through Wednesday afternoon. .LONG TERM...(Thursday through Tuesday) Issued at 400 PM EDT TUE MAY 23 2017 An upper level low will be centered over Kentucky to start out the period Thursday morning, shifting northeast throughout the day and into Thursday night, with rising heights expected across the Commonwealth. Ridging will take hold Friday, however will be dampened as several shortwaves move through the pattern and affect the region over the next couple of days. By Saturday, another upper level low will drop south from central Canada, allowing for longwave troughing to develop across the central U.S. While timing on this system is still somewhat unresolved between the models, as is the intensity of the trough, much of the state can expect some type of height falls and destabilization to occur to round out the weekend and start the beginning of the workweek. Models actually come back into better agreement by the very end of the extended period, with the axis of the trough nearing the state Tuesday, and traversing the state into the day Wednesday. At the surface, the presence of a surface low pressure system just north of the CWA (in conjunction with the upper level low) will result in precip chances throughout the day Thursday. This precip will pull northeast of the region into Friday morning as the surface low exits in this direction. However, given our location on the backside of the cold front, latest forecast soundings aren`t supporting much in the way of instability, so chose to keep out mention of thunder Thursday. A brief area of high pressure will move into place with the building heights, keeping us mostly dry Friday. However, incoming shortwaves that will ride along this pattern will bring the return of unsettled weather and shower/thunderstorm chances by Friday night, continuing through Saturday and increasing in intensity and coverage by Saturday night into Sunday as a surface low moves NE towards the state and a cold front drags eastward. This cold front will cross eastern KY Sunday night into Monday, with another brief area of high pressure moving in behind during the day Monday. Yet another cold front will near the state Tuesday, attached to a stronger surface low to our north (in conjunction with the second upper level low referenced above). This will bring yet another round of precip (showers and thunderstorms) to the region through the day Tuesday. Temperatures should start out below normal during the day Thursday behind the departing cold front, with highs in the mid 60s. stronger S to SW flow will take place by Friday, bumping temps into the mid and upper 70s Friday afternoon, and into the upper 70s and low 80s on Saturday and Sunday afternoon. Despite a cold front moving through on Sunday night/Monday morning, temps will only be slightly (a couple degrees) cooler on Monday and Tuesday than the weekend thanks to the quick return of SW flow behind the frontal passage. && .AVIATION...
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(For the 06Z TAFS through 06Z Wednesday night) ISSUED AT 120 AM EDT WED MAY 24 2017 The period will be met with VFR to airfield mins in relative subsidence between upper level waves. This will lead to varying TAFs overnight for most of the sites and particularly sites that have increased low level moisture form earlier convection. While most of the shower activity has diminished this hour more activity will develop under deepening surface low toward dawn and onward. By this afternoon would suspect CIGs and VIS would lower again to MVFR/IFR at times in heavier shower and thunderstorm activity. Most areas will continue to see light winds, but perhaps some isolated higher gusts are possible with any thunderstorms.
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&& .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...DJ SHORT TERM...GREIF LONG TERM...JMW AVIATION...DJ

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